Assessment of safety and in situ antibacterial activity of Weissella cibaria strains isolated from Campos das Vertentes, Minas Gerais, Brazil for their food application

Abstract Aims: Weissella cibaria W21, W25 and W42 strains have previously been characterized for their antagonism against a range of foodborne pathogens. However, prior to their use as protective agents, further analyses such as their safety and in situ activity are needed. Methods and Results: The safety of W. cibaria W21, W25 and W42 strains was predicted in silico and confirmed experimentally. Analyses of their genomes using appropriate software did not reveal any acquired antimicrobial resistance genes, nor mobile genetic elements (MGE). The survival of each strain was determined in vitro under conditions mimicking the gastrointestinal tract (GIT). Thus, hemolysis, cytotoxicity and the inflammation capabilities of these strains were respectively determined on blood agar, using a mixture of two cell-lines composed of 50% Caco-2/HT-29 and on the promonocytic human cell line U937. The Weissella strains were found to be haemolysis-negative, non-cytotoxic and did not induce any inflammation. Furthermore, these strains adhered tightly to intestinal Caco-2 cell-lines and exerted in situ anti-proliferative activity against methicillin resistant Staphylococcus aureus (strain MRSA S1) and Escherichia coli 181, a colistin resistant strain. However, the W. cibaria strains showed low survival rate under simulated GIT conditions in vitro . Conclusion: The unusual LAB-strains Weissella cibaria strains W21, W25 and W42 are safe and endowed with potent antibacterial activities. These strains are therefore good candidates for industrial applications. Significance and Impact of Study: The results of this study allow a better characterization and to gain insights into Weissella strains, which are considered as unusual LAB, but which prompt a growing interest in their bio-functional properties and their potential industrial applications.