Emergence of NDM-1-producing Acinetobacter baumannii in China

Abstract

To investigate the prevalence of bla_NDM-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 bla_NDM-1 from 57 hospitals representing 18 provinces in China. For bla_NDM-1-positive isolates, antibiotic susceptibilities were assessed and molecular typing was performed using PFGE. The genetic location of bla_NDM-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 bla_NDM-1 were identified in four different provinces in China: no positive isolates were detected among E. coli, K. pneumoniae and P. aeruginosa. These bla_NDM-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 bla_NDM-1 on different plasmids. Plasmids carrying bla_NDM-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.