Molecular characterization and antibacterial activity of colicin-producing Escherichia coli isolated from urinary tract infections.

Urinary tract infections (UTIs) are predominantly caused by Escherichia coli, and the rise of multidrug-resistant strains poses major clinical challenges. Colicin-producing E. coli have attracted interest for their competitive advantage in microbial ecosystems and their potential role as natural antimicrobial agents. Seven E. coli isolates from UTI patients were examined using classical phenotypic assays (Gram staining, biochemical characterization) and molecular tools (16S rRNA sequencing, PCR, and real-time PCR). The colicin N gene (cna) was screened using specific primers. Sequencing results were confirmed through BLAST alignment, and phylogenetic relationships were assessed. Antimicrobial properties of colicin extracts were tested against Staphylococcus aureus, Proteus vulgaris, and Bacillus subtilis using disc diffusion assays. Four isolates carried the cna gene, confirming their colicin-producing ability. Sequence analysis revealed 98.7-99% similarity with reference E. coli strains, while phylogenetic mapping showed close clustering with Shigella spp. Colicin extracts displayed dose-dependent inhibition zones (8-24 mm) against the tested pathogens. All isolates were sensitive to commonly used antibiotics, indicating no compromise in drug susceptibility. This study provides molecular and functional confirmation of colicin N production among clinical E. coli strains from UTIs. The demonstrated antibacterial activity, along with preserved antibiotic susceptibility, underscores the therapeutic promise of colicin-producing strains. Further work should focus on colicin purification, expanded antimicrobial testing, and potential synergistic applications with conventional antibiotics.