United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health June 2009 

_________________________________________________________________________________________________________________________ 

Salmonella on U.S. Beef Cowcalf Operations, 2007–08 

Salmonella bacteria have been isolated from nearly all 

vertebrates, and Salmonella infections have been 

associated with both animal and human disease. Typical 

signs of Salmonella infection in cattle and humans 

include fever and diarrhea. Severe cases can result in 

death. 

Shedding of Salmonella bacteria in cattle often 

occurs in the absence of clinical signs, sometimes for 

extended periods. In some cases, foods of animal origin 

have been implicated as the source of human illness 

caused by Salmonella. Salmonellosis in humans is 

typically self-limiting and most people recover within 

1 week. Antimicrobials are not necessary for treatment 

of most Salmonella infections in humans and animals; 

however, Salmonella resistance to antimicrobials is a 

concern because it can complicate treatment options in 

severe infections. 

NAHMS Beef 2007–08 study 

The U.S. Department of Agriculture’s National 

Animal Health Monitoring System (NAHMS) conducted 

the Beef 2007–08 study, which focused on beef cow-calf 

health and management practices in 24 States from 

three regions of the United States.1

 These States 

represented 79.6 percent of U.S. operations with beef 

cows and 87.8 percent of U.S. beef cows. 

One objective of the Beef 2007–08 study was to 

describe the occurrence of Salmonella and associated 

antimicrobial resistance on beef cow-calf operations in 

the United States. NAHMS also examined Salmonella

occurrence in adult cows on beef cow-calf operations in 

its Beef ‘97 study. For comparison purposes, this 

information sheet presents data from both studies 

Table 1 presents results from the two NAHMS beef 

cow-calf studies. For each of the studies, samples were 

collected from up to 40 fresh fecal pats on the ground. 

Care was taken to ensure samples originated from adult 

beef cows. 

 

1

States/Regions 

West: California, Colorado, Idaho, Montana, New Mexico, Oregon, 

Wyoming 

Central: Iowa, Kansas, Missouri, Nebraska, North Dakota, South 

Dakota 

Southeast: Alabama, Arkansas, Florida, Georgia, Kentucky, 

Louisiana, Mississippi, Oklahoma, Tennessee, Texas, Virginia

For the Beef ‘97 study, samples were taken from 

187 beef cow-calf operations; for the Beef 2007–08 

study, samples were taken from 173 operations. Results 

in table 1 indicate little change occurred from 1997 to 

2007 in the percentage of positive operations and cows 

positive for Salmonella. 

Table 1. Number and Percentage of Operations (and 

Number and Percentage of Cows Sampled) Positive 

for Salmonella

Operations with 

at Least One 

Positive Cow 

Positive 

Sampled Cows 

No. Pct. No. Pct. 

Beef ‘97 21/187 11.2 70/5,049 1.4 

Beef 2007–08 16/173 9.2 31/5,793 0.5 

In the Beef 2007–08 study, the number of 

Salmonella-positive cow-calf operations did not differ 

substantially by herd size2

 or by region. Two cow-calf 

operations tested positive for four different Salmonella

serotypes, and two different serotypes were present on 

three operations. On all other positive operations, only a 

single serotype was identified. S. Montevideo was the 

most common serotype (17.6 percent of isolates 

[table 2]. 

Table 2. Number and Percentage of Salmonella

Isolates (and Number and Percentage of Positive 

Operations), by Serotype 

Isolates* (n=34) Operations (n=16) 

Serotype No. Pct. No. Pct. 

Braenderup 2 5.9 2 12.5 

Meleagridis 2 5.9 1 6.3 

Montevideo 6 17.6 2 12.5 

Newport 2 5.9 2 12.5 

I 3,10:-:1,w 2 5.9 1 6.3 

I 6,7:k:- 3 8.8 1 6.3 

All others** 17 50.0 13 81.3 

*More than one isolate was cultured from two samples. 

**Three untypable isolates are included here, as well as serotypes 

with one isolate each (Anatum, Javiana, Lawndale, Mbandaka, 

Oukam, Rubislaw, Saugas, and seven unnamed serotypes). 

 

2

Herd size (Number of Beef Cows): 1-49, 50-99, 100-199, 200 or more. 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Salmonella antimicrobial susceptibility

None of the Salmonella isolates from the 

Beef 2007–08 study were resistant to any of the 

15 antimicrobials against which they were tested. In the 

Beef ‘97 study, only 12.8 percent of the isolates were 

resistant to at least one antimicrobial (table 3). 

Table 3. Percentage of Resistant Salmonella 

Isolates, by Antimicrobial* 

 Percent Isolates 

Antimicrobial 

Beef ‘97 

(n=78) 

Beef 

2007–08 (n=34)

Amikacin 0.0 0.0 

Amoxicillin-Clavulanic 

acid 0.0 0.0 

Ampicillin 1.3 0.0 

Apramycin 0.0 NA 

Cefoxitin NA 0.0 

Ceftiofur 0.0 0.0 

Ceftriaxone 0.0 0.0 

Cephalothin 0.0 NA 

Chloramphenicol 0.0 0.0 

Ciprofloxacin 0.0 0.0 

Gentamicin 2.6 0.0 

Kanamycin 0.0 0.0 

Nalidixic Acid 0.0 0.0 

Streptomycin 11.5 0.0 

Sulfamethoxazole** 11.5 0.0 

Tetracycline 2.6 0.0 

Ticarcillin 1.3 NA 

TrimethoprimSulfamethoxazole 0.0 0.0 

Resistant to two or 

more antimicrobials 11.5 0.0 

Susceptible to all 

antimicrobials 

tested** 87.2 100.0 

* Intermediate isolates were classified as susceptible. 

**Sulfisoxazole replaced Sulfamethoxazole in 2007–08. 

NA = antimicrobial not included for this study. 

Summary 

The percentage of Salmonella-positive beef cow-calf 

operations in the Beef ‘97 and Beef 2007–08 studies 

was quite low, with Salmonella being found on about 

10 percent of operations in each study. Approximately 

1 percent of samples were positive for Salmonella in 

Beef ‘97 and Beef 2007–08. These results suggest that 

Salmonella are not very common on U.S. beef cow-calf 

operations. It is possible that repeated sampling of these 

same operations over time could identify more positive 

operations. Herd size and region of the United States 

were not associated with the presence of Salmonella on 

operations from the Beef 2007–08 study. Antimicrobial 

resistance was not observed in any of the Salmonella

isolates from the Beef 2007–08 study, and very little 

resistance was seen in isolates from the Beef ‘97 study. 

These results suggest that antimicrobial-resistant 

Salmonella are uncommon in U.S. beef cow-calf 

operations. 

APHIS acknowledges the contributions of the USDA–ARS Bacterial 

Epidemiology and Antimicrobial Resistance Research Unit for their 

participation in the Beef 2007–08 study. 

____________________ 

For more information, contact: 

USDA–APHIS–VS–CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

#N553.0609 

____________________________________ 

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