Study Of Resistant Mechanism And Molecular Epidemiology Of CRE In Respiratory Tract

Objective:To investigate the main mechanism of drug resistance of CRE in respiratory tract and to analyze and compare the drug sensitivity of different strains and strains of different drug resistance genes,so as to provide some guidance for clinical drug use.Methods:553 strains of non-repetitive carbapenem-resistant enterobacteriaceae(CRE)isolated from respiratory specimens were collected from 49 hospitals in China from 2015 to 2017.The strains were identified again by MALDI-TOF-MS.Agar dilution method and micro broth dilution method were used to determine the minimum inhibitory concentration(MIC)of bacterials.The modified CIM test was used to test the phenotype of carbapenemase.A variety of ?-lactamase genes,including carbapenemase,were detected by PCR and the PCR products were sequenced.Multilocus sequence typing(MLST)was used to detect Klebsiella pneumoniae and Escherichia coli respectively.The main epidemic strains and homologies of CRE were analyzed.Using Whonet software to analyse drug-susceptibility of different strains,different drug resistance genes.Results:1.All collected 553 respiratory CRE,465 strains of Klebsiella pneumoniae,49 strains of Escherichia coli,39 strains of Enterobacter cloacae.All had the lowest resistance to polymyxin B(1.4%),followed by tigecycline(1.6%),the resistance rates of three carbapenem antibiotics commonly used were more than 80%,moreover the cephalosporin and its enzyme inhibitor was more than 90%;as for Klebsiella pneumonia,the lowest rate of drug resistance also was polymyxin B(0.9%),followed by tigecyclime(1.3%);strains resistant to tigecycline were not found in Escherichia coli and the resistance rate of polymyxin,was 8.2%;and Ecl was not found to be resistant to polymyxins The drug resistance rates of drug strains and tigecycline were 7.7%.2.mCIM test of all strains of the enzyme-producing gene is positive phenotype,the sensitivity of mCIM test is 100%.3.Among 553 strains of CRE,95.3%of the isolates were detected carbapenemase genes,of which KPC was the main type,KPC-2 was the major subtype and NDM-1 was the major NDM subtype.Escherichia coli and Enterobacter cloacae are mainly NDM gene.The IMP gene is mainly detected in Enterobacter cloacae,the main subtype is IMP-4.The strain MIC?16?g/mL accounted for 89.7%of the strains producing KPC in CRE,and the strain with MIC ?8?g/mL accounted for 74.5%of the strains producing NDM.4.Klebsiella pneumoniae were divided into 48 ST types,with ST11 as the main phenotype,followed by ST 15 and ST17.Escherichia coli was divided into 9 ST types,with ST167 as the main phenotype,followed by ST410 and ST131.Enterobacter cloacae was divided into 10 ST types,there were no major types and widely distributed.Conclusion:The drug resistance of CRE is very serious,only polymyxin and tigecycline showed high sensitivity;Enzyme-producing is the main resistant reason of CRE,Klebsiella pneumoniae is to produce KPC enzyme,Escherichia coli and Enterobacter cloacae is to produce NDM;ST11 is a major epidemic clone of Klebsiella pneumoniae.The major ST type of E.coli is ST167.