Molecular characterization of erythromycin and tetracycline-resistant Enterococcus faecalis isolated from retail chicken meats.

Enterococcus faecalis is a ubiquitous intestinal bacterium in human and animals that can easily acquire antimicrobial resistance, which allows it to play the role of an antimicrobial resistance indicator. The objectives of this study were to characterize erythromycin and tetracycline-resistant E. faecalis isolated from retail chicken meats. A total of 149 among 335 E. faecalis isolates from 7 integrated broiler operations showed the simultaneous resistance to erythromycin and tetracycline, and more than 50% among 149 isolates showed multidrug resistance. The most common resistance genes were ermB (96.0%, 143 isolates) related with macrolides resistance, and tet(M) (95.3%, 142 isolates) and tet(L) (89.3%, 133 isolates) related with tetracycline resistance. Furthermore, 140 (93.9%) isolates simultaneously possessed ermB, and tet(L) and/or tet(M) genes. Eight isolates with transposon of the Tn916/1545-like were detected, which also carried ermB and tet(M) genes. The most prevalent of virulence genes were gelE (142 isolates, 95.3%), ace (137 isolates, 91.9%), and efaA (120 isolates, 80.5%). Also, 5 E. faecalis isolates successfully transferred antimicrobial and virulence genes to E. faecalis FA2-2. Therefore, the antimicrobial-resistant E. faecalis isolates as well as their corresponding genes and mobile genetic elements, such as transposons may be disseminated nationwide by broiler operation system in Korea.