Emergence of NDM-1-producing Acinetobacter baumannii in China

To investigate the prevalence of blaNDM-1 in Gram-negative bacilli in China. A total of 11 298 clinical Gram-negative bacilli, covering Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa, were collected for PCR-based surveillance of blaNDM-1 from 57 hospitals representing 18 provinces in China. For blaNDM-1-positive isolates, antibiotic susceptibilities were assessed and molecular typing was performed using PFGE. The genetic location of blaNDM-1 was determined by analysis of PFGE profiles of S1 nuclease-digested genomic DNA and Southern blot hybridization. Plasmid transfer to E. coli recipients was investigated using filter mating and electroporation. Four A. baumannii isolates with blaNDM-1 were identified in four different provinces in China: no positive isolates were detected among E. coli, K. pneumoniae and P. aeruginosa. These blaNDM-1-positive A. baumannii were resistant to all carbapenems and cephalosporins, and three remained susceptible to fluoroquinolones, aminoglycosides and colistin. The four NDM-1-producing A. baumannii were clonally diverse and carried blaNDM-1 on different plasmids. Plasmids carrying blaNDM-1 were successfully transferred from three of the four isolates to E. coli recipients, although the transconjugants and transformants were prone to lose the transferred plasmids after passage in the absence of ampicillin selection. We describe the emergence of A. baumannii producing NDM-1 in China. Systemic surveillance network should be established for monitoring these resistant bacteria.