Antimicrobial Efficacy and Prevalence of Microcins: Low Molecular Mass Bacteriocins Produced by <i>Escherichia coli</i>

Abstract

IntroductionMicrocin (Mcc) refers to a class of small-sized antimicrobial agents that are produced by various strains of Enterobacterales. Microcins exhibit potent bactericidal characteristics through intricate mechanisms that enable their ingress into both the outer and inner membranes of Gram-negative microorganisms. In this study, we investigated the antibacterial activity of microcins and the prevalence of Mcc genes among Escherichia coli (E. coli) strains. Simulation investigations were additionally carried out on the affixed complex for the purpose of ascertaining its stability.MethodsThis cross-sectional investigation involved the collection of 125 urine and blood specimens during the years 2021 and 2022, from patients who referred to private diagnostic laboratories in Isfahan. Bacteriocin activity was assessed by the agar-well diffusion assay. The complete set of bacterial strains was assessed in order to detect the existence of five specific Mcc, namely B17, H47, J25, M and V. The impact of bacteriocin-producing strains on the growth of pathogenic multidrug-resistant (MDR) E. coli and Salmonella enterica serovar Typhimurium was evaluated by examining the bacterial growth in the culture medium in the presence of metabolites produced by the E. coli strains. Salmonella enterica serovar Typhimurium, which were treated and untreated with CFS, were observed by using the scanning electron microscope (SEM). AutoDock Vina 1.1.2. and AutoDock Tools 1.5.7 automated docking tools were employed to facilitate the docking of MccJ25 peptide with the active enzyme.ResultsOut of 125 clinical specimens, 45 (representing 36 of the sample) demonstrated the presence of significant zones of inhibition in agar well diffusion assay. A total of 36 strains were ascertained to exhibit positivity for the existence of 5 Mcc genes. The cell-free supernatant (CFS), from the cellular lysate of E. coli exhibited inhibitory properties and did not exhibit a cytotoxic impact on the L929 cell line. Moreover, significant binding modes with high docking scores are in the range against selected pathogenic microorganisms.ConclusionThe characteristics of the bacteriocins synthesized by E. coli demonstrated efficacy against pathogenic bacteria, including Salmonella and MDR E. coli, thereby highlighting the substantial potential of bacteriocin as a promising antimicrobial agent. Furthermore, the cytotoxicity test results indicated the safety of its usage, thereby presenting intriguing biotechnological possibilities.