A new Tn1546 type of VanB phenotype–vanA genotype vancomycin-resistant Enterococcus faecium isolates in mainland China

VanB phenotype–vanA genotype vancomycin-resistant Enterococcus faecium (VREF) has never been reported in mainland China. We investigated the frequency and molecular characteristics of this strain in a Beijing tertiary hospital. Of 23 vanA genotype VREF clinical isolates, 12 (54.3%) were VanB phenotype–vanA genotype. Mutilocus sequence typing (MLST) analysis revealed that all isolates belong to a single clonal complex (CC78), which has been disseminated worldwide. Based on MLST and pulsed-field gel electrophoresis, 23 isolates were polyclonal dissemination in our hospital. Tn1546-like element structure analysis showed that of 12 VanB phenotype–vanA genotype isolates, 5 had complete deletion of vanY and vanZ accompanying insertion of IS1216V in vanX–vanY intergenic region, 5 had ISEfa4 insertion in orf2–vanR intergenic region, a new Tn1546 structure type, and 2 were identical to VanA phenotype–vanA genotype VREF. Data showed that the deletion of vanY and vanZ genes or ISEfa4 insertion in orf2–vanR intergenic region can partly explain the causes of difference between phenotype and genotype.