Submitted to: Foodborne Pathogens Analysis Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2001
Publication Date: 7/15/2001
Citation: Jackson, C.R., Cray, P.J., Barrett, J.B., Hall, M.C., Jain, L., Reeves, D.E. Prevalence of aminoglycoside resistance among enterococci isolated from swine. Foodborne Pathogens Analysis Conference. 2001.
Technical Abstract: Aminoglycosides are one class of antimicrobials used in both food animal production and human medicine. They are commonly used in conjunction with cell wall inhibiting antimicrobials such as ampicillin and vancomycin to synergistically kill enterococci. High-level aminoglycoside resistance can diminish the effect of the antimicrobial combination. In this study, the prevalence of resistance to gentamicin and streptomycin in enterococci isolated from swine fecal samples from three different facilities was determined. Two hundred and ninety-one enterococci were isolated and speciated. The predominant species identified was E. durans (n=135) followed by E. faecalis (n=77), and E. faecium (n=53). Approximately 8.9% of the enterococci (26/291) were resistant to gentamicin (MIC > 500 ug/ml) and 31% (90/291) were resistant to streptomycin (MIC >500 ug/ml). Using PCR primers specific for aminoglycoside resistance genes, all but one of the resistant isolates were positive for aadE and none contained aadA. Twelve percent (14/116) of the resistant isolates were resistant to both aminoglycosides. The gene that confers bifunctional aminoglycoside resistance, aac(6')- aph(2"), was also present in 64% (9/14) of the multiple resistant isolates in addition to aadE. One multiple resistant isolate (E. faecalis) was negative by PCR for both aadE and aac-aph, and the mechanism of resistance remains to be determined for this isolate. This study suggests that although aminoglycoside resistance is present in swine enterococcus isolates, the prevalence remains relatively low.