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

Veterinary Services 

Centers for Epidemiology and Animal Health June 2009 

_________________________________________________________________________________________________________________________ 

Enterococcus on U.S. Beef 

Cow-calf Operations, 2007–08 

Most enterococcal bacteria are normal inhabitants of 

human and animal gastrointestinal tracts. However, 

enterococci are also a common cause of hospitalacquired infections in humans, especially after surgery. 

Two species of enterococci, Enterococcus faecalis and 

E. faecium, are responsible for most human disease 

caused by enterococci, with E. faecalis predominantly 

responsible for most infections. However, antimicrobial 

resistance is more common with E. faecium than with E. 

faecalis. 

Antimicrobial resistant enterococci can be found in 

livestock, and there are concerns that the resistance 

components of these enterococci could be transferred to 

other bacteria, including those that cause human illness. 

It is possible that foodborne transmission of enterococci 

could also play a role in human illness. However, the 

extent of any contribution to human illness from 

enterococci of livestock origin is not well understood. 

Beef 2007–08 study 

The U.S. Department of Agriculture’s National 

Animal Health Monitoring System conducted the Beef 

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

and management practices in 24 States.* 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 Enterococcus and associated 

antimicrobial resistance on beef cow-calf operations in 

the United States. 

Testing for Enterococcus was performed on 173 of 

the beef cow-calf operations participating in the study. 

Up to 10 fresh fecal samples from individual fecal pats 

on the ground were taken from each operation and 

tested for presence of Enterococcus. Care was taken to 

ensure that samples originated from adult beef cows. Of 

the 1,479 samples collected, 1,182 (79.9 percent) were 

positive for Enterococcus, and at least one positive 

sample was found on 170 of the 173 operations 

(98.3 percent). 

E. faecalis and/or E. faecium were found on 43.9 

percent of operations. Of the 1,182 positive samples, 

11.5 percent and 3.2 percent were E. faecium 

*

States:

Alabama, Arkansas, California, Colorado, Florida, Georgia, Idaho, 

Iowa, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, 

Nebraska, New Mexico, North Dakota, Oklahoma, Oregon, South 

Dakota Tennessee, Texas, Virginia, and Wyoming.

and E. faecalis, respectively (table 1). The highest 

percentage of isolates (39.0 percent) were identified as 

E. casseliflavus. Of the operations on which enterococci 

were found, 83.5 percent had at least one 

E. casseliflavus isolate and 73.5 percent had at least 

one E. hirae isolate. E. faecium and E. faecalis were 

found on 38.8 percent and 14.1 percent of positive 

operations, respectively. 

Table 1. Number and Percentage of Isolates (and 

Number and Percentage of Positive Operations), by 

Enterococcus Species 

Isolates* 

(n=1,182) 

Operations 

(n=170) 

Species No. Pct. No. Pct. 

E. casseliflavus 461 39.0 142 83.5 

E. hirae 303 25.6 125 73.5 

E. mundtii 169 14.3 73 42.9 

E. faecium 136 11.5 66 38.8 

Not typed 57 4.8 43 25.3 

E. faecalis 38 3.2 24 14.1 

E. gallinarum 9 0.8 6 3.5 

E. durans 6 0.5 5 2.9 

E. avium 3 0.3 3 1.8 

Total 1,182 100.0 NA NA 

*The number of isolates equals the number of positive samples since 

only one Enterococcus species was identified in each sample. 

Enterococcus antimicrobial susceptibility

Of the 1,180 isolates tested for antimicrobial 

susceptibility, 11 (0.9 percent) were susceptible to all 17 

antimicrobials. Two isolates were not viable at the time 

of antimicrobial testing. All of the E. faecalis and 

E. faecium isolates were resistant to at least one 

antimicrobial. Vancomycin resistance is of particular 

interest, since it is commonly used to treat humans with 

serious enterococcal infections.1

 One E. casseliflavus

isolate was resistant to vancomycin, but this was 

determined to be an intrinsic resistance (naturally 

occurring trait) rather than an acquired resistance. None 

of the E. faecalis or E. faecium isolates was resistant to 

vancomycin. Resistance to quinupristin/dalfopristin 

(Synercid®) is also of importance because this 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

antimicrobial is used to treat vancomycin-resistant 

E. faecium infections.1 Only 0.7 percent of E. faecium

and 0.9 percent of other enterococci were resistant to 

Synercid. Over 90 percent of the E. faecium and other 

enterococci were resistant to flavomycin, while none of 

the E. faecalis isolates were resistant to flavomycin. 

Overall, 100.0, 54.1, and 90.7 percent of the 

E. faecalis, E. faecium, and other enterococci, 

respectively, were resistant to lincomycin (table 2). 

Table 2. Percentage of Resistant Enterococcus

Isolates, by Species and by Antimicrobial:* 

 Percent 

E. 

faecalis

(n=38) 

E. 

faecium

(n=135) 

Other 

Enterococci

(n=1,007) 

Antimicrobial Percent Percent Percent 

Chloramphenicol 0.0 0.7 0.0 

Ciprofloxacin 0.0 45.9 4.1 

Daptomycin** 0.0 0.0 5.3 

Erythromycin 0.0 0.7 0.8 

Flavomycin 0.0 92.6 90.3 

Gentamicin 0.0 0.0 0.0 

Kanamycin 0.0 1.5 0.0 

Lincomycin 100.0 54.1 90.7 

Linezolid 0.0 0.0 0.0 

Nitrofurantoin 0.0 3.0 0.1 

Penicillin 2.6 0.7 0.4 

Streptomycin 0.0 0.0 0.0 

Synercid NA*** 0.7 0.9 

Tetracycline 2.6 12.6 18.2 

Tigecycline** 0.0 0.0 0.0 

Tylosin 0.0 0.0 1.1 

Vancomycin 0.0 0.0 0.1**** 

*Intermediate isolates were classified as susceptible. 

**The Clinical and Laboratory Standards Institute has no approved 

standards for daptomycin and tigecycline susceptibility testing. 

***E. faecalis exhibits an intrinsic resistance to synercid. 

****One E. casseliflavus isolate was intrinsically resistant to 

vancomycin. 

Conclusions 

Enterococcus was found on 98.3 percent of the beef 

cow-calf operations tested and in 79.9 percent of the 

samples collected. The high prevalence of enterococci 

was expected, since this organism is a normal inhabitant 

of the gastrointestinal tract of animals and humans. 

E. faecalis or E. faecium, the organisms responsible for 

most of the human illness caused by enterococci, were 

found on less than one-half of operations (43.9 percent). 

E. casseliflavus was the most common species 

identified. Synercid and vancomycin are two of the more 

important antimicrobials used in treating human 

enterococcal infections. There was very little resistance 

to synercid and no notable resistance to vancomycin. 

Resistance to lincomycin and flavomycin was most 

commonly observed in the isolates from this study. 

References 

1. McGowan, LL, Jackson, CR, Barrett, JB, Hiott, LM, FedorkaCray, PJ. 2006. Prevalence and antimicrobial resistance of 

Enterococci isolated from retail fruits, vegetables, and meats. 

J. Food Prot. 69:12;2976-2982. 

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 

#N554.0609 

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