Antimicrobial Resistance,clinical Infection Characteristics Of Carbapenem-resistant Enterobacterales And Whole Genome Sequencing Of Mcr-9 Positive Enterobacter Cloacae

Objective:To analyze the clinical infection characteristics and drug resistance of carbapenem-resistant Enterobacterales（CRE）,as well as the plasmids,drug resistance genes,virulence factors and homology characteristics of mcr-9 positive carbapenem-resistant Enterobacter cloacae,to provide reference for clinical surveillance and control of CRE and mcr-9 positive CRECL infections.Methods:（1）From July 2021 to June 2022,CRE strains isolated from a local tertiary hospital were collected;the clinical data of the patients were collected to analyze the infection characteristics.Drug resistance was analyzed by in vitro drug susceptibility test.Use Carbapenemase phenotype detection and PCR sequencing to analyze the characteristics of drug resistance genes.（2）CRECL strains isolated from patients in hospital from January 2019 to July 2022 were collected,twelve mcr-9-positive CRECL strains were selected for whole genome sequencing to analyze the carrying status,progenicity of plasmids,drug resistance genes,virulence factors.Results:（1）167 CRE bacteria were identified;Klebsiella pneumoniae（38.9%）and Enterobacter cloacae（35.3%）dominated the group,demonstrating a multi-drug resistance phenotype,with three strains（1.8%）exhibiting polymyxin B resistance.Most CRE strains harbour bla _NDM（51.5%）and bla _KPC（33.5%）.Based on carbapenemase,we divide individuals with CRE infection into NDM and KPC groups.According to Chi square test results,comparing risk factors,which include days spent in the ICU longer than one-week,tracheal intubation,use of carbapenems antibiotics etc,we found that the proportion of the NDM group was lower than that of the KPC group（P<0.05）.The cure rate for patients in the NDM group was higher than in the KPC group（P<0.05）.According to multivariate Logistic regression analysis,gastric tube,pulmonary disease,and malignancy are independent risk factors for good prognosis of CRE infection with different carbapenemase genes（P<0.05）.The mgr B gene was altered in the polymyxinβ-resistant strains.It was discovered that seven（4.2%）of the strains that were polymyxinβ-sensitive harboured mcr-9.MIC values of polymyxin B were increased in four CRE strains after polymyxin induction.（2）All the twelve mcr-9-positive CRECL strains were resistant to common antibiotics,the main plasmid was Inc HI2/2A,and there are many drug resistance genes.These genes included bla _NDM,bla _ACT-7,bla _TEM-1Band bla _SHV-12,a variety of antimicrobial resistance genes.All strains carried a variety of virulence factors,including genes for fimbria,biofilm formation,iron uptake,protein secretion,efflux pumps and multiple toxins.MLST typing was ST93.The results of progenicity analysis showed that group A clone was the dominant mcr-9-positive CRECL strain in our hospital,there was a certain range of dissemination in our hospital.Conclusion:（1）Most CRE carried bla _NDMand bla _KPC;some strains carried both mcr-9and bla _NDM,showing multidrug resistance.（2）mcr-9-positive CRECL carried a variety of drug resistance genes and virulence factors,the MLST type was mainly ST93,and there was certain homology among the mcr-9-positive CRECL strains.CRE and mcr-9-positive CRECL should be screened and monitored,effective prevention and control measures should be taken to control the spread of pathogens.