In vitro evaluation of certain probiotic properties of lactic acid bacteria isolates

Süle, Judit and Varga, László and Hatvan, Zoltán and Kerényi, Zoltán (2023) In vitro evaluation of certain probiotic properties of lactic acid bacteria isolates. ÉLELMISZERVIZSGÁLATI KÖZLEMÉNYEK, 69 (1). pp. 4350-4363. ISSN 0422-9576

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Abstract

Bacteria carrying genes responsible for antibiotic resistance cannot be used in food production. For this reason, exploring the antibiotic resistance profile of probiotic candidates and the antimicrobial substances they produce are essential for probiotic strain selection. The aim of this study was to develop and evaluate additional elements of a complex in vitro test system for rapid and efficient selection of a large number of putative probiotic isolates. In a previous work, we had tested bacterial strains (n=217) isolated from Transylvanian raw sheep milk, cultured sheep milk, and sheep cheese samples and we reduced the sample number to a total of six Gram-positive, non-hemolytic, catalase-negative, well-aggregating, good acid and bile acid tolerating strains. In this research, we investigated the antibiotic resistance and antimicrobial production capacity of the pre-selected strains (n=6). The antimicrobial activity of the isolates was determined by the agar well diffusion assay. Strains E15, E66, E173, E198, and E216 were found to inhibit the growth of both Salmonella Enteridis ATCC 13076 and the control strain (i.e., Lactobacillus acidophilus ATCC 4356). Antibiotic resistance tests were performed by the agar disk diffusion method. All six isolates belonging to the species of Levilactobacillus brevis and Lactiplantibacillus plantarum were found to be resistant to several antibiotics and, therefore, cannot be used for the manufacture of commercial probiotic products. In conclusion, our in vitro test system proved to be capable of effectively screening out unsafe isolates.

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