| Objective:To investigate the risk factors,molecular epidemiology and drug resistance mechanism of carbapenem-resistant Enterobacteriaceae(CRE)infection,and to provide a theoretical basis for formulating treatment plan for CRE infection.Methods:Eighty-five strains of CRE isolated from 19 district hospitals in Chongqing from January 2015 to December 2016 were collected.Homology analysis was performed by Pulsed Field Gel Electrophoresis(PFGE)and Multiple Locus Sequence Typing(MLST),two classical methods of molecular epidemiology.PCR amplification of carbapenemase-related resistance genes,extended spectrum beta-Lactamases(ESBLs)-related resistance genes,quinolone-related resistance genes and aminoglycoside-related genes was performed.the positive products were sequenced to identify genotypes.In addition,39 strains of extensively drug-resistant Klebsiella pneumoniae(XDR-KP)were retrospectively analyzed for risk factors.Results:1.The results of antibiotic susceptibility analysis showed that 85 strains of CRE were resistant to ETP.,the overall resistance rate to imipenem(IPM)was 82.3%,meropenem(MEM)was 89.4%.The resistance rates of the three or four generation cephalosporins were 95.2%and 61.2%respectively,and the overall resistance rates to quinolones and aminoglycosides were 58.8%and 52.9%respectively.Lower than beta lactam antibiotics.2.Detection of related drug resistance genes was found that,among 85 CRE strains,80 strains(94.1%)carried the carbapenemase gene,of which 32 carried the blaNDM-1 gene,13 carried the blaNDM-5 gene,1 carried the blanIMP-8 gene,5 carried the blanIMP-4 gene,and 38 carried the blaKPc-2 gene.76 strains(89.4%)carried ESBLs gene,of which 42 carried blaTEM gene,43 carried blasHv gene and 58 carried blacTx-M gene.In addition,73 strains(85.9%)carried the QRDs gene,and 68 strains(80%)carried the ARDs gene.3.PFGE results showed that strains 48,49 and 50 were of the same clonal type and originated from the same hospital,suggesting that nosocomial infection outbreaks might occur.MLST results showed that 49 strains of Klebsiella pneumoniae belonged to ten ST types,of which ST 11(73.4%)was the main type;16 strains of Enterobacter cloacae belonged to eight ST types,of which ST 51(37.5%)was the main type;15 strains of Escherichia coli belonged to eight ST types,of which ST 167(40%)was the main type,and the rest ST types were scattered.4.Multivariate Logistic regression analysis showed that ICU admission(OR:3.01,95%CI:1.12-8.07,P=0.029),drainage tube(OR:3.24,95%CI:1.11-9.45,P=0.032)and Carbapenems exposure(OR:5.08,95%CI:1.42-18.16,P=0.012)were the independent risk factors of XDR-KP infection.Conclusion:1.The CRE strains collected in Chongqing showed a high level of drug resistance,some strains also showed resistance to different types of antibiotics.2.94.1%of the CRE strains collected in Chongqing carried carbapenemase resistance genes with the ability to hydrolyze carbapenem antibiotics,suggesting that carbapenemase production may be the main resistance mechanism of CRE strains in Chongqing.In addition,a strain carrying blaNDM-1,blaKPC-2 and blaIMP-4 genes was found for the first time in this study.3.Epidemiological analysis showed that ST 11 was the main epidemic type of Klebsiella pneumoniae producing KPC-2 in Chongqing.Homologous strains appeared in some hospitals.,but no cross-county outbreaks of homologous strains were found.4.At present,the situation of XDR-KP infection is fairly severe.Strengthening the supervision and control of ICU wards,fewer invasive operations and reasonable use of antibiotics would be necessary in order to prevent the occurrence and prevalence of XDR-KP. |
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