Ligilactobacillus murinus Strains Isolated from Mice Intestinal Tract: Molecular Characterization and Antagonistic Activity against Food-Borne Pathogens

Considering the objectives of “One Health” and the Sustainable development Goals “Good health and well-being” for the development of effective strategies to apply against bacterial resistance, food safety dangers, and zoonosis risks, this project explored the isolation and identification of Lactobacillus strains from the intestinal tract of recently weaned mice; as well as the assessment of antibacterial activity against clinical and zoonotic pathogens. For molecular identification, 16S rRNA gene-specific primers were used and, via BLAST-NCBI, 16 Ligilactobacillus murinus, one Ligilactobacillus animalis, and one Streptococcus salivarius strains were identified and registered in GenBank after the confirmation of their identity percentage and the phylogenetic analysis of the 16 Ligilactobacillus murinus strains and their association with Ligilactobacillus animalis. The 18 isolated strains showed antibacterial activity during agar diffusion tests against Listeria monocytogenes ATCC 15313, enteropathogenic Escherichia coli O103, and Campylobacter jejuni ATCC 49943. Electrophoretic and zymographic techniques confirmed the presence of bacteriolytic bands with a relative molecular mass of 107 kDa and another of 24 kDa in Ligilactobacillus murinus strains. UPLC-MS analysis allowed the identification of a 107 kDa lytic protein as an N-acetylmuramoyl-L-amidase involved in cytolysis and considered a bacteriolytic enzyme with antimicrobial activity. The 24 kDa band displayed similarity with a portion of protein with aminopeptidase function. It is expected that these findings will impact the search for new strains and their metabolites with antibacterial activity as an alternative strategy to inhibit pathogens associated with major health risks that help your solution.