Potential probiotic application of a novel commensal <i>E. coli</i> with antagonistic activity against different enteric pathogens

Abstract Diarrheal diseases remain a leading cause of global morbidity and mortality, and treatment options are increasingly compromised by the global rise in multidrug-resistant (MDR) pathogens. Furthermore, the absence of effective vaccines against many causative agents renders large populations vulnerable. This critical gap necessitates the development of novel alternatives that can function both prophylactically to prevent infection and therapeutically to treat established diseases. Here, we investigated the commensal Escherichia coli strain HK220822 (HK5), which was isolated from a healthy human, as a potential live biotherapeutic. Comprehensive genomic and phenotypic characterization established a robust safety profile, confirming the absence of key virulence genes while demonstrating essential probiotic traits, including high tolerance to gastrointestinal stressors, such as acid and bile. The functional efficacy of Escherichia coli HK5 has been validated in murine models of infection. Prophylactic administration before pathogen exposure significantly inhibited intestinal colonization by Salmonella Typhimurium, Shigella flexneri 2a , and Vibrio cholerae (El Tor O1 strain). Moreover, HK5 demonstrated therapeutic potential by significantly reducing pathogen shedding when administered to previously infected animals. These findings establish commensal E. coli (HK5) as a potent candidate with dual preventative and therapeutic efficacy, offering a promising non-antibiotic strategy to combat diarrheal diseases.