Anti-invasion activities of heat-killed lactic acid bacteria isolates against Salmonella enterica serovar Typhimurium

The most common cause of severe foodborne salmonellosis is 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 Typhimurium towards human intestinal cells. 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 Typhimurium, the adhesion and invasion pattern of Typhimurium on intestinal epithelial cells (Caco-2) and assessing the effect of LAB on the . Typhimurium-host cell interaction. 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 . 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 Typhimurium accordingly. Tairu and R isolates were tested for their antibacterial ability against . Typhimurium. Both R and Tairu isolates displayed strong inhibition zones (27 ± 0.06 mm, 23 ± 0.06 mm) respectively. 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.