High Prevalence of VanB2 Vancomycin-Resistant Enterococcus faecium in Taiwan

Thirty-six VanB glycopeptide-resistant Enterococcus faecium isolates were collected from patients in five different hospitals in Taiwan. The vancomycin resistance genes were amplified by the long vanB PCR, which amplifies the 6,373-bp vanB gene cluster including the vanRB2, vanSB2, vanYB2, vanWB2, vanHB2, vanB2, and vanXB2 genes. The deduced amino acid sequences were found to be 95 to 98% homologous to those of the vanB1 gene cluster: VanRB1, 97%; VanSB1, 97%; VanYB1, 96%; VanHB1, 95%; VanB1, 96%; and VanXB1, 98%. Restriction enzyme analysis of the long vanB PCR products revealed that all 36 isolates had the same vanB2-specific pattern. DNA sequence analysis of the vanB2 gene, which is a d-Ala–d-Lac ligase gene, revealed that none of the 36 sequences were identical to the previously published vanB2 sequence. Thirty-one isolates had 1 nucleotide different from the published vanB2 sequence. The sequences of the other five isolates differed from the published vanB2 sequence by 2 or 3 nucleotides. Four isolates with a low or moderate resistance to vancomycin (MIC = 4 to 32 μg/ml) were found to have the same leucine-to-methionine change at amino acid position 308 of the vanB2 gene. The genomic DNAs of all 36 isolates were digested with SmaI and then typed by pulsed-field gel electrophoresis (PFGE). Eight different PFGE types (I to VIII) were observed, and type I was found to be prevalent in all hospitals examined in this study. This result suggests that intra- and interhospital dissemination of this E. faecium strain has occurred in Taiwan.