Epidemiological characteristics of blaNDM-1 gene in Enterobacteriaceae strains circulating in China during 2013 to 2014

Abstract

Objective To investigate the epidemiological characteristics of blaNDM-1 gene (encoding New Delhi metallo-β-lactamase 1) in Enterobacteriaceae strains circulating in China during July 2013 to June 2014. Methods A total of 2 577 Enterobacteriaceae strains were collected from 19 Class A tertiary hospitals nationwide by China Antimicrobial Resistance Surveillance Trial (CARST). PCR was used to detect the presence of blaNDM-1 gene in those Enterobacteriaceae strains. For blaNDM-1-positive strains, Analytical Profile Index (API) strips and 16S rRNA analysis were used to identify bacterial genus and species. Antibiotic susceptibilities were assessed by detecting minimum inhibitory concentrations (MIC) against them with two-fold agar dilution test. Multilocus-sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) were performed for homology analysis. Results Among the 2 577 strains, 24 from 8 different provinces and cities carried the blaNDM-1 gene, including 11 Klebsiella pneumoniae strains, 4 Enterobacter cloacae strains, 3 Providencia rettgeri strains, 2 Escherichia coli strains, 2 Citrobacter freundii strains, 1 Klebsielia Oxytoca and 1 Serratia marcescens, and all of them were multidrug-resistant (MDR). ST17 (5, 45.45%) and ST20 (3, 27.27%) were the predominant sequence types of Klebsiella pneumoniae strains. Strains of the same STs were clonally related. PFGE analysis showed that 3 Providencia rettgeri strains isolated in Nanjing belonged to the same clone. Conclusion The positive rate of blaNDM-1 gene in Enterobacteriaceae strains isolated during 2013 to 2014 is 0.93%, indicating a significant increase as compared with that during 2009 to 2010 (0%) and 2011 to 2012 (0.32%). The present study first reports the strain of Serratia marcescens harboring NDM-1 gene in China. NDM-1-producing strains are highly resistant to multiple drugs. Most of the NDM-1-producing Enterobacteriaceae strains were Klebsiella pneumoniae strains (45.83%) warranting special attention as there is a risk of endemic outbreak. Key words: Beta-lactamase NDM-1; Enterobacteriaceae; Epidemiology