Characterization of antimicrobial resistance in enterococci of animal origin.

Among 97 enterococci cultured from animals, gentamicin MICs were greater than or equal to 2,000 mu g/ml for 9 isolates and between 250 and 1,024 mu g/ml for 6 isolates. For two isolates tested (gentamicin MICs, 256 and 512 mu g/ml, respectively), there was no in vitro synergy with penicillin plus gentamicin, resistance was transferable, and there was no hybridization with a probe specific for 6'-aminoglycoside acetyltransferase-2 "-aminoglycoside phosphotransferase. The results of the study indicate the presence of a unique gentamicin resistance genotype in enterococci of animal origin.