Contains Nonbinding Recommendations 
Control of Listeria monocytogenes in 
Ready-To-Eat Foods: Guidance for 
Industry 
 Draft Guidance 
 
This guidance is being distributed for comment purposes only. 
 
 
Although you can comment on any guidance at any time (see 21 CFR 10.115(g)(5)), to ensure 
that FDA considers your comment on this draft guidance before we begin work on the final 
version of the guidance, submit either electronic or written comments on the draft guidance 
within 180 days of publication in the Federal Register of the notice announcing the availability of 
the draft guidance. Submit electronic comments to http://www.regulations.gov. Submit written 
comments to the Division of Dockets Management (HFA-305), Food and Drug Administration, 
5630 Fishers Lane, rm. 1061, Rockville, MD 20852. All comments should be identified with the 
docket number FDA2007D0494 listed in the notice of availability that publishes in the 
Federal Register.  
For questions regarding this draft document contact the Center for Food Safety and Applied 
Nutrition (CFSAN) at 240-402-1700. 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Food Safety and Applied Nutrition 
January 2017   Contains Nonbinding Recommendations 
Table of Contents 
 
I.  Introduction 
II.  Background 
A.  Regulatory Framework 
B.  Characteristics of L. monocytogenes 
C.  L. monocytogenes in the Food Processing Environment 
III.  How to Apply This Guidance to Your Operations Based on the Regulatory 
Framework That Applies to Your Food Establishment 
IV.  Controls on Personnel 
A.  Hands, Gloves and Footwear 
B.  Foamers, Footbaths, and Dry Powdered Sanitizers 
C.  Clothing 
D.  Controls on Personnel Associated with Specific Areas in the Plant 
E.  Personnel Who Perform Sanitation, Maintenance, and Similar Functions 
F.  Relevant Sections of Part 117 
V.  Design, Construction, and Operation of Your Plant 
A.  Design and Construction of the Plant 
1. General 
2. Air and air flow 
3. Water systems 
B.  General Operation of the Plant 
C.  Relevant Sections of Part 117 
VI.  Design, Construction, and Maintenance of Equipment 
A.  Design and Construction of Equipment 
B.  Maintenance of Equipment 
C.  Records 
D.  Relevant Sections of Part 117 
VII.  Sanitation 
A.  General Sanitation Program 
1. Written Sanitation Procedures 
2. Frequency of cleaning/sanitizing  Contains Nonbinding Recommendations 
3. Recommendations for cleaning and sanitizing 
4. Equipment and utensils used for cleaning/sanitizing 
B.  Cleaning Drains 
C.  Sanitizers 
D.  Sanitation Monitoring 
E.  Sanitation Records 
F.  Relevant Sections of Part 117 
VIII.  Controls on Raw Materials and Other Ingredients 
A.  Raw Materials and Other Ingredients That are Potential Sources of L. 
monocytogenes 
B.  Controlling L. monocytogenes in Raw Materials and Other Ingredients When 
Contamination With L. monocytogenes Is Reasonably Foreseeable 
1. General 
2. Use of a listericidal control measure 
3. Controls on suppliers 
4. Testing when receiving raw materials and other ingredients under a COC or COA 
5. Testing as the only control on raw materials or other ingredients 
C.  Records 
D.  Relevant Sections of part 117 
IX.  Process Control Based on Formulating an RTE Food to Have Intrinsic 
Characteristics That Prevent the Growth of L. monocytogenes 
A.  Initial Demonstration That a Listeristatic Formulation is Effective (Validation) 
1. pH less than or equal to 4.4 or water activity less than or equal to 0.92 
2. Listeristatic formulation that combines one or more antimicrobial substances and/or one 
or more other intrinsic factors 
B.  Ongoing Activities Relevant to a Process Control Based on a Listeristatic 
Formulation 
1. Monitoring 
2. Verification 
3. Corrective Actions or Corrections 
C.  Records 
D.  Relevant Sections of Part 117  Contains Nonbinding Recommendations 
X.  Listericidal Process Control 
A.  Initial Demonstration That a Listericidal Process Control is Effective (Validation) 
B.  Ongoing Activities Relevant to a Listericidal Process Control 
1. Monitoring 
2. Verification 
3. Corrective Actions or Corrections 
C.  Records 
D.  Relevant Sections of part 117 
XI.  Storage Practices and Time/Temperature Controls 
XII.  Transportation 
XIII.  Environmental Monitoring to Verify Control of Listeria spp. or L. monocytogenes 
A.  Goal of an Environmental Monitoring Program 
B.  Strategies for Environmental Monitoring 
C.  Sampling Areas 
D.  Written Procedures for Environmental Monitoring 
1. Scientifically valid 
2. Test organism 
3. Sample locations and number of sites to be tested 
4. Timing and frequency for collecting environmental samples 
5. Test(s) conducted (including analytical method(s)) 
6. Laboratory that conducts the testing 
7. Corrective action procedures 
8. Periodic verification of the written environmental monitoring procedures 
E.  Corrective Actions if You Detect Listeria spp. on a Non-Food-Contact Surface 
F.  Corrective Actions If You Detect Listeria spp. on a Food-Contact Surface 
1. Recommended corrective actions regarding your plant and your processing 
2. Determining whether Listeria spp. is L. monocytogenes 
3. Hold and Test procedures for RTE food 
G.  Summary of Recommended Corrective Actions When You Detect Listeria spp. in 
an Environmental Sample 
H.  Corrective Actions If You Detect Listeria monocytogenes on a Food-Contact 
Surface  Contains Nonbinding Recommendations 
1. Recommendations regarding your plant and your procedures 
2. Recommendations regarding an RTE food 
I.  Records 
J.  Relevant Sections of part 117 
XIV.  Sampling and Testing of RTE Foods 
A.  Periodic Sampling and Testing of RTE Foods to Verify Adequacy of Your 
Controls 
B.  Corrective Actions If You Detect L. monocytogenes in an RTE Food 
C.  Records 
D.  Relevant Sections of Part 117 
XV.   Analysis of Data for Trends 
A.  Trends in Data Collected from Environmental Monitoring 
B.  Trends in Data Collected from Product Testing 
C.  Records 
XVI.  Training 
XVII.   Procedures to Collect Samples, Prepare Samples for Analysis, and Test 
Samples for Listeria spp. or L. monocytogenes 
XVIII. Records 
XIX.  Glossary 
A.  Terms Defined in 21 CFR part 117 
B.  Terms Defined for the Purpose of This Guidance 
XX.  Table of Abbreviations 
XXI.  References 
Appendix 1.  Potential Sources of L. monocytogenes 
Appendix 2. Examples of Scenarios That Could Lead to Contamination of RTE Foods 
With L. monocytogenes 
Appendix 3.  Schematics Relevant to Recommended Plant Design 
Appendix 4.  Recommended Schedules for Routine Cleaning and Sanitizing 
A.  Food-Contact Surfaces 
B.  Non-Food-Contact Surfaces 
Appendix 5.  Recommended Procedures for Collecting Environmental Samples  Contains Nonbinding Recommendations 
A.   Collecting Samples from Surfaces (Including Both Food-Contact Surfaces and 
Non-Food-Contact Surfaces) 
B.  Collecting Rinse Samples 
C.  Collecting Liquid Samples (Including Floor Drain Effluents) 
D.  Compositing Samples Collected from Sponges or Swabs 
E.  Preparing Samples Collected from Liquids 
F.  Sample Analysis 
 
  Contains Nonbinding Recommendations 
 
 
Control of Listeria monocytogenes in Ready-to-
1
Eat Foods: Guidance for Industry  
 
This draft guidance, when finalized, will represent the current thinking of the Food and 
Drug Administration (FDA or we) on this topic. It does not establish any rights for any 
person and is not binding on FDA or the public. You can use an alternative approach if it 
satisfies the requirements of the applicable statutes and regulations. To discuss an 
alternative approach, contact FDAs Technical Assistance Network by submitting the 
form available at http://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm459719.htm. 
 
 
I.  Introduction 
This guidance is intended for those persons (you) who are subject to our regulation, in 21 CFR 
part 117 (part 117), entitled Current Good Manufacturing Practice, Hazard Analysis, and Risk-
Based Preventive Controls for Human Food and who manufacture, process, pack, or hold 
ready-to-eat (RTE) foods.2 This guidance is intended for you regardless of whether you are only 
subject to the current good manufacturing practice requirements for human food of part 117 
(CGMP requirements), the requirements for hazard analysis and risk-based preventive controls 
for human food in part 117 (PCHF), or both the CGMP requirements and the PCHF 
requirements. See section II.A of this guidance for additional information about the CGMP and 
PCHF requirements. This guidance is intended to help you comply with the CGMP and PCHF 
requirements of part 117 with respect to measures that can significantly minimize or prevent the 
contamination of RTE food with L. monocytogenes whenever a RTE food is exposed to the 
environment prior to packaging and the packaged food does not receive a treatment or 
otherwise include a control measure (such as a formulation lethal to L. monocytogenes) that 
would significantly minimize L. monocytogenes. 
This guidance is not directed to processors of RTE foods that receive a listericidal control 
measure applied to the food in the final package, or applied to the food just prior to packaging in 
a system that adequately shields the product and food contact surfaces of the packaging from 
contamination from the food processing environment. 
This guidance also is not intended for food establishments that are not subject to part 117, such 
as farms.  
FDAs guidance documents, including this guidance, do not establish legally enforceable 
responsibilities. Instead, guidance describes the Agency's current thinking on a topic and should 
                                                
1 This guidance has been prepared by the Office of Food Safety at the U.S. Food and Drug 
Administration. 
2 Ready-to-eat food (RTE food) means any food that is normally eaten in its raw state or any other food, 
including a processed food, for which it is reasonably foreseeable that the food will be eaten without 
further processing that would significantly minimize biological hazards. (21 CFR 117.3) 
  1  Contains Nonbinding Recommendations 
 
be viewed only as recommendations, unless specific regulatory or statutory requirements are 
cited. The use of the word should in Agency guidance means that something is suggested or 
recommended, but not required.  
II.  Background  
A. Regulatory Framework 
Subparts A, B, and F of part 117 include CGMP requirements for manufacturing, processing, 
packing and holding human food. These CGMP requirements address topics such as 
personnel, buildings and facilities, equipment and utensils, production and process controls, and 
warehousing and distribution. With few exceptions (such as for farms and for establishments 
solely engaged in the holding and/or transportation of one or more raw agricultural commodities 
(RACs)), the CGMP requirements in part 117 apply to all persons who manufacture, process, 
pack, or hold human food.3 See Table 1 for a list of the CGMP requirements that we discuss in 
this guidance. 
Table 1.CGMP Requirements Discussed in this Guidance 
Section  Description 
117.10  Personnel 
117.20  Plant and grounds 
117.35  Sanitary operations 
117.37  Sanitary facilities and controls 
117.40  Equipment and utensils 
117.80  Processes and controls 
117.93  Warehousing and distribution 
 
Subparts A, C, D, E, F, and G of part 117 include requirements for hazard analysis and risk-
based preventive controls, for preventive control management components (i.e., monitoring, 
corrective actions and corrections, and verification), and for associated records. In this 
document, we refer to these requirements as the PCHF requirements. With some exceptions, 
the PCHF requirements apply to any food establishment that is required to register as a food 
facility under 21 CFR part 1, subpart H. Exceptions include qualified facilities (e.g., facilities 
that are a very small business as defined in 21 CFR 117.3) and activities that are subject to our 
Hazard Analysis and Critical Control Point (HACCP) requirements for seafood in 21 CFR part 
123 or juice in part 120 at facilities required to comply with those regulations. Some facilities 
(i.e., those solely engaged in the storage of packaged food that is not exposed to the 
environment) are exempt from subpart C, but subject to modified requirements in subpart D of 
part 117 if they store packaged foods that require time/temperature control for safety. See 21 
CFR 117.5 for a complete list of exemptions from the requirements of subpart C.  
Although section VIII.B.3 of this guidance provides general recommendations for controls on 
suppliers, we are providing a separate, comprehensive guidance on the specific PCHF 
requirements for a supply-chain program (part 117, subpart G). That separate guidance will 
provide recommendations for all facilities that are subject to the PCHF requirements, not just to 
those facilities that manufacture, process, pack, or hold RTE foods.  
                                                
3 Although not specified in part 117, we do not apply the CGMP requirements to restaurants and retail 
food establishments. 
  2  Contains Nonbinding Recommendations 
 
See Table 2 for a list of the PCHF requirements that we discuss in this guidance. 
Table 2.PCHF Requirements Discussed in this Guidance 
Section  Description 
117.126  Food safety plan 
117.130  Hazard analysis 
117.135  Preventive controls 
117.139  Recall plan 
117.140  Preventive control management components 
117.145  Monitoring 
117.150  Corrective actions and corrections 
117.155  Verification 
117.160  Validation 
117.165  Verification of implementation and effectiveness 
117.170  Reanalysis 
117.190  Implementation records required for this subpart 
 
 
Section 21 CFR 117.3 defines several terms that apply to the CGMP and PCHF requirements. 
See the Glossary in section XIX of this guidance for the definition of applicable terms used in 
this guidance. The Glossary also includes definitions for some additional terms, not defined in 
21 CFR 117.3, that we define for the purposes of this guidance. See section XX of this guidance 
for a table of abbreviations commonly used in this guidance. 
B. Characteristics of L. monocytogenes  
L. monocytogenes is an environmental pathogen that can contaminate foods and cause a mild, 
non-invasive illness (called listerial gastroenteritis) or a severe, invasive illness (called 
listeriosis). Listeriosis is characterized by a relatively high mortality rate compared to illnesses 
caused by most other foodborne pathogens (~20% compared to <1 % for Salmonella or E. coli 
O157) (Ref. 1 through Ref. 3). Persons who have the greatest risk of experiencing listeriosis 
due to consumption of foods contaminated with L. monocytogenes are pregnant women and 
their fetuses, the elderly, and persons with weakened immune systems (Ref. 4 through Ref. 6 
and Ref. 7). Foods that have caused outbreaks are typically contaminated from the environment 
during manufacturing/processing or packing (see Ref. 8 through Ref. 11 for some examples). 
Although temperatures below freezing prevent the growth of L. monocytogenes (Ref. 12 through 
Ref. 14), L. monocytogenes can multiply slowly at refrigeration temperatures. As a result, 
refrigeration is less effective as a control measure for L. monocytogenes than for other 
foodborne pathogens (such as Salmonella) (Ref. 12 through Ref. 16).  
Listeriosis is largely associated with RTE foods (Ref. 6 and Ref. 7). It is well established that 
foods that pose the greatest risk of foodborne listeriosis are those RTE foods that have intrinsic 
characteristics4 (such as pH and water activity) that support the growth of L. monocytogenes, 
whereas the RTE foods that pose the least risk of foodborne listeriosis are foods that have 
intrinsic characteristics that prevent the growth of L. monocytogenes (Ref. 6 and Ref. 7). 
                                                
4 Intrinsic characteristics include chemical and physical factors that are normally within the structure of the 
food.  
  3  Contains Nonbinding Recommendations 
 
Therefore, formulating RTE food to have intrinsic characteristics that do not support the growth 
of L. monocytogenes has the potential to reduce the risk of foodborne listeriosis.  
It is well established (Ref. 12, Ref. 15, and Ref. 17 through Ref. 20) that L. monocytogenes 
does not grow when: 
  The pH of the food is less than or equal to 4.4; 
  The water activity of the food is less than or equal to 0.92; and 
  The food is formulated to contain a combination of factors scientifically demonstrated to 
be effective in preventing growth (the hurdles concept).  
 
Foods can naturally have characteristics that prevent the growth of L. monocytogenes, or they 
can be deliberately processed to achieve or attain such characteristics. For example, deli-type 
salads (such as potato salad) can be processed to achieve a pH that is less than or equal to 4.4 
by the addition of an acidic substance (such as vinegar).  
Some antimicrobial substances are added to food during production. For example, sorbic acid is 
sometimes added to prevent the growth of L. monocytogenes in foods such as cheeses, and a 
combination of sorbic acid and benzoic acid is commonly added to prevent the growth of L. 
monocytogenes in foods such as deli-type salads (Ref. 21 through Ref. 23). Other antimicrobial 
substances can occur naturally in a food or be produced in a fermented food by the microbial 
fermentation. 
It is possible to effectively prevent the growth of L. monocytogenes in products such as deli 
salads (Ref. 7) through an interactive effect between intrinsic characteristics, processing 
temperature, and formulation (such as the presence of antimicrobial substances and other 
preservatives), even if such factors are not individually effective in preventing the growth of L. 
monocytogenes (Ref. 15 and Ref. 20).  
Whether a particular formulation (such as an antimicrobial substance, or a combination of 
intrinsic characteristics and antimicrobial substances) is effective in preventing the growth of L. 
monocytogenes in a particular food can be demonstrated through scientific studies. A 
formulation is generally considered to be effective in preventing the growth of L. monocytogenes 
if replicate growth studies having samples pulled at various time periods throughout product 
shelf life show less than a one log increase in the number of L. monocytogenes. For an example 
of how such studies are conducted, see Ref. 24 and Ref. 25.  
Examples of RTE foods that support the growth of L. monocytogenes and that have been found 
to be contaminated with L. monocytogenes are unpasteurized and pasteurized milk, high fat 
dairy products, soft unripened cheese (Cottage Cheese, Cream Cheese, Ricotta), cooked 
ready-to-eat crustaceans (shrimp, crab), smoked seafood, fresh soft cheese (Queso Fresco), 
semi-soft cheese (Blue, Brick, Monterey), soft-ripened cheese (Brie, Camembert, Feta), deli-
type salads, sandwiches, fresh-cut fruits and vegetables, and raw molluscan shellfish (Ref. 7, 
Ref. 26, and Ref. 27). An example of an RTE food that does not support the growth of L. 
monocytogenes, but has been found to be contaminated with L. monocytogenes, is ice cream 
(Ref. 28 and Ref. 6). 
  4  Contains Nonbinding Recommendations 
 
C. L. monocytogenes in the Food Processing Environment 
L. monocytogenes is widespread in the environment. It is found in soil, water, sewage, and 
decaying vegetation (silage) (Ref. 29 through Ref. 32 ). It can be readily isolated from humans, 
domestic animals, raw agricultural commodities, and food packing and processing environments 
(particularly cool damp areas) (Ref. 8 through Ref. 11 and Ref. 29 through Ref. 37). L. 
monocytogenes has been shown to persist in equipment and the processing environment in 
harborage sites (Ref. 16 and Ref. 38).  
L. monocytogenes can survive longer under adverse environmental conditions than can many 
other vegetative bacteria that present a food safety concern. In addition to being able to survive 
and grow at refrigeration temperatures, L. monocytogenes tolerates high salt concentrations 
(such as in non-chlorinated brine chiller solutions) and survives frozen storage for extended 
periods (Ref. 39 and Ref. 40). It survives acid conditions and is more resistant to heat than 
many other non-spore forming foodborne pathogens, although it can be killed by heating 
procedures such as those used to pasteurize milk5 (Ref. 17, Ref. 41, and Ref. 42).  
The application of CGMPs and PCHF requirements to the production of RTE foods can 
significantly minimize or prevent contamination of an RTE food with L. monocytogenes (e.g., 
through controls on raw materials or other ingredients, listericidal control measures to 
consistently destroy viable cells of L. monocytogenes, listeristatic formulations to prevent viable 
cells of L. monocytogenes from growing, segregation of foods that have been cooked from 
those that have not, sanitation controls, sanitary equipment design, and physical barriers 
(separation) to avoid cross contamination). Several scientific publications provide detailed 
recommendations for the control of L. monocytogenes in the food processing environment (see, 
e.g., Ref. 16 and Ref. 43 through Ref. 48). Many of the recommendations in this guidance are 
adapted from these published recommendations. 
In Appendix 1 of this guidance, we list potential sources of L. monocytogenes in the food 
processing environment. In Appendix 2 of this guidance, we provide examples of scenarios that 
could lead to contamination of RTE foods with L. monocytogenes.  
III.  How to Apply This Guidance to Your Operations Based 
on the Regulatory Framework That Applies to Your Food 
Establishment  
In this guidance we identify those CGMP requirements that are most relevant to specific 
recommendations, even though additional PCHF requirements may also apply to certain 
facilities. For example, the CGMP requirement in 21 CFR 117.80(c)(4) specifies that measures 
such as sterilizing, irradiating, pasteurizing, cooking, freezing, refrigerating, controlling pH, or 
controlling water activity that are taken to destroy or prevent the growth of undesirable 
microorganisms must be adequate under the conditions of manufacture, handling, and 
distribution to prevent food from being adulterated. Therefore, within this guidance, we note the 
applicability of 21 CFR 117.80(a)(4) to our recommendations for how to validate the adequacy 
of listeristatic and listericidal process controls (see sections IX and X). However, additional 
                                                
5 Because normal pasteurization will effectively eliminate L. monocytogenes, it is generally assumed that 
contamination of products such as pasteurized fluid milk is the result of post-pasteurization contamination 
(see Section V of Ref. 7, p. 170). 
  5  Contains Nonbinding Recommendations 
 
PCHF requirements (in 21 CFR 117.160) for validation of listeristatic and listericidal process 
controls apply to those facilities that are subject to PCHF requirements. 
Some PCHF requirements are expressly directed to L. monocytogenes and to RTE foods. For 
example, the definition of environmental pathogen identifies L. monocytogenes as an 
environmental pathogen (21 CFR 117.3), and the hazard evaluation required by 21 CFR 
117.130 must include an evaluation of environmental pathogens whenever an RTE food is 
exposed to the environment prior to packaging and the packaged food does not receive a 
treatment or otherwise include a control measure (such as a formulation lethal to the pathogen) 
that would significantly minimize the pathogen (21 CFR 117.130(c)(1)(ii)).  
Because some persons who are subject to the CGMP requirements in subpart B are exempt 
from the PCHF requirements in subparts C and G, this guidance: 
  Is written as a set of recommendations even though in some cases part 117 includes an 
explicit requirement. For example, with few exceptions, the PCHF requirements specify 
that you must validate that the preventive controls identified and implemented in 
accordance with 21 CFR 117.135 are adequate to control the hazard as appropriate to 
the nature of the preventive control and its role in the facilitys food safety system (21 
CFR 117.160(a)). If you are a facility subject to the PCHF requirements of part 117, you 
must comply with 21 CFR 117.160(a) even though this guidance recommends 
validation of process controls such as listeristatic and listericidal control measures.  
  Uses general terms such as control and control measure even though in some cases 
the control or control measure is a preventive control.  
You can access part 117 on the Internet from the Federal Digital System of the U.S. 
Government Printing Office. For your convenience, when we refer you to a single section of part 
117, we repeat the text of the section in this guidance. However, when we refer you to more 
than one section, we do not repeat the text of the section in this guidance, because it is 
impractical to do so.  
In general, the recommendations in this guidance complement, but do not supersede, 
recommendations that we have issued in other guidance documents. For example, if you 
process seafood for use as sushi, we continue to recommend that you follow the guidance 
implementing our HACCP regulations for fish and fishery products (Ref. 49). In some cases, 
specific recommendations in other guidance documents could provide more targeted 
recommendations on how to establish and implement a particular control measure for the type 
of products you process. For example, our guidance entitled Guidance for Industry: Guide to 
Minimize Microbial Food Safety Hazards of Fresh-cut Fruits and Vegetables (Ref. 50) includes 
specific recommendations for the design, construction and maintenance of facilities and 
equipment. Targeted information relevant to a fresh-cut processing plant and equipment is 
available in that guidance.  
IV.  Controls on Personnel 
The actions of personnel can transfer L. monocytogenes from the processing environment to 
RTE food (Ref. 16, Ref. 43, and Ref. 46). In this section of this guidance, we provide 
recommendations to minimize the potential for RTE food to become contaminated with L. 
monocytogenes through the actions of personnel.  
  6  Contains Nonbinding Recommendations 
 
A. Hands, Gloves and Footwear 
We recommend that all persons who will enter an area where RTE foods are processed or 
exposed to the environment thoroughly wash their hands before doing so.  
We recommend that personnel use suitable utensils (such as spatulas or tongs), or wear 
gloves, when touching exposed RTE foods, food-contact surfaces (FCSs), and packaging 
materials, and not touch exposed RTE foods, FCSs, and packaging with bare hands. We 
recognize that contact between hands and food or packaging could be necessary under a wide 
variety of circumstances and that gloves could present a risk of introducing foreign material or 
interfere with an individuals ability to do a particular task. You should assess the job 
requirements and the risks of contamination potentially resulting in foodborne illness in making a 
decision that personnel may contact food with bare hands. 
We recommend that gloves and footwear worn by personnel who handle RTE foods, or who 
work in areas where RTE foods are processed or exposed, be made of impermeable material, 
be in good repair and be easily cleanable or disposable. Personnel should not use cleated 
footwear unless it is necessary for their safety, because cleated footwear can collect particles of 
dirt or other waste from inside and outside the plant. When areas in your plant have been 
designated as RTE areas, we recommend that gloves and footwear worn by personnel who 
handle RTE foods or who work in areas where RTE foods are processed or exposed to the 
environment be used only in the RTE area and that gloves and footwear used in a non-RTE 
area of the plant not be used in the RTE area.  
When gloves are used, we recommend that: 
  Personnel wash their hands before putting the gloves on; 
  Multi-use gloves be washed and sanitized before use and after the employee touches 
any non-food-contact surface (non-FCS) (such as clothing, doorknobs, equipment 
control panels, and tools); 
  Single use gloves be discarded and replaced after an individual touches any non-FCS; 
and 
  Gloves worn outside areas where RTE foods are processed or exposed (e.g., 
restrooms) be discarded before returning to the RTE area.  
B. Foamers, Footbaths, and Dry Powdered Sanitizers 
We recommend that you establish procedures to minimize the potential for personnel to transfer 
L. monocytogenes from non-RTE areas of the plant to the RTE area. To do so, we recommend 
that you consider whether the use of foamers or footbaths containing liquid sanitizers, or dry 
powdered sanitizers, is appropriate and useful when personnel enter areas where RTE foods 
are processed or exposed. A foamer delivers an automatic spray of foam disinfectant on the 
floor where personnel (and portable equipment (such as carts and forklifts) that personnel 
transport through the plant) enter the RTE area. A footbath is usually a low flat container, or a 
water tight recess in the floor, that has a non-slip surface and is filled with a suitable sanitizer. 
Foamers or footbaths (which are wet) generally are more appropriate in a wet processing 
environment. A dry powdered sanitizer generally is more appropriate in a dry processing 
environment to keep the environment dry; in dry processing environments, the absence of water 
  7  Contains Nonbinding Recommendations 
 
prevents the growth of L. monocytogenes. When using foamers, footbaths, or a dry powdered 
sanitizer, we recommend you ensure that personnel cannot avoid walking through them and 
cannot jump over them when entering the RTE area. 
You should appropriately maintain foamers to ensure they are properly spraying the correct 
amount of disinfectant over the intended area. If you use non-automatic footbaths, we 
recommend checking them at regular intervals, such as hourly, to ensure they are filled with 
sanitizer and the sanitizer is diluted to the proper concentration.  
C. Clothing 
We recommend that you establish and implement conditions and practices to prevent employee 
clothing from contributing to the contamination of food with L. monocytogenes. Depending on 
the type of operation, such conditions and practices include: 
  Personnel do not wear street clothes in areas where RTE foods are processed or 
exposed unless the street clothes are adequately covered above the knees (e.g., with a 
clean smock); 
  Smocks for personnel in areas where RTE foods are processed or exposed are worn 
only in the designated RTE area and an adjacent vestibule (i.e., the area where the 
smock would be put on); 
  Personnel change into a clean uniform or smock before entering areas where RTE foods 
are processed or exposed; 
  Smocks and uniforms are laundered or disposed of daily; 
  Smocks or uniforms that will be used in areas where RTE foods are processed or 
exposed are distinguished from those that will be used in other areas (particularly areas 
where raw foods are processed or exposed) using a mechanism such as color coding; 
and 
  Smocks or uniforms are distinguished according to the task that the personnel perform 
(e.g., production or maintenance). For example, if you restrict the access of maintenance 
personnel to areas of the plant where finished product is exposed, distinguishing smocks 
or uniforms by color coding helps to identify the personnel with such restricted access. 
 
D. Controls on Personnel Associated with Specific Areas in the 
Plant 
As noted in section V.A.1, we recommend that you provide separate locker areas, break areas, 
and cafeteria areas for personnel who handle RTE foods and personnel who handle raw foods, 
when practical. When doing so is not practical, we recommend that: 
  Your environmental monitoring program (see section XIII of this guidance) include 
monitoring of the travel paths and service areas to show when extra cleaning or a 
procedural modification is needed;  
  You establish a captive shoe policy in which footwear for the RTE area is only worn in 
that area; and 
  8  Contains Nonbinding Recommendations 
 
  You place more emphasis on other controls discussed in this section to minimize the 
potential for contamination of RTE foods by personnel who handle raw foods, such as: 
  Distinguishing smocks or uniforms used in the RTE areas from those used in the 
o
raw area; 
  Providing an entry room to the RTE area to put on, and to store, smocks and 
o
footwear designated for that area; and 
  Establishing a chemical barrier (e.g., footbaths or foamers) to the RTE area.  
o
 
E. Personnel Who Perform Sanitation, Maintenance, and Similar 
Functions 
We recommend that sanitation and maintenance personnel who work in areas where RTE foods 
are processed or exposed follow the same hygiene requirements as production personnel in 
those areas. When practical, we recommend that you provide dedicated tools for the RTE area 
separate from tools in other parts of the plant. (See Ref. 16). If separate tools are not practical, 
we recommend that tools be cleaned and sanitized prior to entering the RTE area. 
We recommend that you ensure that personnel who handle trash, offal, floor sweepings, drains, 
production waste, or scrap product do not handle RTE food, and do not touch RTE food-contact 
surfaces or food packaging material, unless they first change their smocks or uniforms, wash 
and sanitize hands, wear clean gloves, and don and sanitize footwear.  
F. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
personnel hygiene include 21 CFR 117.4, 117.10(a), 117.10(b)(1), 117.10(b)(3), 117.10(b)(5), 
and 117.10(b)(9) 
 
V.  Design, Construction, and Operation of Your Plant 
The processing environment can be a primary source of L. monocytogenes (Ref. 16, Ref. 32, 
and Ref. 43 through Ref. 48). In this section of this guidance, we provide recommendations on 
the design and construction of your plant to reduce the potential for contamination of an RTE 
food from the processing environment. The CGMPs in subpart B require that structures be 
suitable in size, construction, and design to facilitate maintenance and sanitary operations for 
food production purposes (21 CFR 117.20(b)). 
A. Design and Construction of the Plant 
1. General 
During new construction or renovation, we recommend that you design and construct the plant 
to reduce the potential for contamination of RTE foods via air, aerosols, or traffic of personnel or 
equipment. To do so, we recommend that you separate areas where RTE foods are processed, 
exposed or stored from areas where raw foods are processed, exposed or stored, and from 
  9  Contains Nonbinding Recommendations 
 
equipment washing areas, microbiological laboratories, maintenance areas, waste areas, 
offices, lockers and toilet facilities. In addition, it is prudent practice to locate microbiological 
laboratories as far away as practical from the processing area, preferably in another building, 
because routine microbiological testing usually involves enrichment procedures that enable 
microorganisms to multiply before conducting analytical tests to detect them. Even if your 
analytical method tests for an indicator organism rather than a pathogen, if samples you test 
contain the pathogen L. monocytogenes your enrichment procedures have the potential to 
produce increased numbers of L. monocytogenes.  
New construction and renovations could cause significant disruption of air patterns, walls, 
ceilings, and floors thereby leading to enhanced potential for cross contamination of FCSs, non-
FCSs, products, ingredients or packaging. Actions you take can depend on the type of 
construction activity and the potential for contamination. Certain activities such as installing 
small pieces of equipment, painting or caulking windows and doors, or replacing parts on 
equipment are less likely to result in the introduction of L. monocytogenes than activities that are 
more extensive. When construction activities are more extensive, such as removing/replacing 
walls, floors or ceilings or installing major equipment or new processing lines, extra measures to 
ensure control of Listeria are needed. These measures include erecting temporary barriers to 
isolate the construction from the rest of the facility, revising traffic patterns, enhancing cleaning 
and sanitizing, and enhancing environmental monitoring. 
We recommend that you design and construct the plant so that walls, ceilings, windows, doors, 
floors, drains, and overhead fixtures (e.g., pipes, air vents, and lights) in areas where RTE foods 
are processed or exposed resist deterioration by product or cleaning chemicals, and prevent 
condensate buildup and harborage of microorganisms. We also recommend that you design 
and construct the roof so that it drains freely and does not leak. We recommend that you not 
place windows that can be opened in areas where RTE foods are processed or exposed. To 
prevent harborage of microorganisms, we also recommend not using construction materials 
made of porous or absorbent materials, such as wood or foam, in areas where RTE foods are 
processed or exposed and in other wet processing areas in the plant. If your plant already 
contains such porous or absorbent materials, see section XIII of this guidance for 
recommendations on environmental monitoring until such materials can be replaced; following 
those recommendations can help prevent L. monocytogenes from becoming established in 
those materials and becoming a source of contamination in areas where RTE foods are 
processed or exposed. 
When practical, we recommend that you provide separate locker areas, break areas, and 
cafeteria areas for personnel who handle RTE foods and personnel who handle foods that are 
not RTE.  
2. Air and air flow 
We recommend that you design the air flow in your plant to maintain positive air pressure on the 
RTE side of the operation relative to the raw side (i.e., maintain higher air pressures in RTE 
areas and lower air pressures in areas where unprocessed (raw) foods are handled). We 
recommend that you consider the room temperature and the impact of airflow on controlling 
condensation in the plant. We also recommend that you consult individuals with appropriate 
engineering skills to determine how to achieve proper air balance and the desired air exchange 
rate, including determining the number, size, and location of intake and exhaust fans.  
  10  Contains Nonbinding Recommendations 
 
Appendix 3 of this guidance provides some schematic diagrams relevant to air flow and room 
pressure differences. Figure 1 of Appendix 3 relates to air flow, and shows that the 
recommended air flow should have negative pressure in the raw processing area rather than in 
the RTE processing area. In Figures 2 and 3 of Appendix 3, we provide examples of plant 
design, including schematic recommendations related to air flow, product flow, and the use of 
partitions in the design of the plant. In Figure 2 of Appendix 3, the example of a plant design has 
a partition between the raw processing area and the RTE processing area. In Figure 3 of 
Appendix 3, the example of a plant design does not have this partition between the raw 
processing area and the RTE processing area; instead, the plant design in Figure 3 of Appendix 
3 relies on positive air pressure in the RTE processing area.  
We recommend that the location of the air intake not be adjacent to the location of the air 
exhaust or other sources of airborne contamination such as waste disposal areas. This can help 
prevent contamination of intake air. Preventing contamination of intake air is particularly 
important when major construction or remodeling occurs in an existing plant. Using air-tight 
barriers, limiting access between construction and food production areas, and providing proper 
air flow can prevent introduction of contamination into the plant environment.  
There have been isolated reports of contamination associated with air (e.g., air from 
compressed air lines has been implicated in contamination traced to a niche (i.e., growth in a 
filter) near the point of use (Ref. 44). We recommend that you consider filtering the air in rooms 
where RTE foods are processed or exposed to reduce the potential for contamination of RTE 
foods with microorganisms (including L. monocytogenes). If you filter the air, we recommend 
that the final filter have an efficiency of at least 90-95 percent at 1 micron as rated in American 
Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) standard 52.2-
2012.6 Depending on your product, your process and the design and construction of your plant, 
it may be appropriate to use High Efficiency Particulate Air (HEPA) filters that have an efficiency 
of 99.97-99.99 percent at 0.3 micron for removing bacteria, yeasts and molds.  
3. Water systems 
You should take steps to prevent the accumulation of standing water in or around drains, 
because standing water in your plant can be conducive to contamination with L. 
monocytogenes. Examples of such steps include: 
  Designing and constructing the plant in a way that will make drains function adequately;  
  Designing and constructing the plant in a way that will make drains adequately 
accessible for cleaning;  
  Not installing trench drains in areas where RTE foods are processed or exposed and, 
where practical, replacing existing trench drains with enclosed plumbing to a floor drain. 
Where replacement of existing trench drains is not practical, we recommend that you 
keep them clean and consider whether equipping them for automatic flushing would be 
of benefit, taking care to ensure that automatic flushing does not create aerosols that 
could contaminate product; 
                                                
6 American Society of Heating Refrigerating and Air-Conditioning Engineers. Standard 52.2-2012 -- 
Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size.: 
ASHRAE. Available for purchase at http://www.webstore.ansi.org/. 
  11  Contains Nonbinding Recommendations 
 
  Designing and constructing drains so that the drains do not flow from areas where raw 
foods are processed or exposed to areas where RTE foods are processed or exposed. 
In an older plant with existing piping that has some flow from raw areas to RTE areas, 
you should establish systems that ensure adequate control of L. monocytogenes in the 
environment if you do not re-pipe the plant;  
  Designing and constructing drains so that restroom drains are not connected to drains 
serving areas where RTE foods are processed or exposed; 
  Designing and constructing the slope of floors to drains so that floors drain freely and 
water does not accumulate; and  
  Not locating sewer lines above areas where RTE foods, FCSs, or food packaging 
materials are processed or exposed. If this is not practical, we recommend that you take 
steps to protect RTE foods and packaging materials from potential leakage, e.g., by 
shielding the sewer lines to prevent or convey leakage. 
 
Part 117 requires that your plant be designed and constructed in such a manner that drip or 
condensate from fixtures, ducts and pipes does not contaminate food, FCSs, or food packaging 
material (21 CFR 117.20(b)(4)). Measures that can help prevent the formation of condensate 
include exhausting vapors from cooking operations, using dehumidifiers, and providing 
adequate ventilation. Exhausting room air during sanitation also helps to manage humidity. 
Other factors to consider are the room temperature, relative humidity of the air supply, positive 
air pressure, and the air exchange rate. 
B. General Operation of the Plant 
We recommend that you control traffic flow patterns for personnel, food products, food 
packaging materials, and equipment to minimize the potential for transfer of L. monocytogenes 
between areas where raw foods are processed or exposed and areas where RTE foods are 
processed or exposed.  
We recommend that you develop and implement a management program for pallets in areas 
where RTE foods are processed or exposed to ensure the pallets are inspected, clean, and in 
overall good condition such that they do not serve as a source of contamination with 
L. monocytogenes. Both plastic and wooden pallets may be a source of Listeria contamination; 
in general, plastic pallets are better suited than wooden pallets for wet areas. Some 
manufacturers will only allow plastic pallets in production areas, confining wooden pallets to dry 
areas, such as warehouses. We recommend you consider whether such an approach would be 
beneficial for your facility. We also recommend that you designate one set of equipment (such 
as carts, forklifts, mobile racks, and pallets) to areas where raw foods are processed or exposed 
and designate a separate set of such equipment to areas where RTE foods are processed or 
exposed. Where this is not practical, we recommend that you clean and sanitize wheels of 
transport equipment (e.g., carts, forklifts, and mobile racks) before they enter an area where 
RTE foods are processed or exposed. 
With respect to totes and other containers, we recommend that you: 
  Select containers that can be cleaned easily and are fit for their purpose; 
  Dedicate containers by area (e.g., use one set of containers in areas where RTE foods 
are processed or exposed and a different set of containers in areas where raw foods are 
  12  Contains Nonbinding Recommendations 
 
processed or exposed) and clearly distinguish these containers from each other (e.g., by 
color coding). Where this is not practical, they should be cleaned and sanitized prior to 
entering the RTE area; and  
  Dedicate containers by function (e.g., product, rework or waste) and clearly distinguish 
these containers from each other (e.g., by color coding or labeling). 
  
We recommend that you discard or treat continuous use brines and recycled process water 
used in direct contact with RTE foods with sufficient frequency to control L. monocytogenes 
(Ref. 16). We recommend that you use measures such as chlorination, ozonation, heat 
treatment, or other effective treatment to treat such brines and water. We recommend that you 
consider the results of environmental monitoring for L. monocytogenes (see section XIII of this 
guidance) when determining the frequency of treatment.  
To prevent aerosols from contacting RTE food, FCSs, and food packaging materials, personnel 
should not use high-pressure water hoses during production in areas where RTE foods are 
exposed or after equipment has been cleaned and sanitized.  
We recommend that you implement procedures to ensure that compressed gases or air used 
directly in or on RTE food, or on RTE food-contact surfaces, not become a source of L. 
monocytogenes. Examples of such procedures are drying and filtration. We recommend that 
dehydration be done at the source of gas or air supply and that filtration be done at the point of 
use, using a filter that can retain particles larger than 0.3 micron. You should take appropriate 
steps to maintain the filters.  
We recommend that you maintain and inspect the water supply and any treatment systems to 
ensure that they do not become a source of microbial contamination. We also recommend that 
you produce, handle, and store ice and ice utensils in a manner that protects ice from microbial 
contamination. You should avoid storing ice scoops and ice shovels in direct contact with floors 
and other non-FCSs. 
C. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding design 
and construction of the plant include 21 CFR 117.20(b), 117.35(a), 117.37, and 117.40(a). 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
operation of the plant include 21 CFR 117.35, 117.37(a), 117.37(e), 117.40, 117.80(a), 
117.80(b)(1), and 117.80(c)(16). 
VI.  Design, Construction, and Maintenance of Equipment 
The processing environment can be a primary source of L. monocytogenes (Ref. 16, Ref. 32, 
and Ref. 43 through Ref. 48). In this section of this guidance, we provide recommendations on 
the design, construction and maintenance of equipment to reduce the potential for 
contamination of an RTE food from equipment. 
  13  Contains Nonbinding Recommendations 
 
A. Design and Construction of Equipment 
Part 117 requires that equipment and utensils be designed and of such material and 
workmanship as to be adequately cleanable (21 CFR 117.40(a)(1)). We recommend that the 
equipment you purchase and use to process RTE foods be designed and constructed to 
minimize sites where microbial harborage and multiplication can occur. If you will modify 
existing equipment used to process RTE foods, we recommend that you or the manufacturer of 
the equipment review the design of the modifications to ensure that the modified equipment is 
designed and constructed to minimize sites where microbial harborage and multiplication can 
occur. When equipment is modified in-place or new equipment is installed in the establishment, 
there is an increased risk of contamination of FCSs and food with L. monocytogenes. See 
section V.A.1 for recommendations on controlling Listeria during construction. 
We recommend that RTE FCSs be smooth, non-absorbent, sealed, and sloped, where feasible, 
in order to drain freely, and that junctures in RTE FCSs be covered. Piping used to convey RTE 
foods should not have dead ends or cross-connections between conveyance of raw and RTE 
foods. The sanitary standards inventoried by 3-A Sanitary Standards, Inc.7 can be useful when 
designing and constructing equipment containing FCSs. 
We recommend that you design and construct equipment such as catwalk framework, table 
legs, conveyor rollers, and racks so that they cannot collect water that could harbor L. 
monocytogenes (e.g., they should not be hollow or foam filled). You should either modify or 
replace existing equipment not designed this way, or establish and use some other method to 
reduce the risk of L. monocytogenes contamination from such equipment, including a schedule 
for periodic cleaning and sanitizing combined with an environmental monitoring program.  
We recommend that you not position catwalks and stairs with open grating over exposed RTE 
food or FCSs so as to help prevent contamination of RTE foods with L. monocytogenes that 
could be harbored on catwalks, stairs, or bottoms of individuals shoes. If this is not practical, 
you should use ladders and stairs designed to prevent debris from shoes or other personal 
items from falling onto the processing line (e.g., plating covering the underside of the stairs, or 
side plates along the stairs). Plate coverings should be on a cleaning schedule. 
We recommend that you not install stationary equipment used to process RTE foods over floor 
drains. Doing so will help prevent contamination of the equipment (and RTE foods) with L. 
monocytogenes that could be harbored in floor drains. If this is not practical, you should use 
some other method to prevent contamination from L. monocytogenes that could be present in 
the drain and monitor the drain for the presence of L. monocytogenes (see section XIII of this 
guidance for additional information on environmental monitoring).  
We recommend that you sufficiently elevate FCSs (including conveyors) above the floor. Doing 
so will reduce the risk of contamination of RTE foods and FCSs from floor splash/overspray. If 
this is not practical, you should use some other method to prevent contamination from L. 
monocytogenes that could be present on the floor (e.g., cover RTE food contact surfaces) and 
monitor the floor for the presence of L. monocytogenes. Although we are recommending that 
                                                
7 3-A Sanitary Standards, Inc. is a non-profit association, representing equipment manufacturers, 
processors, regulatory sanitarians and other public health professionals, that has established an inventory 
of Sanitary Standards and Accepted Practices for dairy and food processing equipment and systems. 
 
  14  Contains Nonbinding Recommendations 
 
conveyors be elevated, we also recommend that you avoid overhead conveyors whenever 
practical. If overhead conveyors cannot be avoided, they should be designed to be easily 
accessible for cleaning; note that part 117 requires that they be constructed in such a manner 
that drip or condensate from them does not contaminate food, FCSs, or food-packaging 
materials (21 CFR 117.20(b)(4)).  
We recommend that you use wheeled devices that are designed to reduce the risk of 
contamination of RTE foods and FCSs from wheel spray (e.g., guards over the wheels, fully 
enclosed/encased bearings, lowest shelf on the wheeled rack is located above splash height).  
We recommend that condensate from refrigeration evaporation coils be directed to a sanitary 
drain through a hose or, alternatively, collected in a pan that drains through a hose or suitable 
pipe to a sanitary drain. An air gap or other back flow mechanism should be in the drain line to 
prevent back flow from the sewer system to the drip pan. We recommend that you regularly 
inspect the pan and drain to ensure that the hose or pipe does not become clogged. You should 
have a cleaning schedule for hoses and drip pans. 
We recommend that you keep hoses and hose nozzles off the floor or other unclean surfaces 
when not in use. During use, you should ensure that nozzles do not come in contact with the 
floor or other unclean surfaces. Doing so will help prevent hose nozzles (and, subsequently, 
individuals hands or water coming through the nozzle) from becoming contaminated with L. 
monocytogenes that could be present on the floor or other unclean surfaces.  
If you use raw product to cool RTE product in a heat exchanger, we recommend that heat 
exchangers have higher pressure on the RTE side than on the raw side. 
B. Maintenance of Equipment 
We recommend that you establish and use a preventive maintenance program that is designed 
to minimize breakdowns and prevent contamination that could occur during repair of equipment. 
See section IV.C for recommendations for a written preventive maintenance program  
We recommend that you examine and change filters used on intake air and for compressed air 
systems either at a frequency based on the manufacturers specification or more frequently 
based on pressure differential or the results of environmental monitoring.  
As noted in section IV.E, we recommend that tools intended for maintenance of equipment used 
in areas where RTE foods are processed or exposed be dedicated to those areas. (See Ref. 
16). Where this is not practical, you should ensure that tools are adequately washed before use 
in the RTE area and consider sanitizing the tools in addition to washing them.  
Equipment and FCSs used in areas where RTE foods are processed or exposed, including 
equipment that could be contaminated as a result of maintenance on utilities (e.g., air or water 
systems) or plant remodeling, should be cleaned and sanitized after maintenance and prior to 
use in production consistent with the requirements of 21 CFR 117.35(d).  
C. Records 
We recommend that your written program for equipment maintenance include defined 
schedules for examination and maintenance of equipment such as valves, gaskets, O-rings, 
pumps, screens, filters, and heat exchanger plates.  
  15  Contains Nonbinding Recommendations 
 
D. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding design 
and construction of equipment include 21 CFR 117.20(b)(4), 117.37(b)(3), 117.40(a), 117.40(b), 
117.40(c), and 117.40(d). 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
maintenance of equipment include 21 CFR 117.35(d), 117.35(f), 117.40(a), 117.40(g), and 
117.80(c)(1). 
VII.  Sanitation  
The processing environment can be a primary source of L. monocytogenes (Ref. 16, Ref. 32, 
and Ref. 43 through Ref. 48). In this section of this guidance, we provide recommendations on 
sanitation in your plant to reduce the potential for contamination of an RTE food from the 
processing environment. 
A. General Sanitation Program 
To minimize the potential for contamination of RTE food and FCSs with L. monocytogenes, we 
recommend that you establish and use a sanitation program that includes written sanitation 
procedures and a sanitation schedule for areas where RTE foods or FCSs are processed or 
exposed.  
We recommend that you wash equipment in a way that does not result in an increased risk of 
product contamination. In general, you should not wash equipment during times that RTE foods 
or packaging are exposed in the area because of the potential formation of aerosols that could 
contaminate foods or packaging. You should consider the potential for transfer of 
L. monocytogenes during washing procedures, e.g., when equipment used for RTE foods is 
cleaned in the same area as equipment used for raw materials.  
1.  Written Sanitation Procedures 
We recommend that you design the written sanitation procedures to ensure that the RTE area, 
and equipment in the RTE area, are cleaned and sanitized in a manner that reduces the risk of 
contamination of RTE food-contact and non-FCSs with L. monocytogenes. In general, we 
recommend that a written sanitation procedure address:  
  The condition and cleanliness of FCSs, including equipment, utensils, gloves, and outer 
garments; and  
  The prevention of cross-contamination:  
  From insanitary objects to food;  
o
  From insanitary objects to food packaging material and other FCSs (including 
o
equipment, utensils, gloves, and outer garments);  
  From raw food to food that is cooked (or otherwise RTE);  
o
  After any listericidal control measure; and  
o
  As a result of traffic flow patterns for personnel and for equipment. 
o
  16  Contains Nonbinding Recommendations 
 
 
We recommend that you make your written sanitation procedures readily available to personnel 
who are responsible for cleaning, train personnel on the sanitation procedures, and monitor 
adherence to the sanitation procedures.  
We recommend that written sanitation procedures for cleaning equipment and floors identify: 
  Equipment or area to be cleaned;  
  Disassembly of equipment, if applicable;  
  Frequency of cleaning;  
  Type and concentration of cleaning compounds and sanitizers;  
  Type of cleaning tools to be used (e.g., brushes, scrapers, scrubbing pads, mops); 
  Color coding of tools (e.g., red for those related to raw materials or other ingredients and 
blue for those related to RTE areas);  
  Time/temperature of cleaning solutions; and  
  Flow rate (velocity) or pressure of cleaning solution, if applicable. 
 
In practice, equipment, floors, and drains should be cleaned together, with cleaning actions 
carefully sequenced to reduce the risk of contamination. Cleaning operations are followed by a 
sanitizing procedure. We recommend that your written sanitation procedures include the 
following steps: 
1.  Dry Clean  Using appropriate tools (such as brushes, scrapers), remove heavy soils or 
debris from equipment, then floors; 
2.  Pre-Rinse  Working from the top of the equipment down, rinse and scrub equipment to 
remove visible soils. Using appropriate tools, remove any additional debris from the 
floors and drains, and then rinse the floor; 
3.  Soap and Scour  Apply foam cleaner to ensure adequate coverage by first foaming 
walls (if applicable), floors, and then the equipment from the bottom of the equipment to 
the top. Clean drains using appropriate tools. Scour equipment to remove any residues, 
and avoid the drying of the foam cleaner; 
4.  Post-Rinse  Remove the foam cleaner by flood rinsing the walls (if applicable), floors 
and equipment in the same order that the foam cleaner was applied; 
5.  Prepare for Inspection  Remove any possible overhead condensation or standing water 
and prepare the equipment for inspection; 
6.  Pre-Op Inspection  Visually inspect the equipment for cleaning effectiveness and 
correct any deficiencies; 
7.  Sanitize and Assemble  Sanitize the equipment, floors, and (if applicable) walls and 
prepare the equipment for operation, using ATP bioluminescence or other appropriate 
testing as a sanitation check.  
  17  Contains Nonbinding Recommendations 
 
2.  Frequency of cleaning/sanitizing 
You should clean and sanitize with sufficient frequency to ensure control of L. monocytogenes 
and to minimize conditions that promote the survival or multiplication of L. monocytogenes in the 
environment. To determine the cleaning frequency, you should review the sanitary design of the 
room and equipment, the microbiological profile during a production run, the history of Listeria 
spp. in the room and on the line, and the degree of product exposure to the line and the 
environment. See Appendix 4 for examples of schedules for routine cleaning and sanitation. 
You should modify the schedules in Appendix 4 based on the condition of your plant, sanitary 
design, production schedule and product characteristics. You should keep rooms as dry as 
possible because moisture fosters the growth and transfer of L. monocytogenes (Ref. 43).  
3.  Recommendations for cleaning and sanitizing 
For clean in place (CIP) systems, we recommend that you monitor the concentration of cleaning 
solutions and sanitizers and verify flow rate, duration of the cleaning cycle and temperature. For 
clean out of place (COP) systems, we recommend that you monitor the concentration and 
temperature of cleaning solutions and sanitizers.  
Procedures for wet cleaning and sanitizing of equipment should ensure that equipment other 
than that being cleaned is not compromised during cleaning. You should verify that cleaned 
equipment is not compromised by the cleaning of adjacent equipment. We recommend that you: 
  Not perform wet cleaning of equipment (e.g., down lines, storage and spiral coolers, and 
spiral freezers) in a room where RTE food or packaging is exposed, even if you cover 
the RTE food or packaging (e.g., with plastic or paper). If wet cleaning does occur, you 
should remove all exposed RTE food or packaging from a room before beginning any 
wet cleaning of equipment, floors, and other areas; and 
  Remove all exposed RTE food from a cooler or freezer prior to cleaning the cooler or 
freezer, refrigeration condenser units or condensate drip pans and hoses.  
 
If circumstances require you to clean and sanitize a production line in a room where another 
production line is operating, you should follow the recommendations described below to 
minimize the potential for contamination from L. monocytogenes due to overspray, 
condensation, drainage, the environment, or traffic patterns:  
  Overspray  When using hoses, you should avoid contaminating equipment with water 
or chemical overspray while cleaning the adjacent line. The proximity of equipment and 
lines influences the risk of overspray; in general, the risk of contamination from 
overspray increases when using low pressure within 20 feet and when using high 
pressure within 30 feet. One mechanism to reduce the potential for contamination from 
overspray is to erect clean curtains or temporary walls. 
  Condensation  You should sufficiently exhaust condensate from steam, fog, or mist 
generated from cleaning and sanitizing activities to prevent the formation of 
condensation over equipment that is operating.  
  Drainage  You should conduct cleaning activities in a way that does not create drain 
backups in shared floor drains. Cleaning chemicals should not drain to equipment that is 
operating. 
  18  Contains Nonbinding Recommendations 
 
  Environment  You should conduct cleaning activities in a way that does not adversely 
affect room temperature, relative humidity, or air pressure balance. 
  Traffic Patterns  You should take steps to reduce the potential that changes in traffic 
patterns during the cleaning process could contaminate product. 
 
When using CIP systems, we recommend that you dedicate separate CIP systems for cleaning 
equipment used to process RTE food and for cleaning equipment used to process raw food. If 
you are unable to designate separate CIP systems and, thus, use a common CIP system, we 
recommend that you maintain the temperature of an alkaline cleaning solution at or above 71 
degrees C (160 degrees F).  
When using COP systems (e.g., wash tanks), we recommend that you dedicate separate COP 
systems for cleaning equipment used to process RTE food and for cleaning equipment used to 
process raw food. A separate COP system for RTE equipment should be in or near the RTE 
area where practical. Where this is not practical, you should establish other procedures (e.g., 
sequence of washing procedures, wash temperatures) to ensure that using a common COP 
system does not contribute to cross contamination with L. monocytogenes. 
When assembling cleaned and sanitized equipment (e.g., pump impellers, pipes), you should 
not place the equipment directly on the floor or other unclean surfaces, but should place them 
on cleaned and sanitized surfaces. We recommend that you take steps to prevent water from 
the floor or unclean equipment from splashing onto clean equipment.  
4.  Equipment and utensils used for cleaning/sanitizing 
We recommend that all wipes be disposable and discarded after each use on RTE food-contact 
surfaces and that scouring pads be discarded frequently. When scouring pads are not in use 
during the day, we recommend they be kept dry or placed in a sanitizer solution.  
We recommend that you maintain and clean (and sanitize where appropriate) equipment that is 
used for cleaning (e.g., brushes, mops, floor scrubbers, sinks, tubs, and vacuum cleaners) so 
that it does not become a source of contamination. You should not use cleaning tools that are 
used for floors or drains (see section VII.B of this guidance, below) on FCSs. We recommend 
that you dedicate cleaning equipment either to areas where RTE foods are processed or 
exposed, or to areas where raw foods are processed or exposed, using a mechanism (such as 
color coding) that easily distinguishes the equipment dedicated to the two areas.  
B. Cleaning Drains 
We recommend that you clean and sanitize floor drains in a manner that prevents contamination 
of other surfaces in the room. Examples of how to do so include: 
  Avoiding cleaning floor drains during times when RTE foods are processed or exposed 
or when unused packaging is present;  
  Avoiding use of high-pressure hoses to clear or clean a drain, because use of such 
hoses could create aerosols that could spread contamination throughout the room;  
  Using brushes that are at least 14 inch (0.64 cm) smaller than the diameter of a drain 
opening to prevent splattering during cleaning of floor drains; 
  19  Contains Nonbinding Recommendations 
 
  Using a splashguard to prevent splashing during cleaning; and 
  Dedicating tools that you use for cleaning drains to that purpose and taking steps to 
make tools used for cleaning drains easily distinguishable from utensils used for other 
purposes (e.g., by color-coding).  
 
If a drain backs up and water flows into an area where RTE foods are being processed or 
exposed, we recommend that you take steps to avoid splashing any equipment and follow the 
sequence of steps described below to clear the drain and clean the area around it: 
  Stop any production; 
  Remove any uncovered RTE foods from the affected area; 
  Clear the drain; 
  Clean the affected area with an effective cleaner, then rinse and sanitize; and  
  Remove excess water from the floor. 
 
We recommend that personnel who clean a drain change clothes and gloves, and wash and 
sanitize hands before subsequently touching an FCS.  
If you use bactericidal drain rings, we recommend that you monitor them and replace them 
when appropriate.  
C. Sanitizers 
Sanitizers containing quaternary ammonium compounds (QACs), peroxyacetic acid, iodine, or 
chlorine have been used to control L. monocytogenes in various situations (Ref. 43). All 
sanitizers have advantages and disadvantages. Some establishments use QACs for many 
applications, because QACs have been found to be effective against L. monocytogenes and 
leave a residual germicidal effect on surfaces (Ref. 43 and Ref. 51). We note that peroxyacetic 
acid sanitizers have been shown to be effective against biofilms containing L. monocytogenes 
(Ref. 43). Rotating sanitizers has been reported to provide for greater long term effectiveness 
and prevention of L. monocytogenes becoming established in niches in the environment and in 
forming biofilms (Ref. 43 and Ref. 52). However, the most important considerations for selecting 
a sanitizer include: regulatory approval for the intended purpose, efficacy against the target 
organism, and efficacy under conditions of use (concentration, temperature, pH, and water 
hardness). When using a sanitizer, you should take steps to ensure the sanitizer comes into 
contact with the surface to be sanitized, including crevices and niches.  
Sanitizers are subject to registration under the Federal Insecticide, Fungicide, and Rodenticide 
Act (FIFRA), which is administered by the U.S. Environmental Protection Agency. You should 
use sanitizing solutions in accordance with the conditions of use authorized under FIFRA, which 
should be on the product label. You should direct questions regarding the use of the sanitizer to 
control L. monocytogenes to the supplier of the sanitizer, who could have specific 
recommendations regarding factors (such as concentration, temperature, pH, and water 
hardness) that could influence the effectiveness of the sanitizer.  
  20  Contains Nonbinding Recommendations 
 
You can use hot water or steam to sanitize racks and equipment that are difficult to clean (Ref. 
43). Using hot water or steam also can enhance sanitation efforts when addressing harborage 
sites for L. monocytogenes (Ref. 44). 
D. Sanitation Monitoring 
We recommend that you: 
 
  Establish and implement written procedures, including the frequency with which they are 
to be performed, for monitoring sanitation conditions and practices;  
  Monitor sanitation conditions and practices during processing with sufficient frequency to 
ensure the cleanliness of FCSs and prevent cross-contamination; and 
  Correct, in a timely manner, any monitored sanitation conditions and practices that are 
not implemented in accordance with your written sanitation procedures. 
E. Sanitation Records 
We recommend that you establish and maintain sanitation records that document: 
  Your written sanitation procedures; 
  Your written procedures for monitoring sanitation conditions and practices;  
  Your sanitation monitoring; and  
  Corrections of monitored sanitation conditions and practices that are not implemented in 
accordance with your written sanitation procedures. 
F. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding a 
general sanitation program include 21 CFR 117.35(a), 117.35(d)(1), 117.135(d)(3),117.80(c)(1), 
117.80(c)(7), and 117.135(d)(3). 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
cleaning drains include 21 CFR 117.10(b)(1), 117.10(b)(3), 117.35(a), and 117.37(b)(3). 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
sanitizing procedures and solutions include 21 CFR 117.35(a), 117.35(b), 117.35(d), 
117.35(d)(1), and 117.35(d)(2).  
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
sanitation monitoring include 21 CFR 117.35(a) and 21 CFR 117.145. 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
sanitation records include 21 CFR 117.145(c) and 117.190. 
  21  Contains Nonbinding Recommendations 
 
VIII.  Controls on Raw Materials and Other Ingredients 
As discussed in section II.B of this guidance, L. monocytogenes has been detected in raw foods 
(such as raw seafood, raw produce, and unpasteurized milk) and in processed RTE foods (such 
as fresh-cut produce and soft cheeses), both of which can be used as ingredients in the 
manufacture of RTE foods.  
In this section of this guidance, we recommend that you identify raw materials and other 
ingredients that are likely sources of L. monocytogenes and establish, implement, and monitor 
controls to reduce the potential that such an ingredient or other raw material will contaminate a 
finished RTE food with L. monocytogenes.  
A. Raw Materials and Other Ingredients That are Potential Sources 
of L. monocytogenes 
We recommend that you assess which raw materials and other ingredients (such as raw or 
minimally processed foods) are more likely to be contaminated with L. monocytogenes than 
others and focus control efforts on these ingredients. Based on this assessment, you should 
establish a list of raw materials and other ingredients for which it is reasonably foreseeable that 
the ingredients could be contaminated with L. monocytogenes. Depending on how an ingredient 
that you purchase is processed, it could be more or less likely to be contaminated with L. 
monocytogenes.  
Raw materials and other ingredients processed with an adequate listericidal control measure 
that has been validated are not likely to contain L. monocytogenes. Examples of adequate 
listericidal control measures include: 
  Aseptically processed and packaged;  
  Retorted (e.g., canned);  
  Ethylene oxide treated or irradiated in the package; 
  Pasteurized (or equivalent treatment) in the package;  
  Other approved lethal technologies (in the package) 
We recommend that you verify that your supplier has validated the process and has programs 
to ensure that the process is being appropriately implemented and that recontamination is 
prevented on an ongoing basis. (See section VIII.B.3.) 
 
Many raw materials and other ingredients that are not processed with a listericidal control 
measure can be a potential source of contamination. Factors that impact the potential for an 
ingredient to be a source of contamination include: 
  The nature of an ingredient, including intrinsic factors such as pH and water activity; 
  The manufacturing process for the ingredient; 
  Supplier approval programs, programs that follow the practices described in this 
guidance for control of L. monocytogenes, and verification programs.  
 
  22  Contains Nonbinding Recommendations 
 
In the absence of adequate information about the risk presented by a particular ingredient, we 
recommend that you assume that the ingredient could be contaminated with L. monocytogenes.  
B. Controlling L. monocytogenes in Raw Materials and Other 
Ingredients When Contamination With L. monocytogenes Is 
Reasonably Foreseeable 
1.  General  
We recommend that you establish measures to prevent cross-contamination of finished RTE 
food by raw materials and other ingredients.  
In the absence of adequate information about the risk presented by a particular ingredient, we 
recommend that you handle raw foods, and any other food raw materials and other ingredients 
that could be contaminated with L. monocytogenes, as if they are contaminated with L. 
monocytogenes.  
2.  Use of a listericidal control measure 
We recommend that, where practical, you treat raw materials and other ingredients for which it 
is reasonably foreseeable that they will be contaminated with L. monocytogenes with a 
listericidal control measure during the manufacturing process, e.g., before a specific raw 
material or other ingredient is used in manufacture, or at an in-process stage of manufacture 
when the raw material or other ingredient is part of a mixture of ingredients.  
3.  Controls on suppliers 
If you do not use a listericidal control measure, we recommend that you establish and 
implement supply-chain controls designed to reduce the potential that the ingredient or other 
raw material received from a supplier is contaminated with L. monocytogenes.8 We recommend 
controls established in collaboration with your suppliers, rather than testing individual lots of raw 
materials or other ingredients, because limitations on product sampling make product testing a 
tool that primarily adds value in verifying the adequacy of control measures over time. 
We recommend that you establish relationships with suppliers, develop procedures for 
selecting, evaluating and approving suppliers, and conduct periodic onsite audits to ensure that 
your suppliers have proper procedures and food safety programs in place and have a serious 
commitment to food safety. Examples of how to do so include:  
                                                
8 As noted in section II.A of this guidance, subpart G of part 117 establishes PCHF requirements for a 
supply-chain program. If you are a manufacturer/processor that is subject to subpart G of part 117, and 
you determine through your hazard analysis that L. monocytogenes in a raw material or other ingredient 
is a hazard that requires a preventive control and will neither control the hazard yourself nor distribute it to 
another manufacturer/processor who will control the hazard, part 117 requires that you establish and 
implement a risk-based supply-chain program for that raw material or other ingredient (21 CFR 117.405). 
As also noted in section II.A, we are providing a separate, comprehensive guidance on the specific PCHF 
requirements for a supply-chain program. 
  23  Contains Nonbinding Recommendations 
 
  Developing a written supplier approval program based in part on control measures the 
supplier has implemented for L. monocytogenes, using this guidance and relevant 
regulations as a basis for assessing the control measures to ensure that raw materials 
and other ingredients are not adulterated under section 402 of the FD&C Act. As part of 
this program, we recommend that you verify any applicable supplier environmental 
monitoring program, including results. 
  Auditing the suppliers plant to assess whether the suppliers raw materials and other 
ingredients are produced under conditions that are consistent with this guidance. 
  Obtaining the raw material or other ingredient under a suppliers Certificate of 
Conformance (COC) (guarantee). If you do so, we recommend that: 
  Any COC that you rely on include the period of guarantee, product safety 
o
specifications, and a statement that the suppliers raw materials and other 
ingredients are produced under conditions that are consistent with this guidance and 
in compliance with part 117 and  
  You obtain that COC and conduct an onsite audit of the supplier on at least an 
o
annual basis. 
  Obtaining the ingredient under a suppliers Certificate of Analysis (COA) (keeping in 
mind the limitations associated with testing, discussed in section VIII.B.5 of this 
guidance) indicating that the raw material or other ingredient meets the written product 
safety specifications. We recommend that any COA that you rely on include the 
sampling plan and the analytical results of testing to detect Listeria spp. or L. 
monocytogenes, including the analytical method used and limits of the analytical 
method. See section XVII for our recommendations regarding analytical methods to 
detect Listeria spp. or L. monocytogenes.  
4.  Testing when receiving raw materials and other ingredients under a 
COC or COA 
If your controls on raw materials or other ingredients include a COC for L. monocytogenes, we 
recommend that you periodically test raw materials and other ingredients received under the 
COC to verify the efficacy of the suppliers control programs. The frequency of your periodic 
testing should be sufficient to maintain confidence that the suppliers control programs are 
effective and could be reduced if the results of your audits and verification tests demonstrate 
compliance with your specifications and the suppliers COC. 
If your controls on raw materials and other ingredients include a suppliers COA that includes 
test results for L. monocytogenes, we recommend that you verify the results of the suppliers 
COA on multiple lots of raw materials and other ingredients you receive until you have enough 
experience with that supplier to be confident in the results provided on the COA. After you have 
established confidence in your supplier, we recommend that you continue to test raw materials 
and other ingredients that you receive under a COA on a periodic basis (e.g., weekly, monthly, 
or quarterly, based on risk) to verify the efficacy of the suppliers control programs for L. 
monocytogenes. 
We recommend that you establish and follow written procedures for any sampling and testing of 
raw materials and other ingredients, including your sampling plan and procedures for collecting 
samples, preparing samples for analysis, and your analytical methods for testing samples for L. 
  24  Contains Nonbinding Recommendations 
 
monocytogenes. See section XVII of this guidance for our recommendations for such 
procedures. 
5.  Testing as the only control on raw materials or other ingredients 
We emphasize that testing a single lot of a food product for L. monocytogenes is of limited value 
in establishing the acceptability of that lot and cannot substitute for appropriate controls on its 
manufacture/processing. The primary value of product testing is as part of a history of test 
results that is used to verify the adequacy of control measures over time. We also emphasize 
that testing an incoming ingredient does not provide the same level of assurance as developing 
a supplier approval program based, in part, on the control measures the supplier has 
implemented for L. monocytogenes and your periodic verification that the supplier is 
implementing appropriate controls for L. monocytogenes.  
However, if you choose to test an incoming ingredient for the presence of Listeria spp. or L. 
monocytogenes rather than establishing controls on your supplier (such as some or all of the 
controls recommended in section VIII.B.3 of this guidance), we recommend that you test 
incoming raw materials and other ingredients on a periodic basis (e.g., weekly, monthly, or 
quarterly) commensurate with your suppliers demonstrated ability to minimize the presence of 
L. monocytogenes based on your prior test results on raw materials and other ingredients 
provided by your supplier (keeping in mind the limitations associated with testing). Such testing 
should be more frequent if your final product is not formulated to prevent the growth of L. 
monocytogenes.  
You should have a process in place to segregate and hold all raw materials or other ingredients 
that are tested prior to use and products that will be affected by test results. 
C. Records 
We recommend that you establish and maintain the following records regarding your raw 
materials and other ingredients: 
  Your list of raw materials and other ingredients for which contamination with L. 
monocytogenes is reasonably foreseeable;  
  Any written supplier program that you develop;  
  Documentation of the results of any audit of a supplier;  
  Any Certificate of Analysis or Certificate of Conformance (i.e., suppliers guarantee) that 
you rely on to control L. monocytogenes in raw materials or other ingredients;  
  Your written procedures for sampling and testing raw materials and other ingredients, 
including your sampling plan and procedures for collecting samples, preparing samples 
for analysis, and your analytical methods for testing samples for L. monocytogenes;  
  The results of any tests to detect L. monocytogenes in a raw material or other ingredient. 
D. Relevant Sections of part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding control 
of raw materials and other ingredients include 21 CFR 117.80(a), 117.80(b)(2), 117.80(c)(4), 
and subpart G. 
  25  Contains Nonbinding Recommendations 
 
IX.  Process Control Based on Formulating an RTE Food to 
Have Intrinsic Characteristics That Prevent the Growth of L. 
monocytogenes  
As discussed in section II.B of this guidance, it is well established that the foods that pose the 
lowest risk of foodborne listeriosis have intrinsic (physical or chemical) characteristics that do 
not support the growth of L. monocytogenes. Formulating your food product to have one or 
more such intrinsic characteristics can enhance the safety of your product.  
In this section of this guidance, we recommend that, as part of the process of developing an 
RTE food, you consider whether it is practical to use one or more of the following listeristatic 
formulations as a process control for L. monocytogenes: 
  pH less than or equal to 4.4; 
  Water activity less than or equal to 0.92; 
  Formulated to contain one or more inhibitory substances that, alone or in combination, 
prevent the growth of L. monocytogenes, including formulation through processes such 
as fermentation or culturing. 
 
As discussed more fully in sections IX.A and IX.B of this guidance, we also recommend that you 
demonstrate that any listeristatic formulation you use is effective and verify your formulation 
control on an ongoing basis.  
A. Initial Demonstration That a Listeristatic Formulation is Effective 
(Validation) 
Available approaches for demonstrating that your formulation consistently prevents growth of L. 
monocytogenes include (Ref. 53): 
  Historically established formulation controls (e.g., pH less than or equal to 4.4 or water 
activity less than or equal to 0.92); 
  Reference to scientific or technical information (e.g., published, peer-reviewed scientific 
studies that demonstrate the effectiveness of an antimicrobial ingredient to prevent the 
growth of L. monocytogenes in products that you manufacture, such as deli salads); 
  Previous validation studies (published or internal to your establishment) (e.g., if you 
determine that an available validation study for one formulation of a deli salad applies at 
least in part to a second formulation); 
  Mathematical modelling (e.g., using models related to inhibition of growth of L. 
monocytogenes to provide information useful in designing challenge studies); 
  Scientifically valid experimental data (e.g., data from challenge studies that you conduct 
to determine inhibition of L. monocytogenes growth in a specific food). 
 
These approaches are commonly used alone or in combination. For example, some formulation 
controls rely on a single parameter (such as pH alone or water activity alone), whereas other 
  26  Contains Nonbinding Recommendations 
 
formulation controls rely on a combination of parameters (such as an antimicrobial ingredient in 
combination with pH). 
1.  pH less than or equal to 4.4 or water activity less than or equal to 
0.92  
You may rely on data and information available in the scientific literature (e.g., Ref. 12, Ref. 15, 
Ref. 16, and Ref. 18 through Ref. 20) as an adequate demonstration that a listeristatic 
formulation that uses a pH less than or equal to 4.4, or water activity less than 0.92, is effective. 
 
2.  Listeristatic formulation that combines one or more antimicrobial 
substances and/or one or more other intrinsic factors 
We recommend that you demonstrate, through scientific studies that include information from 
the scientific literature, modelling, and, where needed, challenge studies, that a listeristatic 
formulation that combines one or more antimicrobial substances and/or one or more other 
intrinsic factors will consistently prevent the growth of L. monocytogenes. A listeristatic 
formulation is generally considered to be effective if growth studies that include samples at 
various points during product shelf life show an increase of less than 1 log cycle over two or 
more time intervals in the number of L. monocytogenes during replicate trials with the food of 
interest (Ref. 25). For an example of how such studies are conducted, see Ref. 24 and Ref. 25. 
Such studies should be conducted by a microbiologist or other food safety expert (e.g., process 
authority) knowledgeable in food microbiology and pathogen control (Ref. 25). This information 
should provide the parameters (and the associated minimum or maximum values) that you 
would monitor to ensure consistent control of L. monocytogenes. We recommend that you use 
values for operating parameters that incorporate a margin of safety; this could prove useful in 
evaluating process deviations.  
B. Ongoing Activities Relevant to a Process Control Based on a 
Listeristatic Formulation  
1.  Monitoring 
If your formulation control depends upon pH or water activity alone, you should either monitor 
pH or water activity of each batch or monitor that all ingredients in the formulation have been 
added in the appropriate proportions to achieve the desired pH or water activity.  
For other listeristatic formulations, you should monitor applicable process control parameters. 
Examples of how to do so include monitoring the amount of antimicrobial ingredient added, 
and/or the pH and any other parameter that is part of the hurdles that control L. monocytogenes, 
and monitoring that all ingredients in the formulation have been added in the appropriate 
proportions. 
2.  Verification 
For any listeristatic formulation you use, we recommend that you establish and implement 
measures to verify process control on an ongoing basis. In general, these measures should 
  27  Contains Nonbinding Recommendations 
 
ensure that any formulation or process is consistently applied and the applicable control is 
consistently achieved. Examples of such measures include: 
  Calibrating equipment used to measure pH or water activity in accordance with 
recommendations of manufacturers or other authoritative sources, or having someone 
other than those responsible for batch operations periodically observe the determination 
of pH or water activity measurement to verify the test is conducted correctly, when your 
listeristatic formulation is pH or water activity;  
  Having someone other than those responsible for batch operations occasionally observe 
the addition of particular antimicrobial ingredients in specific amounts to verify batch 
control, when your listeristatic formulation involves a combination of one or more 
antimicrobial ingredients and/or one or more other intrinsic factors;  
  Periodically testing a batch of your food product for pH or water activity, if your 
listeristatic control relies on adding ingredients in the formulation in the appropriate 
proportions; or  
  Reviewing records of measurements to ensure the records are accurate and meet the 
minimum or maximum values for the process control parameters. 
3.  Corrective Actions or Corrections 
If you have determined the pH, water activity or addition of antimicrobial ingredients of a batch is 
not correct during production, you can take appropriate actions to adjust the parameter to the 
appropriate value. If you have determined the pH, water activity or addition of antimicrobial 
ingredients of a batch is not correct after packaging, you should evaluate the food for safety and 
not release the food into commerce unless determined to be safe (e.g., by a Preventive Controls 
Qualified Individual (PCQI) if you are a facility subject to subpart C). You should determine what 
caused the problem and take steps to prevent it from reoccurring.  
C. Records 
We recommend that you establish and maintain records of: 
  Process control parameters applicable to the listeristatic formulation, such as pH, water 
activity, and concentration of antimicrobial ingredient;  
  Equipment calibration;  
  Your validation of listeristatic process controls;  
  Your monitoring and/or verification of listeristatic process control parameters (such as 
pH, water activity, and amount of antimicrobial ingredient added) as appropriate;  
  Your review of listeristatic process control records; and 
  Any corrective actions or corrections taken. 
D. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding the 
use of listeristatic formulations include 21 CFR 117.80(c)(4), 117.135(c)(1), 117.145, 117.150, 
117.155, 117.160, 117.165, and 117.190. 
  28  Contains Nonbinding Recommendations 
 
X.  Listericidal Process Control 
In this section of this guidance, we recommend that, as part of the process of developing an 
RTE food, you consider whether it is practical to include a listericidal process control in your 
manufacturing process. As discussed more fully in sections X.A and X.B of this guidance, we 
also recommend that you demonstrate that any listericidal control measure you use is effective 
and verify your listericidal process control on an ongoing basis. See Ref. 16. 
As discussed in section II.C of this guidance, L. monocytogenes has been shown to persist in 
equipment and the processing environment in harborage sites, and can lead to recontamination 
of your RTE food after you apply a listericidal process control. In Appendix 1 of this guidance, 
we list potential sources of L. monocytogenes in the food processing environment. In Appendix 
2 of this guidance, we provide examples of scenarios that could lead to contamination of RTE 
foods with L. monocytogenes. We recommend that you consider the information in Appendices 
1 and 2 to prevent recontamination of your RTE food product after you apply a listericidal 
process control.  
A. Initial Demonstration That a Listericidal Process Control is 
Effective (Validation) 
We recommend that you demonstrate, through scientific studies that include information from 
the scientific literature, modelling, and where needed challenge studies, that a listericidal 
process control that you establish and use consistently destroys viable cells of L. 
monocytogenes and consistently leads to a food product that does not contain detectable L. 
monocytogenes using a method that has a sensitivity of detection of at least 0.04 CFU of L. 
monocytogenes per gram of food (<1 CFU/25 g). Determining the extent of the process 
necessary to achieve that goal depends, in part, upon determining the likely levels of L. 
monocytogenes prior to application of the listericidal process control.  
In the absence of scientific studies, a listericidal process control that provides a reduction of the 
number of viable cells of L. monocytogenes of five orders of magnitude (five logarithms or 
99.999%) could achieve that goal, particularly if the food is unlikely to be contaminated with 
more than 100 CFU/g. If it is reasonably foreseeable that ingredients you use could be 
contaminated with more than 100 CFU/g, then reducing the number of viable cells of L. 
monocytogenes by six orders of magnitude (six logarithms or 99.9999%) could be necessary to 
achieve that goal. Other log reductions, if appropriately validated, may adequately reduce the 
risk from L. monocytogenes to an extent sufficient to prevent illness.  
Available approaches (used alone or in combination) for demonstrating that your process 
consistently destroys viable cells of L. monocytogenes include: 
  Historically established process controls (e.g., milk pasteurization parameters consistent 
with the definition of pasteurized or ultra-pasteurized in 21 CFR 131.3); 
  Reference to applicable scientific or technical information (e.g., a published, peer-
reviewed scientific study that determines the thermal death time for L. monocytogenes in 
corn kernels when manufacturing corn kernels that are blanched and frozen); 
  Previous validation studies (published or internal to your establishment) (e.g., 
determining that an available validation study for one formulation of a vegetarian 
burger applies at least in part to a second formulation); 
  29  Contains Nonbinding Recommendations 
 
  Mathematical modelling (e.g., using thermal death time models in laboratory media to 
inform decisions about appropriate times and temperatures for confirmation studies in a 
specific food); and 
  Scientifically valid experimental data (e.g., data from challenge studies that you conduct 
to determine lethality of L. monocytogenes in a specific food). 
 
In looking for listericidal process controls, we recommend that you consult a food safety expert 
(such as a microbiologist or process authority) knowledgeable in food microbiology and 
pathogen control and consider measures, alone or in combination, such as thermal treatment, 
irradiation (provided that irradiation has been approved as a direct food additive and listed in 21 
CFR part 179), hydrostatic pressure processing, or product formulations that are listericidal. The 
information from validation studies should provide the parameters (and associated minimum or 
maximum values) that you would monitor to ensure consistent control of L. monocytogenes. 
B. Ongoing Activities Relevant to a Listericidal Process Control 
1.  Monitoring 
We recommend that you monitor parameters such as time, temperature, water activity, pH, and 
concentration of a listericidal ingredient with sufficient frequency to ensure that control is 
achieved. When practical, we recommend continuous monitoring and recording of such 
parameters. 
2.  Verification 
For any listericidal process you use, we recommend that you establish and implement 
measures to verify process control on an ongoing basis. In general, these measures should 
ensure that any formulation or process is consistently applied and the applicable control is 
consistently achieved. Examples of such measures include: 
  Calibrating process monitoring and verification equipment;  
  Checking recorder charts, bed depths, pump or conveyor belt speeds, particle size (for 
heat penetration), and other parameters as appropriate during production to ensure they 
are functioning properly;  
  Establishing a standard operating procedure in which an individual is responsible for 
periodically observing the addition of particular antimicrobial ingredients in specific 
amounts, if your listericidal formulation involves a combination of one or more 
antimicrobial ingredients;  
  Verifying that all ingredients in the formulation have been added in the appropriate 
proportions, if you have established a process control parameter (such as pH or water 
activity); and  
  Reviewing records of measurements to ensure the records are accurate and meet the 
minimum or maximum values for the process control parameters. 
  30  Contains Nonbinding Recommendations 
 
3.  Corrective Actions or Corrections 
If you have determined during processing that a process control parameter has not been met, 
you may be able to correct that during operations. For example, if temperature is found to be 
lower than the process control temperature, you may be able to increase the time to achieve an 
equivalent lethality. If you are subject to subpart C, we recommend that your PCQI be involved 
in making this correction. If you have determined after packaging that the process parameter 
was not met, you should evaluate the food for safety and not release the food into commerce 
unless determined to be safe (e.g., by your PCQI if you are a facility subject to subpart C). You 
should determine what caused the problem and take steps to prevent it from reoccurring. If the 
product evaluation indicates a safety concern and the product has been released into 
commerce, you should recall the product.  
C. Records 
We recommend that you establish and maintain records of: 
  All process control parameters for the listericidal process;  
  Equipment calibration;  
  Your validation of listericidal process controls;  
  Your monitoring of listericidal process control parameters (such as temperature, pH, 
water activity, and amount of antimicrobial ingredient added) 
  Your review of listeristatic process control records; and 
  Any corrective actions or corrections taken.  
D. Relevant Sections of part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding the 
use of listericidal control measures include 21 CFR 117.80(c)(4), 117.135(c)(1), 117.145, 
117.150, 117.155, 117.160, 117.165, and 117.190. 
XI.  Storage Practices and Time/Temperature Controls  
As discussed in section II.B of this guidance, L. monocytogenes can multiply slowly at 
refrigeration temperatures. Even though L. monocytogenes can multiply slowly at refrigeration 
temperatures, refrigeration is a key control measure (Ref. 16).  
In this section of this guidance, we recommend that you establish and implement procedures to 
minimize the potential for an increase in numbers of any L. monocytogenes that could be 
present. An example of such a procedure is minimizing the amount of time that ingredients and 
other raw materials, in-process materials, and finished foods are stored under conditions that 
allow growth of L. monocytogenes. In particular, we recommend that you establish and follow 
procedures to use such materials on a first-in, first-out basis or to use those with the shortest 
use by date first.  
We recommend that you establish and implement time/temperature controls designed to ensure 
that foods are not held (e.g., before, during, or after production, or during transport) at a 
  31  Contains Nonbinding Recommendations 
 
combination of time and temperature that would allow a significant increase in the number of L. 
monocytogenes.  
We also recommend that you establish and implement measures to verify time/temperature 
control on an ongoing basis. In general, these measures should ensure that the 
time/temperature controls are consistently applied and consistently achieved.  
In the absence of specific data or other information about appropriate time/temperature controls 
for your particular operations, we recommend that RTE foods be stored at 4C (~40F) or 
below; higher temperatures may be appropriate when consistent with the Pasteurized Milk 
Ordinance (Ref. 54) or Food Code (Ref. 55).  
Many foods are stored in a frozen state  e.g., to extend shelf life before retail sale or as a 
product available to consumers in the frozen state. L. monocytogenes does not grow at 
temperatures below freezing (Ref. 12 and Ref. 13). Therefore, freezing is a particularly effective 
temperature control measure to prevent growth during storage. Freezing will not eliminate L. 
monocytogenes from foods and cannot be relied upon as a control measure for the elimination 
or reduction of Listeria monocytogenes. 
Sections of part 117 relevant to the recommendations in this guidance regarding storage 
practices and time/temperature controls include 21 CFR 117.40(e), 117.80(b)(5) and(6), 
117.80(c)(2), 117.80(c)(3), 117.80(c)(4), 117.93, 117.130(c)(2)(vii), 117.145, and 117.206. 
XII.  Transportation  
Contamination of an RTE food with L. monocytogenes can occur during transportation, and 
viable cells of L. monocytogenes can grow in an RTE food if the temperature is not controlled 
during transportation. In this section of this guidance, we provide recommendations for controls 
on transportation. 
We recommend that you inspect transportation vehicles (trailers and tankers) for structural 
integrity, cleanliness, and overall suitability when unloading ingredients and prior to loading 
finished products.  
We recommend that you transport foods that need temperature control using time/temperature 
controls that minimize the growth of L. monocytogenes (see section XI of this guidance). We 
also recommend that you use transportation vehicles that are equipped to maintain the 
temperature of applicable food (including incoming ingredients and outgoing RTE food 
products), where applicable, by controlling the temperature of the environment within the 
transportation vehicles used for such food. You should ensure food products are at the target 
temperature before loading the product into refrigerated trucks, which are designed to maintain 
a temperature but not to cool a product to the target temperature. Refrigerated vehicles should 
be pre-cooled with the pre-loading temperature documented prior to loading product.  
We recommend that you either dedicate any tankers or repeat use bulk containers used to 
transport ingredients or finished food products to those specific uses or that you establish and 
implement procedures to prevent contamination from previously transported products. You 
should verify that the tanker or container has been adequately cleaned and sanitized prior to 
use (e.g., via wash tag from tanker wash facilities with validated washing procedures).  
  32  Contains Nonbinding Recommendations 
 
We also recommend that you refer to part 1, subpart O (Sanitary Transportation of Human and 
Animal Food) for requirements for shippers, loaders, carriers by motor vehicle and rail vehicle, 
and receivers engaged in the transportation of food to use sanitary transportation practices to 
ensure the safety of the food they transport. For example, see  1.906 for requirements 
applicable to vehicles and transportation equipment and  1.908 for requirements applicable to 
transportation operations.  
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
transportation include 21 CFR 117.93 and 117.130(c)(2)(iv). 
 
XIII.  Environmental Monitoring to Verify Control of Listeria 
spp. or L. monocytogenes 
A. Goal of an Environmental Monitoring Program 
Because of its pervasiveness in the environment, L. monocytogenes can be introduced into the 
environment of your plant. The goal of an environmental monitoring program is to: 
  Verify the effectiveness of your control programs for L. monocytogenes; 
  Find L. monocytogenes and harborage sites if present in your plant; and 
  Ensure that corrective actions have eliminated L. monocytogenes and harborage sites 
when found in your plant. 
 
A well-designed program for monitoring the environment of your plant includes: 
  Collecting environmental samples9 (i.e., collecting samples from FCSs and non-FCSs in 
your plant); 
  Testing the collected environmental samples to identify potential sources of 
contamination; and 
  Taking appropriate corrective actions if test results indicate the presence of Listeria spp. 
or L. monocytogenes in an environmental sample.  
 
A well-designed environmental monitoring program promotes knowledge and awareness of the 
environmental conditions that could result in product contamination and is a more effective 
program than product testing alone.10  
                                                
9 See the glossary in section XIX.B. For the purpose of this guidance we define environmental sample 
as sample that is collected from a surface or area of the plant for the purpose of testing the surface or 
area for the presence of microorganisms, usually environmental pathogens. 
10 Note that part 117 requires, as appropriate to the facility, the food, and the nature of the preventive 
control and its role in the facilitys food safety system, environmental monitoring for L. monocytogenes or 
for an appropriate indicator organism (e.g., Listeria spp.), if contamination of an RTE food with L. 
monocytogenes is a hazard requiring a preventive control (21 CFR 117.165(a)(3)).  
  33  Contains Nonbinding Recommendations 
 
B. Strategies for Environmental Monitoring 
We recommend that your environmental monitoring procedures use a risk-based approach in 
which you establish strategies for environmental monitoring (e.g., environmental sampling, 
sampling sites and frequency, test procedures, and corrective actions) based on both the 
characteristics of your RTE food products and the processing methods used to produce those 
products. In general, the greater the risk that an RTE food could become contaminated with L. 
monocytogenes and support growth of the organism, the greater the frequency of environmental 
sampling and testing, and the more stringent the corrective actions if you detect Listeria spp.  
Table 3 lists a series of questions that you can address through a Yes/No answer. Table 3 then 
specifies how your answer would affect the risk that your RTE food product could become 
contaminated with L. monocytogenes  i.e., present a lower or higher risk. We recommend that 
you consider these questions in evaluating the risk that your RTE food product could become 
contaminated with L. monocytogenes and establishing strategies for environmental monitoring 
commensurate with that risk.  
Table 3.--Questions to Ask in Establishing Strategies For Environmental Monitoring 
Question  Lower Risk  Higher Risk 
Does the food receive a listericidal treatment to adequately 
Yes  No 
reduce L. monocytogenes? 
Is the food formulated to prevent the growth of L. 
monocytogenes or be lethal to L. monocytogenes (e.g., through  Yes  No 
intrinsic characteristics such as pH or water activity)? 
How much handling does the food receive subsequent to a 
Minimal  Extensive 
pathogen reduction step and prior to packaging? 
Does the food receive a listericidal control measure in the 
Yes  No 
package? 
What is the shelf life of the product during refrigerated storage?  Short  Long 
Does the packaged RTE food support the growth of L. 
No  Yes 
monocytogenes under normal storage conditions? 
 
C.  Sampling Areas 
 
We recommend that you characterize areas in your plant according to the potential for product 
contamination for the purpose of collecting and testing environmental samples for the presence 
of Listeria spp. One way to do this is to characterize your plant in terms of a zone system. See 
Table 4 for an example of how to characterize your plant with four zones. 
Table 4.--Example of a Food Plant with Four Zones  
Zones  Description  Examples 
Zone 1  Food-Contact Surfaces  Utensils, table surfaces, 
slicers, pipe interiors, tank 
interiors, filler bowls, 
packaging and conveyors, 
hoppers. 
  34  Contains Nonbinding Recommendations 
 
Zones  Description  Examples 
Zone 2  Non-food-contact surfaces in close proximity to  Equipment housing or 
food and food contact surfaces.  framework, and some walls, 
floors or drains in the 
immediate vicinity of FCSs 
carts 
Zone 3  More remote non-food-contact surfaces that are  Forklifts, hand trucks and 
in or near the processing areas and could lead to  carts that move within the 
contamination of zones 1 and 2  plant and some walls, floors or 
drains not in the immediate 
vicinity of FCSs 
Zone 4  Non-food-contact surfaces, remote areas outside  Locker rooms, cafeterias, and 
of the processing area, from which  hallways outside the 
environmental pathogens can be introduced into  production area or outside 
the processing environment  areas where raw materials or 
finished foods are stored or 
transported 
 
If you do not establish and use a zone-based system, we recommend that you otherwise 
characterize areas where you will collect environmental samples according to potential for 
contamination, and that you distinguish between FCSs and non-FCSs.  
 
D. Written Procedures for Environmental Monitoring  
We recommend that you have written environmental monitoring procedures.  
Your written procedures should: 
  Be scientifically valid;  
  Specify whether you are testing for Listeria spp. or L. monocytogenes; 
  Identify the locations from which samples will be collected and the number of sites to be 
tested during routine environmental monitoring. The number and location of sampling 
sites should be adequate to determine whether Listeria control measures are effective;  
  Identify the timing and frequency for collecting and testing samples. The timing and 
frequency for collecting and testing samples should be adequate to determine whether 
Listeria control measures are effective;  
  Identify the test(s) conducted, including the analytical method(s) used to test for Listeria 
spp. or L. monocytogenes;  
  Identify the laboratory you are using for conducting the testing; and 
  Include corrective action procedures you will use when Listeria spp. or L. 
monocytogenes is found. 
 
We discuss each of these recommendations for your written procedures in sections XIII.D.1 
through XIII.D.7.  
  35  Contains Nonbinding Recommendations 
 
1. Scientifically valid 
Procedures and methods for environmental sampling and the analytical testing of samples 
should be consistent with those described in an authoritative reference such as those by FDAs 
Bacteriological Analytical Manual (BAM), International Commission on Microbiological 
Specifications for Foods (ICMSF), American Public Health Association (APHA), and others (Ref. 
56 through Ref. 60). For examples of procedures we consider to be scientifically valid, see 
Appendix 5 of this guidance for our recommended method to collect environmental samples, 
and see Testing Methodology for Listeria species or L. monocytogenes in Environmental 
Samples (Ref. 60) for our recommended analytical methods for testing environmental samples. 
Additionally, BAM chapter 10 lists rapid screening methods for the detection of Listeria from 
environmental samples (Ref. 59). 
2. Test organism 
Your written environmental monitoring procedures should identify whether you are testing for 
Listeria spp. or L. monocytogenes. We recommend that you test for Listeria spp. because doing 
so will detect both L. monocytogenes as well as species of Listeria that are more common than 
L. monocytogenes and allow you to correct situations that could potentially lead to 
contamination with L. monocytogenes. 
A positive test result for the presence of Listeria spp. on an FCS or non-FCS indicates the 
potential for contamination of an FCS or non-FCS with L. monocytogenes and suggests that 
conditions are suitable for survival and/or growth of L. monocytogenes. A positive test result for 
the presence of Listeria spp. on an FCS or a non-FCS does not establish the presence of L. 
monocytogenes on an FCS or non-FCS.  
3.  Sample locations and number of sites to be tested 
Your written environmental monitoring procedures should specify an appropriate number of 
selected sampling sites. You should select these sites based on the potential for the site to be 
contaminated with L. monocytogenes. Sometimes an establishment will generate an extensive 
list of potential sampling sites and randomly select some number of sites from those listed sites 
at any specific sampling time. We recommend that such a program be designed to test all sites 
on the list within a defined period of time, e.g., one month. We recommend that an 
establishment test both FCS and non-FCS sites at each sampling time. 
We recommend that you determine the appropriate number of FCS and non-FCS sampling sites 
based on the size of the plant, plant features, product flow, characteristics of the RTE food, the 
processing methods used to produce the food, and previous sampling results (if any). The 
number of samples generally is higher in zones 1 and 2 because of the greater risk of food 
contamination if the organism is present in these zones. For examples of FCSs and non-FCSs 
to sample, see the sites that we identify as potential sources of contamination with L. 
monocytogenes in Appendix 1. We recommend that even the smallest processors collect 
samples from at least 5 sites of FCS and 5 sites of non-FCS on each production line for RTE 
foods. We recommend that larger processors determine the appropriate number of sampling 
sites based on the size of the plant. 
  36  Contains Nonbinding Recommendations 
 
Generally we recommend that you do not composite samples taken from FCS sites because 
this can increase the time required to identify the source of contamination should a sample 
result be positive for Listeria spp. 
As discussed in section II.C, L. monocytogenes is widespread in the environment, has been 
isolated from food packing and processing environments, and has been shown to persist in 
equipment and the processing environment in harborage sites. As a result, you should expect to 
detect the presence of Listeria spp. or L. monocytogenes on an occasional basis in 
environmental samples collected from your plant. As discussed in section XIII.A, the goals of an 
environmental monitoring program include finding L. monocytogenes and harborage sites if 
present in your plant and ensuring that corrective actions have eliminated L. monocytogenes 
and harborage sites when found in your plant. If you consistently see negative test results in 
environmental samples collected from your plant, we recommend that you revise your 
environmental monitoring procedures to add, substitute, or both add and substitute other 
surfaces in your plant for sample collection and testing to ensure you are not missing a source 
of contamination.  
4. Timing and frequency for collecting environmental samples 
Your written environmental monitoring procedures should specify the time(s) at which 
environmental samples will be collected. The most important time to collect environmental 
samples is at a time that is several hours into production (e.g., 3 to 4 hours) or preferably just 
prior to cleanup, because this allows time for L. monocytogenes (if present) to work its way out 
of harborage sites and contaminate the environment, the processing line (including FCS sites), 
and, potentially, RTE product. Note that if you take samples too close to the time when surfaces 
have been sanitized, the sanitizer may not be adequately neutralized and could interfere with 
the analytical test.  
Your written environmental monitoring procedures should specify the frequency of sample 
collection. Frequency of routine sampling should be based on risk. We recommend the lowest 
frequency (e.g., monthly) of routine sample collection be for those RTE foods that do not 
support growth of L. monocytogenes. We recommend that the highest frequency (e.g., weekly) 
of routine sample collection be for those RTE foods that support growth of L. monocytogenes. 
Frequency of sampling should be increased when Listeria spp. positive samples are found in 
the plant (see section on Corrective Actions). 
An example of how to specify the frequency of sample collection in a written environmental 
monitoring plan for FCSs in an establishment producing an RTE food that supports growth of L. 
monocytogenes is as follows: 
  Collect environmental samples from specific FCSs on the production lines at least once 
every week when the plant is in operation; and  
  Test each FCS in the plant at least once each month. 
 
An example of how to specify the frequency of sample collection in a written environmental 
monitoring plan for non-FCSs in an establishment producing an RTE food that supports growth 
of L. monocytogenes is as follows: 
  37  Contains Nonbinding Recommendations 
 
  Collect environmental samples from representative sets of non-FCSs at least once 
weekly for zone 2 sites, every two weeks for zone 3 sites, and monthly for zone 4 sites 
when the plant is in operation; and  
  Test all non-FCS sites identified in the monitoring plan at least once each quarter. 
5.  Test(s) conducted (including analytical method(s))  
We recommend that you use the procedures described in Appendix 5 for preparing 
environmental samples for analysis. We recommend that you follow the FDA procedure in 
Testing Methodology for Listeria species or L. monocytogenes in Environmental Samples (Ref. 
60) to test the samples you prepared for analysis. We recommend that you either test the 
individual environmental samples that you collect, or test a composite that you make from 
multiple environmental samples taken from a given area. However, you should not composite 
more than 5 environmental samples, because methods have not been validated to show that 
this does not reduce the sensitivity of detecting the presence of the organism. Consistent with 
our recommendations in section XIII.D.4, when compositing samples taken during production 
you should take samples at least 3 to 4 hours into production.  
Importantly, we do NOT recommend compositing environmental samples when the purpose of 
your sampling is to locate the source of contamination (e.g., if you are conducting follow-up 
sampling after finding a positive test result for Listeria spp.). 
6.  Laboratory that conducts the testing 
You may analyze samples in your own, in-house laboratory or send the samples to an outside 
commercial laboratory for testing. We recommend that you identify in your written environmental 
monitoring procedures the laboratory that will analyze your samples. We recommend that you 
take steps to ensure the laboratory you use is knowledgeable of the most current scientifically 
valid methods applicable to environmental samples. One way to do so is to determine whether 
the laboratory is accredited (e.g., to a laboratory testing standard such as ISO 17025). Because 
multiple, scientifically-valid analytical methods could be available for a particular application, the 
analytical methods used could differ among laboratories.  
7.  Corrective action procedures 
We recommend that your written environmental monitoring procedures include corrective action 
procedures that describe the steps to be taken and assign responsibility for taking those steps, 
to: 
  Ensure that the cause of the contamination is identified and corrected; and 
  Minimize the potential for foods to be contaminated with L. monocytogenes from any 
source (e.g., equipment, people, and the processing or packing environment).  
 
We recommend that your corrective action procedures be risk-based from the perspectives of: 
  The environmental monitoring strategy for the food;  
  Whether the environmental contamination is on an FCS or a non-FCS;  
  38  Contains Nonbinding Recommendations 
 
  Whether testing environmental samples results in an isolated positive result or multiple 
positive results; and 
  The proximity of a contaminated non-FCS to FCSs.  
 
The types of corrective actions are highly varied (e.g., conducting intensified cleaning and 
sanitizing, conducting intensified sampling and testing, conducting a root cause analysis, and 
implementing "hold and test" procedures). Which corrective actions you take depends upon 
your specific situation. For specific recommendations for corrective actions if you detect Listeria 
spp. or L. monocytogenes in environmental samples collected during routine or follow-up 
sampling and testing, see sections XIII.E through XIII.G of this guidance and Appendix 6. We 
have not identified all manners in which foods or FCS can be contaminated, and it is not 
possible to provide a comprehensive set of corrective actions that apply in all situations. The 
actions you take should be based on the risk that contamination could result in contaminated 
food and consumer illness.  
8.  Periodic verification of the written environmental monitoring 
procedures 
We recommend that you periodically verify your written environmental monitoring procedures by 
increased and intensive environmental sampling of the plant to assess whether the sampling 
sites are appropriate. 
E. Corrective Actions if You Detect Listeria spp. on a Non-Food-
Contact Surface 
If you detect Listeria spp. on a non-FCS, as discussed in section XIII.D.7 of this guidance we 
recommend that you follow risk-based corrective action procedures that describe the steps to be 
taken, and assign responsibility for taking those steps, to ensure that the cause of the 
contamination is identified and corrected, and to minimize the potential for FCSs, RTE food, 
ingredients or packaging to become contaminated. In this section, we focus on corrective 
actions for positives in zone 2, which are in close proximity to food and food contact surfaces. 
You should also take corrective actions to eliminate Listeria spp. in zones 3 and 4 so as to 
prevent contamination moving to zones 1 or 2. Corrective actions in zones 3 and 4 may be less 
rigorous than those for zone 2.  
 
As noted in section XIII.D.7, the types of corrective actions are highly varied and depend upon 
your specific situation. However, some of these corrective actions broadly apply to most 
situations. For example, when a follow-up sample taken from a non-FCS is positive for Listeria 
spp. and the applicable food is a food that supports the growth of L. monocytogenes, we 
recommend that intensified cleaning and sanitizing activities include disassembly of affected (or 
potentially affected) equipment11 (if practical), along with sampling and testing, to determine the 
source of Listeria spp.  
                                                
11 In some cases the equipment that is disassembled is (or is part of) the non-FCS that tested positive 
(e.g., support structures for a conveyor). In other cases, the equipment that is disassembled is (or is part 
of) a FCS that is in close proximity to the non-FCS that tested positive (e.g., the food conveyor).  
  39  Contains Nonbinding Recommendations 
 
Immediately below, we describe examples of what your corrective action procedures for positive 
sample results on a non-FCS in zone 2 could include.  
  If the positive test result is from a composite sample, conduct additional testing to 
identify the specific non-FCS that is contaminated with Listeria spp. or, alternatively, take 
action as if each non-FCS site represented by the composite is positive.  
  When you receive notification of a positive result of a routine sample for a non-FCS site, 
pay particular attention to cleaning and sanitizing that site at the end of production and 
retest the non-FCS and surrounding area (i.e., conduct intensified sampling and 
testing12) at least 3 hours into the next production run. 
  If the follow-up samples are negative for Listeria spp., assume the contamination has 
been eliminated and resume routine environmental monitoring during subsequent 
production. 
  If any of the follow-up samples show the presence of Listeria spp. (i.e., if you obtain a 
second positive result), conduct intensified cleaning and sanitizing13, with intensified 
sampling and testing to identify the source of the contamination.  
  For foods that support the growth of L. monocytogenes, based on the likelihood that 
o
the non-FCS could serve as a source of contamination for an FCS and/or food, these 
intensified cleaning and sanitizing activities could include, for example, disassembly 
of affected (or potentially affected) equipment if practical to determine the source of 
Listeria spp. Sample and test areas of the equipment exposed by disassembly prior 
to cleaning and sanitizing the equipment. 
  For foods that do not support the growth of L. monocytogenes, disassembly of 
o
affected (or potentially affected) equipment is less common unless sampling and 
testing conducted after a second positive result results in a third positive. 
  If your intensified sampling and testing results are all negative, return to routine 
environmental monitoring. 
  If your intensified sampling and testing results are not all negative, conduct a root cause 
analysis, escalate mitigation efforts to identify and eliminate the Listeria spp. source, and 
consider consultation with a Listeria control expert. Take risk-based actions to determine 
how the site became contaminated, including activities involved in a comprehensive 
investigation as discussed in section XIII.F. These actions vary depending on the risk 
that an FCS or food could become contaminated from the positive non-FCS site and the 
risk that a contaminated food would present to the consumer (e.g., based on whether the 
potentially contaminated food supports growth of L. monocytogenes). Repairing or 
replacing broken equipment and plant construction may be needed to remedy problems. 
                                                
12 Intensified sampling and testing involves collecting and testing follow-up samples to a positive test site. 
The follow-up samples should include the positive site and at least 3 surrounding sites, which could 
include both FCSs and non-FCSs in close proximity to the positive site. 
13 Intensified cleaning and sanitizing includes sanitation measures that are performed in addition to 
normal sanitation procedures and are escalated in response to continuing findings of positives. Intensified 
cleaning and sanitizing can include increasing the frequency of cleaning and sanitizing for certain pieces 
of equipment, breaking down the equipment into its parts for further cleaning, and steam treating 
equipment. 
  40  Contains Nonbinding Recommendations 
 
See Figure 1 for a flow diagram that is a visual representation of the example corrective actions 
described above. (While these focus on zone 2, similar corrective actions can be applied in 
other zones.) See Table 6 in section XIII.G for an alternative presentation, in table format, of the 
flow diagram in Figure 1. Table 6 summarizes the recommended corrective actions when you 
detect Listeria spp. in an environmental sample taken from non-FCSs and FCSs. For each type 
of surface (i.e., non-FCS and FCS), Table 6 also compares the corrective actions for growth 
foods to the corrective actions for non-growth foods. 
   
  41  Contains Nonbinding Recommendations 
 
Figure 1.--Example of Non-FCS* testing and follow up activities for Zone 2. 
 
  42  Contains Nonbinding Recommendations 
 
The example in Figure 1 addresses testing and follow-up actions for specific positive findings of 
Listeria spp. in Zone 2 during one sampling period. Detecting Listeria spp. at several Zone 2 
sampling locations during the same sampling period could indicate that your routine sanitation 
procedures are inadequate, and could indicate that the Listeria spp. has become established in 
one or more harborages in Zone 2. In such situations, the risk associated with cross-
contamination from a contaminated Zone 2 site to Zone 1 or food increases as the number of 
contaminated Zone 2 sites increases. When several Zone 2 site positives are detected during 
one sampling period, we recommend that you review your written sanitation procedures to 
identify and implement more effective routine sanitation procedures and escalate your corrective 
actions until the situation is resolved.    
In general, there is minimal value in determining whether Listeria spp. detected on a non-FCS is 
L. monocytogenes, because you should eliminate the Listeria spp. regardless of whether it is L. 
monocytogenes. If you find Listeria spp. on a non-FCS or in the same general area on multiple 
occasions, we recommend that you conduct a root cause analysis to determine why this area 
continues to be a source of positive results and take actions to eliminate the contamination, 
such as by determining the efficacy of your sanitation procedures and modifying them as 
necessary. (See Analysis of Data for Trends in Section XV.)  
We also recommend that you establish and maintain a record of all corrective actions taken. 
 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
corrective actions if you detect Listeria spp. or L. monocytogenes on a non-FCS include 21 CFR 
117.35, 117.80(a), and 117.150. 
F. Corrective Actions If You Detect Listeria spp. on a Food-Contact 
Surface 
If you detect Listeria spp. on an FCS, as discussed in section XIII.D.7 of this guidance we 
recommend that you follow risk-based corrective action procedures that describe the steps to be 
taken, and assign responsibility for taking those steps, to ensure that the cause of the 
contamination is identified and corrected, and to minimize the potential for release of RTE food 
that is contaminated with L. monocytogenes. In this section XIII.F, we describe corrective action 
procedures that differ based on whether a food supports growth of the pathogen or not. 
However, we recommend that for a food that does not support growth and that is specifically 
intended for establishments such as hospitals and nursing homes (where the food would be 
consumed by populations at high risk for listeriosis), you take corrective actions in a similar 
manner as for foods that support growth. 
1.  Recommended corrective actions regarding your plant and your 
processing 
If you detect Listeria spp. on an FCS, we recommend that you conduct a comprehensive 
investigation (i.e., an expanded root cause analysis) and take corrective actions immediately 
based on your written environmental monitoring procedures.  
Immediately below, we provide an example of a comprehensive investigation. 
  Examine the equipment that yielded the positive finding and the area surrounding the 
positive site in all directions for potential sources of Listeria spp. or L. monocytogenes as 
  43  Contains Nonbinding Recommendations 
 
described in Appendix 1 of this guidance (Categories C, D and E). Pay particular 
attention to possible niches that allow harborage of L. monocytogenes; 
  Review your HACCP or Food Safety Plan, if any, and its implementation to determine if 
there are any design or execution flaws and modifying your plan as necessary;  
  Conduct intensified sampling and testing of sites that represent a potential source of L. 
monocytogenes identified in the earlier examination, collecting samples several times 
during production to identify the source of contamination (the number of samples 
collected during production depends on the product and the production process); 
  Test upstream from the positive FCS in the production area to help identify a source of 
contamination;  
  Check maintenance records for modifications or repairs to major equipment;  
  Interview and observe sanitation, maintenance, and production personnel to determine 
whether appropriate procedures are being followed;  
  Review production, maintenance, and sanitation procedures to determine whether to 
modify the procedures to prevent contamination and then make those modifications 
identified by the review;  
  Review the scenarios that we provide in Appendix 2 of this guidance as an aid to 
identifying causes of contamination;  
  Review traffic patterns, equipment layout, and adherence to personnel hygiene 
procedures; and 
  Take appropriate actions based on findings of the above activities. 
 
As noted in section XIII.D.7, the types of corrective actions are highly varied and depend upon 
your specific situation. However, some of these corrective actions broadly apply to most 
situations. For example, when a follow-up sample taken from an FCS is positive for Listeria 
spp., we recommend that intensified cleaning and sanitizing activities include disassembly of 
affected equipment (if practical), along with sampling and testing, to determine the source of 
Listeria spp. For the purpose of this guidance we assume that a lot of food is one days 
production on a processing line, with cleaning and sanitizing between production lots. 
Immediately below, we describe examples of what your corrective action procedures for positive 
sample results on an FCS could include.  
  Although we do not recommend composite sampling for FCS sites, if you initially tested 
a composite sample, conduct additional testing to identify the specific FCS that is 
contaminated with Listeria spp. or, alternatively, take action as if each FCS site 
represented by the composite is positive.  
  When you receive notification of a positive result of a routine sample for an FCS site, 
pay particular attention to cleaning and sanitizing that site at the end of production and 
retest the FCS and surrounding area (i.e., conduct intensified sampling and testing) at 
least 3 hours into the next production run. 
  44  Contains Nonbinding Recommendations 
 
  If the follow-up samples from intensified sampling and testing are negative for Listeria 
spp., assume the contamination has been eliminated and resume routine environmental 
monitoring during subsequent production. 
  If any follow-up sample from intensified sampling and testing is positive for Listeria spp. 
(second FCS positive), take enhanced corrective actions such as: 
  Conduct intensified cleaning and sanitizing, including disassembly of equipment if 
o
practical to determine the source of Listeria spp. Sample and test areas of the 
equipment exposed by disassembly prior to cleaning and sanitizing the equipment.  
  Conduct intensified sampling and testing. 
o
  Follow Hold and Test procedures as appropriate: 
o
  When food supports growth of L. monocytogenes, hold the production lot 
associated with that production day and test the food for presence of L. 
monocytogenes using a statistically-based sampling protocol and methods that 
provide a level of confidence in the results which the firm deems appropriate 
based on risk (e.g., a 95% confidence of detecting L. monocytogenes in the 
sample if present). (See section XIII.F.3 for our recommendations regarding 
Hold and Test procedures for RTE food.)  
  When the food does not support growth of L. monocytogenes, consider whether 
to hold and test the production lot associated with that production day. (The 
decision should be based on the likelihood of product contamination and the risk 
that contaminated product presents to the consumer.) 
  Conduct a comprehensive investigation to determine and mitigate Listeria sources, and 
modify procedures where appropriate. 
  On the next two production days, continue your enhanced corrective actions: 
  Conduct intensified cleaning and sanitizing, including disassembly of equipment. 
o
Sample and test areas of the equipment exposed by disassembly prior to cleaning 
and sanitizing the equipment.  
  Conduct intensified sampling and testing. 
o
  Hold product from these two production days. (Disposition of these lots will depend 
o
on results of the environmental testing for FCS sites taken during production and on 
results of the previous days product being tested.) 
  If results from the product lot that was tested (taken after the second FCS positive for 
food that supports growth and possibly for food that does not support growth) are 
negative for L. monocytogenes and the retest of the FCS is negative for three sequential 
days, release that product lot. 
  Resume routine production, release additional product on hold, and return to routine 
environmental monitoring after all results for FCS samples taken during 3 sequential 
production days yield negative results for Listeria spp. 
  If the food tests positive for L. monocytogenes, reprocess, divert to non-food use, send 
for use in food to be consumed by animals where appropriate, or destroy that product lot 
and the additional product lots on hold, and consider whether there is product in 
commerce that should be recalled.  
  45  Contains Nonbinding Recommendations 
 
  If a follow-up sample from intensified sampling and testing continues to detect Listeria 
spp. (third positive) on an FCS site, assume that you have a harborage site.  
  For foods that support growth of L. monocytogenes, stop production and consult 
food safety experts familiar with troubleshooting L. monocytogenes 
contamination problems in plants to conduct a comprehensive investigation and 
make recommendations for appropriate actions to take based upon that 
investigation. After these corrective actions have been taken and production 
begins, hold and test product and conduct intensified sampling and testing until 
you have three consecutive dates of negative results for FCSs and product. 
  For foods that do not support growth of L. monocytogenes, after the third FCS 
positive, take the same corrective actions as you would take for a food that 
supports growth after a second FCS positive, including the same hold and test 
procedure for foods that support growth.  
 
See Figure 2 for a flow diagram that is a visual representation of the example corrective actions 
described immediately above. See Table 6 in section XIII.G for an alternative presentation, in 
table format, of the flow diagram in Figure 2. Table 6 summarizes the recommended corrective 
actions when you detect Listeria spp. in an environmental sample taken from non-FCSs and 
FCSs. For each type of surface (i.e., non-FCS and FCS), Table 6 also compares the corrective 
actions for growth foods to the corrective actions for non-growth foods. 
  
   
  46  Contains Nonbinding Recommendations 
 
Figure 2.--Example of FCS* testing and follow-up activities.  
   
  47  Contains Nonbinding Recommendations 
 
The example in Figure 2 addresses testing and follow-up actions for specific positive finding of 
Listeria spp. on an FCS during one sampling period. Detecting Listeria spp. at several FCS 
sampling locations during the same sampling period could indicate that your routine sanitation 
procedures are inadequate, and could indicate that the Listeria spp. has become established in 
one or more harborages sites that are FCS or in Zone 2 nearby FCS. In such situations, the risk 
associated with cross-contamination from contaminated FCS sites to food increases as the 
number of contaminated FCS sites increases. When several FCS site positives are detected 
during one sampling period, we recommend that you immediately review your written sanitation 
procedures to identify and implement more effective routine sanitation procedures, escalate 
your corrective actions, and conduct a root cause analysis to identify and eliminate the Listeria 
spp. source. 
If you find Listeria spp. on FCS sites in the same general area on multiple occasions, we 
recommend that you conduct a root cause analysis to determine why this area continues to be a 
source of positive results and take actions to eliminate the contamination, such as by 
determining the efficacy of your sanitation procedures and modifying them as necessary. (See 
Analysis of Data for Trends in Section XV.) 
2.  Determining whether Listeria spp. is L. monocytogenes 
If an FCS tests positive for the presence of Listeria spp., we recommend that your corrective 
action procedures specify when to determine whether the Listeria spp. is L. monocytogenes. In 
general, the greater the risk of foodborne illness presented by the RTE food being produced on 
an FCS that has tested positive for Listeria spp., the greater the importance of determining 
whether any Listeria spp. you detect on an FCS is L. monocytogenes.  
3.  Hold and Test procedures for RTE food 
FSIS has issued guidelines to help establishments that produce certain RTE meat or poultry 
products to comply with FSIS requirements (established in 9 CFR part 430) for the control of L. 
monocytogenes in those RTE meat and poultry products (Ref. 61) (the FSIS Guidelines). The 
FSIS guidelines include procedures to hold and test RTE foods for L. monocytogenes, The FSIS 
guidelines describe ICMSFs scientifically-based sampling plans that can be used to provide 
statistical confidence for results of product testing (Ref. 61). The following description is based 
on the discussion of the ICMSF sampling plans in the FSIS guidelines.  
ICMSF categorizes microbial hazards according to risk:  
1)  Moderate  
2)  Serious  
3)  Severe  
 
ICMSF ranks L. monocytogenes as either a serious hazard in foods for the general population 
or a severe hazard in foods for restricted populations (high risk groups e.g., hospital and nursing 
home patients) (Ref. 62). ICMSF does not identify any circumstances in which L. 
monocytogenes would be ranked as a moderate hazard. 
ICMSF describes 15 different cases of sampling plans (Ref. 62), with sampling plan stringency 
based on degree of risk and the effect on risk of the conditions of use. Cases 10, 11, and 12 
would apply to the serious category of microbial hazards and cases 13, 14, or 15 would apply to 
the severe category of microbial hazards. ICMSF considers cases 13, 14, and 15 to apply to 
  48  Contains Nonbinding Recommendations 
 
foods intended specifically for highly susceptible individuals (e.g., patients in hospitals and 
nursing homes) because a large proportion of the individuals would be potentially susceptible to 
foodborne illness; thus, increasing the stringency of the sampling plans is appropriate.  
For cases 10 or 13, conditions of use reduce risk (e.g., the numbers of L. monocytogenes will 
decrease). For cases 11 and 14, conditions cause no change in the hazard (e.g., L. 
monocytogenes cannot grow), and for cases 12 and 15, conditions could increase the risk (e.g., 
foods in which L. monocytogenes can grow are subjected to conditions that allow growth). 
Sampling plans for the cases are given in Table 5, where n is the number of samples and c=0 
means that none of the n samples can be positive for L. monocytogenes. The table also 
provides the sampling plan performance, assuming a log-normal distribution with a standard 
deviation of 0.8; lots having the calculated mean concentrations or greater will be rejected with 
at least 95% confidence. Each of these plans achieves assurance that L. monocytogenes is 
present at <1 CFU in the sample size.  
We recommend analyzing a 25 g sample. If the risk of the population is unknown, we 
recommend that you use cases 13-15. 
Table 5.--Sampling plans for ICMSF cases 10  15  
Conditions Reduce Concern14  Conditions cause no change15  Conditions increase concern16 
in concern 
Case 10  Case 11  Case 12 
n17=5, c18=0  n=10, c=0  n=20, c=0 
Mean Concentration  Mean Concentration  Mean Concentration 
1 cfu/32g  1 cfu/83g  1 cfu/185g 
Case 13  Case 14  Case 15 
n=15, c=0  n=30, c=0  n=60, c=0 
Mean Concentration  Mean Concentration  Mean Concentration 
1 cfu/135g  1 cfu/278g  1 cfu/526g 
 
When RTE products are sampled (hold and test), the number of samples (randomly selected) 
would be as specified for these cases based on the risk of the product and the intended 
consumers.  
The number of samples recommended should be collected in one day and all affected products 
should be held during the testing period. Testing can be for Listeria spp. or L. monocytogenes. If 
you obtain any positive results from this follow-up testing (using the ICMSF approach), you 
should conduct more significant investigations of the cause of the contamination and rigorous 
corrective actions. 
                                                
14 Conditions prior to consumption will result in a decrease of the number of L. monocytogenes (e.g., 
product will be heated prior to consumption, thereby killing L. monocytogenes). 
15 Conditions prior to consumption are not likely to change the number of L. monocytogenes (i.e., the 
organism will neither die off nor multiply). 
16 Conditions prior to consumption could result in an increase in the number of L. monocytogenes (i.e., the 
food will be held under conditions in which L. monocytogenes can multiply). 
17 n is the number of samples to be tested. 
18 c is the number of samples that can be positive. 
  49  Contains Nonbinding Recommendations 
 
G. Summary of Recommended Corrective Actions When You 
Detect Listeria spp. in an Environmental Sample 
 See Figure 1 in section XIII.E and Figure 2 in section XIII.F.1 for flow diagrams of examples 
applying the recommendations and example corrective action procedures discussed regarding 
your plant and your processing, including recommendations and example corrective action 
procedures for testing non-FCSs and FCSs, respectively, and for follow up actions based on the 
test results. Table 6 summarizes the recommended corrective actions when you detect Listeria 
spp. in an environmental sample taken from non-FCSs and FCSs. For each type of surface (i.e., 
non-FCS and FCS), Table 6 also compares the corrective actions for growth foods to the 
corrective actions for non-growth foods.  
 
Table 6.--Corrective Actions when Listeria species is found in an environmental sample 
  Non-FCS  Non-FCS  FCS  FCS 
Food supports  Food does not  Food supports  Food does not support 
growth  support  growth  growth* 
growth 
Routine    Clean and    Clean and    Clean and    Clean and sanitize 
sampling  sanitize area of  sanitize area  sanitize area of  area of positive 
positive #1  positive  of positive  positive    Retest during next 
  Retest during    Retest    Retest during  production cycle 
next production  during next  next production    Conduct 
cycle  production  cycle 
comprehensive 
cycle    Conduct  investigation 
comprehensive 
investigation 
Follow up    Intensified    Intensified    Intensified    Intensified cleaning 
sampling  cleaning and  cleaning and  cleaning and  and sanitizing (including 
positive #2  sanitizing  sanitizing   sanitizing  disassembly of 
(possibly    Intensified  (including  equipment) 
including  sampling and  disassembly of    Intensified sampling 
disassembly of  equipment) 
testing  and testing 
equipment)    Intensified    Consider hold and 
  Intensified  sampling and 
test 
sampling and  testing 
  Comprehensive 
testing    Hold and test 
investigation 
product  
  Reprocess, 
divert or destroy 
product on hold if 
there is positive 
product 
  Comprehensive 
investigation 
  50  Contains Nonbinding Recommendations 
 
  Non-FCS  Non-FCS  FCS  FCS 
Food supports  Food does not  Food supports  Food does not support 
growth  support  growth  growth* 
growth 
Follow up  Root cause  Root cause    Stop production    Intensified cleaning 
sampling  analysis  analysis  and consult  and sanitizing (including 
positive #3  experts for  disassembly of 
comprehensive  equipment) 
investigation    Intensified sampling 
  Intensified  and testing 
cleaning and    Hold and test product 
sanitizing 
  Expand 
(escalated, e.g., 
comprehensive 
steam equipment) 
investigation 
  Intensified 
  Hold and test product 
sampling and 
testing    Reprocess, divert or 
destroy positive product 
  Resume 
lots 
production with 
product hold and   
test until 3 
consecutive days 
of product and 
FCSs are negative 
Follow up        Stop production and 
sampling  consult experts for 
positive #4  comprehensive 
investigation 
 
* We recommend that corrective actions for non-growth foods specifically intended for 
establishments such as hospitals and nursing homes be similar to those for foods that 
support growth. 
H. Corrective Actions If You Detect Listeria monocytogenes on a 
Food-Contact Surface 
1.  Recommendations regarding your plant and your procedures 
If you detect L. monocytogenes on an FCS, we recommend that you follow a risk-based 
corrective action procedure that describes the steps to be taken, and assigns responsibility for 
taking those steps, to ensure that the cause of the contamination is identified and corrected. We 
specifically recommend that your corrective actions regarding your plant and your procedures 
include the recommendations in section XIII.F.1 of this guidance. The goal is to find the source 
of contamination and eliminate it. 
2.  Recommendations regarding an RTE food 
If you detect L. monocytogenes on an FCS, you should either reprocess with a validated 
listericidal control measure, divert to a use in which the food will not be consumed by humans or 
animals, send for use in food to be consumed by animals where appropriate, or destroy that lot 
of RTE food, and consider whether there is product in commerce that should be recalled. 
  51  Contains Nonbinding Recommendations 
 
I.  Records 
We recommend that you establish and maintain records of: 
  Your written procedures for environmental monitoring, including procedures for collecting 
samples, procedures for preparing environmental samples for analysis, your analytical 
methods for testing environmental samples for Listeria spp. or L. monocytogenes, and 
your corrective action procedures;  
  Any corrective actions that you take after detecting contamination (with Listeria spp. or L. 
monocytogenes) on an FCS or non-FCS; and 
  The results of any tests to detect Listeria spp. or L. monocytogenes on an FCS or non-
FCS.  
J. Relevant Sections of part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
environmental monitoring in your plant include 21 CFR 117.80(a)(5), 117.150, 117.155, and 
117.165 
XIV. Sampling and Testing of RTE Foods 
A. Periodic Sampling and Testing of RTE Foods to Verify Adequacy 
of Your Controls  
Periodic sampling and testing of RTE foods that you produce can provide a historical reference 
of performance for your production plant and verify the adequacy of your control of L. 
monocytogenes over time. We recommend that you test food products for L. monocytogenes 
rather than for Listeria spp. because of the risk to public health from L. monocytogenes in food. 
If you choose to test food for Listeria spp. and find it to be positive, we recommend you 
determine whether the Listeria spp. is L. monocytogenes or treat the food as if it were 
contaminated with L. monocytogenes. We recommend that you hold all product that is 
represented by the food you test, e.g., food lots produced from cleanup to cleanup.  
We recommend that you establish and implement a written procedure for the periodic collection 
of samples of your RTE food product, and for testing those samples for the presence of L. 
monocytogenes. We recommend that your written procedure include the frequency of sampling 
(e.g., monthly, quarterly) and the sampling plan. The frequency of sampling and the sampling 
plan will depend on many things, such as customer requirements, the risk of foodborne illness if 
the finished product is contaminated with L. monocytogenes, and the frequency of detection of 
Listeria spp. in environmental samples.  
For recommendations on corrective actions to take if you find L. monocytogenes in samples of 
an RTE food, see section XIV.B of this guidance.  
B. Corrective Actions If You Detect L. monocytogenes in an RTE 
Food 
If you detect L. monocytogenes in an RTE food, we recommend that: 
  52  Contains Nonbinding Recommendations 
 
  You reprocess with a validated listericidal control measure, divert to a use in which the 
food will not be consumed by humans or animals, send for use in food to be consumed 
by animals where appropriate, or destroy the lot(s) of RTE food in which L. 
monocytogenes has been detected. You should consider lots produced between two 
cleaning and sanitizing cycles to be implicated by the product positive; 
  You determine whether other lot(s) of food are potentially contaminated with L. 
monocytogenes and segregate and hold those lots of food. We recommend that you 
also review environmental monitoring results to determine if other lots could be 
contaminated. We recommend that you subject potentially contaminated lots to hold 
and test procedures (see our recommendations for hold and test procedures in section 
XIII.F.3 of this guidance). You should reprocess with a validated listericidal control 
measure, divert, or destroy any lot of RTE food in which L. monocytogenes is detected; 
  Your corrective actions regarding your plant and your procedures include intensified 
sampling and testing of FCSs and non-FCSs, followed by the corrective actions we 
discuss in sections XIII.E and XIII.F of this guidance, until you find the source of 
contamination and eliminate it; and 
  You determine whether food in commerce would be subject to a recall.  
C. Records 
We recommend that you establish and maintain records of: 
  Your written procedures for sampling and testing RTE food, including your sampling plan 
and procedures for collecting samples, procedures for preparing samples for analysis, 
your analytical methods for testing samples for L. monocytogenes, and your corrective 
action procedures;  
  Any corrective actions that you take after detecting contamination with L. 
monocytogenes in an RTE food; and 
  The results of any tests to detect L. monocytogenes in an RTE food.  
D. Relevant Sections of Part 117 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
sampling and testing of RTE food include 21 CFR 117.80(a)(5) and (6), 117.150, 117.155, and 
117.165. 
XV.  Analysis of Data for Trends 
A. Trends in Data Collected from Environmental Monitoring 
As discussed in section XIII.A, a well-designed environmental monitoring program promotes 
knowledge and awareness of the environmental conditions that could result in product 
contamination. The goal of an environmental monitoring program is to: 
  Verify the effectiveness of your control programs for L. monocytogenes; 
  Find L. monocytogenes and harborage sites if present in your plant; and 
  53  Contains Nonbinding Recommendations 
 
  Ensure that corrective actions have eliminated L. monocytogenes and harborage sites 
when found in your plant. 
 
To make the best use of the verification data that you collect through your environmental 
monitoring program, we recommend that you analyze the data you collect through your 
environmental monitoring program over time for trends that can help you to continuously 
improve sanitation conditions in your plant by reducing the percentage of overall positive 
environmental samples in your plant. This trend analysis could provide evidence that L. 
monocytogenes in your plant is not being controlled (e.g., if a resident strain has become 
established in a niche environment) so that you can take steps to control it. Examples of trends 
that could indicate that L. monocytogenes in your plant is not being controlled are: 
  Increases in positive environmental samples in particular sites or areas;  
  Finding Listeria in the same area on multiple but non-consecutive sampling occasions 
(e.g., positive one week and negative the next, appearing to be isolated positives); and 
  An increase in the percentage of overall positive environmental samples in the plant. 
Even if you have taken appropriate corrective actions for individual positive sites from a 
particular area, the continued finding of positive environmental samples in that area over time 
could indicate a continuing problem such as an unidentified harborage site. We recommend you 
conduct a more complete investigation to determine if further actions are warranted if your 
analysis of data for trends indicates a continuing problem in a particular area.  
If your trend analysis shows an increased incidence of Listeria species in the plant, we 
recommend that you conduct an investigation of the reasons and take appropriate corrective 
actions to reduce the incidence. 
B. Trends in Data Collected from Product Testing 
As discussed in section XIV, periodic sampling and testing of RTE foods that you produce can 
provide a historical reference of performance for your production plant and verify the adequacy 
of your control of L. monocytogenes over time. To make the best use of the verification data that 
you collect through your product testing program, we recommend that you analyze the data you 
collect through your product testing program over time for trends that can help you to 
continuously improve the performance of your production plant. As with the analysis of data 
collected from your environmental monitoring program, this trend analysis could provide 
evidence that L. monocytogenes in your plant is not being controlled so that you can take steps 
to control it. If your trend analysis shows an increased incidence of positive sample findings in 
product, we recommend that you conduct an investigation of the reasons and take appropriate 
corrective actions to reduce the incidence. 
C. Records 
We recommend that you establish and maintain a record of any trend analysis that you conduct. 
  54  Contains Nonbinding Recommendations 
 
XVI. Training  
Part 117 requires that all individuals engaged in manufacturing, processing, packing or holding 
food, (including temporary or seasonal personnel, or the supervisors of such individuals) receive 
training in the principles of food hygiene and food safety, including the importance of personal 
health and personal hygiene as appropriate to the food, the facility, and the individuals 
assigned duties (21 CFR 117.4(b)(2)). 
We recommend that you provide training in health and hygienic practices specific to control of 
L. monocytogenes for all personnel and contractors who enter production and storage areas 
(e.g., individuals who conduct production, maintenance, quality assurance, quality control, or 
warehousing operations). The training should emphasize each individuals role in control of 
L. monocytogenes  why that role is important, and managements expectations for adherence to 
the program. We also recommend that the training be conducted before the individual performs 
job activities, with refresher training on at least an annual basis. 
We recommend that personnel who supervise or are otherwise responsible for the activities 
listed below successfully complete training in the application of the principles of the practices 
recommended in this guidance to the control of L. monocytogenes in RTE food.  
  Establishing effective listericidal and listeristatic controls and ensuring that such controls 
consistently operate as intended;  
  Collecting and testing environmental samples and samples of RTE food products;  
  Determining and taking corrective actions; and  
  Establishing and using written sanitation procedures and conducting associated 
monitoring. 
Sections of part 117 that are relevant to the recommendations in this guidance regarding 
training include 21 CFR 117.4. 
XVII.   Procedures to Collect Samples, Prepare Samples 
for Analysis, and Test Samples for Listeria spp. or L. 
monocytogenes 
We recommend that you use the following procedures to collect samples, prepare samples for 
analysis, and test the prepared samples for the presence of Listeria spp. or L. monocytogenes: 
  Use the procedures described in Appendix 5 for preparing environmental samples for 
analysis.  
  Use FDAs Testing Methodology for Listeria species or L. monocytogenes in 
Environmental Samples (Ref. 60) for testing environmental samples. 
  Use the procedures described in FDAs Bacteriological Analytical Manual Online (BAM), 
Chapter 10  Listeria monocytogenes, Detection and Enumeration of Listeria 
monocytogenes in Foods (Ref. 56) for preparing food samples and testing them for the 
presence of L. monocytogenes.  
  55  Contains Nonbinding Recommendations 
 
You can conduct the tests yourself or use an outside commercial testing laboratory to conduct 
the tests. See our recommendations in section XIII.D.6 regarding the use of an outside 
commercial testing laboratory for testing. 
If you or an outside commercial testing laboratory use an analytical method other than those we 
recommend in this section, we recommend that the method be a written, scientifically valid 
method that is at least equivalent to the recommended method in accuracy, precision, and 
sensitivity for detecting Listeria spp. and L. monocytogenes. 
XVIII. Records  
For your convenience, in this section of this guidance we list the records that we have 
recommended throughout this guidance. 
  Your written program for equipment maintenance;  
  The following sanitation records: 
  Your written procedures for monitoring sanitation conditions and practices;  
o
  Your sanitation monitoring; and  
o
  Corrections of monitored sanitation conditions and practices that are not 
o
implemented in accordance with your written sanitation procedures  
  The following records regarding your raw materials and other ingredients: 
  Your list of ingredients and other raw materials for which contamination with L. 
o
monocytogenes is reasonably foreseeable;  
  Any written supplier program that you develop; 
o
  Documentation of the results of any audit of a supplier; 
o
  Any Certificate of Analysis or Certificate of Conformance (i.e., suppliers guarantee) 
o
that you rely on to control L. monocytogenes in raw materials or other ingredients;  
  Your written procedures for sampling and testing raw materials and other 
o
ingredients, including your sampling plan and procedures for collecting samples, 
preparing samples for analysis, and your analytical methods for testing samples for 
L. monocytogenes; and 
  The results of any tests to detect L. monocytogenes in a raw material or other 
o
ingredient. 
  The following records applicable to a listeristatic process control:  
  Process control parameters applicable to the listeristatic formulation, such as pH, 
o
water activity, and concentration of antimicrobial ingredient;  
  Equipment calibration;  
o
  Your validation of listeristatic process controls;  
o
  Your monitoring of listeristatic process control parameters (such as pH, water 
o
activity, and amount of antimicrobial ingredient added);  
  Your review of listeristatic process control records; and 
o
  Any corrective actions or corrections taken. 
o
  56  Contains Nonbinding Recommendations 
 
  The following records applicable to a listericidal process control;  
  All process control parameters for the listericidal process;  
o
  Equipment calibration;  
o
  Your validation of listericidal process controls;  
o
  Your monitoring of listericidal process control parameters (such as temperature, pH, 
o
water activity, and amount of antimicrobial ingredient added) 
  Your review of listericidal process control records; and 
o
  Any corrective actions or corrections taken. 
o
  The following records applicable to an environmental monitoring program: 
  Your written procedures for environmental monitoring, including procedures for 
o
collecting samples, procedures for preparing environmental samples for analysis, 
your analytical methods for testing environmental samples for Listeria spp. or L. 
monocytogenes, and your corrective action procedures;  
  Any corrective actions that you take after detecting contamination (with Listeria spp. 
o
or L. monocytogenes) on an FCS or non-FCS; and 
  The results of any tests to detect Listeria spp. or L. monocytogenes on an FCS or 
o
non-FCS. 
  The following records applicable to sampling and testing RTE food: 
  Your written procedures for sampling and testing RTE food, including your sampling 
o
plan and procedures for collecting samples, procedures for preparing samples for 
analysis, your analytical methods for testing samples for L. monocytogenes, and 
your corrective action procedures;  
  Any corrective actions that you take after detecting contamination with L. 
o
monocytogenes in an RTE food; and 
  The results of any tests to detect L. monocytogenes. 
o
We recommend that you review and update, as needed, your written procedures at least once a 
year.  
XIX. Glossary 
A. Terms Defined in 21 CFR part 117 
Acid foods or Acidified foods: Foods that have an equilibrium pH of 4.6 or below. 
Adequate: That which is needed to accomplish the intended purpose in keeping with good 
public health practice. 
Allergen cross-contact: The unintentional incorporation of a food allergen into a food. 
Correction: An action to identify and correct a problem that occurred during the production of 
food, without other actions associated with a corrective action procedure (such as actions to 
reduce the likelihood that the problem will recur, evaluate all affected food for safety, and 
prevent affected food from entering commerce). 
  57  Contains Nonbinding Recommendations 
 
Critical control point (CCP): A point, step, or procedure in a food process at which control can 
be applied and is essential to prevent or eliminate a food safety hazard or reduce such hazard 
to an acceptable level. 
Environmental pathogen: A pathogen capable of surviving and persisting with the 
manufacturing processing, packing, or holding environment such that food may be 
contaminated and may result in foodborne illness if that food is consumed without treatment to 
significantly minimize the environmental pathogen. Examples of environmental pathogens 
include Listeria monocytogenes and Salmonella spp. but do not include the spores of 
pathogenic spore forming bacteria. 
Facility: A domestic facility or foreign facility that is required to register under section 415 of the 
Federal Food, Drug, and Cosmetic Act, in accordance with the requirements of 21 CFR part 1, 
subpart H. 
Food: Includes (1) articles used for food or drink for man or other animals, (2) chewing gum, 
and (3) articles used for components of any such article and includes raw materials and 
ingredients. 
Food allergen: A major food allergen as defined in section 201(qq) of the Federal Food, Drug, 
and Cosmetic Act (e.g., any of the following: (1) Milk, egg, fish (e.g., bass, flounder, or cod), 
Crustacean shellfish (e.g., crab, lobster, or shrimp), tree nuts (e.g., almonds, pecans, or 
walnuts), wheat, peanuts, and soybeans. (2) A food ingredient that contains protein derived 
from a food specified in paragraph (1), except any highly refined oil derived from a food 
specified in paragraph (1) and any ingredient derived from such highly refined oil.) 
Food-contact surfaces (FCS): Those surfaces that contact human food and those surfaces 
from which drainage, or other transfer, onto the food or onto surfaces that contact the food 
ordinarily occurs during the normal course of operation. Food contact surfaces includes 
utensils and food-contact surfaces of equipment. 
Hazard: Any biological, chemical (including radiological), or physical agent that has the potential 
to cause illness or injury.  
Hazard requiring a preventive control: A known or reasonably foreseeable hazard for which a 
person knowledgeable about the safe manufacturing, processing, packing, or holding of food 
would, based on the outcome of a hazard analysis (which includes the severity of the illness or 
injury if the hazard were to occur and the probability that the hazard will occur in the absence of 
preventive controls) establish one or more preventive controls to significantly minimize or 
prevent the hazard in a food and components to manage those controls (such as monitoring, 
corrections or corrective actions, verification and records) as appropriate to the food, the facility 
and the nature of the preventive control and its role in the facilitys food safety system.  
Known or reasonably foreseeable hazard: A potential biological, chemical (including 
radiological), or physical hazard that is known to be, or has the potential to be, associated with 
the facility or the food. 
Lot: the food produced during a period of time and identified by an establishments specific 
code. 
  58  Contains Nonbinding Recommendations 
 
Microorganisms: Yeast, molds, bacteria, viruses, protozoa, and microscopic parasites and 
includes species that are pathogens. The term undesirable microorganisms includes those 
microorganisms that are pathogens, that subject food to decomposition, that indicate that food is 
contaminated with filth, or that otherwise may cause food to be adulterated. 
Monitor: To conduct a planned sequence of observations or measurements to assess whether 
a process, point, or procedure is under control and to produce an accurate record for use in 
verification.  
Pathogen: A microorganism of public health significance. 
Pest: Any objectionable animals or insects including birds, rodents, flies, and larvae. 
Plant: the building or structure or parts thereof, used for or in connection with the 
manufacturing, processing, packing, or holding of human food. 
Preventive controls: Those risk-based, reasonably appropriate procedures, practices, and 
processes that a person knowledgeable about the safe manufacturing, processing, packing, or 
holding of food would employ to significantly minimize or prevent the hazards identified under 
the hazard analysis that are consistent with the current scientific understanding of safe food 
manufacturing, processing, packaging, or holding at the time of the analysis. 
Preventive controls qualified individual (PCQI): A qualified individual who has successfully 
completed training in the development and application of risk-based preventive controls at least 
equivalent to that received under a standardized curriculum recognized as adequate by FDA or 
is otherwise qualified through job experience to develop and apply a food safety system. 
Qualified individual: A person who has the education, training, or experience (or a 
combination thereof) necessary to manufacture, process, pack, or hold clean and safe food as 
appropriate to the individuals assigned duties. A qualified individual may be, but is not required 
to be, an employee of the establishment. 
RTE (Ready-to-eat) food: Any food that is normally eaten in its raw state or any other food, 
including a processed food, for which it is reasonably foreseeable that the food will be eaten 
without further processing that would significantly minimize biological hazards. 
Sanitize: To adequately treat cleaned surfaces by a process that is effective in destroying 
vegetative cells of pathogens, and in substantially reducing numbers of other undesirable 
microorganisms, but without adversely affecting the product or its safety for the consumer. 
Significantly minimize: To eliminate or reduce to an acceptable level, including to eliminate. 
Validation: Obtaining and evaluating scientific and technical evidence that a control measure, 
combination of control measures, or the food safety plan as a whole, when properly 
implemented, is capable of effectively controlling the identified hazards. 
Verification: The application of methods, procedures, tests and other evaluations, in addition to 
monitoring, to determine whether a control measure or combination of control measures is or 
has been operating as intended and to establish the validity of the food safety plan. 
  59  Contains Nonbinding Recommendations 
 
B. Terms Defined for the Purpose of This Guidance 
Adequately reduce: capable of reducing the presence of L. monocytogenes to an extent 
sufficient to prevent illness.  
Certificate of Analysis: a document, provided for a food prior to or upon receipt of the food, 
that documents certain characteristics and attributes of the food. 
Certificate of Conformance: a suppliers guarantee stating that raw materials and ingredients 
conform to a product safety specification. 
Clean in place (CIP): The removal of soil from product contact surfaces in their process 
position by circulating, spraying, or flowing chemical solutions and water rinses onto and over 
the surfaces to be cleaned.  
 
Clean out of place (COP): A system (e.g., cleaning tanks) used to clean 
equipment parts, piping, etc. after disassembly. 
Control point (CP): Any step at which biological, physical, or chemical factors can be 
controlled.  
Cleaning: The removal of soil, food residue, dirt, grease or other objectionable matter. 
Control, Control measure: See Preventive controls 
Corrective action: An action to identify and correct a problem that occurred during the 
production of food, including actions associated with a corrective action procedure (such as 
actions to reduce the likelihood that the problem will recur, evaluate all affected food for safety, 
and prevent affected food from entering commerce).  
Environmental sample: A sample that is collected from a surface or area of the plant for the 
purpose of testing the surface or area for the presence of microorganisms, usually 
environmental pathogens. 
 
Food safety plan: A set of written documents that is based upon food safety principles and 
incorporates hazard analysis, preventive controls, and delineates monitoring, corrective action, 
and verification procedures to be followed, including a recall plan. 
Food Safety System: The result of the implementation of a food safety plan. 
HACCP, Hazard Analysis and Critical Control Point: A system which identifies, evaluates, 
and controls hazards that are significant for food safety.  
Hazard analysis: The process of collecting and evaluating information on hazards and 
conditions leading to their presence to decide which should be addressed through a preventive 
control. 
  60  Contains Nonbinding Recommendations 
 
High efficiency particulate air (HEPA) filter: an air filter that has an efficiency of 99.97 
percent to 99.99 percent when tested using the dioctylphthalate (DOP) test with a particle size 
of 0.3 microns. Such filters can remove all yeast, mold, bacteria and other particles that are 
larger than 0.3 microns. 
Hold and test procedures: procedures establishing the criteria for releasing product after 
receiving the results of tests conducted to determine the presence of a pathogen on an FCS. 
Lethality treatment: a process, including the application of an antimicrobial agent, that 
eliminates or reduces the number of pathogens on or in a product to make the product safe for 
human consumption.  
Listeria species (Listeria spp.): microorganisms within the genus Listeria, including the 
species L. monocytogenes. 
Listericidal control: a control that will consistently destroy viable cells of L. monocytogenes 
and consistently lead to a finished food that contains less than 0.04 colony forming units (CFU) 
of L. monocytogenes per gram (g) of food.  
Listeristatic formulation: pH less than or equal to 4.4; water activity less than or equal to 0.92; 
and formulations (including those established in whole or in part through processes such as 
fermentation or culturing) containing a combination of factors scientifically demonstrated to be 
effective in preventing growth. 
Non-food-contact surface (non-FCS) any surface that, under normal operating procedures, 
does not contact food or the food-contact surfaces of equipment. Examples of non-FCSs 
include, depending on the circumstances, equipment, vents, fixtures, drains, walls, floors, and 
employee clothing, shoes, and accessories.  
Operating limits: Criteria that could be more stringent than minimum or maximum values for 
process parameters and are established for reasons other than food safety.  
Prerequisite programs: Procedures, including CGMPs, that provide the basic environmental 
and operating conditions necessary to support the Food Safety Plan. 
Severity: The seriousness of the effects of a hazard.  
We, us, and our: the U.S. Food and Drug Administration.  
You: A person who is subject to part or all of part 117 and who manufactures, processes, 
packs, or holds RTE food. 
Zone means a designation about a surface or area reflecting how near that surface or area is to 
a ready-to-eat food and the risk the surface or area poses to ready-to-eat food if the surface or 
area is contaminated with L. monocytogenes. 
XX.  Table of Abbreviations 
Abbreviation  What It Means 
  61  Contains Nonbinding Recommendations 
 
Abbreviation  What It Means 
2003 Risk  Quantitative Assessment of the Relative Risk to Public Health 
Assessment  from Foodborne Listeria monocytogenes Among Selected 
Categories of Ready-to-Eat Foods 
ASHRAE  American Society of Heating Refrigerating and Air-Conditioning 
Engineers 
a   Water activity 
w
CCP  Critical control point 
CDC  Centers for Disease Control and Prevention 
CIP  Clean in place 
CFR  Code of Federal Regulations 
CGMP  Current good manufacturing practice 
COA  Certificate of Analysis 
COC  Certificate of Conformance 
Codex  Codex Alimentarius Commission 
COP  Clean out of place 
CP  Control point 
D/E broth  Dey-Engley broth 
EPA  U.S. Environmental Protection Agency 
EPIA  Egg Products Inspection Act 
FCS  Food-contact surface 
FDA  U.S. Food and Drug Administration 
FD&C Act  Federal Food, Drug, and Cosmetic Act 
FMIA  Federal Meat Inspection Act 
FSIS  Food Safety and Inspection Service of the U.S. Department of 
Agriculture 
  62  Contains Nonbinding Recommendations 
 
Abbreviation  What It Means 
FSIS Guidelines  FSIS Compliance Guideline: Controlling Listeria 
monocytogenes in Post-Lethality Exposed Ready-To-Eat Meat 
and Poultry Products 
HACCP  Hazard Analysis and Critical Control Point 
ICMSF  International Commission on Microbiological Specifications for 
Foods 
LM  Listeria monocytogenes 
LS  Listeria spp. 
NFCS, non-FCS  Non-food-contact surface 
PCHF   Hazard Analysis and Risk- Based Preventive Controls for 
Human Food  
PCQI  Preventive controls qualified individual 
RTE food  Ready-to-eat food 
Subpart B  21 CFR part 117, subpart B--Current Good Manufacturing 
Practice 
Subpart C  21 CFR part 117, subpart C--Hazard Analysis and Risk-Based 
Preventive Controls 
Subpart G  21 CFR part 117, subpart G--Supply-Chain Program 
USDA  U.S. Department of Agriculture 
 
XXI. References 
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future surveillance needs in Australia. The Medical journal of Australia 165(11-12):672-675. 
Ref. 2. de Valk H, Jacquet C, Goulet V, Vaillant V, Perra A, Simon F, Desenclos JC, Martin P. 
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disease bulletin 10(10):251-255. 
Ref. 3. Scallan E, Hoekstra R, Angulo F, Tauxe R, Widdowson M, Roy S, Jones J, Griffin P. 
2011. Foodborne illness acquired in the United States--major pathogens. Emerging Infectious 
Diseases 17(1):7-15 
  63  Contains Nonbinding Recommendations 
 
Ref. 4. Goulet V, Hebert M, Hedberg C, Laurent E, Vaillant V, De Valk H, Desenclos JC. 2012. 
Incidence of listeriosis and related mortality among groups at risk of acquiring listeriosis. Clinical 
infectious diseases : an official publication of the Infectious Diseases Society of America 
54(5):652-660. 
Ref. 5. Pouillot R, Hoelzer K, Jackson K, Henao O, Silk B. 2012. Relative risk of listeriosis in 
Foodborne Diseases Active Surveillance Network (FoodNet) sites according to age, pregnancy, 
and ethnicity. Clinical infectious diseases : an official publication of the Infectious Diseases 
Society of America 54 Supplement 5:S405-410. 
Ref. 6. Pouillot R, Hoelzer K, Chen Y, Dennis S. 2015. Listeria monocytogenes dose response 
revisited--incorporating adjustments for variability in strain virulence and host susceptibility. Risk 
Analysis 35(1):90-108. 
Ref. 7. U.S. Food and Drug Administration (FDA) and U.S. Food Safety and Inspection Service 
(FSIS). 2003. Quantitative Assessment of the Relative Risk to Public Health from Foodborne 
Listeria monocytogenes Among Selected Categories of Ready-to-Eat Foods. 
(http://www.fda.gov/Food/ScienceResearch/ResearchAreas/RiskAssessmentSafetyAssessment
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Ref. 8. Lyytikaninen O, Autio T, Maijala R. et al. 2000. An outbreak of Listeria monocytogenes 
serotype 3a infection from butter in Finland Journal of Infectious Diseases 181: 1838-1841. 
Ref. 9. FDA. 2012. Information on the recalled Jensen Farms whole cantaloupes. 
(http://www.fda.gov/Food/RecallsOutbreaksEmergencies/Outbreaks/ucm272372.htm). 
Ref. 10. FDA. 2013. FDA investigates a multi-state outbreak of Listeria monocytogenes linked to 
certain Crave Brothers farmstead classics cheeses. 
(http://www.fda.gov/Food/RecallsOutbreaksEmergencies/Outbreaks/ucm359588.htm), 2013 
Ref. 11. FDA. 2014. Notice of Opportunity for Hearing (NOOH) - Roos Foods Inc, 3/11/14. 
(Letter dated March 11, 2014, from Margaret A. Hamburg of FDA to Ana Roos of Roos Foods, 
Inc.). (http://www.fda.gov/regulatoryinformation/foi/electronicreadingroom/ucm388921.htm) 
Ref. 12. International Commission on Microbiological Specifications for Foods (ICMSF). 1996. 
Chapter 8. Listeria monocytogenes. In Microorganisms in Foods 5 - Characteristics of Microbial 
Pathogens. pp. 141-182. Blackie Academic & Professional, London.  
Ref. 13. Lou Y, Yousef AE. 1999. Characteristics of Listeria monocytogenes important to food 
processors. In Listeria, Listeriosis, and Food Safety, eds. ET Ryser and EH Marth. pp. 131-224. 
New York: Marcel Dekker, Inc. Ref. 14. El-Kest SE, Marth, EH. 1992. Freezing of Listeria 
monocytogenes and other microorganisms: a review. Journal of Food Protection. 55: 639-648. 
Ref. 15. Institute of Food Technologists. 2001. Evaluation and Definition of Potentially 
Hazardous Foods. IFT/FDA Contract No. 223-98-2333. 
(http://www.fda.gov/food/foodscienceresearch/safepracticesforfoodprocesses/ucm094141.htm)  
Ref. 16. Codex Alimentarius Commission. 2007. Guidelines on the application of the General 
Principles of Food Hygiene to the control of Listeria monocytogenes in foods. CAC/GL 61-2007. 
  64  Contains Nonbinding Recommendations 
 
Ref. 17. Sorrells KM, Enigl DC, Hatfield JR. 1989. Effect of pH, acidulant, time, and temperature 
on the growth and survival of Listeria monocytogenes. Journal of Food Protection 52 (8): 571-
573. 
Ref. 18. Petran RL, Zottola EA. 1989. A Study of factors affecting growth and recovery of 
Listeria monocytogenes Scott A. Journal of Food Science 54 (2): 458-460. 
Ref. 19. Tienungoon S, Ratkowsky DA, McMeekin TA, Ross T. 2000. Growth limits of Listeria 
monocytogenes as a function of temperature, pH, NaCl, and lactic acid. Applied and 
Environmental Microbiology 66 (11): 4979-4987. 
Ref. 20. Leistner L. 1995. Principles and applications of hurdle technology. In New Methods of 
Food Preservation, ed GW Gould. pp. 1-21. London: Blackie Academic & Professional. 
Ref. 21. Liewen MB. Marth, EH. 1985. Growth and inhibition of microorganisms in the presence 
of sorbic acid: a review. Journal of Food Protection 48:364-375. 
Ref. 22. Vermeulen A, Smigic N, Rajkovic A, Gysemans K, Bernaerts K, Geeraerd A, Van Impe 
J, Debevere J, Devlieghere F. 2007. Performance of a growthno growth model for Listeria 
monocytogenes developed for mayonnaise-based salads: influence of strain variability, food 
matrix, inoculation level, and presence of sorbic and benzoic acid. Journal of Food Protection 
70: 2118-2126. 
Ref. 23. Tassou CC, Samaras FJ, Arkoudelos JS, Mallidis CG. 2009. Survival of acid-adapted 
or non-adapted Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7, 
in traditional Greek salads, International Journal of Food Science & Technology 44: 279287. 
Ref. 24. Scott VN, Swanson KMJ, Freier TA, Pruett WP, Sveum WH, Hall PA, Smoot LA, Brown 
DG. 2005. Guidelines for conducting Listeria monocytogenes challenge testing of foods. Food 
Protection Trends 25 (11): 818-825. 
Ref. 25. National Advisory Committee on Microbiological Criteria for Foods. 2010. Parameters 
for determining inoculated pack/challenge study protocols. Journal of Food Protection 73 (1): 
140-202. 
Ref. 26. Gombas DE, Chen Y, Clavero RS, Scott VN. 2003. Survey of Listeria monocytogenes 
in ready-to-eat foods. Journal of Food Protection 66: 559-569.  
Ref. 27. J. Kozak, T. Balmer, R. Byrne, K. Fisher. 1996. Prevalence of Listeria monocytogenes 
in foods: incidence in dairy products. Food Control 7: 215-221. 
Ref. 28. CDC. 2015. Multistate Outbreak of Listeriosis Linked to Blue Bell Creameries Products 
(Final Update). (http://www.cdc.gov/listeria/outbreaks/ice-cream-03-15/) 
Ref. 29. Weller D, Shiwakoti S, Bergholz P, Grohn Y, Wiedmann M, Strawn LK. 2016. Validation 
of a previously developed geospatial model that predicts Listeria monocytogenes prevalence for 
New York State produce fields. Applied and Environmental Microbiology 82(3), 797-807. 
Ref. 30. Weller D, Wiedmann M, Strawn LK. 2015. Spatial and temporal factors associated with 
an increased prevalence of Listeria monocytogenes in spinach fields in New York State. Applied 
and Environmental Microbiology 81 (17), 6059-6069. 
  65  Contains Nonbinding Recommendations 
 
Ref. 31. Weller D, Wiedmann M, Strawn LK. 2015. Irrigation Is significantly associated with an 
increased prevalence of Listeria monocytogenes in produce production environments in New 
York State. Journal of Food Protection 78 (6), 1132-1141. 
Ref. 32. National Advisory Committee on Microbiological Criteria for Foods. 1991. Listeria 
monocytogenes. Recommendations by the National Advisory Committee on Microbiological 
Criteria for Foods. International Journal of Food Microbiology 14 (3-4): 185-246.  
Ref. 33. Nightingale KK, Schukken YH, Nightingale CR, Fortes ED, Ho AJ, Her Z, Grohn YT, 
McDonough PL, Wiedmann M. 2004. Ecology and transmission of Listeria monocytogenes 
infecting ruminants and in the farm environment. Applied and Environmental Microbiology 70: 
44584467. 
Ref. 34. Nightingale KK, Windham K , Wiedmann M. 2005. Evolution and molecular phylogeny 
of Listeria monocytogenes isolated from human and animal listeriosis cases and foods. Journal 
of Bacteriology 187: 55375551. 
Ref. 35. Crepet A, Albert I, Dervin C, Carlin F. 2007. Estimation of microbial contamination of 
food from prevalence and concentration data: application to Listeria monocytogenes in fresh 
vegetables. Applied and Environmental Microbiology 73: 250-258. 
Ref. 36. Fenlon DR, Wilson J, Donachie W. 1996. The incidence and level of Listeria 
monocytogenes contamination of food sources at primary production and initial processing. 
Journal of Applied Bacteriology 81 (6): 641-650.  
Ref. 37. Fenlon DR. 1999. Listeria monocytogenes in the natural environment. Eds. ET Ryser 
and EH Marth. pp. 21-37. New York: Marcel Dekker, Inc. . 
Ref. 38. Carpentier B, Cerf O. 2011. Persistence of Listeria monocytogenes in food industry 
equipment and premises. International Journal of Food Microbiology 145: 1-8. 
Ref. 39. Miller, AJ, Call, JE, Eblen BS. 1997. Growth, injury, and survival potential of Yersinia 
enterocolitica, Listeria monocytogenes, and Staphylococcus aureus in brine chiller conditions. 
Journal of Food Protection, 60: 1334-1340. 
Ref. 40. Golden DA, Beuchat LR, Brackett, RE. 1988. Inactivation and injury of Listeria 
monocytogenes as affected by heating and freezing. Food Microbiology 5:17-23. 
Ref. 41. Conner, DE, Scott, VN, Bernard, DT. 1990. Growth, inhibition, and survival of Listeria 
monocytogenes as affected by acidic conditions. Journal of Food Protection 53: 652-655. 
Ref. 42. Doyle ME, Mazzotta AS, Wang T, Wiseman DW, Scott VN. 2001. Heat resistance of 
Listeria monocytogenes. Journal of Food Protection 64 (3): 410-429. 
Ref. 43. Tompkin RB, Scott VN, Bernard DT, Sveum WH, Gombas KS. 1999. Guidelines to 
prevent post-processing contamination from Listeria monocytogenes. Dairy, Food and 
Environmental Sanitation 19 (8): 551-562. 
Ref. 44. Tompkin RB. 2002. Control of Listeria monocytogenes in the food-processing 
environment. Journal of Food Protection 65 (4): 709-725. 
  66  Contains Nonbinding Recommendations 
 
Ref. 45. Moretro T, Lansgrund S. 2004. Listeria monocytogenes: Biofilm formation and 
persistence in food processing environments. Biofilms 1: 107-121. 
Ref. 46. Gall K, Scott VN, Collette R, Jahncke M, Hicks D, Wiedmann M. 2004. Implementing 
targeted good manufacturing practices and sanitation procedures to minimize Listeria 
contamination of smoked seafood products. Food Protection Trends 24 (5): 302-315. 
Ref. 47. Kornacki JL. 2005. Controlling Listeria in the food processing environment. Food 
Technology 59 (11): 36-42. 
Ref. 48. Scott VN, Wiedmann M, Collette R, Jahncke ML, Gall K. 2005. Guidelines for Listeria 
testing of environmental, raw product and finished product samples in smoked seafood 
processing facilities. Food Protection Trends 25 (1): 23-24. 
Ref. 49. FDA. 2011. Fish and Fisheries Products Hazards and Controls Guidance, 4th ed. 
(http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Seaf
ood/ucm2018426.htm)  
Ref. 50. FDA. 1998. Guidance for Industry: Guide to Minimize Microbial Food Safety Hazards 
for Fresh Fruits and Vegetables. 
(http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/Pro
duceandPlanProducts/ucm064574.htm) 
Ref. 51. Fatemi P. Frank JF. 1999. Inactivation of Listeria monocytogenes/Pseudomonas 
biofilms by peracid sanitizers. Journal of Food Protection 62(7):761-5. 
Ref. 52. FSIS. 2014. Best practices guidance for controlling Listeria monocytogenes in retail 
delicatessens. (http://www.fsis.usda.gov/wps/portal/fsis/topics/regulatory-
compliance/compliance-guides-index#Listeria) 
Ref. 53. Codex Alimentarius Commission 2008. Guidelines for the Validation of Food Safety 
Control Measures, CAC/GL 69-2008. 
(www.codexalimentarius.org/input/download/standards/11022/CXG_069e.pdf) 
Ref. 54.FDA. 2015. Grade A Pasteurized Milk Ordinance. 
(http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Milk/
ucm2007966.htm) 
Ref. 55. FDA. 2013. Food Code. 
(http://www.fda.gov/Food/GuidanceRegulation/RetailFoodProtection/FoodCode/ucm374275.htm
) 
Ref. 56. Hitchins AD (ret.), Jinneman K, Chen, Y. 2003. U.S. Food and Drug Administration, 
Bacteriological Analytical Manual, Ch. 10, Detection and enumeration of Listeria 
monocytogenes in foods. 
(http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm071400.htm) 
Ref. 57. Ryser E, Donnelly C. 2013. Listeria. In Compendium of Methods for the Microbiological 
Examination of Foods, eds. Stephanie Doores, Yvonne Salfinger, Mary Lou Tortorello. 
Washington, DC: American Public Health Association. 
(http://ajph.aphapublications.org/doi/pdf/10.2105/MBEF.0222.040)  
  67  Contains Nonbinding Recommendations 
 
Ref. 58. ICMSF. 2002. Chapter 11. Sampling to assess control of the environment. In 
Microorganisms in Foods 7: Microbiological Testing in Food Safety Management. pp. 199-224. 
Kluwer Academic/ Plenum Publishers, NY.  
Ref. 59. ICMSF. 2011. Chapter 4. Verification of environmental control. In Microorganisms in 
Foods 8: Use of Data from Assessing Process Control and Product Acceptance. pp 41- 45. 
Springer. NY. 
Ref. 60.FDA. 2015. Testing Methodology for Listeria species or L. monocytogenes in 
Environmental Samples. 
(http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm114664.htm) 
Ref. 61. FSIS. 2014. Compliance Guideline: Controlling Listeria monocytogenes in Post-
Lethality Exposed Ready-To-Eat Meat and Poultry Products, 
(http://www.fsis.usda.gov/wps/portal/fsis/topics/regulatory-compliance/compliance-guides-
index#Listeria) 
Ref. 62. ICMSF. 2002. Chapter 8. Selection of cases and attributes plans. In Microorganisms in 
Foods 7: Microbiological Testing in Food Safety Management. pp. 145-165. Kluwer 
Academic/Plenum publishers.  
Ref. 63. FDA. 2015. Microbiological Methods & Bacteriological Analytical Manual (BAM). 
(http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm114664.htm) 
 
  68  Contains Nonbinding Recommendations 
 
Appendix 1.  Potential Sources of L. monocytogenes 
Category  Description of  Potential Sources of L. monocytogenes* 
Category 
A  Ingredients    Raw foods, such as: 
  Raw meat, poultry, and seafood 
o
  Raw milk  
o
  Raw produce 
o
B  Processing    Compressed air 
materials    Ice 
  Brine solutions used in chilling refrigerated RTE foods 
C  Contact    Fibrous and porous-type conveyor belts 
surfaces for    Filling and packaging equipment 
RTE foods    Belts, peelers, and collators 
  Containers, bins, tubs and baskets 
  Slicers, dicers, shredders and blenders 
  Utensils 
  Gloves  
D  Surfaces that    In-floor weighing equipment 
generally do    Cracked hoses 
not contact    Hollow rollers for conveyances 
RTE foods     Equipment framework 
  Wet, rusting, or hollow framework 
  Open bearings within equipment 
  Poorly maintained compressed air filters 
  Condensate drip pans 
  Motor housings 
  Maintenance tools (e.g., wrenches and screw drivers) 
  Forklifts, hand trucks, trolleys, and racks 
  On/off switches 
  Vacuum cleaners and floor scrubbers 
  Trash cans and other such ancillary items 
  Tools for cleaning equipment (e.g., brushes and scouring pads) 
  Spiral freezers/blast freezers 
  Ice makers 
  Aprons 
E  Plant    Floors, especially cracks and crevices 
environment    Walls  
  Drains 
  Ceilings, overhead structures, and catwalks 
  Wash areas (e.g., sinks), condensate, and standing water 
  Wet insulation in walls or around pipes and cooling units 
  Rubber seals around doors, especially in coolers 
  Metal joints, especially welds and bolts 
  Contents of vacuum cleaners 
* Adapted from Ref. 43.
  69  Contains Nonbinding Recommendations 
 
Appendix 2. Examples of Scenarios That Could Lead to 
Contamination of RTE Foods With L. monocytogenes 
The examples below of scenarios that could lead to contamination of RTE foods with L. 
monocytogenes are adapted from Ref. 43 and Ref. 47. 
  A packaging line is moved or modified significantly. 
  Used equipment is brought from storage or another plant and installed into the process 
flow. 
  An equipment breakdown occurs. 
  Construction or major modifications are made to an area where RTE foods are 
processed or exposed (e.g., replacing refrigeration units or floors, replacing or building 
walls, modifications to sewer lines). 
  A new employee, unfamiliar with the operation and L. monocytogenes controls, has 
been hired to work in, or to clean equipment in, the area where RTE foods are 
processed or exposed. 
  Personnel who handle RTE foods touch surfaces or equipment likely to be contaminated 
(e.g., floor, trash cans) and do not change gloves or follow other required procedures 
before handling the food. 
  Periods of heavy production make it difficult to clean the floors of holding coolers as 
scheduled. 
  A drain backs up. 
  Product is caught or hung-up on equipment. (Stagnant product in a system can be a 
major site of microbial growth during production.)  
  Raw or under-processed foods are placed in an area designated for cooked foods.  
  Frequent product changes on a packaging line cause you to change packaging film, 
labels, forming pockets or molds, line speeds, etc. 
  Personnel are used interchangeably for packaging raw and cooked foods. 
  Increased production causes you to perform wet cleaning of lines that have been taken 
down from production in the same room as lines that are running product. 
  Heat exchangers have become compromised (e.g., with pinholes).  
  Equipment parts, tubs, screens, etc. are cleaned on the floor. 
  Waste bins in the RTE area are not properly maintained, cleaned and sanitized. 
  Personnel handling RTE foods come into contact with these items and then contaminate 
the foods and/or food contact surfaces.  
  Re-circulating pumps and lines are not cleaned and sanitized. 
  Indiscriminate use of high-pressure hoses in cleaning. 
  Inappropriate use of footbaths in dry processing areas. 
  70  Contains Nonbinding Recommendations 
 
  Water is sprayed on wheels on transport cars when in-process product is stored near the 
wheels. 
 
 
  71  Contains Nonbinding Recommendations 
 
Appendix 3.  Schematics Relevant to Recommended Plant 
Design 
 
Figure 1.--Air Flow 
Recommended Not Recommended
ARraewa AAIRIR ProAcreesased ARraewa AIR ProAcreesased
Raw Area has Negative Air Pressure Raw Area has Positive Air Pressure
   
  72  Contains Nonbinding Recommendations 
 
Figure 2.-- Separation of Raw and RTE Areas by Partitions 
   
  73  Contains Nonbinding Recommendations 
 
Figure 3.-- Separation of Raw and RTE Areas by Air Flow 
   
  74  Contains Nonbinding Recommendations 
 
Appendix 4.  Recommended Schedules for Routine 
Cleaning and Sanitizing 
A. Food-Contact Surfaces 
In general, we recommend that you clean and sanitize FCSs at least once every 24 hours, with 
sanitizing or sanitary wipe-downs as needed. However, you may establish the 
cleaning/sanitizing schedule for any particular surface based on the characteristics of your 
products and processes. If you clean and sanitize less frequently than every 24 hours, you 
should validate the frequency of your cleaning and sanitizing by microbial testing and not allow 
the reduced frequency of cleaning and sanitizing to impact the microbiological condition of the 
production equipment.  
If the results of environmental monitoring or product testing indicate a problem, you should 
consider increasing the frequency of cleaning and sanitizing as part of an overall corrective 
action procedure. 
B. Non-Food-Contact Surfaces 
The recommendations in the following table are adapted from Ref. 43.  
If the results of environmental monitoring or product testing indicate a problem, you should 
consider increasing the frequency of cleaning and sanitizing as part of an overall corrective 
action procedure. 
 
  75  Contains Nonbinding Recommendations 
 
Surface, Area, or Equipment  Frequency of Cleaning and Sanitizing a 
Drains and floors  Daily 
Waste containers  Daily 
Cleaning tools (e.g., mops, brushes)  Daily 
Surfaces that have a greater potential to  Daily 
become a source of L. monocytogenes 
contamination (e.g., surfaces likely to be 
touched by personnel who touch product or 
FCSs during operations, or areas where there 
could be a build-up of moisture or product 
residue) 
Condensate drip pans  Weekly/Monthly 
Motor housings, external surfaces of enclosed  Weekly 
processing systems 
Overhead piping, ceilings and wallsb  Weekly/Monthly 
Coolers  Weekly/Monthly 
Freezers (e.g., spiral, blast, tunnel) containing  Semi-annually 
exposed RTE foodsc 
HVAC  Weekly/Monthly 
Interiors of Ice Makers  Semi-annually 
 
a Production environments vary, along with the soil characteristics of the product being 
produced. It may be appropriate to increase or decrease cleaning frequencies depending on the 
specific circumstances of the product area. 
 
b We recommend that that you clean and sanitize some walls and ceilings (e.g., those in close 
proximity to a production line) at the same time as the production equipment (e.g., daily). 
c If the manufacturer of the equipment recommends cleaning on a more frequent basis, we 
recommend that you increase this frequency to match the recommendations of the 
manufacturer.    
  76  Contains Nonbinding Recommendations 
 
Appendix 5.  Recommended Procedures for Collecting 
Environmental Samples  
We recommend that you use FDAs Testing Methodology for Listeria species or L. 
monocytogenes in Environmental Samples (version 1, Oct 2015) (Ref. 60). We describe 
additional recommendations related to environmental sampling in the remainder of this 
appendix. Because we periodically add and update microbiological methods on our Web site 
"Microbiological Methods & Bacteriological Analytical Manual (BAM)" (Ref. 63), we recommend 
that you periodically check that Web site for any updates to the procedure described in this 
appendix. 
Laboratory analysis of samples should only be conducted by persons with appropriate 
microbiological training or experience. Listeria monocytogenes infection can cause serious 
illness and death, including fetal death. We recommend that pregnant women and persons who 
are immunocompromised because of illness, medication, or advanced age avoid working with 
this organism. Contaminated equipment and media should be sterilized before disposal or 
reuse. 
A.  Collecting Samples from Surfaces (Including Both Food-Contact 
Surfaces and Non-Food-Contact Surfaces)  
The two most common methods to collect samples are surface sponging and swabbing. In 
general, we recommend that you sample most surfaces using surface sponging, except for 
small or hard-to-access surfaces where swabbing works better. Another method used for 
sampling difficult to clean areas is liquid rinse samples.  
The sample size depends on the methodology being used; to the extent practical this should be 
from as large an area as possible (e.g., 1 ft by 1 ft), except where sampling small nooks and 
crannies that can serve as harborage sites. Use swabbing or a rinse method to sample areas 
such as head screws, small water collection points, screw holes, threaded surfaces or interior 
corners of equipment.  
We recommend that you wear sterile gloves. For wet surfaces, wipe and absorb moisture and 
wet product and residue with the sponge. For dry surfaces, wipe the sample site area with a 
sponge or swab moistened with D/E broth. Use a systematic technique that swabs in multiple 
directions. Add more buffer if necessary.  
We recommend that you package properly identified samples with ice packs and ship them 
under refrigerated conditions within 24 hours after sampling. We recommend that the maximum 
time frame between sampling and receipt at an external or internal pathogen testing laboratory 
be 48 hours. You should not freeze samples.  
B. Collecting Rinse Samples 
To collect samples using a rinse technique, add small pieces from equipment (such as screws, 
nuts or gaskets) directly to the bag containing D/E broth and hand massage the bag for 
sufficient time to remove soil and residues (approximately 1 min.). Then aseptically remove the 
items from the bag and subject the broth to analysis. 
  77  Contains Nonbinding Recommendations 
 
In some situations involving small cracks and crevices, try using a plastic bulb transfer pipette 
and tubes containing 10 mL sterile D/E broth. Pull the D/E broth into the pipette bulb and 
transfer the D/E broth to the crack or crevice, then pull it back into the bulb. Repeat this several 
times to thoroughly rinse the crack or crevice. Then aseptically transfer the D/E broth to a sterile 
container for further analysis. 
C. Collecting Liquid Samples (Including Floor Drain Effluents) 
We recommend that you use a sterile beaker or similar container to collect 110 + 5 ml of liquids, 
where possible, such as drainage effluents, standing water, melt water from thawed processing 
ice, and vacuum or drip pan condensate. We recommend that you immediately transfer the 
collected sample into a sterile screw-capped bottle and then chill and store the bottle at 5 
degrees C (41 degrees F), including during transport to the testing laboratory. 
D. Compositing Samples Collected from Sponges or Swabs 
A common technique is to combine analytical portions from several samples and analyze the 
mixture of the portions (which is referred to as a composite). A recommended composite 
scheme can be used to composite up to 5 sponges or swabs. Individual samples are subject to 
primary enrichment as described in Testing Methodology for Listeria species or L. 
monocytogenes in Environmental Samples (version 1, Oct 2015). During the transfer from the 
primary enrichment to the secondary enrichment, 0.1  0.02 ml of each primary enrichment is 
transferred into an appropriate amount of secondary enrichment broth (i.e., the volume required 
for one sample times the number of samples) (e.g., for five sponges it would be 0.1 ml from 
each primary enrichment into 5 x 10 mL of secondary enrichment broth). The reserve portion of 
the primary enrichment can be stored at refrigeration temperature for up to 48 h, and used to 
analyze for Listeria species in each individual samples if the composite is determined to be 
presumptive positive. 
E. Preparing Samples Collected from Liquids 
For larger samples (e.g., 100 mL or greater), we recommend that you filter 100 ml of the 
collected liquid through one or more sterile 0.45 micron pore-diameter filters as soon as 
possible after sample collection. If particulate content is high (e.g., judging from the sample 
turbidity), we recommend that you pass the liquid through a sterile glass pre-filter before the 
0.45 micron filter. Rinse the retentate on the filter plus any pre-filter with 5-10 ml of D/E broth to 
remove any residual inhibitory substances. If necessary, excise the filters from the funnel 
devices, using sterile scalpels. Put each filter and the pre-filter, if any, in a sterile bag (if you will 
use a Stomacher) or in a sterile container (such as a blender jar, if you use a blender). Add 225 
mL of UVM broth, and follow procedures in Testing Methodology for Listeria species or L. 
monocytogenes in Environmental Samples (version 1, Oct 2015) beginning with incubation of 
the primary enrichment. 
 
For small volumes of liquid samples, we recommend that you add the liquid sample to 225 mL 
of UVM broth, and follow procedures in Testing Methodology for Listeria species or L. 
monocytogenes in Environmental Samples (version 1, Oct 2015) beginning with incubation of 
the primary enrichment. 
 
  78  Contains Nonbinding Recommendations 
 
Note: If composites are made from the filters, cut filter and any pre-filter in half using sterile 
instruments. Use one half of each filter to form a composite and retain the other half at 5 
degrees C (41 degrees F) as a reserve for analysis if the composite is positive for Listeria spp.  
F. Sample Analysis  
See Testing Methodology for Listeria species or L. monocytogenes in Environmental Samples 
(version 1, Oct 2015). 
 
 
 
 
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