Submitted to: Proceedings of the International Conference on Emerging Infectious Diseases
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2006
Publication Date: March 21, 2006
Citation: Jackson, C.R., Cray, P.J., Barrett, J.B., Hiott, L.M., Woodley, T.A. 2006. Prevalence of streptogramin resistance in enterococci from animals: identification of the first vatd from enterococci in the united states [abstract]. Proceedings of the International Conference on Emerging Infectious Diseases. 415:171. Technical Abstract: Background: Streptogramins are combination antimicrobials which are divided into two groups: streptogramin A and B. Virginiamycin and Quinupristin-Dalfopristin (Q/D), both combination streptogramins, are used in animals and humans, respectively. There is much debate over the use of virginiamycin in animals to the contribution of Q/D resistance in humans. In this study, prevalence and mechanisms of streptogramin resistance in enterococci from animals and the environment was investigated. Methods: From 2000-2004, enterococci were isolated from poultry carcass rinsates, fruits, vegetables, retail meats, and environmental rinsates or from swine and cattle fecal samples collected on-farm. Enterococcus isolates were identified to species and then analyzed for antimicrobial susceptibility to a panel of 17 antimicrobials. Q/D resistant isolates (MIC >4) were subjected to PCR using primers to streptogramin resistance genes (ermB, msrC, vatD, and vatE,). Results: From the analysis, 1029/6227 (17%) Q/D resistant, non-E. faecalis enterococci were identified. The majority of Q/D isolates were E. hirae (n=349), followed by E. casseliflavus (n=271) and E. faecium (n=259). Using PCR, 56% (n=571) were positive for ermB, 3% (n=34) for msrC, 2% (n=20) for vatE, and 0.3% (n=3) for vatD; 39% (n=401) of the isolates were negative for all genes tested. The vatD positive samples were E. faecium (n=2) from chicken carcass rinsates, and E. hirae from a swine fecal sample. The nucleotide sequence of vatD from the three isolates was 100% homologous to published vatD sequences. In addition, PFGE patterns of vatD E. faecium isolates were indistinguishable. Conclusions: These data indicate that Q/D resistance among enterococci from animals remains low even with the long use of virginiamycin. To date, this is the first report of vatD from enterococci in the US. Prevalence of vatD was very low suggesting that the gene has not been widely disseminated among these isolates. More study is needed to investigate the mechanism of resistance to streptogramins in isolates for which resistance genes remain unidentified.