Resistance Mechanism And Epidemiological Analysis Of Carbapenem-resistant Enterobacteriaceae In Suqian

Background and Objective:Enterobacteriaceae are common conditional pathogens that cause nosocomial infections.Among the drugs used to treat enterobacteriaceae bacterial infections,carbapenem antibiotics are most clinically applied for the advantages including low toxicity,broad antibacterial spectrum,and strong antibacterial activity against extended spectrum β-lactamases(ESBLs)or AmpC.However,with the widespread and unreasonable application of such antibiotics in clinical practice,in recent years,the carbapenem-resistant Enterobacteraceae(CRE)appear and even present outbreak in many regions and hospitals,which causes a serious threat to the health and safety of human life.The relevant studies and reports from institutions in many countries and regions showed that the epidemic type and distribution characteristics of CRE vary depending on the different countries and regions.Therefore,early detection and monitoring of CRE,research on its distribution characteristics and mechanisms of drug resistance are particularly important to control the emergence and spread of bacterial resistance in the region.At present,few investigation about the distribution characteristics of CRE was reported in Suqian,and the present study aims to investigate the mechanism and epidemiological characteristics of CRE in Suqian,which may contribute to the control of nosocomial infections caused by CRE.Methods:1.The CRE were collected and isolated from clinical non-repeating samples from patients in Suqian in the past three years.The clinical distribution characteristics and drug resistance of isolated CRE were retrospectively analyzed.The bacterial identification and drug susceptibility testing was performed using the VITEK2 COMPACT automatic bacterial identification and drug sensitivity analyzer,and the production of carbapenemase was detected using the modified carbapenem inactivation method(mCIM).Carbapenemase gene was verified using the polymerase chain reaction(PCR)method,the drug resistance genes include blaKPC,blaNDM,blaVIM,blaIMP,blaOXA-48 and the polymyxin resistance gene mcr-1.3.The homology of drug-resistant bacteria was analyzed using pulsed-fi eld gel electrophoresis(PFGE).4.The representative major epidemic strain Klebsiella pneumoniae was selected for whole genome sequencing analysis.Results:1.Carbapenem-resistant Enterobacteriaceae in Suqian,the proportion of Klebsiella pneumoniae was up to 82.1%,followed by Escherichia coli(10.3%).The Klebsiella and Serratia accounted for 5.1%and 2.6%,respectively.About 35.9%(14/39)of these strains are distributed in the ICU,25.6%(10/39)in surgical department,15.4%(6/39)in respiratory department and 7.7%(3/39)hematology department.About 58.9%(23/39)of the samples were from sputum,15.4%were from urine and 7.7%were from blood.Besides,the result showed that 100%of these strains were resistant to ampicillin,ampicillin-S,ceftizoxime,ceftriaxone,ertapenem,and imipenem;above 90%to piperacillin/tazobactam,ceftazidime,ciprofloxacin and levofloxacin were all,above 80%to cefotetan,cefepime,azithromycin,gentamicin;79.5%to cotrimoxazole,69.2%to tobramycin;and 46.2%to amikacin.2.The screening results of common resistance genes in CRE in Suqian showed that 94.8%of the strains carried the carbapenemase gene including blaKPC(accounted for 84.62%),blaNDM(accounted for 12.82%),and mcr-1(accounted for 5.3%).Two strains of Escherichia coli(4768,4771)carry both blaNDM and mcr-1.one strain of Escherichia coli(4774)and one strain of Klebsiella pneumoniae(4776)carry both blaKPC and blaNDM gene.3.A total of 8 types of carbapenem-resistant Klebsiella pneumoniae were obtained by PFGE pattern bands analysis,including A type(23 strains),B type(2 strain),C type(2 strain),D type(1 strain),E type(1 strain),F type(1 strain),G type(1 strain)and H type(1 strain).Among the subtypes,A3 subtype(15 strains)were dominant in the A type,followed by A4 subtype(3 strain).Two strains in type C is the same type.Type A accounting for 40.62%(13/32)is mainly distributed in the intensive care unit(ICU),of which A3 subtype accounts for 15.62%(5/32),and A4 subtype accounts for 6.25%(2/32).4.Analysis and comparison of the whole genome sequencing results revealed that the ST type of Klebsiella pneumoniae that is prevalent in Suqian area is ST11 type.In addition,the type VI secretion system(T6SS)was suggested based on the virulence gene and it carried iutA、iroN,etc Klebsiella pneumoniae rare virulence geneConclusion:1.CRE in Suqian area is mainly Klebsiella pneumoniae,followed by Escherichia coli.The sputum and urine specimens have higher detection rates compared with other samples.Strains with drug-resistant are mainly concentrated in the ICU,surgery and respiratory departments.The CRE resistance to conventional antibiotics in this region is very serious.2.The KPC-2 carbapenemase resistance is the main gene contributing to drug resistance in carbapenem-resistant Klebsiella pneumoniae in Suqian area.The carbapenem-resistant Escherichia coli contains two different resistances.Carbapenem-resistant Escherichia coli containing two different drug resistance genes accounted for a large proportion.3.The PFGE type of Klebsiella pneumoniae in Suqian is mainly A3 subtype.A clonal spread of A3 and A4 subtype is present in the ICU ward.The remaining types of CRE appear scattered between different departments.4.The prevalent Klebsiella pneumoniae strain in Suqian area is ST11 type,and virulence genes such as iutA and iroN have been found.In addition,a type VI secretion system(T6SS)has been suggested.