Molecular Epidemiological Analysis In Carbapenem-resistant Enterobacter Strains In The General Hospital Of Western Theater Command

Objective: To investigate the molecular epidemiological characteristics and homology of the carbapenem-resistant Enterobacter(CRE)isolated from the General Hospital of Western Theater Command from January 2015 to December 2018.Methods: 1)A total of 121 Carbapenem-resistant Enterobacteriaceae strains were isolated from patients in General Hospital of Western Theater Command from January 2015 to December 2018.The in vitro antimicrobial susceptibility was determined by VITEK 2-Compact microbiological analysis system after resuscitation of the bacteria.2)The primers of carbapenemase,extended spectrum β-lactamases(ESBLs),cephalosporinase(Amp C)and outer membrane porins(OMPs)gene were designed and synthesized.The PCR method was applied to detect the genes,then the amplified productions were sequenced and compared with gene from NCBI.3)Enterobacteial repetitive intergenic consensus polymerase chain action(ERIC-PCR)was used to analyze homology of bacterial isolates.4)We retrospectively studied medical history of those patients to analyze the clinical characteristics of patients with CRE infection and colonization.Results: 1.There were 121 non repetitive CRE strains,incuding 56(46.3%)strains of Klebsiella pneumoniae,26(21.5%)strains of Escherichia coli,23(19.0%)strains of Enterobacter cloacae,5(4.1%)strains of Klebsiella oxytoca,4(3.3%)strains of Citrobacter freundii,4(3.3%)strains of Serratia marcescens,and 3(2.5%)strains of Klebsiella areogene.2.121 carbapenem-resistant Enterobacter strains were distributed in 33 wards and founded mainly in cadre ICU(15.7%),general surgery(14.8%),neurosurgery(13.2%)and cadre ward(9.1%).3.The main sources of specimen were sputum(46.3%).Other sites included urine(15.9%),blood(11.6%),drainage(10.7%),bile(6.6%)and wound secretion(5.0%).4.Antimicrobial susceptibility testing indicated that these isolates were highly resistant to penicillins and cephalosporins,but least resistant to amikacin,the ratio was 42.1%.The drug resistant rate were various and carbapenem-resistant klebsiella pneumoniae had the highest resistant rate to each antibiotic among different bacteria genus.5.Carbapenem-resistant klebsiella pneumoniae was significantly more than Escherichia coli(P<0.001)and Enterobacter cloacae(P=0.002)among bacteriea with ertapenem MIC≥8mg/L.Carbapenem-resistant klebsiella pneumoniae was also significantly more than Escherichia coli(P<0.001)and Enterobacter cloacae(P<0.001)among bacteriea with imipenem MIC ≥ 16 mg/L.6.The sequences of the drug resistance gene showed that 96 isolates were carbapenemase producing Enterobacteriaceae,including bla KPC-2(65,67.7%),bla NDM-1(25,26.0%),bla OXA-48(7,7.3%),bla VIM(2,2.1%).Two strains carried bla KPC-2 and bla NDM-1 gene,one strain carried bla KPC-2 and bla VIM simultaneously.The bla IMP and bla GES genes were not identified.The prevalance of bla SHV,bla TEM,bla DHA and bla CIT gene were 46.3%,47.1%,37.2% and 26.4%,respectively.The deletion or mutation rates of OMPF and OMPC were 48.1% and 84.6%.Deletion or mutation of OMPK35 and OMPK36 was identified in 35.7% and 91.1% of the strains,respectively.Most of strains carried both carbapenemase gene and delected or mutated outer membrane porins,the ratio was 56.2%.7.ERIC-PCR results showed that 56 carbapenem-resistant klebsiella pneumoniae strains were classified into 5 different genotypes,26 Escherichia coli and 23 Enterobacter cloacae strains could be classified into 3 genotypes,respectively.8.Patients with CRE infection or colonization often had the following characteristics: ICU stay,mechanical ventilation >3d and a variety of serious basic diseases.Common basic diseases included tumor,chronic lung disease,diabetes and congestive heart failure.There were 73 patients infected by CRE according to the nosocomial infection criteria.The 28-day mortality rate of CRE infection was 32.9%,and the 28-day mortality rate of bloodstream infection was 35.7%.Conclusion:1.The main type of CRE in our hospital from 2015 to 2018 was CRKP,and the detection rate was highest in 2018.2.121 carbapenem-resistant Enterobacter strains were distributed in 33 wards and founded mainly in surgical departments,cadre ward and intensive care unit.3.The main sources of specimen were sputum.Other sites included urine,blood,drainage,bile and wound secretion.4.Multidrug resistance were commom among CRE strains and some of isolates showed pan-drug even full-drug resistance.The drug resistant rate were various and carbapenem-resistant klebsiella pneumoniae had the highest resistant rate to each antibiotic among different bacteria genus.5.Carbapenem-resistant klebsiella pneumoniae was significantly more than Escherichia coli and Enterobacter cloacae among bacteriea with ertapenem MIC≥8mg/L.Carbapenem-resistant klebsiella pneumoniae was also significantly more than Escherichia coli and Enterobacter cloacae among bacteriea with imipenem MIC≥16mg/L.6.CRE had multiple resistance mechanisms and carried multi-resistant genes,of which producing carbapenemase was the major resistance mechanisms to carbapenem.The main encoding gene of CRKP was bla KPC-2 in our study.Carbapenem-resistant Escherichia coli and Enterobacter cloacae mainly carried bla NDM-1.Deletion or mutation of outer membrane porins combined with high production of ESBLs and Amp C enzyme was also one of the resistance mechanisms of CRE to carbapenem.7.According to the results of ERIC-PCR,some strains of CRE show high homology,suggesting clonal transmission in the hospital.8.Patients with CRE infection or colonization often had the following characteristics: ICU stay,mechanical ventilation>3d and a variety of serious basic diseases.The 28-day mortality of CRE infection was 32.9%,and the 28-day mortality of bloodstream infection was 35.7%.