Thymol and Carvacrol Downregulate the Expression ofSalmonella typhimuriumVirulence Genes during an In Vitro Infection on Caco-2 Cells

Salmonella typhimuriumis one of the major bacteria responsible for gastroenteritis in humans caused by foodborne pathogens. As pork is one of the main routes of transmission, bioactive compounds used as feed additives may be an important strategy to controlSalmonella typhimurium. The aim of this study was to assess the antimicrobial activity of several organic acids and nature identical compounds againstSalmonella typhimuriumATCC(R)6994 (TM). Moreover, the effect of sub-lethal concentrations of thymol and carvacrol in counteracting aSalmonella typhimuriumin vitro infection on Caco-2 cells was evaluated, focusing on the maintenance of the epithelial barrier and the alteration ofSalmonellavirulence genes. The results showed a protective effect of the compounds on the integrity of the intestinal monolayer, improving transepithelial electrical resistance and bacterial translocation compared to the non-treated cells. A real-time PCR study highlighted a significant downregulation of the main virulence genes ofSalmonella(hilA,prgH,invA,sipA,sipC,sipD,sopB,sopE2). These findings indicate that thymol and carvacrol could be good candidates for the control ofSalmonella typhimuriumin pigs.