Abstract:
Objective To understand the drug susceptibility of diarrheagenic Escherichia coli isolated from outpatients aged ≤5 years in diarrhoeal disease outpatient service in Beijing.
Methods From 2017 to 2024, stool samples were collected from pediatric diarrhea cases aged ≤5 years in Beijing for diarrheagenic E. coli isolation, culture and identification by standard microbiological procedures. Drug susceptibility testing was performed by minimum inhibitory concentration method. Total genomic nucleic acids of all the diarrheagenic E. coli isolates were extracted for whole-genome sequencing. Extended spectrum β-lactamase (ESBL)-producing strains were further subjected to single-molecule nanopore sequencing to generate complete genomes for the comprehensive characterization of the genetic determinants underlying ESBLs–mediated resistance.
Results A total of 200 diarrheagenic E. coli strains were isolated from children aged ≤5 years in Beijing from 2017 to 2024. According to the drug susceptibility analysis, the resistances of diarrheagenic E. coli to ampicillin and tetracycline were most severe, with resistance rates of 56.50% and 52.00%, respectively. The resistance rate to ceftazidime was 5.00%, and resistance to fluoroquinolones remained low. In the diarrheagenic E. coli strains, 22 were ESBLs producing ones, which all carried the blaCTX genes with blaCTX-M-15 gene being the most common (11/22, 50.00 %). Whole genome analyses showed that except for1 diarrheagenic E. coli strain in which blaCTX-M-3 was chromosomally encoded, the remaining 21 strains carried blaCTX genes on plasmids, with IncF-type plasmids being the most common incompatibility group.
Conclusion Drug resistance of diarrheagenic E. coli strains isolated from children aged ≤5 years should not be neglected and strengthened surveillance and targeted control measures are needed.
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