Diversity of New Delhi metallo-beta-lactamase-producing bacteria in China.

Objectives: The prevalence and dissemination of diverse NDM-producing bacteria in China was investigated.

Methods: We collected 1,162 isolates from 8 cities during December 2013∼May 2015 in China. The NDM-positive strains as well as the NDM genotypes in these sample were detected via Vitek 2 compact system (bioMérieux, France), 16S rRNA gene sequencing, PCR and an S1- pulsed-field gel electrophoresis assay and Southern blot hybridization. The horizontal-transfer capability of the bla gene was assessed by filter mating by using a standard E.coli J53 azide-resistant strain as the recipient.

Results: Three genotypes (NDM-1, NDM-3 and NDM-5) of NDM-producing bacteria were identified, among which the NDM-1-positive isolates were the most frequent one. For the first time, we found NDM-5-produing S.typhimurium and NDM-3-produing E.coli in China. We also found that the NDM-positive (especially NDM-3 and NDM-5) strains were completely resistant to nearly all of the antimicrobial drugs utilized and bla was mostly located on diverse plasmids with sizes ranging from 30 to 670kb.

Conclusion: Various species of bacteria especially the enteric pathogens with diverse NDM genotypes had spread in China. Hence, an ongoing surveillance of their dissemination is essential to prevent and control the spread of these organisms.