Characterization of vancomycin-resistant Enterococcus faecium isolated from swine in three Michigan counties

Vancomycin-resistant enterococci are a major cause of nosocomial infections but are rarely found in humans in the community and have not been identified in food animals in the United States. We evaluated a total of 360 fecal specimens from humans and their animals being raised for exhibit at three county fairs in Michigan. Fecal samples from 158 humans, 55 swine, 50 cattle, 25 horses, 57 sheep, 14 goats, and 1 llama were obtained and plated onto Enterococcosel agar containing 16 microg/ml of vancomycin. Vancomycin-resistant Enterococcus faecium (VREF) was isolated from six pigs but not from humans or any animal other than pigs. All six VREF isolates had a MIC to vancomycin of ≥256 microg/ml and contained the vanA gene. Pulsed-field gel electrophoresis (PFGE) patterns of the six VREF isolates were ≥80% similar. Multilocus sequence typing (MLST) revealed sequence type 5 (ST5) (n = 2), ST6 (n = 3), and ST185 (n = 1), which are E. faecium sequence types belonging to clonal complex 5 (CC5). These findings show the dissemination of VREF strains among pigs in three Michigan counties. This is the first report of VRE found in food animals in the United States.