Comparative genomics of DH5α-inhibiting Escherichia coli isolates from human feces reveals common co-occurrence of bacteriocin genes with virulence factors and antibiotic resistance genes.

The presence of multi-drug-resistant (MDR) bacteria in healthy individuals poses a significant public health concern, as these strains may contribute to or even facilitate the dissemination of antibiotic resistance genes (ARGs) and virulence factors. In this study, we investigated the genomic features of antimicrobial-producing Escherichia coli strains from the gut microbiota of healthy individuals in Singapore. Using a large-scale screening approach, we analyzed 3,107 E. coli isolates from 109 fecal samples for inhibitory activity against E. coli DH5 and performed whole-genome sequencing on 37 representative isolates. Our findings reveal genetically diverse strains, with isolates belonging to five phylogroups (A, B1, B2, D, and F) and 23 unique sequence types (STs). Bacteriocin gene clusters were widespread, with colicins and microcins dominating the profiles. Notably, we identified a hcp-et3-4 gene cluster, encoding an effector linked to Type VI secretion system. Approximately 40% of the sequenced isolates were MDR, with resistance for up to eight antibiotic classes in one strain. Plasmids were the primary vehicles for ARG dissemination, but chromosomal resistance determinants were also detected. Additionally, over 55% of isolates were classified as potential extraintestinal pathogenic E. coli (ExPEC), raising concerns about their potential pathogenicity outside the intestinal tract. Our study highlights the co-occurrence of bacteriocins, ARGs, and virulence genes in gut-residing E. coli, underscoring their potential role in shaping microbial dynamics and antibiotic resistance. While bacteriocin-producing strains show potential as probiotic alternatives, careful assessment of their safety and genetic stability is necessary for therapeutic applications. ImportanceThis study provides genomic insights into the diverse repertoire of potential bacteriocin production in E. coli strains isolated from a cohort of healthy human subjects in Southeast Asia. Our findings suggest that the co-occurrence of bacteriocin genes with multiple antibiotic resistance and virulence genes is a common feature among non-clinical isolates. This genetic linkage could contribute to the increased abundance of multi-drug-resistant and virulent strains within individual hosts. Moreover, this co-occurrence may facilitate the host colonization with strains carrying antibiotic resistance and virulence determinants, potentially also contributing to the dissemination of resistant and pathogenic strains within the local population and beyond.