Research Paper

Microbiological Testing Results of Boneless and Ground Beef

Purchased for the U.S. National School Lunch Program, School

Years 2015 to 2018

SCOTT L. VIAL,1 DARIN R. DOERSCHER,2 CRAIG W. HEDBERG,1 WILLIAM A. STONE,2 STEPHEN J. WHISENANT,2

AND CARL M. SCHROEDER2*

1Environmental Health Sciences, School of Public Health, University of Minnesota, 420 East Delaware Street, Minneapolis, Minnesota 55455, USA; and 2Livestock and Poultry Program, Agricultural Marketing Service, U.S. Department of Agriculture, 1400 Independence Avenue,

Washington, DC 20250, USA

MS 19-241: Received 20 May 2019/Accepted 20 June 2019/Published Online 20 September 2019

ABSTRACT

The Agricultural Marketing Service (AMS) purchases beef for the National School Lunch Program and other federal

nutrition assistance programs. For beef that will be delivered to food service facilities raw, each ca. 900-kg lot of boneless beef

raw material and each ca. 4,500-kg sublot of resultant ground beef is tested for standard plate count (SPC) organisms, coliforms,

Escherichia coli, Salmonella, and E. coli O157:H7. In addition, 1 of every 10 lots of boneless beef, randomly selected, is tested

for E. coli O26, O45, O103, O111, O121, and O145. For beef that will be cooked using a validated lethality step at a federally

inspected establishment before delivery, each lot of boneless beef and each sublot of ground beef is tested for SPC organisms,

coliforms, and E. coli only. Any lot or sublot exceeding predefined critical limits (CLs) of 100,000 CFU g 1 for SPC organisms,

1,000 CFU g 1 for coliforms, or 500 CFU g 1 for E. coli or for beef containing Salmonella or any of previously mentioned E.

coli serotypes is rejected for purchase. For school years 2015 through 2018 (July 2014 through June 2018), 220,497,254 kg of

boneless beef and 189,347,318 kg of ground beef were produced for AMS. For boneless beef, 133 (0.06%), 164 (0.07%), and

106 (0.04%) of 240,488 lots exceeded CLs for SPC organisms, coliforms, and E. coli, respectively; 2,038 (1.30%) and 116

(0.07%) of 156,671 lots were positive for Salmonella and E. coli O157:H7, respectively; and 59 (0.36%) of 16,515 lots were

positive for non-O157 Shiga toxin producing E. coli. For ground beef, 46 (0.10%), 27 (0.06%), and 19 (0.04%) of 45,769

sublots exceeded CLs for SPC organisms, coliforms, and E. coli, respectively; and 329 (1.40%) and 18 (0.08%) of 23,475

sublots were positive for Salmonella and E. coli O157:H7, respectively. All lots and sublots found to exceed indicator organism

CLs or to contain pathogens were identified, rejected for purchase, and diverted from federal nutrition assistance programs.

HIGHLIGHTS

AMS purchases beef for the National School Lunch Program.

Less than 0.10% of beef samples exceeded indicator organism critical limits.

Salmonella was found in 1.4% and E. coli O157:H7 was found in 0.08% of samples.

Indicator critical limit exceedance was weakly associated with pathogen presence.

Beef with excessive indicator organisms or containing pathogens was rejected for purchase.

Key words: Beef; Escherichia coli O157:H7; National School Lunch Program; Salmonella

The Agricultural Marketing Service (AMS) purchases

food for federal nutrition assistance programs. Prominent

among these, the National School Lunch Program (NSLP)

provides food to approximately 31 million schoolchildren in

more than 100,000 participating institutions (26). Boneless

and ground beef are staples of the NSLP, with average

purchases of 46.7 million kg per year for 2015 through 2018

(1).

AMS purchase specifications for boneless and ground

beef include requirements for domestic origin, harvest

(slaughter), quality control, and animal handling and

welfare (3). Food safety requirements are also included in

the purchase specifications. These include that beef must be

produced under a grant of federal inspection and that

harvest establishments identify and implement at least two

pathogen intervention steps, one of which must be

scientifically validated to achieve a 3-log reduction of

enteric pathogens.

AMS also tests boneless and ground beef it intends to

purchase for various microorganisms (3). For raw beef * Author for correspondence. Tel: 202-692-0342; Fax: 202-720-1112;

E-mail: carl.schroeder@usda.gov.

1761

Journal of Food Protection, Vol. 82, No. 10, 2019, Pages 1761 1768

https://doi.org/10.4315/0362-028X.JFP-19-241

Published 2019 by the International Association for Food Protection

Not subject to U.S. Copyright



 











–

–
scheduled to be delivered directly to schools, every

approximately 900 kg of boneless beef used as raw material

and every 4,500 kg of ground beef finished product are

tested for the presence of Escherichia coli O157:H7 and

Salmonella and for concentrations of standard plate count

(SPC) organisms, coliforms, and E. coli. Since June 2014, 1

of every 10 lots of boneless beef, randomly selected, has

been tested for non-O157 Shiga toxin producing E. coli

(STEC; E. coli O26, O45, O103, O111, O121, and O145).

For boneless beef and coarse ground beef raw materials

scheduled to be cooked using a validated lethality step at a

federally inspected establishment and then delivered to

schools, each lot is tested for concentrations of SPC

organisms, coliforms, and E. coli only. Lots positive for

E. coli O157:H7, non-O157 STEC, or Salmonella or with

concentrations exceeding predefined critical limits (CLs) of

indicator microorganisms are rejected for purchase and

diverted from federal nutrition assistance programs.

To keep stakeholders informed, data generated from

AMS testing of boneless and ground beef are summarized

quarterly and posted to the AMS Web site (2). More

detailed analyses are done throughout the year to better

understand the findings, identify causes of contamination,

help guide the development and implementation of

corrective actions, and revise AMS purchase program

requirements. Data for school years 2011 through 2014

were analyzed and described previously (13). Here, we

describe data for school years 2015 through 2018 (July 2014

through June 2018).

MATERIALS AND METHODS

Sample collection. All samples were collected by trained

employees of AMS vendor establishments (4). For boneless beef,

samples representing the beef carcass exterior were collected

using one of two sampling methods from each approximately 900-

kg lot by AMS vendor establishment employees. The two

sampling method options were the N60 excision procedure (28)

and the N60 Plus modified excision mechanical sampling

procedure (21). Establishments using the latter method provided

in-house validation study documentation, indicating it was as

effective as the excision method at recovering comparable

microbial loads in boneless beef trimmings. For daily production

lots of ground beef, grab samples were collected randomly for

each approximately 4,500-kg sublot.

Microbiological analyses were done according to the Food

Safety and Inspection Service (FSIS) Microbiology Laboratory

Guidebook (28). In 2014, FSIS increased the sample size of

boneless and ground beef for Salmonella testing from 25 to 325 g.

However, AMS did not require vendors to collect the larger

sample size until March 2015. Therefore, an 8-month aggregate of

data within school year 2015, from July 2014 to March 2015, is

affected. Until March 2015, a 325-g 6 10% (293- to 358-g)

sample was collected and used in the assay to detect E. coli

O157:H7 and a separate 25-g 6 10% (2.5-g) sample was collected

and used in the assay to detect Salmonella. Beginning in March

2015, a single 325-g 6 10% (293- to 358-g) sample was collected

and used in the assay to detect E. coli O157:H7 and Salmonella.

For boneless beef only, this sample was also used for 1 of every 10

lots, randomly selected by the laboratory, for testing for non-O157

STEC. A separate 25-g 6 10% (23- to 28-g) sample was collected

and used in the assay to quantify SPC organisms, coliforms, and E.

coli for both boneless and ground beef. In all cases, fresh (not

frozen) samples were collected and aseptically transferred into

Whirl-Pak bags, sealed, and placed on prefrozen gel ice packs in

insulated shipping containers.

All samples collected by AMS vendor establishment

employees were sent to an AMS-designated laboratory (ADL).

Establishment employees completed sample submission forms

(which included tracking numbers, weight of product samples, lot

numbers, and similar information) supplied by the ADL. Sample

submission forms were placed with the samples inside the

insulated shipping containers and sent overnight to the ADL.

Sample receipt and processing. Sample receipt and

processing was done as previously described (13). Salmonella

isolates recovered through the AMS testing program were sent by

AMS ADLs to the FSIS Eastern Laboratory in Athens, Georgia,

where they were serotyped using the method described by

McQuiston et al. (19) and tested for antimicrobial susceptibility

using the methods and interpretive criteria of the National

Antimicrobial Resistance Monitoring System (NARMS) (20).

The following antimicrobials and resistance breakpoints (in

micrograms per milliliter) were included: gentamicin ( 16),

kanamycin ( 64), streptomycin ( 32), amoxicillin clavulanic

acid ( 32/16), meropenem ( 4), cefoxitin ( 32), ceftriaxone

( 4), sulfamethoxazole or sulfisoxazole ( 512), trimethoprimsulfamethoxazole ( 4/76), azithromycin ( 32), ampicillin ( 32),

chloramphenicol ( 32), ciprofloxacin ( 1), nalidixic acid ( 32),

and tetracycline ( 16).

For detecting and quantifying SPC organisms, total coliforms, and E. coli in boneless beef, protocols described in Section

3.2 of the FSIS Microbiology Laboratory Guidebook (28) were

used. A 25-g sample was placed into a sterile blender jar or

stomacher bag, 450 mL of sterile Butterfield’s phosphate diluent

or buffered peptone water was added, and the sample was blended

or shaken vigorously for 2 min. The resultant homogenate was

serially diluted. SPC organisms were quantified using the Petrifilm

method described in Section 3.6.2 of the FSIS Microbiology

Laboratory Guidebook (28). Total coliforms and E. coli were

quantified using the method described in Section 3.7.2 of the FSIS

Microbiology Laboratory Guidebook (28).

Result reporting. Microbiological results were provided by

the ADL to the AMS in comma-separated value files uploaded to a

Microsoft SQL database. Serotype information was provided

quarterly by electronic mail from FSIS to AMS and manually

input into Microsoft Excel spreadsheets.

Data analysis. Microbiological test results were organized

and summarized using Microsoft Excel pivot table functions.

Tibco Spotfire Desktop 7.13.0 was used to examine the data for

relationships between pathogen-positive samples and those in

which indicator microorganisms exceeded CLs. Odds ratios (ORs)

were calculated using Stata 14.2.

The Centers for Disease Control and Prevention (CDC)

National Outbreak Reporting System (NORS) was queried for

Salmonella and E. coli outbreaks in school settings between

calendar years 2010 and 2017 (10). Outbreak vehicle and type of

school setting were determined to identify any outbreaks

associated with ground beef obtained through the NSLP.

RESULTS

During school years 2015 through 2018, 220,497,254

kg of boneless beef was tested (Table 1). The boneless beef

1762 VIAL ET AL. J. Food Prot., Vol. 82, No. 10



 

  

 

  

  



–

–
was tested in 240,488 lots (an average of 917 kg per lot).

Testing showed 133 lots (0.06%) exceeded the SPC CL, 164

lots (0.07%) exceeded the coliform CL, and 106 lots

(0.04%) exceeded the E. coli CL.

Of the 240,488 boneless beef lots, 156,671 (65.15%)

were scheduled for use as raw materials for uncooked

ground beef delivery to federal nutritional assistance

programs and were therefore tested for E. coli O157:H7,

Salmonella, and non-O157 STEC (Table 2). Testing showed

116 lots (0.07%) were positive for E. coli O157:H7, and

2,038 lots (1.30%) tested positive for Salmonella. In

addition, 59 (0.36%) of 16,515 randomly selected boneless

beef lots tested positive for non-O157:H7 STEC (Table 3).

Lots produced from school year 2016 onward and that

exclusively used the larger 325-g coenriched pathogen

sample were significantly more likely to test positive for

Salmonella than lots produced in school year 2015 (OR 1⁄4

1.55, 95% confidence interval [95% CI] 1⁄4 1.39 to 1.73). In

contrast, lots produced from school year 2016 onward were

significantly less likely to test positive for E. coli O157:H7

compared with previous years (OR1⁄40.35, 95% CI1⁄40.24 to

0.51).

For the same school years, 189,347,318 kg of ground

beef was tested for indicator microorganisms (Table 4). The

ground beef was tested in 45,769 sublots (an average of

4,137 kg per sublot). Testing showed that 46 sublots

(0.10%) exceeded the SPC CL, 27 sublots (0.06%)

exceeded the coliform CL, and 19 sublots (0.04%) exceeded

the E. coli CL. Of the 45,769 sublots, 23,475 (51.29%) were

scheduled for raw, uncooked delivery to federal nutrition

assistance programs and thus tested for E. coli O157:H7 and

Salmonella (Table 5). Of these sublots, 18 (0.08%) tested

positive for E. coli O157:H7 and 329 (1.40%) tested

positive for Salmonella. Sublots of ground beef produced

between school years 2016 and 2018 were significantly

more likely to test positive for Salmonella than lots

produced in school year 2015 (OR 1⁄4 2.28, 95% CI 1⁄4 1.75

to 3.00). There was no significant difference in E. coli

O157:H7 positive samples in school year 2015 compared

with subsequent years (OR 1⁄4 1.31, 95% CI 1⁄4 0.45 to 4.25).

Pathogen prevalence in ground beef was compared

with its prevalence in source boneless beef. Salmonella

prevalence was higher in ground beef (1.40%) compared

with boneless beef (1.30%), but the difference was not

statistically significant (OR 1⁄4 1.08, 95% CI 1⁄4 0.96 to 1.21).

Similarly, E. coli O157:H7 prevalence was higher in ground

beef (0.08%) than boneless beef (0.07%), but the difference

was not statistically significant (OR 1⁄4 1.04, 95% CI 1⁄4 0.59

to 1.71).

Associations between CL exceedance and pathogen

presence were weak. Of the 95 boneless beef lots that

exceeded the SPC CL, 2 (2.11%) were Salmonella positive.

Of the 164 lots that exceeded the coliform CL, 3 (1.83%)

were Salmonella positive. Of the 106 lots that exceeded the

E. coli CL, 3 (2.83%) were Salmonella positive. Exceeding

CLs was not associated with significantly increased

Salmonella presence for SPC organisms (OR 1⁄4 1.63, 95%

CI 1⁄4 0.19 to 6.07), coliforms (OR 1⁄4 1.41, 95% CI 1⁄4 0.29 to

TABLE 1. AMS boneless beef indicator microorganism performance by school year

School yeara Total kg, no. Lots, no. (%)

SPC critical limit

exceeded, no. (%)

b

Coliform critical limit

exceeded, no. (%)

c

E. coli critical limit

exceeded, no. (%)

d

2015 50,258,723 54,284 (22.6) 18 (0.03) 38 (0.07) 24 (0.04)

2016 55,751,935 60,801 (25.3) 32 (0.05) 40 (0.07) 27 (0.04)

2017 58,641,394 64,289 (26.7) 52 (0.08) 34 (0.05) 24 (0.04)

2018 55,845,202 61,114 (25.4) 31 (0.05) 52 (0.09) 31 (0.05)

Total 220,497,254 240,488 (100.0) 133 (0.06) 164 (0.07) 106 (0.04)

a July through June. b Standard plate count (SPC) critical limit: 100,000 CFU g 1

. c Total coliform critical limit: 1,000 CFU g 1

. d E. coli critical limit: 500 CFU g 1

.

TABLE 2. AMS boneless beef E. coli O157:H7 and Salmonella performance by school year

School yeara Total kg, no. Lots, no. (%)

E. coli O157:H7

positive, no. (%)

b,c

Salmonella

positive, no. (%)

b,d

2015e 42,508,987 45,849 (29.3) 63 (0.14) 431 (0.94)

2016 47,766,214 52,021 (33.2) 18 (0.03) 931 (1.79)

2017 27,398,382 29,887 (19.1) 15 (0.05) 394 (1.32)

2018 26,662,635 28,914 (18.5) 20 (0.07) 282 (0.98)

Total 144,336,217 156,671 (100.0) 116 (0.07) 2,038 (1.30)

a July through June. b E. coli O157:H7 and Salmonella critical limit: positive (þ) result 325 g 1

. c Odds of E. coli O157:H7 presence from school years 2016 through 2018 compared with school year 2015: OR 1⁄4 0.35, 95% CI 1⁄40.24 to

0.51.

d Odds of Salmonella presence from school years 2016 through 2018 compared with school year: OR 1⁄4 1.55, 95% CI 1⁄4 1.39 to 1.73. e July 2014 to February 2015; Salmonella critical limit: positive (þ) result, 25 g 1

.

J. Food Prot., Vol. 82, No. 10 NATIONAL SCHOOL LUNCH PROGRAM BEEF TESTING 1763











–
4.21), or E. coli (OR 1⁄4 2.21, 95% CI 1⁄4 0.45 to 6.65).

Pearson correlations between SPC, coliforms, and E. coli

with Salmonella were low (r 1⁄4 0.145, 0.135, and 0.168,

respectively). No boneless beef lot that exceeded an

indicator CL was positive for E. coli O157:H7.

For ground beef, of 25 sublots that exceeded the SPC

CL, 1 (4%) was positive for Salmonella. Exceeding the SPC

CL was not significantly associated with Salmonella

presence (OR 1⁄4 2.94 95% CI 1⁄4 0.07 to 18.12). Pearson

correlation between SPC CL exceedance and Salmonella in

ground beef was 0.199. Of the 15 sublots that exceeded the

coliform CL, none tested positive for Salmonella or E. coli

O157:H7. Of the 9 sublots that exceeded the E. coli CL,

none tested positive for Salmonella or E. coli O157:H7.

A total of 1,309 Salmonella isolates from 2,038

boneless beef lots were serotyped and tested for antimicrobial susceptibility. Salmonella Dublin was the most frequent

serotype (n 1⁄4 681, 52.0%), followed by Salmonella

Newport (n 1⁄4 141, 10.8%) and Salmonella Montevideo (n

1⁄4 105, 8.0%; Table 6). In addition, 475 isolates (36.3%)

were susceptible to all antimicrobials on the panel

(pansusceptible), 35 isolates (2.7%) were resistant to no

more than two antimicrobials, and 799 isolates (61.0%)

were resistant to at least three antimicrobials (Table 7).

In ground beef, Salmonella isolates from 251 sublots

were serotyped and tested for antimicrobial susceptibility.

Salmonella Montevideo was the most frequent serotype (n1⁄4

85, 33.9%), followed by Salmonella Dublin (n1⁄4 35, 13.9%)

and Salmonella Newport (n 1⁄4 24, 9.6%; Table 8). In

addition, 173 (68.9%) ground beef isolates were pansusceptible, 13 (5.2%) were resistant to no more than two

antimicrobials, and 65 (25.9%) were resistant at least three

antimicrobials (Table 9). Salmonella isolates recovered

from ground beef were significantly more likely to be

pansusceptible (OR 1⁄4 3.89, 95% CI 1⁄4 2.89 to 5.27) and

significantly less likely to be resistant to at least three

antimicrobials (OR 1⁄4 0.22, 95% CI 1⁄4 0.16 to 0.30) than

those recovered from boneless beef.

For school years 2015 through 2018, the six most

frequently reported Salmonella serotypes in boneless and

ground beef were identical. These were Salmonella

serotypes Dublin, Newport, Montevideo, Typhimurium,

Muenchen, and Anatum. While boneless and ground beef

each had the same six most frequent serotypes, the order of

the six was different. Salmonella Dublin composed 52.0%

of isolates in boneless beef compared with 13.9% of isolates

in boneless beef (OR 1⁄4 6.69, 95% CI 1⁄4 4.58 to 10.01). In

contrast, Salmonella Montevideo composed 8.0% of

isolates in boneless beef and 33.9% of isolates in ground

beef (OR 1⁄4 0.17, 95% CI 1⁄4 0.12 to 0.24). The prevalence of

Salmonella Dublin detection in boneless and ground beef

was 43.5 of 10,000 lots and 14.9 of 10,000 sublots,

respectively. The prevalence of Salmonella Montevideo

TABLE 3. AMS boneless beef non-O157 STEC performance by

school year

School yeara Total kg, no. Lots, no. (%)

Non-O157

STEC positive,

no. (%)

b,c

2015 4,500,603 4,692 (28.4) 19 (0.40)

2016 5,099,809 5,562 (33.7) 30 (0.54)

2017 2,957,906 3,231 (19.6) 6 (0.19)

2018 2,802,325 3,030 (18.4) 4 (0.13)

Total 15,360,643 16,515 (100.0) 59 (0.36)

a July through June. b E. coli serotypes O26, O45, O103, O111, O121, and O145. c Non-O157 STEC critical limit: positive (þ) result, 325 g 1

.

TABLE 4. AMS ground beef indicator organism performance by school year

School yeara Total kg, no. Sublots, no. (%)

SPC critical limit

exceeded, no. (%)

b

Coliform critical limit

exceeded, no. (%)

c

E. coli critical limit

exceeded, no. (%)

d

2015 39,552,867 9,453 (20.7) 24 (0.25) 3 (0.03) 3 (0.03)

2016 47,401,073 11,216 (24.5) 11 (0.10) 4 (0.04) 9 (0.08)

2017 52,869,100 12,713 (27.8) 4 (0.03) 13 (0.10) 4 (0.03)

2018 49,524,277 12,387 (27.1) 7 (0.06) 7 (0.06) 3 (0.02)

Total 189,347,318 45,769 (100.0) 46 (0.10) 27 (0.06) 19 (0.04)

a July through June. b Standard plate count (SPC) critical limit: 100,000 CFU g 1

. c Total coliform critical limit: 1,000 CFU g 1

. d E. coli critical limit: 500 CFU g 1

.

TABLE 5. AMS ground beef E. coli O157:H7 and Salmonella

performance by school year

School

yeara

Total kg,

no.

Sublots,

no. (%)

E. coli O157:H7

positive,

no. (%)

b,c

Salmonella

positive,

no. (%)

d

2015e 38,855,723 9,287 (39.6) 6 (0.06) 74 (0.80)

2016 18,042,628 4,236 (18.0) 7 (0.17) 48 (1.13)

2017 20,742,450 4,892 (20.8) 3 (0.06) 56 (1.14)

2018 19,737,271 5,060 (21.6) 2 (0.04) 151 (2.98)

Total 97,378,072 23,475 (100.0) 18 (0.08) 329 (1.40)

a July through June. b E. coli O157:H7 and Salmonella critical limit: positive (þ) result,

325 g 1

. c Odds of E. coli O157:H7 presence from school years 2016

through 2018 compared with school year 2015: OR 1⁄4 1.31, 95%

CI 1⁄4 0.45 to 4.25. d Odds of Salmonella presence from school years 2016 through

2018 compared with school year 2015: OR 1⁄4 2.28, 95% CI 1⁄4

1.75 to 3.00. e July 2014 to February 2015, Salmonella critical limit: positive

(þ) result, 25 g 1

.

1764 VIAL ET AL. J. Food Prot., Vol. 82, No. 10












detection in boneless and ground beef was 6.7 of 10,000 lots

and 36.2 of 10,000 sublots, respectively. Salmonella Dublin

isolates were frequently antimicrobial resistant in both

boneless and ground beef. Among Salmonella Dublin

isolates from boneless beef lots and ground beef sublots,

95.7 and 100%, respectively, displayed resistance to at least

three antimicrobials. The reduction in Salmonella Dublin

prevalence from boneless to ground beef led to the overall

reduction of antimicrobial-resistant Salmonella in ground

beef compared with boneless beef.

Twenty-nine outbreaks of Salmonella and STEC

infections in U.S. schools, colleges, and universities

between 2010 and 2017 were reported to the CDC through

NORS: 19 outbreaks of Salmonella and 10 outbreaks of

STEC. Twelve outbreaks occurred in schools serving

kindergarten through 12th grade (eight Salmonella and four

STEC). None of these outbreaks were associated with beef

products procured by AMS for the NSLP.

DISCUSSION

In procuring ground beef, AMS requires microbiological testing at two critical points in the production

continuum: after harvesting when carcasses are converted

into boneless beef trim and before final packaging of ground

product. Concentrations of indicator microorganisms are

used as measures of overall process control, and dispositional testing for pathogens is done to monitor the safety of

beef that will be delivered raw.

Indicator microorganisms are helpful for examining the

hygiene of beef carcasses and their resultant products and

for evaluating the effectiveness of processing aids and

interventions (8, 23). The observation that less than 0.10%

of boneless beef lots produced for AMS in school years

2015 through 2018 exceeded CLs for SPC organisms,

coliforms, or E. coli, suggests the beef was produced under

stringent sanitary controls. Compared with boneless beef

produced for AMS during school years 2011 through 2014

(13), boneless beef produced for AMS during school years

TABLE 6. Salmonella serotypes recovered from boneless beef

during school years 2015 to 2018a

Salmonella serotype No. (%) of isolates

Dublin 681 (52.02)

Newport 141 (10.77)

Montevideo 105 (8.02)

Typhimurium 43 (3.28)

Muenchen 36 (2.75)

Anatum 31 (2.37)

Give 27 (2.06)

Cerro 22 (1.68)

Muenster 22 (1.68)

Kentucky 15 (1.15)

Agona 14 (1.07)

Infantis 12 (0.92)

Altona 11 (0.84)

Meleagridis 10 (0.76)

Cubana 9 (0.69)

Norwich 9 (0.69)

Oranienburg 8 (0.61)

I4,5,12:i: 7 (0.53)

Thompson 7 (0.53)

Uganda 7 (0.53)

Barranquilla 6 (0.46)

Bredeney 6 (0.46)

Mbandaka 6 (0.46)

Schwarzengrund 6 (0.46)

Enteritidis 5 (0.38)

Minnesota 5 (0.38)

Senftenberg 4 (0.31)

a n 1⁄4 1,309. In addition to the serotypes shown in the table, three

isolates were recovered of Albany, Brandenburg, Kiambu,

Poona, Rissen, Rough O:z4,z23: , and Sandiego; two isolates

were recovered of 6,14,25:a:1,7, Braenderup, Falkensee, Havana, Manhatta, and Memphis; and one isolate was recovered of

13,23: :l,w, 3,10: :l,w, 6,7:Nonmotile, Adelaide, Berta, Blockley, Choleraesuis, Derby, Johannesburg, Lille, Livingstone,

Orion_var_15þ, Orion_var_15þ,3, Oslo, Panama, Reading,

Rough_O:k:1,5, Rough_O:gms: , Saintpaul, Soerenga, and

Tennessee.

TABLE 7. Salmonella antimicrobial resistance profiles recovered

from boneless beef during school years 2015 to 2018a

Resistance profile No. (%) of isolates

Pansusceptible 475 (36.29)

Aug Amp Fox Tio Axo Chl Str Fis Tet 232 (17.72)

Aug Amp Fox Tio Axo Chl Nal Str Fis Tet 115 (8.79)

Aug Amp Fox Axo Chl Str Fis Tet 114 (8.71)

Chl Fis Str Tet 55 (4.20)

Aug Amp Fox Axo Chl Nal Str Fis Tet 48 (3.67)

Chl Nal Fis Str Tet 26 (1.99)

Aug Amp Fox Tio Axo Chl Gen Fis Tet 23 (1.76)

Aug Amp Tio Axo Chl Str Fis Tet 19 (1.45)

Aug Amp Fox Tio Axo Chl Str Fis Tet Cot 18 (1.38)

Amp Str Fis Tet 15 (1.15)

Tet 14 (1.07)

Aug Amp Axo Chl Nal Str Fis Tet 12 (0.92)

Nal Str Fis Tet 11 (0.84)

Aug Amp Chl Nal Str Fis Tet 10 (0.76)

Aug Amp Axo Chl Str Fis Tet 9 (0.69)

Aug Amp Fox Axo ChlStr Fis Tet Cot 9 (0.69)

Aug Amp Chl Str Fis Tet 8 (0.61)

Aug Amp Tio Axo Chl Nal Str Fis Tet 8 (0.61)

Fis 5 (0.38)

Str Tet 5 (0.38)

Amp Chl Str Fis Tet 4 (0.31)

Aug Amp Fox Tio Axo Str Fis Tet 4 (0.31)

Fis Tet 4 (0.31)

Str Fis Tet 4 (0.31)

Aug Amp Fox Tio Axo Chl Gen Fis 3 (0.23)

Aug Aump Fox Tio Axo Chl Nal Str Fis Tet Cot 3 (0.23)

Aug Amp Fox Tio Axo Chl Str Tet 3 (0.23)

Chl Str Fis Tet Cot 3 (0.23)

a n 1⁄4 1,309. Amp, ampicillin; Aug, amoxicillin clavulanic acid;

Axo, ceftriaxone; Chl, chloramphenicol; Cot, trimethoprimsulfamethoxazole; Fis, sulfamethoxazole-sulfisoxazole; Fox,

cefoxitin; Gen, gentamicin; Nal, nalidixic; Str, streptomycin;

Tet, tetracycline; Tio, ceftiofur. In addition to those shown in the

table, two isolates were recovered for each of 14 separate

antimicrobial resistance profiles and one isolate was recovered

for each of 25 separate antimicrobial resistance profiles.

J. Food Prot., Vol. 82, No. 10 NATIONAL SCHOOL LUNCH PROGRAM BEEF TESTING 1765





 



–
2015 through 2018 was significantly less likely to have SPC

concentrations exceeding the CL (0.06% of samples from

2015 through 2018 compared with 0.10% of samples from

2011 through 2014) but significantly more likely to have E.

coli concentrations exceeding the CL (0.04% of samples

from 2015 through 2018 compared with 0.03% of samples

collected from 2011 to 2014). The reasons for this are not

clear. AMS will continue to closely monitor indicator

organism performance of boneless beef and partner with

vendors to help ensure process control is maintained.

Pathogen testing helps detect, and subsequently remove

from the AMS procurement program, pathogen-positive

product. Slightly more than 1% of the boneless beef lots

produced for AMS for school years 2015 through 2018 were

found to be positive for Salmonella, and less than 0.50% of

the lots were found to be positive for E. coli O157:H7 and

other STEC serotypes. The low level of pathogens found in

boneless beef produced for AMS likely results from the

multipronged approach to food safety used by the beef

processing industry (32). That AMS was able to identify

these pathogen-positive lots and remove them from

production resulted in decreased incidence of Salmonella

and E. coli O157:H7 in ground beef compared with what it

would have otherwise been. The increase in Salmonella

positive boneless beef lots is likely due to the sampling

change mid-school year 2015, in which sample size was

increased from 25 to 325 g. Before implementation, FSIS

projected that the Salmonella sample size change would

result in an increase in the number of Salmonella-positive

samples (27). Data from this study suggest the prediction

was accurate.

Observations made for ground beef produced for school

years 2015 through 2018 were like those made for boneless

beef during the same period. Less than 0.10% of the lots of

ground beef produced for AMS contained concentrations of

indicator organisms exceeding CLs, again demonstrating

the strong process control maintained by AMS vendors.

Salmonella-positive ground beef sublots, although found at

an incidence of under 1.50%, were more likely to occur for

school years 2015 through 2018 compared with school

years 2011 through 2014 (1.40% compared with 0.77%)

(13). As with boneless beef, this is likely because of the

sampling protocol change mid-school year 2015, in which

sample size was increased from 25 to 325 g. However,

ground beef sampling size for E. coli O157:H7 remained

constant at 325 g throughout school years 2011 through

2018; thus, sampling size variation does not explain the

observation that E. coli O157:H7 positive lots of boneless

beef were more likely to occur for school years 2015

through 2018 compared with school years 2011 through

2014. The increase in E. coli O157:H7 positive lots,

although unexplained, highlights the need for continued

investigation into methods for modeling pathogenic E. coli

distribution during grinding (17, 18) and developing

mitigations to further limit it (25, 34, 35).

Salmonella Dublin, a host-adapted serotype found in

both symptomatic and asymptomatic North American dairy

cattle (12, 16, 29, 31), was the most commonly detected

Salmonella serotype in boneless beef produced for school

years 2015 through 2018. Its underlying prevalence in

source herds is likely a key factor in its occurrence in

boneless beef produced for AMS. On-farm mitigations,

including purchasing animals from Salmonella Dublin

negative herds and good pen management, appear effective

TABLE 8. Salmonella serotypes recovered from ground beef

during school years 2015 to 2018a

Salmonella serotype No. (%) of isolates

Montevideo 85 (33.86)

Dublin 35 (13.94)

Newport 24 (9.56)

Anatum 15 (5.98)

Typhimurium 13 (5.18)

Muenchen 10 (3.98)

Meleagridis 8 (3.19)

Give 6 (2.39)

I4,5,12:i: 6 (2.39)

Cerro 5 (1.99)

Mbandaka 5 (1.99)

Norwich 5 (1.99)

Agona 4 (1.59)

Hadar 3 (1.20)

Muenster 3 (1.20)

Derby 2 (0.80)

Johannesburg 2 (0.80)

Reading 2 (0.80)

Sandiego 2 (0.80)

Senftenberg 2 (0.80)

a n 1⁄4 251. In addition to the serotypes shown in the table, one

isolate of each of the following serotypes was recovered:

13,23: :l,w, 3,10: :l,w, 6,7:Nonmotile, Adelaide, Berta, Blockley, Choleraesuis, Derby, Johannesburg, Lille, Livingstone,

Orion_Var_15þ, Orion_Var_15þ,3... , Oslo, Panama, Reading,

Rough O:k:1,5, Rough O:gms: , Saintpaul, Soerenga, and

Tennessee.

TABLE 9. Salmonella antimicrobial resistance profiles recovered

from ground beef during school years 2015 to 2018a

Resistance profile No. (%) of isolates

Pansusceptible 173 (68.92)

Aug Amp Fox Axo Chl Str Fis Tet 22 (8.76)

Aug Amp Fox Tio Axo Chl Nal Str Fis Tet 11 (4.38)

Aug Amp Fox Tio Axo Chl Str Fis Tet 11 (4.38)

Aug Amp Fox Axo Chl Nal Str Fis Tet 6 (2.39)

Tet 5 (1.99)

Str Tet 4 (1.59)

Amp Str Fis Tet 3 (1.20)

Chl Str Fis Tet 3 (1.20)

Amp Chl Str Fis Tet 2 (0.80)

Str Fis 2 (0.80)

a n 1⁄4 251. Amp, ampicillin; Aug, amoxicillin clavulanic acid;

Axo, ceftriaxone; Chl, chloramphenicol; Cot, trimethoprimsulfamethoxazole; Fis, sulfamethoxazole-sulfisoxazole; Fox,

cefoxitin; Gen, gentamicin; Nal, nalidixic; Str, streptomycin;

Tet, tetracycline; Tio, ceftiofur. In addition to those shown in the

table, one isolate was recovered for each of nine separate

antimicrobial resistance profiles.

1766 VIAL ET AL. J. Food Prot., Vol. 82, No. 10



 



–

–

–

-

–
in limiting Salmonella Dublin (22). More research is needed

to define additional mitigation strategies.

Salmonella Montevideo was the most commonly

detected Salmonella serotype in ground beef produced for

AMS. Salmonella Montevideo occurs on dairy farms (9)

and thus may be introduced into beef during slaughter and

processing. In addition, Salmonella Montevideo has been

shown to colonize cattle lymph nodes (21), and although

AMS requires removal of major lymph glands from

boneless beef before grinding, it is possible that grinding

of smaller lymph nodes helps explain the increased

incidence of Salmonella Montevideo in ground beef

procured by AMS.

Approximately 65% of Salmonella isolates from

boneless beef and approximately 30% of those from ground

beef were resistant to one or more antimicrobials. Extendedspectrum cephalosporins are important antimicrobials for

treating salmonellosis in children. The observation of

ceftriaxone and/or cefoxitin resistance among the Salmonella isolates recovered in this study is thus concerning.

Neither ceftriaxone nor cefoxitin is approved for therapeutic

use in food animals, but a closely related cephalosporin,

ceftiofur, has been approved (30). Ceftiofur use may thus

help explain the occurrence of ceftiofur-ceftriaxone-cefoxitin coresistant Salmonella isolates in boneless and ground

beef produced for AMS.

Data from this study suggest some additional general

conclusions about the AMS boneless and ground beef

purchase program and are helpful for guiding future

research. First, a key factor likely behind the relatively

low incidence of Salmonella-positive boneless beef lots and

ground beef sublots is the AMS purchase requirement that

major lymph glands be removed from boneless beef (3).

Salmonella is found in the lymph nodes of asymptomatic

cattle (24), where they may persist for up to a month (14).

Thus, removing lymphatic material from boneless beef

before grinding is a key mitigation in the AMS purchase

program. As the impact of cattle type, location, and season

on Salmonella carriage in bovine lymph nodes is elucidated

(5, 7, 21, 33), beef producers and processors will likely be

able to further mitigate the occurrence of Salmonella in

boneless and ground beef. The efficacy of and feasibility for

implementing Salmonella vaccination programs in cattle

(11, 15) should continue to be explored.

Second, indicator organism CL exceedance was not

significantly correlated with pathogen presence. Although

past research suggests a lack of correlation between

indicator organisms and pathogen presence (23), a study

of pig slaughtering in Belgium found small but significant

associations between Enterobacteriaceae concentrations

and Salmonella presence (6). However, our study examined

correlation between CL exceedance and pathogen presence

and not, more broadly, a continuum of indicator concentration and pathogen presence. The risk of pathogen presence

within the AMS data sets may also vary by indicator

concentration. We are exploring relationships that may exist

between the indicator concentrations and the pathogens

described in this study.

Third, the extent to which testing and subsequent

removal of pathogen-positive boneless beef lots reduced the

amount of pathogen contamination in ground beef is not

clear. It is tempting to suggest that because of the

differences in lot and sublot sizes tested (900 kg for

boneless beef and 4,500 kg for ground beef), the reduction

of E. coli O157:H7 and Salmonella between boneless and

ground beef is greater than it first appears. However,

differences in sampling confounds such comparisons. Work

to mathematically model the impact of removing pathogenpositive boneless beef lots and pathogen-positive ground

beef sublots on recipient exposure is needed.

Taken cumulatively, findings from this study suggest

that beef produced for the NSLP and other federal nutrition

assistance programs during school years 2015 through 2018

was done so under well-controlled food safety systems.

Given the setting in which most beef procured by AMS is

consumed school cafeterias any outbreak of illness is

likely to be ascertained by public health authorities; yet to

the best of our knowledge, no outbreaks of foodborne

illness have been attributed to beef procured by AMS (10).

In an effort to ensure federal nutrition assistance program

recipients receive safe food, AMS will continue to engage

the full spectrum of stakeholders to refine and strengthen its

beef purchase specifications, and it will work with partners

at the Food and Nutrition Service and elsewhere to help

provide safe food handling and related training to those who

prepare and serve the beef it procures.

ACKNOWLEDGMENTS

We thank the vendors that produced the beef described in this report;

staff at ADLs and at the FSIS Eastern Laboratory for sample analysis; staff

at the CDC for providing data from the NORS; J. Mark Carter, Kari

Godbey Houchens, Stephen W. Mamber, Ken Melton, and Angie Siemens

for comments during manuscript preparation; and Bruce Alexander, Jeff

Bender, Rod Bowling, Mohammed Atif Jalal, Terry Lutz, and Scott Wells

for technical support.

REFERENCES

1. Agricultural Marketing Service. 2019. AMS purchases by commodity. Available at: https://www.ams.usda.gov/reports/ams-purchasescommodity. Accessed 22 April 2019.

2. Agricultural Marketing Service. 2019. Microbiological testing of

AMS purchased meat, poultry and egg commodities. Available at:

https://www.ams.usda.gov/resources/microbiological-testing. Accessed 22 April 2019.

3. Agricultural Marketing Service. 2019. Product specifications &

requirements: beef. Available at: https://www.ams.usda.gov/sellingfood/product-specs#Beef. Accessed 22 April 2019.

4. Agricultural Marketing Service. 2019. Qualified bidders list.

Available at: https://www.ams.usda.gov/selling-food/becomingapproved. Accessed 22 April 2019.

5. Belk, A. D., A. N. Arnold, J. E. Sawyer, D. B. Griffin, T. M. Taylor,

J. W. Savell, and K. B. Gehring. 2018. Comparison of Salmonella

prevalence rates in bovine lymph nodes across feeding stages. J.

Food Prot. 81:549 553.

6. Biasino, W., L. De Zutter, W. Mattheus, S. Bertrand, M. Uyttendaele,

and I. Van Damme. 2018. Correlation between slaughter practices

and the distribution of Salmonella and hygiene indicator bacteria on

pig carcasses during slaughter. Food Microbiol. 70:192 199.

7. Brown, T. R., T. S. Edrington, G. H. Loneragan, D. L. Hanson, K.

Malin, J. J. Ison, and D. J. Nisbet. 2015. Investigation into possible

differences in Salmonella prevalence in the peripheral lymph nodes

of cattle derived from distinct production systems and of different

breed types. J. Food Prot. 78:2081 2084.

8. Camargo, A. C., M. V. C. Cossi, W. P. D. Silva, L. D. S. Bersot, M.

Landgraf, J. Baranyi, B. Franco, and N. Luis Augusto. 2019.

J. Food Prot., Vol. 82, No. 10 NATIONAL SCHOOL LUNCH PROGRAM BEEF TESTING 1767

— —

–

–

–
Microbiological testing for the proper assessment of the hygiene

status of beef carcasses. Microorganisms 7:86.

9. Cao, H., A. K. Pradhan, J. S. Karns, E. Hovingh, D. R. Wolfgang, B.

T. Vinyard, S. W. Kim, S. Salaheen, B. J. Haley, and J. A. S. Van

Kessel. 2019. Age-associated distribution of antimicrobial-sesistant

Salmonella enterica and Escherichia coli isolated from dairy herds in

Pennsylvania, 2013 2015. Foodborne Pathog. Dis. 16:60 67.

10. Centers for Disease Control and Prevention. 2019. National Outbreak

Reporting System (NORS). Available at: https://www.cdc.gov/nors/.

Accessed 22 April 2019.

11. Cernicchiaro, N., S. E. Ives, T. S. Edrington, T. G. Nagaraja, and D.

G. Renter. 2016. Efficacy of a Salmonella siderophore receptor

protein vaccine on fecal shedding and lymph node carriage of

Salmonella in commercial feedlot cattle. Foodborne Pathog. Dis.

13:517 525.

12. Cummings, K. J., P. D. Virkler, B. Wagner, E. A. Lussier, and B. S.

Thompson. 2018. Herd-level prevalence of Salmonella Dublin

among New York dairy farms based on antibody testing of bulk

tank milk. Zoonoses Public Health 65:1003 1007.

13. Doerscher, D. R., T. L. Lutz, S. J. Whisenant, K. R. Smith, C. A.

Morris, and C. M. Schroeder. 2015. Microbiological testing results of

boneless and ground beef purchased for the National School Lunch

Program, 2011 to 2014. J. Food Prot. 78:1656 1663.

14. Edrington, T. S., G. H. Loneragan, K. J. Genovese, D. L. Hanson, and

D. J. Nisbet. 2016. Salmonella persistence within the peripheral

lymph nodes of cattle following experimental inoculation. J. Food

Prot. 79:1032 1035.

15. Edrington, T. S., G. H. Loneragan, J. Hill, K. J. Genovese, D. M.

Brichta-Harhay, R. L. Farrow, N. A. Krueger, T. R. Callaway, R. C.

Anderson, and D. J. Nisbet. 2013. Development of challenge models

to evaluate the efficacy of a vaccine to reduce carriage of Salmonella

in peripheral lymph nodes of cattle. J. Food Prot. 76:1259 1263.

16. Gutema, F., G. Agga, R. Abdi, L. D. Zutter, L. Duchateua, and S.

Gabriel. 2019. Prevalence and serotype diversity of Salmonella in

apparently healthy cattle: systematic review and meta-analysis of

published studies, 2000 2017. Front. Vet. Sci. 6:102.

17. Kitanov, P. M., and A. R. Willms. 2018. Probability of Escherichia

coli contamination spread in ground beef production. Math. Biosci.

Eng. 15:1011 1032.

18. Loukiadis, E., C. Bieche-Terrier, C. Malayrat, F. Ferre, P. Cartier, and

J. C. Augustin. 2017. Distribution of Escherichia coli O157:H7 in

ground beef: assessing the clustering intensity for an industrial-scale

grinder and a low and localized initial contamination. Int. J. Food

Microbiol. 250:75 81.

19. McQuiston, J. R., R. J. Waters, B. A. Dinsmore, M. L. Mikoleit, and

P. I. Fields. 2011. Molecular determination of H antigens of

Salmonella by use of a microsphere-based liquid array. J. Clin.

Microbiol. 49:565 573.

20. National Antimicrobial Resistance Monitoring System. 2016.

Manual of laboratory methods. Available at: https://www.fda.gov/

media/101423/download. Accessed 10 May 2019.

21. Nickelson, K. J., T. M. Taylor, D. B. Griffin, J. W. Savell, K. B.

Gehring, and A. N. Arnold. 2019. Assessment of Salmonella

prevalence in lymph nodes of U.S. and Mexican cattle presented

for slaughter in Texas. J. Food Prot. 82:310 315.

22. Nielsen, T. D., I. L. Vesterbaek, A. B. Kudahl, K. J. Borup, and L. R.

Nielsen. 2012. Effect of management on prevention of Salmonella

Dublin exposure of calves during a one-year control programme in

84 Danish dairy herds. Prev. Vet. Med. 105:101 109.

23. Saini, P. K., H. M. Marks, M. S. Dreyfuss, P. Evans, L. V. Cook, Jr.,

and U. Dessai. 2011. Indicator organisms in meat and poultry

slaughter operations: their potential use in process control and the

role of emerging technologies. J. Food Prot. 74:1387 1394.

24. Samuel, J. L., D. A. O Boyle, W. J. Mathers, and A. J. Frost. 1980.

Isolation of Salmonella from mesenteric lymph nodes of healthy

cattle at slaughter. Res. Vet. Sci. 28:238 241.

25. Sheen, S., J. Cassidy, B. Scullen, and C. Sommers. 2015. Inactivation

of a diverse set of Shiga toxin producing Escherichia coli in ground

beef by high pressure processing. Food Microbiol. 52:84 87.

26. U.S. Department of Agriculture, Food and Nutrition Service. 2010.

USDA foods in the National School Lunch Program. Available at:

https://www.fns.usda.gov/fdd/usda-foods-national-school-lunchprogram-white-paper. Accessed 18 June 2019.

27. U.S. Department of Agriculture, Food Safety and Inspection Service.

2015. Changes to Salmonella verification sampling program: analysis

of raw beef for Shiga toxin producing Escherichia coli and

Salmonella. Fed. Regist. 79:32436 32440.

28. U.S. Department of Agriculture, Food Safety and Inspection Service.

2019. Microbiology laboratory guidebook. Available at: https://www.

fsis.usda.gov/wps/portal/fsis/topics/science/laboratories-andprocedures/guidebooks-and-methods/microbiology-laboratoryguidebook/microbiology-laboratory-guidebook. Accessed 18 June

2019.

29. U.S. Food and Drug Administration. 2017. The National Antimicrobial Resistance Monitoring System: NARMS integrated report,

2015. Available at: https://www.fda.gov/animal-veterinary/nationalantimicrobial-resistance-monitoring-system/2015-narms-integratedreport. Accessed 18 June 2019.

30. U.S. Food and Drug Administration. 2019. Animal drugs @ FDA.

Available at: https://animaldrugsatfda.fda.gov/adafda/views/#/search.

Accessed 24 April 2019.

31. Valenzuela, J. R., A. K. Sethi, N. A. Aulik, and K. P. Poulsen. 2017.

Antimicrobial resistance patterns of bovine Salmonella enterica

isolates submitted to the Wisconsin Veterinary Diagnostic Laboratory: 2006 2015. J. Dairy Sci. 100:1319 1330.

32. Viator, C. L., S. C. Cates, S. A. Karns, and M. K. Muth. 2017. Food

safety practices in the U.S. meat slaughter and processing industry:

changes from 2005 to 2015. J. Food Prot. 80:1384 1392.

33. Webb, H. E., D. M. Brichta-Harhay, M. M. Brashears, K. K.

Nightingale, T. M. Arthur, J. M. Bosilevac, N. Kalchayanand, J. W.

Schmidt, R. Wang, S. A. Granier, T. R. Brown, T. S. Edrington, S. D.

Shackelford, T. L. Wheeler, and G. H. Loneragan. 2017. Salmonella

in peripheral lymph nodes of healthy cattle at slaughter. Front.

Microbiol. 8:2214.

34. Wolf, M. J., M. F. Miller, A. R. Parks, G. H. Loneragan, A. J.

Garmyn, L. D. Thompson, A. Echeverry, and M. M. Brashears. 2012.

Validation comparing the effectiveness of a lactic acid dip with a

lactic acid spray for reducing Escherichia coli O157:H7, Salmonella,

and non-O157 Shiga toxigenic Escherichia coli on beef trim and

ground beef. J. Food Prot. 75:1968 1973.

35. Zhou, Y., M. V. Karwe, and K. R. Matthews. 2016. Differences in

inactivation of Escherichia coli O157:H7 strains in ground beef

following repeated high pressure processing treatments and cold

storage. Food Microbiol. 58:7 12.

1768 VIAL ET AL. J. Food Prot., Vol. 82, No. 10

–

–

– – ’

–

–

–

–

– –

–

–

–

–

–

– –

–

–

–

–

–

–

–