Characterization of Lactiplantibacillus Plantarum TO-A Growth Inhibition Activity against Pathogenic Bacteria.

Lactiplantibacillus plantarum is commonly used in pharmaceuticals and foodstuffs. Some L. plantarum strains are known as lactic acid bacteria that can inhibit the growth of pathogenic bacteria. A significant reclassification of the genus Lactobacillus was carried out in 2020. However, L. plantarum TO-A, which was isolated and registered in 1997, has not been sufficiently characterized. Therefore, in this study, we conducted a taxonomic re-identification of L. plantarum TO-A and judged that it should be classified as L. plantarum subsp. plantarum. Using in vitro experiments, we also determined that L. plantarum TO-A has a higher lactic acid production capability than other lactic acid bacteria (L. plantarum ATCC14917, L. reuteri NBRC15892, L. gasseri ATCC19992, and L. rhamnosus ATCC53103) and that L. plantarum TO-A inhibits the proliferation of four pathogenic bacteria (Escherichia coli ATCC8739, methicillin-resistant Staphylococcus aureus ATCC33591, Clostridium perfringens ATCC 13124, and Clostridium difficile ATCC17859). In parallel experiments, we used Caenorhabditis elegans to confirm that L. plantarum TO-A prevents bacterial infection of the host in vivo. Consequently, compared with nematodes fed E. coli OP50, nematodes fed L. plantarum TO-A exhibited longer survival in the presence of methicillin-resistant S. aureus. Moreover, in in vitro experiments, we showed that L. plantarum TO-A eliminated up to 65.3 % of mucin adherent methicillin-resistant S. aureus. Our study thus suggests that L. plantarum TO-A used in pharmaceuticals and foodstuffs can help protect the host from various pathogenic bacteria.