Characterization of Carbapenemase Genes in Enterobacteriaceae Species Exhibiting Decreased Susceptibility to Carbapenems in a University Hospital in Chongqing, China

Background: Our study was to investigate the prevalence of carbapenemase genes in strains of Enterobacteriaceae species exhibiting decreased susceptibility to carbapenems in our hospital. Methods: The carbapenemase producing Enterobacteriaceae species were confirmed by modified Hodge test (MHT) and EDTA-disc synergy test which indicating the production of class B carbapenemases. PCR and sequencing analysis were used to identify the drug-resistant genes. DNA fingerprinting based on enterobacterial repetitive intergenic consensus (ERIC)-PCR was applied to investigate the homology of Enterobacteriaceae species. Results: From a collection of 1,472 Enterobacteriaceae species, 18 isolates with decreased susceptibility to carbapenem treatment were identified and 9 of which were positive by MHT, and 6 of which produced class B carbapenemases. PCR and sequencing analysis of the 18 isolates revealed 4 different carbapenemase genes (bla(IMP-8), bla(oxa-1), bla(IMP-26), and bla(oxa-47)) in 10 isolates, with the bla(IMP-8) and bla(oxa-1) genes being the most common (60-70% prevalence). ERIC-PCR showed 5, 2, and 2 unique genotypes for Enterobacter cloacae, Escherichia coli, and Klebsiella pneumoniae, respectively. Three E. coli strains isolated from different patients from the urologic surgery department exhibited the same DNA banding pattern, suggesting a possible clonal dissemination. Majority (17/18) of the carbapenem-unsusceptible Enterobacteriaceae species isolates was obtained from the surgery department of our hospital. Conclusions: The main carbapenemase genes of Enterobacteriaceae species in our hospital were bla(IMP-8) and bla(oxa-1). Prevalence of carbapenem resistance may be existed in surgery department and infection control should be taken for preventing further dissemination of drug-resistant strains.