[Study on genotype and clinical characteristics of infection of carbapenemase-producing Enterobacter cloacae].

OBJECTIVE: To study the genotypes and clinical characteristics of carbapenemase-producing Enterobacter cloacae (E.cloacae), and lay the foundation for active control of nosocomial infection.

METHODS: E.cloacae isolates were collected from January 2007 to December 2014. Strains which showed decreased sensitivity to carbapenem were screened out by the modified Hodge test (MHT) and EDTA-disk synergy test. The genotype of blaKPC, blaIMP, blaVIM, blaOXA-48 and blaNDM-1 were detected by PCR amplication, the product of PCR was sequenced and conducted by Blast (https://blast.ncbi.nlm.nih.gov/Blast.cgi). Conjugal transfer experiment was conducted to prove horizontal transmit of carbapenemase gene produced by E.cloacae. Meanwhile, the clinical epidemiological data of patients infected by selected strains were also analyzed.

RESULTS: Sixty-four carbapenemase producing E.cloacae were detected by MHT, EDTA-disk synergy test and PCR amplification. Forty-five strains (70.3%) out of 64 strains infection came from nosocomial infection, while 19 strains (29.7%) from the community infection. The strains were mainly isolated from secretions samples and sputum samples, which accounted for 65.6% (42/64) and 23.4% (15/64) separately. The mainly clinical departments were orthopaedics (43.8%), department of burn (21.9%), ICU (18.8%) and pediatrics (14.1%). Bed changing, invasive operation and indwelling catheter were risk factors for the transmission of carbapenemase producing E.cloacae, and infected patients had longer time of staying in hospital, lower cure rate and higher frequency of cephalosporins enzyme inhibitor compound or carbapenem agents administration (all P<0.05). Sixty-four strains showed increased MIC to most of the antibiotics except for polymyxin and tigecycline. Among the 64 strains, 29 strains were genotype blaIMP-4 and 35 strains were genotype blaIMP-8 by Blast alignment, no genotype blaVIM, blaOXA-48 and blaNDM-1 were detected. Result of conjugal transfer experiment showed that receptor strain obtained carbapenem resistance, and the sequence of resistance gene of receptor strain was the same to the donator strain.

CONCLUSIONS: The drug resistance of E.cloacae are growing, IMP-4 and IMP-8 carbapenemase are the main enzymes produced by strains. As the resistance gene can horizontal transmit between strains through conjugal transfer system, the strains have been locally spread in hospital departments, thus it is important to control risk factors of transmission timely.