Pathotype-specific antimicrobial resistance in diarrheagenic Escherichia coli: gene variants, resistance mechanisms, and evolution of treatment strategies.

Diarrheagenic Escherichia coli (DEC) is still a prominent cause of diarrheal disease and mortality in children under five, and it continues to be a significant worldwide health concern. This review summarises and analyses recent findings (2015-2025) on the classification, geographic distribution, antimicrobial resistance (AMR) patterns, and emerging treatment options for six principal DEC pathotypes: enterotoxigenic (ETEC), enteropathogenic (EPEC), enteroaggregative (EAEC), Shiga toxin-producing (STEC/EHEC), enteroinvasive (EIEC), and adherent-invasive (AIEC) strains. Across diverse regions, diarrheagenic E. coli remains widespread in low- and middle-income populations. However, the epidemiological landscape is changing, as EAEC increasingly replaces traditional pathotypes in parts of Africa and Asia. Resistance levels to ampicillin and trimethoprim-sulfamethoxazole frequently surpass 50%, and rising resistance to fluoroquinolones, azithromycin, and third-generation cephalosporins is increasingly documented. The expansion of multidrug resistance is driven by various mechanisms, including the production of extended-spectrum β-lactamase (ESBL), the transfer of plasmid-borne resistance genes, the activation of efflux pumps, and the formation of biofilms. Novel interventions, including bacteriophage therapy, ETEC-focused vaccine candidates, anti-virulence agents, and approaches to modulate gut microbiota, are progressing from laboratory research to clinical evaluation. Addressing the AMR threat in DEC will need integrated One Health surveillance strategies and tailored antimicrobial stewardship measures. The current evidence highlights an urgent need for coordinated international action to reduce the clinical and public health burden associated with DEC.