Antimicrobial susceptibility analysis of diarrhoeagenic Escherichia coli isolated from outpatients in Beijing, from 2021 to 2024.

OBJECTIVES

This study aimed to investigate the prevalence of diarrhoeagenic Escherichia coli (DEC) among outpatients in Beijing, and to analyse the antimicrobial susceptibility profiles and antimicrobial resistance gene characteristics of the isolated strains.

METHODS

From 2021 to 2024, DEC strains were collected from outpatient specimens. After isolation and identification, the minimum inhibitory concentration (MIC) method was used to assess their susceptibility to 16 antibiotics. Whole-genome sequencing was conducted for further analysis.

RESULTS

Among the 1209 DEC strains, the highest resistance rates were observed for ampicillin (63.28%) and tetracycline (45.57%). In contrast, significantly lower rates were found for tigecycline (0.41%), amikacin (0.66%), meropenem (3.97%), ertapenem (6.70%), ceftazidime (7.20%), and ciprofloxacin (9.26%). The 0-5 age group demonstrated higher resistance rates to most antibiotics compared with other age groups. Multi-locus sequence typing revealed significant genetic diversity among all strains, with the predominant sequence types identified as ST10 (5.96%), ST1491 (5.21%), ST4 (4.22%), and ST48 (3.47%). Among 111 fluoroquinolone-resistant strains, chromosomal mutations in gyrA and parC genes were predominant (56.76%). Among 612 cephalosporin-resistant isolates, the blaCTX-M gene was the most prevalent resistance gene (30.72%).

CONCLUSIONS

DEC infections and the spread of resistance genes pose a significant health threat, especially in children. Consequently, there is an urgent need to enhance the surveillance and research of resistance genes and to promote the rational use of antibiotics.