Molecular characterization and epidemiology of carbapenem non- susceptible Enterobacteriaceae isolated from the Eastern region of Heilongjiang Province, China

Background: The aim of this study was to elucidate the molecular epidemiology of carbapenem non-susceptible Enterobacteriaceae(CNSE) isolated in the Eastern region of Heilongjiang Province, China, and the mechanism of carbapenem resistance. Methods: A total of 53 CNSE isolates were collected in a grade-3 hospital in Heilongjiang province. Sensitivity to antibiotics was determined using the VITEK-2 Compact automatic system. The modified Hodge test (MHT) and modified carbapenem inactivation test (mCIM) were performed for phenotypic identification. Beta-lactamases gene were detected by Polymerase chain reaction(PCR) and DNA sequencing. The transfer of bla(NDM) and bla(KPC) was investigated through conjugation experiment The clinical data of patients were retrospectively reviewed. Homology of Carbapenem-resistant Klebsiella pneumoniae(CRKP) was conducted by multilocus sequence typing (MLST). Results: CNSE were highly resistant to the majority of antimicrobial agents. The resistance rate was 100% for first, third, fourth generation cephalosporins and enzyme inhibitor compounds. Gentamicin and tobramycin recorded a resistance rate higher than 80%. Less than 30% resistance was detected for amikacin and levofloxacin. Among CNSE 52(98.1%) and 48(90.6%) of CNSE were positive for mCIM and MHT respectively. There were 42 positive bla(KPC) genes, three bla(NDM-1) genes, three bla(NDM-5) genes, one bla(NDM-7) gene, and six bla(IMP-4 )genes. Most isolates harbored multiple drug resistance gene, especially as related to extended-spectrum-beta-lactamases, bla(SHV), bla(TEM) and bla(CTX-M-15) genes.The resistant gene was transferred into recipient Escherichia coil J53 through conjugation in 21.3% (10/47) of the strains. MLST revealed that ST76 (n = 36) was the most predominant clone, followed by ST896, ST323 and ST11. A new one ST 2946 was identity by this study. Conclusion: The carbapenem resistance phenomenon is alarming and bla(KPC-2) is the main resistant gene of CNSE in our hospital. This is the first report of an outbreak caused by bla(KPC-2) positive K. pneumoniae ST76 in the Eastern region of Heilongjiang Province, China. Relevant departments should implement infection control and prevention measures to avoid further dissemination of the multi drug-resistant bacteria (MDR).