Organic acids – a dual-action mode influencing both host and pathogen integrity to reduce Salmonella infection

In this study, we aimed to describe the mechanism by which a blend of organic acids (AuraShield - As) prevents Salmonella Typhimurium SE10/72 infection of primary chicken caecal epithelial cells (PECC) and caecal biopsies. First, our results show a MIC of 0.50% and an MBC of 1% against Salmonella Typhimurium SE10/72, with a sub-inhibitory concentration of 0.25% selected for further experiments. At this level, in vitro and ex vivo, As significantly decreased the ability of S. Typhimurium to attach to and invade PECC cells and caecal biopsies alongside bacterial motility and biofilm formation. The sub-inhibitory concentration also considerably reduced LDH release from infected PECC cells. It drastically attenuated the inflammatory response, as measured by levels of interferons (IFN) and cytokines IL-1β, IL-6, and IL-8 in infected PECC cells and in chicken caecal biopsies. These results were also mirrored when caecal biopsies were infected. The presence of As during infection also significantly reduced intracellular Ca²⁺ levels in both PECC cells and caecal biopsies and restored TEER levels. Conclusively, As reduces bacterial invasion in PECC cells and caecal biopsies, impairs bacterial growth, and causes bacterial membrane permeabilisation. It further reduces cytotoxicity and inflammation in PECC cells and caecal biopsies, apparently through a mechanism that involves regulation of intracellular calcium levels.