Dissemination and characterization of NDM-1-producing Acinetobacter pittii in an intensive care unit in China

The sporadic emergence of New Delhi metallo-β -lactamase-1 (NDM-1)-producing Acinetobacter spp. has been reported in China; however, NDM-1-positive bacteria epidemics are rarely reported in intensive care units (ICUs) in China, or even in the world. During 15 months' surveillance Acinetobacter spp. isolated from patients, heathcare workers and surfaces of a Chinese ICU were screened for the blaNDM-1 gene. A total of 27 of 3114 Acinetobacter spp. strains were NDM-1 positive and identified as A. pittii with sequence type 63 (ST63) by multilocus sequence typing. Of the 27 NDM-1-positive A. pittii strains, 22 were isolated from the ICU surfaces and grouped into a major clone A using pulsed-field gel electrophoresis typing, while the other five strains isolated from the patients were classified into three clones (A, B and C). The blaNDM-1 gene was located on a 45-kb plasmid for all three A. pittii clones. The plasmid could be transferred to A. pittii and A. baumannii recipients at both 30 and 37°C but not to Escherichia coli J53. The plasmid could not be classified into any of the known plasmid incompatibility groups. The blaNDM-1 region in the plasmid was flanked by two insertion sequence elements, ISAba125 and ISAba11, and no other carbapenemase gene was present in this NDM-1-positive A. pittii isolate. Thus, we present the first report on the transmission and characterization of NDM-1-producing A. pittii in an ICU in China as well as a novel blaNDM-1 gene-bearing plasmid.