#209 
 
 
Guidance for Industry 
 
 
The Judicious Use of Medically Important 
Antimicrobial Drugs in Food-Producing Animals 
 
Submit comments on this guidance at any time.  Submit written comments to the Division 
of Dockets Management (HFA-305), Food and Drug Administration, 5630 Fishers Lane, 
Room 1061, Rockville, MD 20852.  Submit electronic comments on the guidance at 
http://www.regulations.gov.  All written comments should be identified with the Docket 
No. FDA-2010-D-0094.  
For further information regarding this document, contact William T. Flynn, Center for 
Veterinary Medicine (HFV-1), Food and Drug Administration, 7519 Standish Place, 
Rockville, MD 20855, 240-276-9084. E-mail: william.flynn@fda.hhs.gov.   
Additional copies of this guidance document may be requested from the Communications 
Staff (HFV-12), Center for Veterinary Medicine, Food and Drug Administration, 7519 
Standish Place, Rockville, MD  20855, and may be viewed on the Internet at either 
http://www.fda.gov/AnimalVeterinary/GuidanceComplianceEnforcement/GuidanceforIndu
stry/default.htm or http://www.regulations.gov. 
 
 
 
 
U.S. Department of Health and Human Services  
Food and Drug Administration  
Center for Veterinary Medicine  
April 13, 2012 
 
 
  Contains Nonbinding Recommendations 
 
 
 
TABLE OF CONTENTS 
 
I.  Executive Summary ........................................................................................................... 3 
 
II.  Introduction ...................................................................................................................... 4 
 
III.  Key Reports and Peer-Reviewed Scientific Literature on the Issue ............................... 5 
 
IV.  Strategies for Controlling Antimicrobial Resistance Are Needed ................................ 17 
 
V.  Current Regulatory Framework ..................................................................................... 18 
 
VI.  Status of FDAs Current Activities............................................................................... 19 
 
VII.  Recommended Principles Regarding Judicious Use in Animals ................................ 20 
 
VIII.  Conclusion ................................................................................................................. 22 
 
IX.  References..................................................................................................................... 23 
 
  2  Contains Nonbinding Recommendations 
 
 
The Judicious Use of Medically Important Antimicrobial Drugs 
in Food-Producing Animals 
This guidance represents the Food and Drug Administrations (FDA) current thinking on 
this topic. It does not create or confer any rights for or on any person and does not operate to 
bind FDA or the public. You can use an alternative approach if the approach satisfies the 
requirements of the applicable statutes and regulations. If you want to discuss an alternative 
approach, contact the FDA staff responsible for implementing this guidance. If you cannot 
identify the appropriate FDA staff, call the number listed on the previous page of this 
guidance. 
 
I.  Executive Summary 
Antimicrobial drugs have been widely used in human and veterinary medicine for more 
than 50 years, with tremendous benefits to both human and animal health.  The development 
of resistance to this important class of drugs, and the resulting loss of their effectiveness as 
antimicrobial therapies, poses a serious public health threat.  Misuse and overuse of 
antimicrobial drugs creates selective evolutionary pressure that enables antimicrobial 
resistant bacteria to increase in numbers more rapidly than antimicrobial susceptible bacteria 
and thus increases the opportunity for individuals to become infected by resistant bacteria.  
Because antimicrobial drug use contributes to the emergence of drug resistant organisms, 
these important drugs must be used judiciously in both animal and human medicine to slow 
the development of resistance.  Efforts have been made to promote the judicious use of these 
drugs in humans (see http://www.cdc.gov/getsmart/index.html) as well as in animals (see 
http://www.avma.org/issues/default.asp).  Using these drugs judiciously means that 
unnecessary or inappropriate use should be avoided.  The focus of this document is on the 
use of medically important antimicrobial drugs1 in food-producing animals.  Based on a 
consideration of the available scientific information, FDA is providing a framework for the 
voluntary adoption of practices to ensure the appropriate or judicious use of medically 
important antimicrobial drugs in food-producing animals.  This framework includes the 
principles of phasing in such measures as 1) limiting medically important antimicrobial drugs 
to uses in food-producing animals that are considered necessary for assuring animal health; 
and 2) limiting such drugs to uses in food-producing animals that include veterinary 
oversight or consultation.  Developing strategies for reducing antimicrobial resistance is 
critically important for protecting both public and animal health.  Collaboration involving the 
public, the public health, animal health, and animal agriculture communities on the 
development and implementation of such strategies is needed to assure that the public health 
is protected while also assuring that such strategies are feasible and that the health needs of 
animals are addressed.   
                                                 
1 The term medically important antimicrobial drugs generally refers to antimicrobial drugs that are 
important for therapeutic use in humans.   
  3  Contains Nonbinding Recommendations 
 
 
FDAs guidance documents, including this guidance, do not establish legally 
enforceable responsibilities. Instead, guidances describe the Agencys current 
thinking on a topic and should be viewed only as recommendations, unless specific 
regulatory or statutory requirements are cited. The use of the word should in 
Agency guidances means that something is suggested or recommended, but not 
required. 
 
II.  Introduction 
Antimicrobial resistance2, and the resulting failure of antimicrobial therapies in 
humans, is a mounting public health problem of global significance. This phenomenon is 
driven by many factors including the use of antimicrobial drugs in both humans and 
animals.  In regard to animal use, this document addresses the use of medically important 
antimicrobial drugs in food-producing animals for production or growth-enhancing 
purposes.  These uses, referred to as production3 uses throughout this document, are 
typically administered through the feed or water on a herd- or flock-wide basis and are 
approved for such uses as increasing rate of weight gain or improving feed efficiency.  
Unlike other uses of these drugs in animals (e.g., for the treatment, control, and prevention 
of disease), these production uses are not intended to manage a specific disease that may 
be ongoing or at risk of occurring, but rather are expressly indicated and used for the 
purpose of enhancing the production of animal-derived products (e.g., increasing rate of 
weight gain or improving feed efficiency).  This document summarizes some of the key 
reports and scientific literature related to the use of antimicrobial drugs in animal 
agriculture and outlines FDAs current thinking on strategies for assuring that medically 
important antimicrobial drugs are used judiciously in food-producing animals in order to 
help minimize antimicrobial resistance development.  In finalizing this guidance, FDA has 
considered comments that were submitted to the docket, and other relevant information.  If 
you have additional relevant information, please submit it to the docket at any time.  We 
are particularly interested in any new information regarding the use of medically important 
antimicrobials in food-producing animals and its impact on the development of drug-
resistant bacteria.   
 
                                                 
2 The term antimicrobial refers broadly to drugs with activity against a variety of microorganisms including 
bacteria, viruses, fungi, and parasites.  Antimicrobial drugs that have specific activity against bacteria are 
referred to as antibacterial or antibiotic drugs.  However, the broader term antimicrobial, commonly used in 
reference to drugs with activity against bacteria, is used in this document interchangeably with the terms 
antibacterial or antibiotic.  Antimicrobial resistance is the ability of bacteria or other microbes to resist the 
effects of a drug.  Antimicrobial resistance, as it relates to bacterial organisms, occurs when bacteria change 
in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to treat 
bacterial infections. 
3 Production uses are also referred to as nontherapeutic or subtherapeutic uses, terms that we believe lack 
sufficient clarity.   
  4  Contains Nonbinding Recommendations 
 
 
III.  Key Reports and Peer-Reviewed Scientific Literature on the Issue 
Questions regarding the use of antimicrobial drugs in food-producing animals have 
been raised and debated for many years.  A variety of recognized international, 
governmental, and professional organizations have studied the issue.  We have briefly 
summarized below the findings and recommendations from some of the notable reports that 
have addressed this issue over the past 40 years.  These reports provide context to FDAs 
current thinking on this issue, and highlight the longstanding concerns that have been the 
subject of discussion in the scientific community as a whole.   
We have also provided a list below of some of the more recent primary scientific 
literature that FDA has considered.  This is not intended to represent an exhaustive 
summary of the scientific literature, but rather to highlight some of the more recent 
scientific research related to the use of antimicrobial drugs in animal agriculture and the 
impact of such use on antimicrobial resistance.  We acknowledge that a significant body of 
scientific information exists, including some information that may present equivocal 
findings or contrary views.   
Unless otherwise indicated, the page numbers cited in this section refer to the 
relevant page numbers in the referenced report.  A complete list of the reports summarized 
in this section is provided at Section IX of this document. 
Reports Prepared by Various International, Governmental, and Professional 
Organizations 
1969 Report of the Joint Committee on the Use of Antibiotics in Animal Husbandry and 
Veterinary Medicine 
In July 1968, a Joint Committee was established in the United Kingdom to obtain 
information regarding the use of antibiotics in animal husbandry and veterinary medicine, 
particularly with respect to antibiotic resistance.  This report, often referred to as the 
Swann Report, was presented to Parliament in November 1969 by the Secretary of State 
for Social Services, the Secretary of State for Scotland, the Minister of Agriculture, 
Fisheries and Food, and the Secretary of State for Wales.  The report concluded that the 
administration of antimicrobials to food-producing animals, particularly at subtherapeutic 
levels, poses a hazard to human and animal health.  
The report stated, It is clear that there has been a dramatic increase over the years in 
the numbers of strains of enteric bacteria of animal origin which show resistance to one or 
more antibiotics.  Further, these resistant strains are able to transmit this resistance to other 
bacteria.  This resistance has resulted from the use of antibiotics for growth promotion and 
other purposes in farm livestock (Ref. 1, p. 60).  The report also noted, There is ample 
and incontrovertible evidence to show that man may commonly ingest enteric bacteria of 
animal origin (Ref. 1, p. 60).   
  5  Contains Nonbinding Recommendations 
 
 
The report provided a number of recommendations including that only antimicrobials 
which "have little or no application as therapeutic agents in man or animals and will not 
impair the efficacy of a prescribed therapeutic drug or drugs through the development of 
resistant strains of organisms" should be used without prescription in animal feed (Ref. 1, p. 
61). Furthermore, the report concluded that antimicrobials used for therapeutic purposes in 
food-producing animals should remain available but only under veterinary supervision. 
1970 FDA Task Force Report, The Use of Antibiotics in Animal Feed 
In April 1970, FDA established a task force of scientists to undertake a 
comprehensive review of the use of antibiotics in animal feed (Ref. 2).  The task force 
included ten specialists on infectious diseases and animal science from FDA, the National 
Institutes of Health, the U.S. Department of Agriculture, and the Centers for Disease 
Control and Prevention, as well as five consultants from universities and industry.   
This task force acknowledged that the understanding at the time it conducted its study 
was that the use of antimicrobials in food-producing animals, especially in subtherapeutic 
amounts, was associated with the development of resistant bacteria, and that treated animals 
might serve as a reservoir of antimicrobial-resistant pathogens that could produce human 
disease.  
The recommendations of the Task Force included that antimicrobial drugs used in 
human clinical medicine that failed to meet certain guidelines established by the Task Force 
should be prohibited from growth promotion and any subtherapeutic use in food-producing 
animals by certain dates.  Furthermore, those antimicrobials that failed to meet the guidelines 
should be limited to short-term therapeutic use and use only by a veterinarian or on a 
veterinarians prescription.   
As a consequence of the 1970 Task Force report, requirements for data to address 
microbiological safety concerns for subtherapeutic uses of antimicrobials in food-producing 
animals were outlined in the Code of Federal Regulations (21 CFR 558.15).  Sponsors of 
antibiotic products administered in animal feed for subtherapeutic purposes were required to 
submit study results demonstrating that their product did not promote bacterial drug 
resistance.  Depending on the class of drug, sponsors were required to submit all information 
to the agency on the impact of their drug on enteric salmonella in treated animals by specific 
dates.   
1980 National Academy of Sciences Report, The Effects on Human Health of 
Subtherapeutic Use of Antimicrobial Drugs in Animal Feeds   
In 1977, FDA proposed to withdraw the new animal drug approvals for 
subtherapeutic uses of penicillin and tetracyclines in animal feed on the ground that 
evidence showed that these drugs, when used for such purposes in animal feed, had not 
been shown to be safe. These two drugs were chosen because of their importance in human 
medicine. The proposal was criticized because, at that time, there was not adequate 
epidemiological evidence (or only just-emerging evidence) to show that drug-resistant 
  6  Contains Nonbinding Recommendations 
 
 
bacteria of animal origin were commonly transmitted to humans and caused serious illness. 
Subsequently, Congress directed FDA to conduct further studies related to the use of 
antimicrobials in animal feed and to hold in abeyance the implementation of the proposed 
antimicrobial withdrawal actions pending the outcome of these studies.   
In accordance with Congress directive to conduct further studies, FDA contracted 
with the National Academy of Science to conduct a study of the safety issues related to the 
use of antimicrobials in animal feed.  In particular, FDA asked the National Academy of 
Science to: 1) study the human health effects of the subtherapeutic use of penicillin and 
tetracycline in animal feed; 2) review and analyze published and unpublished data relevant 
to assessing human health consequences of such use; 3) assess the scientific feasibility of 
additional epidemiological studies; and (4) make recommendations about additional 
research needed. 
The National Academy of Sciences issued a study report in 1980.  The study report 
concluded that a very limited amount of epidemiological research had been completed on 
either the subtherapeutic or therapeutic use of antimicrobials in animal feed.  According to 
the study report, much of the information available on the subject involved poorly 
controlled studies of small numbers of subjects for brief periods (Ref. 3, p. 52).  Based on 
a consideration of available evidence, the report concluded that existing data could neither 
prove nor disprove the postulated hazards to human health from subtherapeutic 
antimicrobial use in animal feed.  However, the report cautioned that The lack of data 
linking human illness with subtherapeutic levels of antimicrobials must not be equated with 
proof that the proposed hazards do not exist.  The research necessary to establish and 
measure a definitive risk has not been conducted and, indeed, may not be possible (Ref. 3, 
p. 53). 
1984 Seattle-King County Study:  Surveillance of the Flow of Salmonella and 
Campylobacter in a Community 
As noted above, Congress directed FDA to hold in abeyance any implementation of the 
proposed withdrawal of new animal drug approvals for the subtherapeutic uses of penicillin 
and tetracyclines in animal feed, pending completion of additional studies related to the use 
of antimicrobials in animal feed.  Therefore, in addition to the National Academy of 
Sciences study described above, the FDA also contracted with the Seattle-King County 
Health Department to complete a study intended to provide additional information 
regarding potential public health concerns regarding the use of antimicrobial drugs in 
animal feed.  Under the contract, the Communicable Disease Control Section of the 
Seattle-King County Health Department was tasked with studying the relationship between 
the occurrence of Salmonella spp. (Salmonella) and Campylobacter jejuni (C. jejuni) in 
foods of animal origin and the occurrence of human illness caused by those two organisms.  
These two organisms, Salmonella and C. jejuni, were chosen to serve as models to estimate 
the flow of potentially pathogenic bacteria from animals to man through the food chain.  
The study involved a two-pronged surveillance system that included sampling of retail 
meats over a 20 month period and simultaneous investigation of Salmonella and C. jejuni 
enteritis cases in humans.  Bacterial isolates from food and human cases were subjected to 
  7  Contains Nonbinding Recommendations 
 
 
antibiotic susceptibility testing, plasmid analysis, and serotyping.  In 1984, the Seattle-King 
County Health Department prepared a report summarizing the results of the study.  The 
1984 study report found that C. jejuni was a more common cause of enteritis than 
Salmonella.  Also, it concluded that C. jejuni "does appear to flow from chickens to man 
via consumption of poultry products" (Ref. 4, p. 3).  The report stated, "isolates from 
human cases and those from retail poultry had similar antibiotic susceptibility patterns, 
including prevalence of 29.7% and 32.8%, respectively, for tetracycline resistance, which 
was found to be plasmid-mediated" (Ref. 4, p. 3). 
1988 Institute of Medicine (IOM) Report:  Human Health Risks with the Subtherapeutic 
Use of Penicillin or Tetracyclines in Animal Feed 
In 1987, FDA asked the IOM to conduct an independent review of the human health 
risks associated with the subtherapeutic use of penicillin and tetracycline in animal feed.  
IOM established a committee and directed it to perform a quantitative risk assessment of 
these human health consequences and to assess the adequacy of the existing human health 
data and use such data to arrive at an estimate of risk (Ref. 5, p. iii).  If quantification of 
human health risks was not possible due to inadequate data, the Committee was to evaluate 
the scientific information that had become available since the 1980 National Academy of 
Science report cited above. 
The Committee developed a risk-analysis model, using data only on Salmonella 
infections that resulted in human death.  However, the Committee was unable to find a 
substantial body of direct evidence demonstrating that the subtherapeutic use of penicillin 
or tetracycline in animal feed posed a human health hazard.  Nonetheless, the Committees 
1988 report found a considerable body of indirect evidence implicating both subtherapeutic 
and therapeutic use of antimicrobials as a potential human health hazard. The Committee 
also strongly recommended further study of the issue. 
1997 World Health Organization (WHO) Report, The Medical Impact of Antimicrobial 
Use in Food Animals 
In October 1997, the WHO convened a meeting of experts to examine the question of 
whether the use of antimicrobials in livestock production, including through use in animal 
feed, contributes to the escalation of antimicrobial resistance in humans.  The findings of 
the meeting, which were summarized in a report, included the conclusion that all uses of 
antimicrobials lead to the selection of resistant forms of bacteria.  Furthermore, the report 
stated that low-level, long-term exposure to antimicrobials may have greater selective 
potential than short-term, full-dose therapeutic use (Ref. 6, p. 5).  The report found that the 
selection of resistant bacteria has adverse consequences for preventing and treating disease 
in humans, animals, and plants. 
The WHO expert committee recommended that the use of antimicrobial drugs for 
growth promotion in animals be terminated if these drugs are also prescribed for use as 
anti-infective agents in human medicine or if they are known to induce cross-resistance to 
antimicrobials used for human medical therapy. The Committee also recommended the 
  8  Contains Nonbinding Recommendations 
 
 
development of a systematic approach towards replacing growth-promoting antimicrobials 
with safer non-antimicrobial alternatives.  The expert committee called for enhanced 
monitoring of resistance among isolates of enteric bacteria from food animals and food of 
animal origin. In addition, the Committee recommended managing risk at the primary 
production level through measures that promote the prudent use of antimicrobials, 
including enforcement of relevant laws pertaining to antimicrobial use, education for 
prescribers and producers, and requiring that use of antimicrobials for treatment of 
infections in animals be prescribed by veterinarians.  
1999 National Research Council (NRC) Report:  The Use of Drugs in Food Animals  
Benefits and Risks 
The Panel on Animal Health, Food Safety, and Public Health, jointly sponsored by 
the NRCs Board on Agriculture and IOMs Food and Nutrition Board, initiated a project 
to review the issues and relevant information regarding the use of drugs in food-producing 
animals and to make recommendations about such use.  The panel convened the Committee 
on Drug Use in Food Animals to examine the benefits and risks associated with drug use in 
food-producing animals and to prepare a report and make recommendations.   
The Committees 1999 report included a review of the issues related to antibiotic use 
in food-producing animals and provided a number of recommendations.  The report 
recommended establishing national databases to support scientific process and policy 
development for the approval and use of antibiotics in food-producing animals. The report 
also recommended that FDA use interdisciplinary panels of experts so that "further 
development and use of antibiotics in both human and animal medicine have oversight by 
an interdisciplinary panel of experts composed of representatives of the veterinary and 
animal health industry, the human medicine community, consumer advocacy groups, the 
animal production industry, and the regulatory agencies" (Ref. 7, p. 11). 
1999 United States Government Accountability Office (GAO) Report  Food Safety:  The 
Agricultural Use of Antibiotics and Its Implications for Human Health 
In response to a request from Congress, the GAO initiated a study in May 1998 to 
examine: 1) how antibiotics are used in agriculture and the implications of that use for 
human health; 2) federal roles and responsibilities for overseeing the use of antibiotics in 
agriculture; and 3) issues surrounding the debate over whether to further regulate or restrict 
the use of antibiotics in agriculture (Ref. 8, p. 1).  
In its study report, dated April 1999, GAO concluded that although research has 
linked the use of antibiotics in agriculture to the emergence of resistant foodborne 
pathogens, there are no current comprehensive estimates of the extent to which antibiotic-
resistance strains have resulted in illness and deaths (Ref. 8, p. 1).  GAO concluded that 
the debate over whether antibiotic use should be restricted in agriculture centers on the risk 
antibiotics pose to human health relative to their benefits to agriculture.  The GAO report 
recommended that the departments of Agriculture and Health and Human Services work 
  9  Contains Nonbinding Recommendations 
 
 
together to develop and implement a plan with specific goals, time frames and resources 
needed for determining the safe use of antibiotics in agriculture. 
1999 European Commission Report, Opinion of the Scientific Steering Committee on 
Antimicrobial Resistance  
Due to the public and animal health concerns associated with the increasing rate of 
antimicrobial resistance development, the European Commission, Directorate-General 
XXIV, asked that organizations Scientific Steering Committee to scientifically evaluate 
the current position regarding the prevalence and development of antimicrobial resistance, 
examine its implications for human and animal health, particularly with regard to the 
development and management of infections (Ref. 9, p. 7). 
The Committees report concluded that actions should be taken promptly to reduce 
the overall use of antimicrobials. Four primary recommendations were forwarded: (1) 
antimicrobial drugs should be used prudently; (2) infections should be prevented and 
resistant organisms contained; (3) research for new modalities of prevention and treatment 
of infections should be undertaken; and (4) the effects of such interventions should be 
monitored and evaluated.   
2000 World Health Organization (WHO) Expert Consultation:  WHO Global Principles 
for the Containment of Antimicrobial Resistance in Animals Intended for Food 
The Food and Agriculture Organization of the United Nations (FAO) and the World 
Organization for Animal Health (OIE) participated in the June 2000 WHO expert consultation, 
the purpose of which was to develop global principles for minimizing the negative public 
health impact associated with the use of antimicrobial agents in food-producing animals while 
providing for their safe and effective use in veterinary medicine (Ref. 10).  
The principles were part of a comprehensive WHO global strategy for the 
containment of antimicrobial resistance and provided a framework of recommendations to 
reduce the overuse and misuse of antimicrobials in food-producing animals for the 
protection of human health. The principles strengthened and endorsed earlier WHO 
recommendations such as the need to terminate the use of antimicrobial growth promoters 
pending comprehensive human health safety evaluations, the need to ensure that all 
antimicrobials for animal use are only supplied through authorized outlets (e.g., by 
veterinary prescription), and the need to establish surveillance systems on antimicrobial 
drug consumption. 
2003 Report, Joint FAO/OIE/WHO Expert Workshop on Non-Human Antimicrobial 
Usage and Antimicrobial Resistance:  Scientific assessment 
In December 2003, the Food and Agriculture Organization of the United Nations 
(FAO), the World Organization for Animal Health (OIE), and the World Health 
Organization (WHO) convened a workshop to perform a scientific assessment of the 
antimicrobial resistance risks arising from non-human usage of antimicrobials and to 
  10  Contains Nonbinding Recommendations 
 
 
formulate recommendations and options for future risk management actions to be 
considered by the Codex Alimentarius Commission (Codex) and OIE (Ref. 11, p. 1). 
The expert panels findings from the workshop were documented in a report which 
contained a number of conclusions, including: 1) there is clear evidence of adverse human 
health consequences due to resistant organisms resulting from non-human usage of 
antimicrobials; 2) the amount and pattern of non-human usage of antimicrobials impact 
the occurrence of resistant bacteria in animals and on food commodities and thereby human 
exposure to these resistant bacteria; 3) the foodborne route is the major transmission 
pathway for resistant bacteria and resistance genes from food animals to humans, but other 
routes of transmission exist; and 4) the consequences of antimicrobial resistance are 
particularly severe when pathogens are resistant to antimicrobials critically important in 
humans (Ref. 11, p. 1). 
The expert panel recommended that WHO appoint a group of experts to define which 
antimicrobials are considered critically important in humans.  In addition, the panel 
commented on the need to further develop risk assessment approaches that adequately 
address the broad range of potential human health impacts and encouraged OIE to continue 
its work on risk analysis in coordination with FAO and WHO.  Finally, the panel 
recommended that Codex collaborate with OIE to define a more efficient risk management 
system for addressing the risks. 
2003 Institute of Medicine (IOM) Report, Microbial Threats to Health:  Emergence, 
Detection and Response 
The Committee on Emerging Microbial Threats to Health in the 21st Century was 
charged by the IOM to review the current state of knowledge on the emergence of 
infectious diseases; assess the capacity of the United States to detect and respond to 
microbial threats to public health; and identify potential challenges and opportunities for 
public health actions, both global and domestic, to strengthen capabilities in prevention, 
detection, and response (Ref. 12, p. 3). 
The Committees report discussed thirteen factors4 that account for the emergence of 
new or enhanced microbial threats.  The report noted the convergence of any number of 
factors can create an environment where infectious diseases can emerge... (Ref. 12, p. 4).  
In addition, the Committee provided a number of recommended actions for responding to 
the increasing infectious disease rates prompted by these emergence factors.  One of the 
recommendations was to more finely target the use of antimicrobials including 
expanding efforts to decrease the inappropriate use of antimicrobials in human medicine 
(Ref. 12, p. 6).  In addition, the committee recommended that FDA ban the use of 
                                                 
4 The thirteen factors included 1) microbial adaptation and change, 2) human vulnerability, 3) climate and 
weather, 4) changing ecosystems, 5) economic development and land use, 6) human demographics and 
behavior, 7) technology and industry, 8) international travel and commerce, 9) breakdown of public health 
measures, 10) poverty and social inequality, 11) war and famine, 12) lack of political will, and 13) intent to 
harm. 
  11  Contains Nonbinding Recommendations 
 
 
antimicrobials for growth promotion in animals if those classes of antimicrobials are also 
used in humans (Ref. 12, p. 15). 
2004 Report, Second Joint FAO/OIE/WHO Expert Workshop on Non-Human 
Antimicrobial Usage and Antimicrobial Resistance:  Management Options 
As summarized above, a preliminary scientific assessment of the antimicrobial 
resistance risks arising from non-human usage of antimicrobials was conducted by the first 
Joint Expert Workshop on Non-Human Antimicrobial Usage in December 2003 in Geneva 
(Ref. 13).  The outcome of the first workshop, plus other relevant information, formed the 
basis for consideration by this second workshop.  The report of this second workshop 
included suggestions to Codex, FAO, WHO, and OIE for moving forward on the issue.   
Some of the key conclusions and recommendations in the report included: 1) the risks 
associated with non-human antimicrobial use and antimicrobial resistance should be part of 
human safety assessments for regulatory decisions relating to veterinary antimicrobials, 2) 
the concept of critically-important classes of antimicrobials for humans should be 
developed by WHO, 3) good agricultural practices can reduce the necessity for 
antimicrobials, 4) there is a need for capacity building and networking to help implement 
antimicrobial resistance surveillance systems in various countries, and 5) a Codex/OIE 
Task Force should be established to develop risk management options for antimicrobial 
resistance related to non-human use of antimicrobials.   
2004 United States Government Accountability Office (GAO) Report  Antibiotic 
Resistance:  Federal Agencies Need to Better Focus Efforts to Address Risks to Humans 
from Antibiotic Use in Animals 
In response to a request from Congress, GAO initiated a study in May 2003 to 
examine 1) scientific evidence on the transference of antibiotic resistance from animals to 
humans and extent of potential harm to human health, 2) agencies efforts to assess and 
address these risks, 3) the types of data needed to support research on these risks and extent 
to which the agencies collect these data, 4) use of antibiotics in animals in the United States 
compared with its key agricultural trading partners and competitors, and 5) information on 
how use has affected trade (Ref. 14, p. 3). 
In its study report, dated April 2004, GAO concluded that antibiotic-resistant bacteria 
have been transferred from animals to humans.  GAO also stated that many of the studies 
reviewed as part of GAOs research found that this transference from animals to humans 
poses significant risks for human health. According to GAOs findings, studies have shown 
two types of evidence related to the transfer of antibiotic-resistant bacteria from animals to 
humans. First, some studies have provided evidence of associations between changes in 
antibiotic use in animals and resistance to antibiotics in human bacteria. For example, 
researchers have found that antibiotic-resistant Escherichia coli (E. coli) and 
Campylobacter increased in humans as use of the antibiotics increased in animals.  
Second, GAO concluded that studies that have examined the genetic makeup of the 
bacteria have provided stronger scientific evidence that antibiotic-resistant Campylobacter 
  12  Contains Nonbinding Recommendations 
 
 
and Salmonella bacteria are transferred from animals to humans. In those studies, strains of 
antibiotic-resistant bacteria infecting humans were indistinguishable from those found in 
animals, leading researchers to conclude that the animals were the source of human 
infection.  
The GAO report noted that researchers disagree about the extent of the human health 
risk caused by this transference. According to the report, many researchers contend that 
antibiotic use in animals poses significant risk for human health.  The GAO report also 
noted that a small number of studies contend that the health risks of the transference are 
minimal (Ref. 14, p. 23).  
GAO recommended that the Commissioner of FDA expedite FDAs risk 
assessments of the antibiotics used in animals that the agency has identified as critically 
important to human health to determine if action is necessary to restrict or prohibit animal 
uses in order to safeguard human health (Ref. 14, p. 48).  GAO also recommended that the 
Secretaries of Agriculture and of Health and Human Services jointly develop and 
implement a plan for collecting data on antibiotic use in animals... (Ref. 14, p. 48). 
The Department of Health and Human Services (HHS) reviewed and subsequently 
responded to the 2004 GAO Report on Antibiotic Resistance. In its response, HHS cited 11 
additional supporting studies not included in the GAO report (See End Note)i, and provided 
the following comments: 
The draft report presents or refers to significant and growing evidence demonstrating 
the human health consequences of drug resistant infections related to antibiotic use in 
agriculture. These [11 additional] studies, along with those cited in the GAO report, all 
demonstrate a relationship between the use of antimicrobials in food-producing animals, 
antibiotic resistance in humans, and adverse human health consequences as a result. We 
believe that there is a preponderance of evidence that the use of antimicrobials in food-
producing animals has adverse human consequences. There is little evidence to the 
contrary.  
2005 Codex Alimentarius Commission (Codex),  Code of Practice to Minimize and 
Contain Antimicrobial Resistance (Code of Practice) 
The Code of Practice provides guidance for the responsible and prudent use of 
antimicrobials in food-producing animals (Ref. 15).  Its objectives are to minimize adverse 
impacts on public health associated with the use of antimicrobial drugs in food-producing 
animals.   
The Code of Practice makes a number of recommendations regarding the responsible 
use of antimicrobials in food-producing animals.  For example, the document recommends 
that responsible use 1) should be controlled by the veterinary profession or other parties 
with the requisite expertise, and 2) does not include the use for growth promotion of 
veterinary antimicrobial drugs that belong to or are able to cause cross-resistance to classes 
  13  Contains Nonbinding Recommendations 
 
 
of antimicrobial agents used in humans (or submitted for approval for use in humans) in the 
absence of an appropriate risk analysis.    
2006 Antimicrobial Resistance: Implications for the Food System, Comprehensive 
Reviews in Food Science and Food Safety  
This report was conducted under the auspices of the Institute of Food Technologists 
and the IFT foundation (Ref. 16). The panelists found the extent to which antibiotic use in 
food animals produces clinically important antibiotic resistant infections in humans is 
unknown. However, they do state in their recommendations that In veterinary medicine 
and production agriculture implementation of various management strategies (such as 
responsible use guidelines, quality assurance programs, and antibiotic alternatives), 
coupled with government regulations, should decrease opportunities for the selection of 
antibiotic resistant microorganisms. Specifically, they stated Always practice prudent use 
of antimicrobials to limit resistance selection and to maintain maximal benefit of 
antimicrobials in the future. 
2009 American Academy of Microbiology.  Antibiotic Resistance: An Ecological 
Perspective on an Old Problem  
This report emphasizes the ecological fact that antibiotic resistance is a natural 
phenomenon that cannot be eliminated (Ref. 17).  The practical approach is to find effective 
ways to cope with antibiotic resistant bacteria harmful to humans and animals and to 
control the development of new types of resistance.  Controlling antibiotic-resistant 
bacteria and subsequent infections requires vigilance on many fronts.  The prudent and 
responsible use of antibiotics and the elimination of unnecessary use (e.g., viral infections; 
unnecessary, prolonged treatment) are noted as mandatory steps to an appropriate public 
health strategy to limit infections by resistant organisms. 
2011 WHO Report:  Tackling antibiotic resistance from a food safety perspective in 
Europe   
This report follows a long series of WHO reports addressing antibiotic resistance in 
the food chain (Ref. 18).  The WHO continues to highlight the urgent need for action in 
remediating antibiotic resistance through a holistic, intersectoral, and multifaceted 
approach that includes all efforts to reduce unnecessary use of antibiotics, including those 
uses in food production.  Specific regulatory strategies include: 1) eliminating the use of 
antibiotics as growth promoters in food animals; 2) requiring that antibiotics be 
administered to animals only when prescribed by a veterinarian; and 3) requiring the 
antibiotics identified as critically important in human medicine - especially 
fluoroquinolones and third- and fourth-generation cephalosporins - only be used in food 
animals when their use is justified. 
 
 
  14  Contains Nonbinding Recommendations 
 
 
Brief Summary of Recent Peer-Reviewed Scientific Literature 
2008. Applied and Environmental Microbiology. Longitudinal study of antimicrobial 
resistance among Escherichia coli isolates from integrated multisite cohorts of humans and 
swine. Alali et al. 
 
This study longitudinally examined the relationship between antimicrobial resistant E. coli 
from human wastewater and swine fecal samples and several risk factors including host 
species, production type, vocation (e.g., slaughter plant workers), and season.  Authors 
reported that the higher levels of E. coli resistance in swine isolates as compared with 
human isolates was likely associated with either the past or current use of injectable 
antimicrobial agents (e.g., ceftiofur sodium) or the use of antimicrobial agents in feed (e.g., 
chlortetracycline) or water.  Furthermore, slaughter plant workers were shown to be at 
higher risk of carrying multidrug-resistant E. coli than non-swine workers.  
2008. Applied and Environmental Microbiology. Diversity and distribution of commensal 
fecal Escherichia coli bacteria in beef cattle administered selected subtherapeutic 
antimicrobials in a feedlot setting. Sharma et al. 
This study investigated the influence of administration of chlortetracycline alone or in 
combination with sulfamethazine on the development of resistance, dissemination of 
defined strain types, and prevalence of resistance determinants in feedlot cattle (Ref. 20). 
Shedding of tetracycline-resistant E. coli was higher in animals receiving both treatments. 
While tetracycline resistance was detected in cattle with no prior antimicrobial exposure, 
shedding of tetracycline-resistant E. coli was higher in animals subjected to either of the 
two treatments.   
2008. Applied and Environmental Microbiology. Effect of subtherapeutic administration of 
antibiotics on the prevalence of antibiotic-resistant Escherichia coli bacteria in feedlot 
cattle. Alexander et al.  
This study involved the collection of 3,300 fecal samples over a 314-day period from 300 
feedlot steers receiving subtherapeutic levels of antibiotics (Ref. 21).  Study findings 
indicated that administration of tetracycline in combination with sulfamethazine clearly 
increased the prevalence of tetracycline- and ampicillin-resistant E. coli in cattle and the 
numbers of resistant E. coli organisms shed. 
2009. American Journal of Veterinary Research. A metagenomic approach for determining 
prevalence of tetracycline resistance genes in the fecal flora of conventionally raised 
feedlot steers and feedlot steers raised without antimicrobials. Harvey et al.  
This study compared the prevalence of tetracycline-resistance genes in the fecal flora of 
conventionally raised feedlot steers and feedlot steers raised without antimicrobials (Ref. 
22).  Authors observed that the percentage of fecal samples with 11 tetracycline resistance 
genes was significantly higher for fecal samples from conventionally raised cattle (35/61 
[57%]) than for fecal samples from antimicrobial-free cattle (16/61 [26%]).  
  15  Contains Nonbinding Recommendations 
 
 
2009. Foodborne Pathogens and Disease. Association between tetracycline consumption 
and tetracycline resistance in Escherichia coli from healthy Danish slaughter pigs. Vieira et 
al.  
The objective of this Danish study was to investigate the association between tetracycline-
resistant Escherichia coli isolates from the intestinal tract of healthy pigs and patterns of 
tetracycline consumption in the herds of origin, together with other risk factors (Ref. 23).  
The study showed that the larger the time since the last administration of tetracycline, the 
lower the likelihood of isolating a resistant E. coli  . 
2009. Preventive Veterinary Medicine. Associations between reported on-farm 
antimicrobial use practices and observed antimicrobial resistance in generic fecal 
Escherichia coli isolated from Alberta finishing swine farms. Varga et al.  
This study used statistical models to evaluate the associations between various 
antimicrobial use practices and resistance to antimicrobials among generic fecal 
Escherichia coli isolated from Alberta finishing swine (Ref. 24). In-feed antimicrobial use 
was significantly associated with an increased risk of resistance to ampicillin, 
chloramphenicol, streptomycin, and sulfisoxazole in E. coli isolates. Chlortetracycline use 
in grower rations was associated with ampicillin and tetracycline resistance.  
2010. International Journal of Food Microbiology. Farm-to-fork characterization of 
Escherichia coli associated with feedlot cattle with a known history of antimicrobial use. 
Alexander et al.  
This study investigated antimicrobial-resistant Escherichia coli isolated from cattle fed 
diets containing chlortetracycline plus sulfamethazine (AS700) (Ref. 25).  Compared to the 
control, in which no feed antibiotics were administered, the prevalence of ampicillin-
resistant and tetracycline-resistant E. coli was three- and four-fold greater in feces from 
treated animals respectively, but was similar between treatments for animal hide samples.  
2011. Environmental Health Perspectives. Lower prevalence of antibiotic-resistant 
Enterococci on U.S. conventional poultry farms that transitioned to organic practices. 
Sapkota et al.  
This study compared antimicrobial resistance in enterococci recovered from conventional 
poultry farms using antibiotics with farms that transitioned to antibiotic-free production 
practices and had just received organic certification (Ref. 26).  Over 40% of Enterococcus 
faecalis isolates from conventional poultry houses were multidrug resistant, compared with 
10% of isolates from newly organic poultry houses.  In addition, 84% of Enterococcus 
faecium isolates from conventional poultry houses were multidrug resistant, compared with 
17% of isolates from newly organic poultry houses.   
2011. Foodborne Pathogens and Disease. Association between antimicrobial resistance in 
Escherichia coli isolates from food animals and blood stream isolates from humans in 
Europe: an ecological study. Vieira et al.  
  16  Contains Nonbinding Recommendations 
 
 
The authors analyzed the correlation between the prevalence of antimicrobial resistance in 
E. coli isolates from blood stream infections in humans and in E. coli isolates from poultry, 
pigs, and cattle in 11 countries between 2005 and 2008 (Ref. 27).  Resistance against 
multiple drugs in E. coli isolates from food animals (especially poultry and pigs) was 
highly correlated with resistance in isolates from humans.  
2011. BMC Microbiology. Distribution and characterization of ampicillin- and 
tetracycline-resistant Escherichia coli from feedlot cattle fed subtherapeutic antimicrobials. 
Mirzaagha et al. 
 
Authors characterized E. coli isolates recovered from cattle that either received no dietary 
antimicrobials or were intermittently administered subtherapeutic levels of 
chlortetracycline, chlortetracycline and sulfamethazine (SMX), or virginiamycin over a 9-
month feeding period (Ref. 28).  This study showed that strains exhibited multidrug 
resistance to SMX and chloramphenicol (a drug not in the antibiotic regimen) more 
frequently when obtained from steers fed chlortetracycline plus sulfamethazine than from 
cattle treated with either chlortetracycline alone or with virginiamycin.   Results further 
suggested that the administration of chlortetracycline, even in the absence of SMX, can 
lead to the emergence of resistance to SMX, as well as other antibiotics, including 
ampicillin and chloramphenicol. 
2012. Proceedings of the National Academy of Sciences. In-feed antibiotic effects on the 
swine intestinal microbiome. Looft et al.   
This study involved pigs raised in a highly controlled environment, with one group of 
littermates receiving a diet containing a growth-enhancing antibiotic combination product 
[chlortetracycline, sulfamethazine, and penicillin (known as ASP250)] and the other 
receiving the same diet without the antibiotics (Ref. 29).  Even a low, short-term (14-day) 
dose of in-feed antibiotics increased the prevalence and diversity of antibiotic resistance 
genes, including resistance to antibiotics not administered in the study, and increased the 
prevalence of E. coli.   
IV.  Strategies for Controlling Antimicrobial Resistance Are Needed 
As summarized above in Section III, the public health concerns associated with the 
use of medically important antimicrobial drugs in food-producing animals have been the 
subject of scientific interest for the past 40 years.  FDA has considered all available 
information and believes that the weight of scientific evidence supports the 
recommendations outlined in this guidance document. 
To effectively respond to the public health concerns associated with antimicrobial 
resistance, FDA believes it is important to broadly consider how antimicrobial drugs are 
being used.  The scientific community generally agrees that antimicrobial drug use is a key 
driver for the emergence of antimicrobial-resistant bacteria.   It is imperative that strategies 
  17  Contains Nonbinding Recommendations 
 
 
for controlling antimicrobial resistance include a consideration of how antimicrobial drugs 
are being used and measures to address those uses that are injudicious in nature.   
V.  Current Regulatory Framework 
FDA considers the issue of antimicrobial resistance as part of its human food safety 
review related to new animal drugs used in food-producing animals.  FDA considers an 
antimicrobial new animal drug to be safe if the agency concludes that there is 
reasonable certainty of no harm to human health from the proposed use of the drug in 
food-producing animals.  This standard applies to safety evaluations completed prior to 
new animal drug approvals, as well as to those completed for drugs after approval.  If this 
safety standard is not met before approval, the drug cannot be approved.  If safety issues 
arise after approval, the Federal Food, Drug, and Cosmetic Act (the Act) provides grounds 
for withdrawal of approval of new animal drug applications for safety reasons.  For 
example, section 512(e)(1)(B) of the Act provides for withdrawal of new animal drug 
application approvals when new evidence, along with evidence contained in the 
application, shows that the drug is not shown to be safe under the approved conditions of 
use.  Under this provision, if FDA initiates a withdrawal action, it must produce evidence 
to show that there is a reasonable basis from which serious questions may be inferred about 
the ultimate safety of the drug and any substance that may be formed in or on food as a 
result of use of such drug under approved conditions.  Once the agency meets this initial 
burden, the burden then shifts to the sponsor to demonstrate the safety of the drug (Docket 
no. 00N-1571, at p. 5, Mar. 16, 2004). 
In 2003, FDA implemented new policies for evaluating antimicrobial resistance 
associated with use of antimicrobial new animal drugs in food-producing animals through the 
issuance of Guidance for Industry (GFI) #152, Evaluating the Safety of Antimicrobial New 
Animal Drugs with Regard to their Microbiological Effects on Bacteria of Human Health 
Concern 
(http://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/GuidanceforIndu
stry/UCM052519.pdf).  This guidance document describes a risk-based assessment process for 
evaluating antimicrobial resistance associated with the use of antimicrobial new animal drugs 
in food-producing animals.  The guidance also recommends measures for mitigating such risk.   
In general, FDAs GFI #152 is premised on the concept that increasing the exposure of 
bacterial populations to antimicrobial drugs increases the risk of generating resistance to those 
antimicrobial drugs.  Pursuant to this principle, the administration of medically important 
antimicrobial drugs to entire herds or flocks of food-producing animals (e.g., for production 
purposes) would represent a use that poses a qualitatively higher risk to public health than the 
administration of such drugs to individual animals or targeted groups of animals (e.g., to 
prevent, control, or treat specific diseases).  In addition to factors that impact the potential 
extent of use of the drug, the guidance also considers such factors as the properties of the drug 
in question including mechanism of action and mechanism of resistance, the prevalence of 
zoonotic foodborne bacteria in the food-producing animal species for which the drug is 
intended, and the importance of the drug in question as a therapy in humans.  Risk mitigating 
  18  Contains Nonbinding Recommendations 
 
 
factors that are considered include such limitations as restricting use of the drug to use by or on 
the order of a veterinarian. 
Although FDA developed GFI #152 primarily to assess antimicrobial resistance risks as 
part of the new animal drug approval process, the underlying concept described above is also 
applicable to safety evaluations conducted for previously-approved antimicrobial new animal 
drugs.  Therefore, FDA considers this same concept when it conducts safety evaluations for 
currently approved antimicrobial drugs, including those approved for use in animal feed.   
From a practical standpoint, however, some significant differences exist between 
applying the GFI #152 risk assessment approach to the pre-approval process and applying it to 
safety reviews of currently-approved products.  On the pre-approval side, the GFI #152 
assessment process, including the various risk mitigation measures described, is taken into 
consideration by drug sponsors upstream in the drug development process and, in effect, steers 
product development in a direction that is most consistent with the guidance.  On the post-
approval side, FDA may examine certain currently-approved products to determine whether 
such products appear consistent with GFI #152.  However, initiating action to withdraw an 
approved new animal drug application (NADA), in whole or in part, based on the results of a 
post-approval safety review would require the agency to make the showing required under 
section 512(e)(1) of the Act. 
Alternatively, concerns associated with approved NADAs can sometimes be addressed 
through more informal processes.  For example, in certain cases FDA has worked 
collaboratively with the sponsor of an NADA to address concerns raised regarding their 
product and has initiated steps to permit the sponsor to voluntarily withdraw part or all of the 
NADA or to revise the product labeling to address the concern.  This alternative pathway can 
in some cases be an effective and expedient mechanism for resolving issues associated with an 
NADA.    
VI.  Status of FDAs Current Activities  
In general, the antimicrobial new animal drug applications that FDA is addressing as 
part of its efforts to evaluate the public health concerns associated with the use of 
medically important antimicrobial drugs in food-producing animals can be divided into two 
broad categories:  1) those NADAs submitted after the issuance of GFI #152 in 2003 and 
for which FDA is assessing the microbiological safety of the new animal drug on a pre-
approval basis using the principles outlined in GFI #152; and 2) those NADAs approved 
before the final version of GFI#152 was issued in 2003.  In regard to the first category, 
FDA believes the approach outlined in GFI #152 for evaluating microbiological safety as 
part of the drug approval process has been very effective.  As noted above, that assessment 
process and the associated risk mitigation measures are usually taken into consideration by 
industry during the drug development process.  Thus, products that ultimately move 
forward toward approval are those products that include use conditions that are consistent 
with the guidance and are intended to minimize the extent to which product use would 
contribute to resistance development.   
  19  Contains Nonbinding Recommendations 
 
 
FDA believes the approach outlined in GFI #152 is scientifically sound and is 
protective of the public health.  FDA recognizes that the list of drugs in Appendix A is not 
static and should be periodically reassessed and updated as necessary.  Such reassessment 
is necessary to take into consideration such factors as the development of new 
antimicrobials for human therapy, the emergence of diseases in humans, or changes in 
prescribing practices in the United States.  FDA will update Appendix A, as necessary, 
through a separate process that will also be subject to public comment.   
The second category of products are those antimicrobial NADAs that were approved 
prior to the implementation of GFI #152.  Some of the products in this category include 
products that were approved for use in food-producing animals more than 30 years ago.  Of 
particular concern, as discussed in section IV, are those products that are approved for use 
in animal feed for production or growth-enhancing purposes.  Although these products are 
FDA-approved, their approval occurred prior to implementation of current processes for 
assessing safety with respect to antimicrobial resistance.  Furthermore, the scientific 
understanding regarding antimicrobial resistance has advanced significantly over this time 
frame and, as discussed earlier in this document, a number of scientific reports have raised 
public health concerns regarding the use of medically important antimicrobials in food-
producing animals.   
As a result, FDA is examining available information regarding medically important 
antimicrobial drugs currently approved for use in food-producing animals and considering 
potential steps for agency action.   
VII.  Recommended Principles Regarding Judicious Use in Animals 
The continued availability of effective antimicrobial drugs is critically important for 
combating infectious disease in both humans and animals.  This includes the continued 
availability of feed and water uses of such drugs for managing disease in animal 
agriculture.  Therefore, it is in the interest of both human and animal health that we take a 
more proactive approach to considering how antimicrobial drugs are being used, and take 
steps to assure that such uses are appropriate and necessary for maintaining the health of 
humans and animals.  Using medically important antimicrobial drugs as judiciously as 
possible is key to minimizing resistance development and preserving the effectiveness of 
these drugs as therapies for humans and animals.  Although FDA applauds the efforts to 
date by various veterinary and animal producer organizations to institute guidelines for the 
judicious use of antimicrobial drugs, the agency believes additional, voluntary steps are 
needed. 
To further address this public and animal health concern, FDA is recommending two 
additional principles about the appropriate or judicious use of medically important 
antimicrobial drugs in food-producing animals.  These principles are consistent with the 
recommendations of a number of recent scientific panels or committees referenced earlier 
in this document including the 1997, 2000, and 2011 reports of the WHO, the 2003 IOM 
Report, and the 2005 Codex Code of Practice.   
  20  Contains Nonbinding Recommendations 
 
 
FDA recognizes the need to collaborate with the animal health and animal producer 
communities on strategies for minimizing animal health impacts or industry disruption that 
may be associated with the implementation of changes by animal drug sponsors to 
voluntarily align the use conditions of affected drug products with the principles outlined 
below.  Furthermore, FDA intends to consult with the United States Department of 
Agriculture (USDA) on implementation strategies, including the development of a 
framework for veterinary oversight and consultation requirements.  FDA is committed to 
assuring that the public health is protected while also assuring that the health needs of 
animals are addressed.  
Principle 1:  The use of medically important antimicrobial drugs in food-producing 
animals should be limited to those uses that are considered necessary for assuring animal 
health. 
In light of the risk that antimicrobial resistance poses to public health, FDA believes the 
use of medically important antimicrobial drugs in food-producing animals for production 
purposes (e.g., to promote growth or improve feed efficiency) represents an injudicious use 
of these important drugs.  Production uses are not directed at any specifically identified 
disease, but rather are expressly indicated and used for the purpose of enhancing the 
production of animal-derived products.  In contrast, FDA considers uses that are associated 
with the treatment, control, or prevention5 of specific diseases, including administration 
through feed or water, to be uses that are necessary for assuring the health of food-producing 
animals.    
  Some may have concerns that the use of medically important antimicrobial drugs in 
food-producing animals for disease prevention purposes is not an appropriate or judicious 
use.  However, FDA believes that some indications for prevention use are necessary and 
judicious as long as such use includes professional veterinary involvement.  Veterinary 
involvement in the decision-making process associated with the use of medically important 
antimicrobial drugs is an important aspect of assuring appropriate use, including judicious 
prevention use.  When determining the appropriateness of a prevention use, veterinarians 
consider several important factors such as determining the medical rationale for such use, 
and that such use is appropriately targeted at a specific etiologic agent and appropriately 
timed relative to the disease.  For example, if a veterinarian determines, based on the 
clients production practices and herd health history, that cattle being transported or 
otherwise stressed are more likely to develop a certain bacterial infection, preventively 
treating these cattle with an antimicrobial approved for prevention of that bacterial 
infection would be considered a judicious use.  Another example would be the prevention 
of necrotic enteritis in broiler chickens.  In this case, the prevention use of an antimicrobial 
is important to manage this disease in certain flocks in the face of concurrent coccidiosis, a 
significant parasitic disease in chickens.  On the other hand, FDA would not consider the 
administration of a drug to apparently healthy animals in the absence of any information 
                                                 
5 Disease prevention involves the administration of an antimicrobial drug to animals, none of which are 
exhibiting clinical signs of disease, in a situation where disease is likely to occur if the drug is not 
administered.   
  21  Contains Nonbinding Recommendations 
 
 
that such animals were at risk of a specific disease to be a judicious use.  The decision to 
use a specific drug or combination drug is generally based on factors that veterinarians are 
uniquely qualified to consider, including the mode of antibacterial action, drug distribution 
in specific tissues, and the duration of effective drug levels at the site of infection.   
Principle 2:  The use of medically important antimicrobial drugs in food-producing 
animals should be limited to those uses that include veterinary oversight or consultation. 
Most of the feed-use antimicrobial drugs are currently approved for over-the-counter 
use in food-producing animals for purposes that include the treatment, control, and 
prevention of disease as well as for production purposes (i.e., for growth promotion uses such 
as increased rate of weight gain).  In addition to instituting voluntary measures that would 
limit use of medically important antimicrobial drugs in food-producing animals to uses that 
are considered necessary to assure the animals health, FDA also believes it is important to 
phase-in the voluntary practice of including veterinary oversight or consultation in the use of 
these drugs.  As noted above, FDA believes that this practice is an important mechanism for 
helping to assure appropriate use.  Veterinarians can play a critical role in the diagnosis of 
disease and in the decision-making process related to instituting measures to treat, control, or 
prevent disease.  FDA recognizes that the nature of veterinary involvement can vary due to 
numerous factors such as geographic location and animal production setting.  In fact, there 
are limited numbers of large animal veterinarians, which can make consultation or oversight 
challenging in certain situations.  For example, some animal disease events require 
immediate attention.  In some cases, veterinarians may be directly diagnosing and 
administering therapies, while in other cases they are visiting and consulting with producers 
periodically to establish customized disease management protocols for that producers herd 
or flock.  Of key importance to FDA is the fact that, in both of these cases, the veterinarian is 
involved in the decision-making process regarding antimicrobial drug use.  FDA recognizes 
that increasing veterinary involvement in the use of antimicrobial drugs has significant 
practical implications for animal producers, veterinary practitioners, and the veterinary 
profession as whole.  Therefore, FDA is particularly interested in receiving comments on 
strategies for effectively promoting the voluntary adoption of such a change. 
VIII.  Conclusion 
  In order to minimize the development of antimicrobial resistance, FDA believes 
that it is important to ensure the judicious use of medically important antimicrobial drugs in 
animal agriculture.  We recommend several steps to accomplish this including voluntary 
measures that would limit medically important antimicrobial drugs to uses in food-
producing animals that are considered necessary for assuring animal health and that include 
veterinary oversight or consultation.  Such limitations would reduce overall medically 
important antimicrobial drug use levels, thereby reducing antimicrobial resistance selection 
pressure, while still maintaining the availability of these drugs for appropriate use.   
  22  Contains Nonbinding Recommendations 
 
 
IX.  References  
1.  1969 Report of the Joint Committee on the Use of Antibiotics in Animal Husbandry and 
Veterinary Medicine. 
2.  1970 FDA Task Force Report, The Use of Antibiotics in Animal Feed. 
3.  1980 National Academy of Sciences Report, The Effects on Human Health of 
Subtherapeutic Use of Antimicrobial Drugs in Animal Feeds. 
4.   1984 Seattle-King County Study:  Surveillance of the Flow of Salmonella and 
Campylobacter in a Community. 
5.  1988 Institute of Medicine (IOM) Report:  Human Health Risks with the 
Subtherapeutic Use of Penicillin or Tetracyclines in Animal Feed. 
6.  1997 World Health Organization (WHO) Report, The Medical Impact of Antimicrobial 
Use in Food Animals. http://whqlibdoc.who.int/hq/1997/WHO_EMC_ZOO_97.4.pdf  
7.  1999 National Research Council (NRC) Report:  The Use of Drugs in Food Animals  
Benefits and Risks. 
8.  1999 United States Government Accountability Office (GAO) Report  Food Safety:  
The Agricultural Use of Antibiotics and Its Implications for Human Health. 
http://www.gao.gov/archive/1999/rc99074.pdf  
9.  1999 European Commission Report, Opinion of the Scientific Steering Committee on 
Antimicrobial Resistance. http://ec.europa.eu/food/fs/sc/ssc/out50_en.pdf  
10.  2000 World Health Organization (WHO) Expert Consultation:  WHO Global 
Principles for the Containment of Antimicrobial Resistance in Animals Intended for 
Food. http://whqlibdoc.who.int/hq/2000/WHO_CDS_CSR_APH_2000.4.pdf  
11.  2003 Report, Joint FAO/OIE/WHO Expert Workshop on Non-Human Antimicrobial 
Usage and Antimicrobial Resistance: Scientific assessment. 
http://www.who.int/foodsafety/publications/micro/en/amr.pdf    
12.  2003 Institute of Medicine (IOM) Report, Microbial Threats to Health:  Emergence, 
Detection and Response. 
13.  2004 Report, Second Joint FAO/OIE/WHO Expert Workshop on Non-Human 
Antimicrobial Usage and Antimicrobial Resistance:  Management options. 
http://www.oie.int/fileadmin/Home/eng/Conferences_Events/docs/pdf/WHO-CDS-
CPE-ZFK-2004.8.pdf       
  23  Contains Nonbinding Recommendations 
 
 
14.  2004 United States Government Accountability Office (GAO) Report  Antibiotic 
Resistance:  Federal Agencies Need to Better Focus Efforts to Address Risks to 
Humans from Antibiotic Use in Animals. http://www.gao.gov/new.items/d04490.pdf   
15.  2005 Codex Alimentarius Commission (Codex), Code of Practice to Minimize and 
Contain Antimicrobial Resistance. 
http://www.codexalimentarius.net/download/standards/10213/CXP_061e.pdf  
16. 2006 Antimicrobial Resistance: Implications for the Food System, Comprehensive 
Reviews in Food Science and Food Safety, Vol. 5, 2006. 
 
17. 2009. American Academy of Microbiology.  Antibiotic Resistance: An Ecological 
Perspective on an Old Problem. 1752 N Street, NW Washington, DC 20036 
http://www.asm.org  
18. 2011. Tackling antibiotic resistance from a food safety perspective in Europe. World 
Health Organization (WHO), Regional Office for Europe Scherfigsvej 8, DK-2100 
Copenhagen , Denmark. 
http://www.euro.who.int/__data/assets/pdf_file/0005/136454/e94889.pdf  
19. 2008. Longitudinal study of antimicrobial resistance among Escherichia coli isolates 
from integrated multisite cohorts of humans and swine. Alali WQ, Scott HM, Harvey 
RB, Norby B, Lawhorn DB, Pillai SD. Appl Environ Microbiol. 74(12):3672-81.  
20. 2008. Diversity and distribution of commensal fecal Escherichia coli bacteria in beef 
cattle administered selected subtherapeutic antimicrobials in a feedlot setting. Sharma 
R, Munns K, Alexander T, Entz T, Mirzaagha P, Yanke LJ, Mulvey M, Topp  E, 
McAllister T. Appl Environ Microbiol.;74(20):6178-86.  
21. 2008. Effect of subtherapeutic administration of antibiotics on the prevalence of 
antibiotic-resistant Escherichia coli bacteria in feedlot cattle. Alexander, T.W., L.J. 
Yanke, E. Topp, M.E. Olson, R.R. Read, D.W. Morck, and T.A. McAllister. Applied 
and Environmental Microbiology. 74:4405-4416. 
22. 2009. A metagenomic approach for determining prevalence of tetracycline resistance 
genes in the fecal flora of conventionally raised feedlot steers and feedlot steers raised 
without antimicrobials. Harvey, R., J. Funk, T.E. Wittum, and A.E. Hoet. American 
Journal of Veterinary Research. 70:198-202. 
23. 2009. Association between tetracycline consumption and tetracycline resistance in 
Escherichia coli from healthy Danish slaughter pigs. Vieira, A.R., H. Houe, H.C. 
Wegener, D.M. Lo Fo Wong, and H.D. Emborg. Foodborne Pathogens and Disease. 
6:99-109. 
24. 2009. Associations between reported on-farm antimicrobial use practices and observed 
antimicrobial resistance in generic fecal Escherichia coli isolated from Alberta 
  24  Contains Nonbinding Recommendations 
 
 
finishing swine farms. Varga C., A. Rajic, M.E. McFall, R.J. Reid-Smith, A.E. Deckert, 
S.L. Checkley, and S.A. McEwen. Preventive Veterinary Medicine. 88:185-192. 
25. 2010. Farm-to-fork characterization of Escherichia coli associated with feedlot cattle 
with a known history of antimicrobial use. Alexander, T.W., G.D. Inglis, L.J. Yanke, E. 
Topp, R.R. Read, T. Reuter, and T.A. McAllister. International Journal of Food 
Microbiology. 137:40-48. 
26. 2011. Lower prevalence of antibiotic-resistant Enterococci on U.S. conventional 
poultry farms that transitioned to organic practices. Sapkota AR, Hulet RM, Zhang G, 
McDermott P, Kinney EL, Schwab KJ, Joseph SW. Environ Health Perspect. 
119(11):1622-8.   
27. 2011. Association between antimicrobial resistance in Escherichia coli isolates from 
food animals and blood stream isolates from humans in Europe: an ecological study. 
Foodborne Pathogens and Disease. Vieira, A.R., P. Collignon, F.M. Aarestrup, S.A. 
McEwen, R.S. Hendriksen, T. Hald, and H.C. Wegener. 8:1295-1301. 
28. 2011. Distribution and characterization of ampicillin- and tetracycline-resistant 
Escherichia coli from feedlot cattle fed subtherapeutic antimicrobials. Mirzaagha P, 
Louie M, Sharma R, Yanke LJ, Topp E, McAllister TA. BMC Microbiol. 19;11:78.  
29. 2012. In-feed antibiotic effects on the swine intestinal microbiome. Looft, T., T.A. 
Johnson, H.K. Allen, D.O. Bayles, D.P. Alt, R.D. Stedtfeld, W.J. Sul, T.M. Stedtfeld, 
B. Chai, J.R. Cole, S.A. Hashsham, J.M. Tiedje, and T.B. Stanton. Proceedings of the 
National Academy of Sciences USA. 109:1691-1696. 
 
 
                                                 
End Note 
 
Other studies referenced by the Department of Health and Human Services in response to 
2004 United States Government Accountability Office (GAO) Report  Antibiotic 
Resistance:  Federal Agencies Need to Better Focus Efforts to Address Risks to Humans 
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  25  Contains Nonbinding Recommendations 
 
 
                                                                                                                                                    
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