<p>Microbiological Characteristics of Carbapenem-Resistant <em>Enterobacteriaceae</em> Clinical Isolates Collected from County Hospitals</p>

Abstract

ObjectiveTo investigate the molecular characteristics of carbapenem-resistant Enterobacteriaceae (CRE) from county hospitals in China.Materials and MethodsForty-three sequential non-duplicate CRE strains (including 33 Klebsiella pneumoniae isolates, 4 Enterobacter cloacae isolates, 3 Escherichia coli isolates, 1 Serratia marcescens, 1 Morganella morganii and 1 Citrobacter freundii) were collected from 4 county hospitals and 2 municipal hospitals. Antimicrobial susceptibility testing was conducted by broth microdilution method, using 3-aminophenylboronic acid and EDTA and the modified carbapenem inactivation method (mCIM) to screen phenotype of carbapenemase. β-Lactamases were characterized by polymerase chain reaction (PCR) and DNA sequencing. The transferability of blaNDM-5 was investigated by transformation experiment. Clonal relatedness was evaluated by pulsed-field gel electrophoresis and multilocus sequence typing .ResultsThe results of antimicrobial susceptibility testing indicated that 43 CRE strains were resistant to most of the antimicrobial agents, except tigecycline and colistin. Overall, 93%, 93%, and 97.7% of these strains were resistant to imipenem, meropenem, and ertapenem, respectively. PCR and DNA sequencing indicated that 67.4% (29/43) were blaKPC-2 positive isolates, in which 3.4% (1/29) was coproduced with blaNDM-1. In addition, 7.0% (3/43), 4.7% (2/43), 4.7% (2/43), 2.3% (1/43), 2.3% (1/43) were blaNDM-1, blaNDM-16, blaNDM-4, blaNDM-5, blaIMP-4 positive isolates, respectively. The 29 blaKPC-2-positive isolates belonged to 12 different PFGE type and designated as ST11 (n=20) and ST15, ST39, ST116, ST667, ST2245, ST2338. The plasmid bearing blaNDM-5 could be transferred into recipient E. coli J53 through transformation.ConclusionOur study indicated the dissemination of CRE between the tertiary hospitals and secondary hospitals.