Drug resistance characteristics,virulence gene distribution,and phylogenetic typing of Escherichia coli in blood culture
Objective To detect and analyze the drug resistance characteristics,phylogenetic typing,and virulence gene distribution of Escherichia coli(E.coli)in blood culture.Methods The strains of E.coli isolated from consecutive non-repetitive blood cultures in our hospital from January 1,2019 to December 13,2020 were collected.The sensitivity of E.coli to 17 antibiotics was determined u-sing the micro-broth method.The bacterial genomic DNA was extracted using the boiling method,and then the arpA,chuA,yjaA,TspE4C2,ArpAgpE and trpAgpC genes were detected by PCR to determine the bacterial phylogroup.The virulence genes,including iutA,fimH,fyuA,kpsMT Ⅱ,cnf1,cvac,hlyA,traT,kpsMT Ⅲ,and PAI,were detected using the multiplex PCR.The differences in drug resistance and virulence gene distribution among different phylogroups were analyzed by the Chi-square test.Results 270 strains of E.coli in blood culture showed high resistance rates to ceftriaxone,compound sulfamethoxazole,ampicillin,ampicillin sulbactam,cefazolin,and ciprofloxacin,all exceeding 50.0％.They had good susceptibility to imipenem,ertapenem,amikacin,and piperacillin tazobactam,with resistance rates all below 5.0％.The most common phylogroups were types B2 and D,accounting for 38.0％and 16.2％,respectively,while type E and hidden branch type I were relatively rare,accounting for less than 1.0％.The virulence gene analysis revealed that the distribution rates of fimH and fyuA genes were the highest,both above 99.0％.The distribution rates of kpsMT Ⅲ,hlyA,and cvaC genes were relatively low,all below 20.0％.The Chi-square test showed that the distribution rates of viru-lence genes such as iutA,fimH,fyuA,kpsMT Ⅱ,cnf1,and PAI in the B2 group were significantly higher than those in the non-B2 group(P<0.05).The distribution rates of iutA,fyuA,kpsMT Ⅱ,cnf1,and PAI genes in the B2 group were significantly higher than those in the D group(P<0.05).Conclusion When treating bloodstream infections caused by E.coli,caution should be exercised in the use of drugs such as ceftriaxone,compound sulfamethoxazole,ampicillin,ampicillin sulbactam,cefazolin,and ciprofloxacin.When bloodstream infections are caused by phylogroup B2 E.coli,middle-stream urine culture should be performed simultaneously to confirm the source of infection and monitor the success rate of treatment.
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