Molecular And Drug Resistance Characteristics Of Carbapenem Resistant Enterobacter Cloacae And Klebsiella Pneumoniae

ObjectiveCarbapenem resistant Enterobacteriaceae(CRE)has a high mortality rate,which poses a serious threat to clinical management and public health,and poses a great challenge to clinical treatment.The elucidation of resistance,transmission mechanism and epidemic characteristics of CRE plays an important role in the treatment and prevention and control of infection.At present,There was few multicenter research on carbapenem-resistant Enterobacter cloacae(CRECL)in China and CRE in Yanbian has not been studied.The purpose of this study is to investigate the molecular and drug resistance characteristics of CRECL in China and Molecular and drug resistance characteristics of CRE in Yanbian.This study provides scientific basis for the treatment,prevention and infection control of CRE infectionMethods1.Total 55 non-repetitive strains of CRECL were collected from 12 hospitals in 11 Chinese cities(Nov 2012-Aug 2016).Minimum inhibitory concentrations(MICs)were determined by the agar dilution method.Carbapenemase and other β-lactamase genes were detected with polymerase chain reaction assay(PCR)and sequencing.Multilocus sequence typing(MLST)and plasmid conjugation tests were performed.We selected 23 NDM-1-positive isolates,pulsed-field gel electrophoresis(PEGE),S1-nuclease PFGE and Southern blotting were performed.2.non-duplicate CRECL strains isolated from Yanbian and non-duplicate carbapenem resistant Klebsiella pneumonia(CRKP)strains from PICU in Yanbian were collected.The strains were subjected to phenotypic screening for the detection of antibiotic resistance genes such as the carbapenemase and other β-lactamase genes,with the use of the PCR.Finally,MLST and PFGE-based homology analysis were applied.3.clinical information of patients with CRKP isolated in PICU were collected.Results1.All strains were sensitive to polymyxin B 100%,followed by amikacin 89.1%,Tigecycline78.2%,imipenem 12.7%and meropenem 16.4%.The sensitivity rates to minocycline,levofloxacin,ciprofloxacin and piperacillin/tazobactam were 52.7%,30.9%,25.5%and 20.0%,respectively,and the sensitive rates to ceftriaxone,ceftazidime,cefotaxime and cefepime were 1.8%.2.Among the 55 E.cloacae strains,50 strains were detected to produce 7 types of carbapenemase including NDM-1,NDM-5,IMP-4,IMP-26,IMP-1,KPC-2 and VIM-1.NDM-1 accounted for 68.0%(34/50).3.Among the 55 E.cloacae strains,A total of 24 sequence types were identified and ST418 was the most common,accounting for 20%,followed by ST93(14.5%).Plasmids from 9 carbapenemase-producing Enterobacter cloacae strains were successfully transferred to EC600.For further investigation,23 isolates yielded 13 PFGE patterns,which were designated as type A-M.Eight isolates obtained from Shenzhen had the same PFGE pattern(type A)and the remaining 15 isolates belonged to the other 12 PFGE patterns(type B-M)..Sl-nuclease PFGE and Southern blotting results showed that the plasmids harboring the blaNDM-1 gene ranged in size from approximately 52～58 kilobases.4.Four types of carbapenemases namely IMP-26,NDM-5,NDM-1,and KPC-2 were identified in 12 CRECL strains.IMP-26 was the most prevalent type(50%),followed by NDM-5(25%).The results of MLST revealed that these 12 strains could be divided into five sequence types.among which,ST544 was the dominant type(6/12 strains,50%).The PFGE results divided the 12 strains into four clusters.5.Two carbapenemase genes,KPC-2 and NDM-1(in eight and six strains,respectively),were detected in 14 CRKP strains in PICU.MLST enabled the division of the strains into two sequence types,ST11 and ST1224(containing eight and six strains,respectively).PFGE results classified the 14 strains into clonotypes A-D,of which clonotypes A and B belonged to ST11,while clonotypes C and D belonged to ST1224.6.All patients suffered from neonatal pneumonia or severe pneumonia and used second or fourth generation cephalosporinsConclusion1.The susceptibility rate of all beta-lactam drugs is very low.Only a few drugs are available(polymyxin B,tegacycline and amikacin).In multicenter studies,carbapenemase production was the main cause of drug resistance,among which NDM-carrying strains were the first.ST418 was the main epidemic clone and MLST typing,showing differences in different regions.NDM-1 is carried by plasmid with a size of 52～58 Kb and is clonally transmitted.2.Carbapenemase producing is the main mechanism of resistance to CRECL in Yanbian,mainly IMP-26 type enzyme.The homology analysis results show that ST544 is the main epidemic strain in Yanbian.3.ST1224 and ST11-CRKP were the main epidemic strains in Yanbian in PICU.The risk factors of CRKP may be the presence of basic diseases and the use of second or fourth generation cephalosporins...