Antagonistic Evaluation of Lactic Acid Bacteria Isolated from Commercial Cheese Against Foodborne Pathogens in Saudi Arabia

In fermented foods, lactic acid bacteria are important for flavor enhancement, preservation, and pathogen control via the production of antimicrobial compounds, such as bacteriocins. This study aimed to isolate and characterize lactic acid bacteria from cheese that can produce bacteriocin-like inhibitory substances and to evaluate their antibacterial activity against foodborne pathogens. Lactic acid bacteria were isolated from two cheese samples using de Man, Rogosa and Sharpe agar and were preliminarily identified through phenotypic and biochemical tests, including Gram staining and carbohydrate fermentation. Antibacterial activity was tested using live cells (cell culture), cell-free supernatants (CFS), and neutralized CFS against Escherichia coli, Salmonella Typhimurium, Klebsiella pneumoniae, and Listeria monocytogenes using the agar well diffusion method. Seven lactic acid bacterial strains were gram-positive, rod-shaped, catalase-negative, and showed a positive reaction to the methyl red test. The results showed strong inhibition of E. coli and S. Typhimurium, moderate inhibition of K. pneumoniae, and no inhibition of L. monocytogenes. The strongest antibacterial activity was observed with lactic acid bacteria cultures, followed by CFS and neutralized CFS. Bacteriocin-like inhibitory substances-producing strains were identified as Lacticaseibacillus rhamnosus, Lactiplantibacillus pentosus, and Lentilactobacillus parabuchneri. These findings emphasize the potential of lactic acid bacteria as natural antimicrobial agents and bio-preservatives, providing a promising strategy for enhancing safety and reducing foodborne pathogens in foods.