<i>Lacticaseibacillus rhamnosus</i> DTA 73 Exhibits Superior Anti-adhesion Activity against <i>Salmonella typhimurium</i> DTA 41 in Caco-2 cells

Background: A challenge in choosing probiotic strains is to identify, in each one, specific positive health effects to offer a tailored product. An important health claim of probiotics is the competitive exclusion of pathogens and the consequent prevention and treatment of diarrhea. Objective: The aim of the study was to evaluate the ability of lactobacilli strains to adhere to intestinal epithelial Caco-2 cells and to inhibit Salmonella adhesion in vitro and in situ. Methods: The ability to inhibit Salmonella biofilms by four strains of Lacticaseibacillus paracasei, three strains of Lacticaseibacillus rhamnosus, two strains of Limosilactobacillus fermentum, and a commercial strain of Lacticaseibacillus casei, was evaluated in vitro on hydrophobic polystyrene surfaces and in situ using Caco-2 cells. Results: All strains showed a high adhesion capacity to Caco-2 cells, with no significant difference between isolated strains and the commercial probiotic strain. In polystyrene surfaces, inhibition of Salmonella biofilms by lactobacilli through the competition and exclusion mechanisms was significantly more effective when compared to displacement. However, in Caco-2 cells, the isolates were more effective in inhibiting Salmonella biofilms. Conclusion: It is concluded that hydrophobicity was not a good indicator of adhesion capability. Although all lactobacilli strains have low cell surface hydrophobicity, they showed high adhesion capacity in Caco-2 cells. The most promising strain, Lacticaseibacillus rhamnosus DTA 73, was able to inhibit Salmonella adhesion in Caco-2 cells by competition, exclusion and displacement with the same efficiency, suggesting that it could be effective not only in preventing but also in treating diarrhea.