Characterization and molecular identification of lactic acid bacteria isolated from kefir and evaluation of their antibacterial activity against food-borne pathogens in Saudi Arabia

M.O.I. Albureikan

Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia. malboraikan@kau.edu.sa

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• Biology

OBJECTIVE: Pathogenic bacteria are usually present in raw milk. In order to prevent pathogens from growing, milk should be fermented. The present research work aimed to isolate lactic acid bacteria (LAB) from kefir, a fermented milk beverage, and assess their antibacterial activity against chosen pathogenic strains of bacteria.

MATERIALS AND METHODS: An experimental investigation was carried out in the laboratory. Samples of kefir were collected from a local organic food store in Jeddah City, Saudi Arabia. LAB isolates were identified phenotypically and biochemically. The agar well diffusion technique evaluated the antimicrobial activities (AMAs) of LAB isolates against Escherichia coli, Listeria monocytogenes, and Salmonella Typhimurium. The isolates were molecularly identified through polymerase chain reaction PCR amplification of the 16S rRNA gene.

RESULTS: Six LAB isolates were identified and given the following numbers: SK9, SK17, SK23, SK24, SK28, and SK33. The isolates belong to Enterococcus durans and Leuconostoc mesenteroides. After screening for antibacterial activity against food-borne bacteria, SK28 showed the strongest AMA against E. coli and S. Typhimurium. SK23 showed the highest AMA against L. monocytogenes, while SK33 showed no AMA against L. monocytogenes.

CONCLUSIONS: LAB isolates exhibited AMA against the selected strains of bacteria. Enterococcus isolates showed the highest antibacterial activities against the tested bacterial strains. Therefore, in the era of antimicrobial resistance, they might serve as antibiotic alternatives. L. monocytogenes was the least sensitive to the antimicrobial activities of LAB isolates. Further experiments are required to isolate and identify the molecules responsible for the antimicrobial activities.

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