Epidemiological Characteristics of blaNDM-1 in Enterobacteriaceae and Acinetobacter calcoaceticus–Acinetobacter baumannii Complex in China from 2011 to 2012

Abstract

Objectives: The study aimed to investigate the prevalence and the epidemiological characteristics of blaNDM-1 in Enterobacteriaceae and Acinetobacter calcoaceticus–Acinetobacter baumannii complex (ABC) in China from July 2011 to June 2012. Methods: All organisms studied were screened for the presence of blaNDM-1 using PCR. For those blaNDM-1- positive strains, 16S rRNA along with API strips were performed to validate the bacterial genus and species. The ABCs were reconfirmed by PCR detection of blaOXA-51-like. The antibiotic susceptibilities were assessed by determining minimum inhibitory concentration (MIC) of them using two-folder agar dilution test recommended by the Clinical and Laboratory Standards Institute (CLSI). Molecular typing was performed using pulsed-field gel electrophoresis (PFGE). An S1 nuclease PFGE (S1-PFGE) and Southern blot hybridization were conducted to ascertain the gene location of blaNDM-1. Results: Among 2170 the family Enterobacteriaceae and 600 ABCs, seven Enterobacteriaceae strains and two A. calcoaceticus isolates from five different provinces carried the blaNDM-1 gene. The seven Enterobacteriaceae strains were four Klebsiella pneumoniae, one Enterobacter cloacae, one Enterobacter aerogen and one Citrobacter freundii, respectively. All of them showed non-susceptible to any agent of imipenem, meropenem, panipenem and ertapenem. Two A. calcoaceticus were both resistant to imipenem and meropenem. Three K. pneumoniae showed the same PFGE profiles. Eight blaNDM-1 genes were located on plasmids and one on chromosome. Conclusions: Compared with the previous reports, the numbers and species of the blaNDM-1 in Enterobacteriaceae have been significantly increased in China and most of them can disseminate which should be drawn great attention. Consecutive surveillance should be implemented and focused on the dissemination of blaNDM-1 among gram-negative clinical isolates as well.