Antimicrobial efficacy and prevalence of colicinogenic E. coli in faecal matter of human, cow and sheep.

Colicinogenic Escherichia coli in the human or animal gut prevent pathogen accumulation, thereby protecting against severe gut infections. This ability of commensal human and animal E. coli to restrain Gram-negative pathogens was evaluated invitro. Approximately 13.2% of E. coli isolates inhibited the growth of target pathogens. The greatest inhibition of 36% was observed against E. coli O157:H7 followed by 35%, 27%, 24% and 13% inhibition against E. coli O26:H11, Pseudomonas aeruginosa, Salmonella enterica and Klebsiella pneumoniae, respectively. Detection of 20 colicin determinants in colicinogenic E. coli revealed that >50% isolates exhibited multiple colicin genes. Among all isolates, 70.4% of E. coli had the col E6 gene followed by col Ib (66.4%), E4 (53.6%), E7 (49.9%), J (35.3%) and M (35.2%) determinants. The frequency of col D (8.8%), Ia (27.9%), S4 (12%), E3 (13.2%) and E9 (2.9%) was greater in human samples compared with samples from cows and sheep, whereas col10 (5.8%) and E5 (4.4%) were produced only by cow-derived E. coli. Colicinogenic E. coli belonging to phylogenetic group B2 (52.8%) were more prevalent followed by D1 (16%), B1 (13.2%), A1 (11.6%) and A0 (5.8%). The 16S rRNA sequencing of all colicinogenic E. coli provided 27 non-clinical variants of E. coli that can be further explored for their probiotic properties to minimize risk of gut diseases.