Exploring the probiotic potential of Limosilactobacillus reuteri VTC 864: Antimicrobial activity, safety profile, and biofilm inhibition against Listeria monocytogenes ATCC 19115

Probiotics are generally regarded as safe and represent a natural strategy for preventing infections caused by pathogenic microorganisms. This study investigated the probiotic properties, antimicrobial activity, safety profile, biofilm-related gene expression, and anti-biofilm potential of Limosilactobacillus reuteri strain VTC 864. The results demonstrated that L. reuteri VTC 864 effectively tolerated harsh gastrointestinal (GI) conditions. The strain exhibited notable functional properties, including hydrophobicity (63.58%), auto-aggregation (46.10%), co-aggregation (57.22%), and antioxidant activity (61.90% in the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay and 69.70% in the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay), as well as a cholesterol reduction capacity of 55.62%. Furthermore, L. reuteri VTC 864 showed strong anti-infective activity against Listeria monocytogenes , reducing pathogen adhesion by 57.40%, 50.62%, and 28.10% through competition, inhibition, and displacement mechanisms, respectively. The strain exhibited an adhesion rate of 13.15% to epithelial cells, was susceptible to most tested antibiotics, and displayed no DNase or hemolytic activity. The antimicrobial activity of the acidified cell-free supernatant (aCFS) revealed that L. monocytogenes was the most sensitive microorganism, with an inhibition zone of 10.65 mm, whereas Escherichia coli was the least sensitive, showing an inhibition zone of 6.35 mm. In addition, treatment with the cell-free supernatant (CFS) significantly inhibited L. monocytogenes biofilm formation and downregulated biofilm-related gene expression. Overall, the strong survival of L. reuteri VTC 864 under simulated GI conditions, together with its antimicrobial, anti-biofilm, and safety characteristics, highlights its potential for application in dietary supplementation and medical interventions