Evaluation of the Antimicrobial Activity of Bacteriocin-Producing Lactic Acid Bacteria Isolated from Human Intestine against Pathogenic Microorganisms

Currently, it is crucial to screen efficient, safe, and accessible therapies from a variety of prospective antimicrobial agents due to the rapid development of microbial resistance against chemotherapeutic drugs (mainly antibiotics). Bacteriocins are a type of antimicrobial peptide created by bacteria that are ribosomally synthesized. Bacteriocins have evolved into one of the tools used to combat bacteria because of their distinctive traits. Therefore, bacteriocins may replace antibiotics to treat multiple drugs resistance pathogens. Accordingly, the purpose of this study was to investigate the antibacterial effects of secondary metabolites from two bacteriocinproducing strains (Lactobacillus acidophilus (LA102) and Lacticaseibacillus casei (LC232)) on 24 pathogenic and spoilage microorganisms either alone or in combination. The 50% inhibitory concentration, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), or minimum fungicidal concentration (MFC) were determined. The fractional inhibitory concentration (FIC) and its effect were also defined. Results showed that all the 12 bacterial and ten fungal strains were inhibited by both bacteriocin-producing strains and only four fungal strains were not affected by all studied 12 strains. It was found that the bactericidal activity of both bacteriocin-producing strains against S. aureus, L. monocytogenes, and the fungi strains M. phaseolina was the highest among all the tested strains. It was also noticed that a combination of (LA102) and (LC232) gives a 20% synergistic effect and 40 % additive relationship and indifferent relationship without any microbes showing an antagonistic relationship. Moreover, to screen for better functional and bacteriocin-producing strains, this study offers a practical, thorough, and shared profile of newly developed antimicrobial agents.