Study On The Resistance Mechanism And Molecular Epidemiology Of Carbapenem Resistant Enterobactrriaceae In ChangShu

Background and ObjectiveEnterobacteriaceae bacteria are the most common bacteria causing nosocomial infections,including Klebsiella pneumoniae,Escherichia coli,Enterobacter cloacae,and Citrobacter florida.Carbapenems have good antibacterial activity,mainly for the treatment of infections caused by multi-drug resistant strains such as extended-spectrum β-lactamase(ESBLs)and cephalosporinase(Ampc).However,with the widespread use and unreasonable use of the carbapenems,resistant strains are increasing and becoming a popular trend,which needs to be widely concerned.Nowdays,the research on the resistantance mechanism and molecular epidemiology of carbapenem-resistant Enterobacteriaceae(CRE)in Changshu has not been reported.The purpose of this study was to investigate the isolation rate of carbapenem-resistant Enterobacteriaceae from January 2016 to December 2017 in Changshu,and to analyze the resistance mechanism and molecular epidemiology of CRE in this area.Then,instruct clinicians to use antibiotics rationally and develope a treatment plan for infection caused by CRE.MethodsThe Enterobacteriaceae clinical isolates from January 2016 to December 2017 of the Changshu Medical Laboratory were tested by the French Meilie Vitek2-Compact automatic.Collect these isolates which resistant to any antibiotics of imipenem,meropenem,and ertapenem as research strains.Then further confirm drug resistance again by the paper method(K-B method).PCR technology was used to detect resistance gene related to carbapenemase including blaKPC,blaNDM,blaIMP,blaVIM,blaOXA-48 and polymyxin gene mcr-1.The transferability of carbapenemase genes by plasmids was studied by conjugational transfer experiment.Pulsed field gel electrophoresis(PFGE)and Multilocus Sequencing Typing(MLST)were used to analyze the molecular epidemiology of CRE in ChangShu.ResultsA total of 51 non-duplicated clinical isolates of carbapenems-resistant Enterobacteriacease were collected from January 2016 to December 2017 in changshu area,including 34 Klebsiella pneumonia isolates,8 Escherichia coli isolates,5 Serratia marcescens isolates,1 Enterobacter cloacae isolate,1 C.faecalis isolate,1 Klebsiella oxysporum isolate.These Enterobacteriacease were mainly collected from sputum,with 21 strains,accounting for 41.2%,followed by 14 strains of blood,accounting for 27.5%.The source of the strain department was mainly concentrated in the emergency department,neurosurgery department and Intensive care unit(ICU)which accounting for 31.4%(16/51),31.4%(16/51)and 23.6%(12/51).The resistance rates of 51 strains of Enterobacteriaceae to imipenem and meropenem in carbapenems were 100%,and to cephalosporins,β-lactams and quinolones were over 90%.The resistance rate to aminoglycosides was slightly lower,among which the resistance rate to gentamicin was 88.2%,the resistance rate to amikacin was 79.2%,and there was no resistance to tigecycline.The PCR results showed that there were 42 carbapenemase-positive strains with a detection rate of 82.3%(42/51).34 strains were KPC positive strains,accounting for 66.7%.7 strains were positive for NDM,accounting for 13.7%.3 strains were positive for IMP,accounting for 5.9%.In addition,there were two strains carrying not only blaKPC but also blaNDM(CS13 and CS14).The genes of blaVIM,blaOXA-48 and the polymyxin resistance gene mcr-1 were negative for all tested strains.The conjugative transfer test on 42 strains which carrying the carbapenemase gene showed that a total of 31 strains were successfully combined accounting for 73.8%.31 were all successfully combined with KPC.However,10 strains carrying the blaNDM and blaIMP genes failed to transfer.There were 11 genotypes(A-K)in the 34 strains of carbapenem resistant klebsiella pneumonia.Among them,15 strains belong to type A(12 of which were isolated from emergency department of Changshu No.1 People’s Hospital),9 strains belong to type B(6 of which were isolated from neurosurgery department of Changshu No.2 People’s Hospital).Two strains belonged to type C.MLST analysis showed that the dominant clonotype of Klebsiella pneumoniae was ST11(100%,34/34),and the two major types of PFGE belonged to ST11.Conclusion1.CRE strains isolated from ChangShu were mainly carbapenem resistant klebsiella pneumonia.The study suggests that KPC-2 type carbapenemase is the main contributor to CRE in changshu area.Plasmid might play an important role in the spread of blaKPC-2.2.The carbapenem-resistant Enterobacteriaceae in Changshu is highly resistant to common clinical antibiotics,most of which were multi-drug resistant bacteria,and there was no resistance to tigecycline.3.The result of homology analysis for the 34 strains of CRKP suggest that there was the phenomenon of small spread of CRKP cloning in changshu area,which mainly involved by type A and type B.The clonal strains mainly limited to the emergency department and neurosurgery department of individual hospitals.There was no cross-hospital transmission of the same clonal strains.4.ST11 is the dominant ST type of CRKP in Changshu,which was the same with the most popular in China.