| Objective:Bloodstream infections（BSIs）are one of the most common serious infections,and have been proved to be associated with higher mortality and higher medical costs.Among the Gram-negative bacilli causing BSIs,Escherichia coli（E.coli）is the main pathogen.The study retrospectively analyzed the drug sensitivity,drug resistance gene distribution and homology of E.coli isolated from BSIs of inpatients in our hospital,so as to provide epidemiological basis for controlling nosocomial infection and guiding clinical rational drug use.Methods:1.E.coli in blood culture of inpatients in Shanxi Provincial People’s Hospital from October 2019 to September 2020 were collected continuously.When E.coli was cultured repeatedly from the same patient during the same hospitalization,only the strain cultured for the first time was collected.2.The susceptibility test was performed according to the disk diffusion method recommended by the Clinical Laboratory Standardization Committee（CLSI）,and the confirmative test for Extended-spectrum beta-lactamases（ESBLs）production was performed using the two-paper diffusion method（cefotaxime and cefotaxime-clavulanic acid,ceftazidime and ceftazidime-clavulanic acid）.The ESBLs and carbapenemase resistance genes of E.coli were detected by polymerase chain reaction（PCR）.3.Polymerase chain reaction（PCR）was used to detect chu A,yja A,Tsp E4.C2DNA fragments and seven housekeeper genes.Goe Burst was used for multi-locus sequence typing.Goe BURST was used for multilocus sequence typing.Results:1.A total of seventy-six non-replicating E.coli isolates were collected.2.The results of drug sensitivity test showed that E.coli had the highest resistance rate to ampicillin（90.7%）,followed by ciprofloxacin（69.7%）,cefazolin（65.7%）,levofloxacin（63.1%）,ceftriaxone（56.5%）and cefotaxime（56.5%）.In contrast,the sensitivity of carbapenems,piperacillin tazobactam,amikacin and tigecycline to E.coli was 100.0%.Among the 76 E.coli strains,43 strains produced ESBLs,and no carbapenemase producing strain was found.3.The results of drug resistance gene analysis showed that a total of 71 resistant genes were detected in 43 ESBLs-producing strains,among which 17 strains contained only one ESBLs gene,21 strains contained two ESBLs genes,and 4 strains contained three ESBLs genes.The highest detection rate was bla CTX-M-14（39.4%,28/71）,followed by bla TEM-1（28.2%,20/71）、bla CTX-M-15（14.1%,10/71）、bla OXA-1（9.8%,7/71）and bla CTX-M-55（8.5%,6/71）.4.Phylogenetic analysis showed that group D（42.1%）was the main group,followed by group B2（34.2%）,group A（18.4%）and group B1（5.2%）.The distribution of phylogenetic groups in ESBLs producing bacteria and non ESBLs producing bacteria was consistent,mainly in group D and B2.5.The results of multi locus sequence typing showed that 28 different sequence types（STs）were identified in the 76 isolates,among which ST131（19.7%,15/76）was the most common ST type,followed by ST69（15.7%,12/76）,ST38（7.8%,6/76）and ST1193（6.5%,5/76）.Conclusion:This study is the first to report the phenotypic and molecular characteristics of E.coli isolated from BSIs in Shanxi,China.Our results indicated that the antimicrobial resistance rates were high.We can empirically choose carbapenems,piperacillin-tazobactam,amikacin and tigecycline to treat BSIs caused by E.coli.B2-ST131 and D-ST69 clones were most common in Shanxi Province.Phylogenetic analysis showed that E.coli isolated from blood had genetic diversity.To develop and implement effective prevention strategies,better monitoring of the epidemiology of E.coli in bloodstream infections is needed. |
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