Genomic epidemiology and antimicrobial resistance of diarrheagenic Escherichia coli isolated from kindergarten children without diarrhoea symptoms in Hengyang, China

Asymptomatic carriage of diarrheagenic Escherichia coli (DEC) in kindergarten children without diarrhoea symptoms represents an important yet underexplored component of community transmission. This study aimed to investigate the prevalence, genomic epidemiology, and antimicrobial susceptibility of DEC recovered from kindergarten children without diarrhoea symptoms in Hengyang, China. Faecal samples (n = 150) were collected from kindergarten children without diarrhoea symptoms in Hengyang City in 2024. Molecular screening of these samples was performed using multiplex real-time PCR targeting sixteen enteric pathogens. PCR-positive samples were subjected to bacterial isolation, antimicrobial susceptibility testing, and whole-genome sequencing. Overall, 37 samples (24.7%) were PCR-positive for at least one enteric pathogen. DEC was the only pathogen group successfully recovered by culture, yielding 20 isolates, including 12 enteroaggregative E. coli (EAEC), 7 enteropathogenic E. coli and 1 enterotoxigenic E. coli. Core genome multilocus sequence typing identified a highly conserved EAEC cluster comprising four isolates with zero allelic differences, alongside additional closely related isolates. Antimicrobial susceptibility testing revealed resistance to nalidixic acid, streptomycin, and ampicillin, while most isolates remained susceptible to critically important antibiotics. Genomic surveillance revealed that kindergarten children without diarrhoea asymptomatically carry genetically diverse DEC, including closely related EAEC lineages, underscoring the epidemiological relevance of asymptomatic carriage in community settings beyond clinically apparent diarrhoeal disease.