Control of Listeria monocytogenes ATCC 19115 biofilm formation and virulence by a food-derived Lactobacillus acidophilus VBFDP771 isolate with predictive assessment of robustness

Biofilm formation by foodborne pathogens such as Listeria monocytogenes significantly contributes to their persistence in food-related environments and resistance to conventional control strategies. The use of food-derived lactic acid bacteria (LAB) represents a promising biological approach for mitigating pathogenic biofilms and associated virulence traits. In this study, a Lactobacillus acidophilus VBFDP771 isolate obtained from traditional yogurt was evaluated for its ability to control L. monocytogenes ATCC 19115 biofilm formation and suppress virulence-associated gene expression, while assessing its physiological robustness under gastrointestinal-relevant conditions. The isolate exhibited strong tolerance to acidic conditions (pH 3–5) and bile salts (0.2–0.6%), maintaining a viable count of 7.45 log CFU/mL after simulated gastrointestinal transit. It showed notable surface hydrophobicity (60.85%), auto-aggregation (43.61%), co-aggregation (46.63%), and adhesion to Caco-2 intestinal cells (12.63%), supporting its functional stability. The strain significantly inhibited L. monocytogenes adhesion through competitive exclusion (46.71%), inhibition (40.88%), and displacement (26.86%) mechanisms. Treatment with cell-free supernatant markedly reduced biofilm biomass and resulted in substantial downregulation of key virulence- and biofilm-associated genes ( sigB, flaA, inlB, agrA, hly, prfA, and plcB ). In addition, the isolate demonstrated antioxidant activity (DPPH: 62.85%; ABTS: 63.55%) and cholesterol assimilation capacity (58.80%), and exhibited a favorable safety profile, including the absence of hemolytic activity, DNase production, and biogenic amine synthesis, as well as acceptable antibiotic susceptibility. Gaussian Process Regression (GPR) modeling further supported strain robustness by accurately predicting acid and bile tolerance responses (R² = 0.97 and 0.94, respectively). Overall, these findings highlight a food-oriented biological strategy for controlling L. monocytogenes persistence through biofilm inhibition and virulence attenuation, while demonstrating the utility of integrating functional and predictive assessments for food safety applications.