anti-invasion activities of heat-killed lactic acid bacteria isolates against salmonella enterica serovar typhimurium

Background and objectives: the most common cause of severe foodborne salmonellosis is s. typhimurium. its interaction with intestinal epithelial cells is little known. lactic acid bacteria (lab) were recognized as a prominent probiotic gastrointestinal microbiota of humans and animals that confer health-promoting and protective effects. this study aims to determine the anti-invasion and antibacterial effects of heat-killed lab (hk-lab) isolates against s. typhimurium towards human intestinal cells.materials and methods: 12 hk-lab isolates from 3 sources of origin (stingless bee, plant, and food) were tested to determine the adhesion of hk-lab to caco-2 cells, anti-invasion and antibacterial activities against s. typhimurium, the adhesion and invasion pattern of s. typhimurium on intestinal epithelial cells (caco-2) and assessing the effect of lab on the s. typhimurium-host cell interaction.results: tairu isolates from food have the highest adhesion rate with 19 ± 1.32/10 caco-2 cells followed by hk-lab r-isolate from plant 17 ± 0.70/10 caco-2 cells, which is similar to the control (lactobacillus casei). in the anti-invasion assay, the two hk-lab isolates that had the strongest adherence to caco-2 cells, tairu-isolate inhibited at 78.1 ± 3.06% and r-isolate inhibited at 64.76 ± 9.02% compared to the positive control (63.81 ± 1.15%), which led to increased suppression of s. typhimurium accordingly. tairu and r isolates were tested for their antibacterial ability against s. typhimurium. both r and tairu isolates displayed strong inhibition zones (27 ± 0.06 mm, 23 ± 0.06 mm) respectively.conclusion: these findings suggest that the anti-invasion activities of hk-lab r and tairu may correlate to their bactericidal effects that serve to protect the host from infection.