Bacteriocin Distribution Patterns in Enterococcus faecium and Enterococcus lactis: Bioinformatic Analysis Using a Tailored Genomics Framework

Multidrug-resistant Enterococcus faecium represent a major concern due to their ability to thrive in diverse environments and cause life-threatening infections. While antimicrobial resistance and virulence mechanisms have been extensively studied, the contribution of bacteriocins to E. faeciums adaptability remains poorly explored. E. faecium, within the Bacillota phylum, is a prominent bacteriocin producer. Here, we developed a tailored database of 76 Bacillota bacteriocins (217 sequences, including 40 novel bacteriocins) and applied it to uncover bacteriocin distribution patterns in 997 quality-filtered E. faecium and Enterococcus lactis (former E. faecium clade B) genomes. Curated using computational pipelines and literature mining, our database demonstrates superior precision versus leading public tools in identifying diverse bacteriocins. Distinct bacteriocin profiles emerged between E. faecium and E. lactis, highlighting species-specific adaptations. E. faecium strains from hospitalized patients were significantly enriched for bacteriocins as entA, bac43, bacAS5 and bacAS11. These bacteriocins strongly associated with antibiotic resistance, particularly vancomycin and ampicillin, and Inc18 rep2_pRE25-derivative plasmids, classically associated with vancomycin resistance transposons. Our integrated genomic and epidemiological analysis elucidates meaningful connections between bacteriocin determinants, antimicrobial resistance, mobile genetic elements, and ecological origins in E. faecium. This work significantly expands the knowledge on the understudied bacteriocin diversity in opportunistic enterococci, revealing their contribution to environmental adaptation. Further characterization of strain-level bacteriocin landscapes could inform strategies to combat high-risk clones. Overall, these insights provide a framework for unravelling bacteriocins therapeutic and biotechnological potential.