Analysis of drug resistance characteristics of diarrheagenic Escherichia coli isolated from diarrhea surveillance cases in Tongzhou District, Beijing City

ObjectiveTo investigate the prevalence and antimicrobial resistance of diarrheal Escherichia coli （DEC） isolated from surveillance cases of diarrhea from 2016 to 2023 in Tongzhou District， Beijing.MethodsThe antimicrobial susceptibility tests were carried out using microbroth dilution method. The whole genome was sequenced on illumina sequencing platform， and the antimicrobial resistance genes were identified through blasting with CARD database.ResultsFrom 2016 to 2023， the detection rate of DEC in Tongzhou District was 7.45% （226/3 033）. Among all DEC isolates， most of them were enterotoxigenic Escherichia coli （ETEC）， followed by enteropathogenic Escherichia coli （EPEC） and enteroagglutinative Escherichia coli （EAEC）. The multi-drug resistant rate was 41.59% （94/226）， from which strains resistant to three antimicrobials were dominant. The antimicrobial resistance rate of all isolates was higher against ampicillin， tetracycline， nalidixic acid and cotrimoxazole， and was relatively lower against polymyxin E， tigecycline and amikacin. The changes of antimicrobial resistance rates of ampicillin， ampicillin-sulbactam and ciprofloxacin in different years were statistically significant， and an increasing trend in antimicrobial resistance rates was observed. The multidrug-resistant isolates carried 64 antimicrobial resistance genes in 8 classes， including β-lactam （blaTEM， blaCTX， blaAmpC， blaEC）， Tetracycline （tetA）， quinolones （qnrS1） and folate pathway antagonists （sul1， sul2， drfA17）.ConclusionHigh multidrug resistant rate of DEC in Tongzhou District， and the harboring of multiple antimicrobial resistance genes in DEC， which have the potential to spread among different bacteria through horizontal gene transfer， were raising a public health concern. Therefore， antimicrobial resistance monitoring should be strengthened to provide better guidance for clinical antibiotic usage.