Occurrence of the van genes in Enterococcus faecalis and Enterococcus faecium from clinical isolates in Korea

Enterococcus faecalis and Enterococcus faecium isolated from Korea patients in 1998 and 2005 were tested for susceptibility to nine different antimicrobial agents, including vancomycin and teicoplanin. Polymerase chain reaction (PCR) was used for the detection of several vancomycin resistance genes such as vanA ('high level'), vanB ('moderate high level'), vanC1 and vanC2 ('low level'). Both E. faecalis and E. faecium exhibited a resistance of 80% and more than 60% to synercid and mupirocin, respectively. Moreover, an average of 76% of all isolates was resistant to ciprofloxacin, gentamicin, lincomycin, cefotaxime, and meropenem, confirming the multiple drug resistance of most of the isolates. No resistance to vancomycin or teicoplanin was observed in the 1998 E. faecalis and E. faecium isolates. However, the 2005 E. faecalis and E. faecium isolates exhibited resistance of 16% and 12% to vancomycin and teicoplanin, respectively. In addition, vanA gene was detected in 4 strains of 2005 E. faecium isolates, thus showing a high resistance to vancomycin. No other vancomycin resistance genes, including vanB, vanC1, and vanC2, were found in our isolates. In this study, we compared the occurrence of antimicrobial resistance and the presence of specific resistance genes in E. faecalis and E. faecium. The results showed that the 2005 isolates were usually more resistant than the 1998 isolates.