Prevalence of Staphylococcus aureus and MRSA Carriage in Three Populations
ACVIM 2008
S. Kottler1; J.R. Middleton1; J.S. Weese2; L.A. Cohn1
1University of Missouri College of Veterinary Medicine, Columbia, MO, USA; 2Ontario Veterinary College, University of Guelph, Guelph, ON, Canada

Considered primarily a human pathogen, methicillin-resistant Staphylococcus aureus (MRSA) can colonize animals. Prior studies have demonstrated a higher prevalence of MRSA colonization in healthcare workers (human and veterinary) than in the people with non-medically related occupations. We hypothesized that the prevalence of MRSA colonization would be higher in people and pets who reside in households with veterinary or human healthcare workers than in households without healthcare workers. One healthy volunteer (nasal swab) and a pet from the same household (nasal and rectal swabs) were sampled. Swabs were placed in enrichment broth and coagulase positive staphylococci (CPS) were identified by standard methods. CPS were classified as S. aureus using a latex agglutination test (LAT) and polymyxin B susceptibility. Staphylococcus aureus isolates were screened for methicillin resistance via PBP2a LAT and mecA PCR. Proportional data were compared using the Chi square test (P < 0.05).

Six hundred and one sample sets (1,803 samples) were obtained; 202 sets were from households with human healthcare workers (group 1), 223 veterinary healthcare workers (group 2), and 176 from non-healthcare workers (group 3). 103/601 (17.1%) pets sampled were cats and 498/601 (82.9%) were dogs. Overall, S. aureus was isolated from 166/601 (27.6%) of humans and 79/601 (13.1%) of pet nasal and rectal samples. For 26/245 (10.6%) S. aureus isolates, both a human and animal in the same household were colonized. Shared colonization was equally likely in all groups (10 from group 1, 10 group 2, and 6 from group 3).

Of 245 S. aureus isolates, 49 were MRSA (20%). Among S. aureus isolates, 31 of 166 human isolates (18.7%) were MRSA while 18/79 (22.8%) pet isolates were MRSA (Table). MRSA was present in 31/601 (5.2%) of humans sampled and 18/601 (3.0%) pets. There were no differences in prevalence of MRSA between groups of humans (9/202 group 1, 13/223 group 2, 9/176 group 3) or pets (6/202 group 1, 4/223 group 2, and 8/176 group 3). For 6/49 (12.2%) of the MRSA isolates, both an animal and human in the same household were colonized representing two households per group.


Group 1

Group 2

Group 3


MRSA among human SA isolates

9/60 (15%)

13/60 (22%)

9/46 (20%)

31/166 (19%)

MRSA among pet SA isolates

6/22 (27%)

4/34 (12%)

8/23 (35%)

18/79 (23%)

We were unable to demonstrate that colonization with S. aureus or MRSA was more common in households with healthcare workers. However, we found a greater prevalence of both S. aureus and MRSA in pet animals than has been previously demonstrated, and demonstrated that MRSA is found as commonly among S. aureus isolates from pets as from human isolates.

Speaker Information
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Stephanie Kottler

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