Antibacterial Activity of Lactiplantibacillus Strains Isolated from Commercial Yogurt against Foodborne Pathogenic Bacteria

Lactic acid bacteria are well known as beneficial microorganisms and most of them are probiotic distributed widely, especially in fermented dairy products e.g. yogurt. This study aimed to isolate, characterize and assess antimicrobial effects of lactic acid bacteria producing bacteriocin-like inhibitory substances against foodborne pathogenic bacteria.

In the present study, 17 lactic acid bacteria strains were isolated from 10 commercial yogurt samples and the antibacterial effects of lactic acid bacterial cell culture, cell-free supernatant and neutralized cell-free supernatant was assessed against standard foodborne pathogenic bacteria of Escherichia coli, Listeria monocytogenes, Klebsiella pneumonia and Salmonella typhimurium using agar well diffusion assay. Although various treatments were used, most of the lactic acid bacterial isolates showed antimicrobial activity against the foodborne pathogenic bacteria. Moreover, Lactiplantibacillus pentosus (SY1), Lacticaseibacillus rhamnosus (SY5), Lactiplantibacillus plantarum (SY8) and Lactiplantibacillus plantarum (SY9) showed significantly the best antimicrobial activity against the foodborne pathogens and thus were further identified using 16S rRNA gene molecular method.

Results showed that four isolates could produce bacteriocin-like inhibitory substances, which was significantly effective to inhibit growth of the pathogens. Primary screening for antimicrobial activity showed that 10 lactic acid bacterial strains inhibited Escherichia coli. The results revealed that Listeria monocytogenes and Salmonella typhimurium was inhibited by six and one lactic acid bacterial isolates. Moreover, results showed that Klebsiella pneumoniae was not affected by the isolates or treatment methods. It is concluded that a bacteriocin-like inhibitory substance of lactic acid bacterial isolates was effective; hence, it could be used as a natural food additive to prevent foodborne infections and improve the food quality.