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

Anis Syahirah, Saifor Adzuan and Sharifah Aminah, Syed Mohamad and Rashidah, Iberahim and Noor Nadia Syahira, Mohd Kamal and Nurliana, Abd Mutalib and Nur Intan, Hasbullah and Muneer, Alsaydi and Nor'aishah, Hasan and Low, Kheng Oon and Olaide, Olawunmi Ajibola and Rozila, Alias and Maimunah, Mustakim and Azlin, Sham Rambely and Emida, Mohamed and Mohammad Reza, Pourmand (2024) Anti-invasion activities of heat-killed lactic acid bacteria isolates against Salmonella enterica serovar Typhimurium. Iranian Journal of Microbiology, 16 (6). pp. 763-772. ISSN 2008-3289

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Abstract

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 gastroin- testinal 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-iso- late 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. Ty- phimurium 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 bacteri- cidal effects that serve to protect the host from infection.

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