Virulence expression difference to intestinal cells of different pathogenic Listeria monocytogenes contaminating sausages after simulated digestive tract

This study investigated the difference in survival among Listeria monocytogenes (LM) 10403S (highly pathogenic strain) and M7 (low pathogenic strain) in sausage under a simulated digestive environment, and established intestinal organoids and macrophages co-culture model to further explore the virulence expression difference to intestinal cells between LM 10403S and M7 after in vitro gastrointestinal digestion. Results showed that, compared with LM M7, LM 10403S exhibited a high survival rate during in vitro digestion, which may be due to the increased expression of stress response-related genes. In addition, the expression of virulence genes in LM 10403S was significantly higher than in LM M7 under the gastrointestinal environment. Furthermore, in the intestinal organoids and macrophages co-culture model infected by LM 10403S and M7 after in vitro gastrointestinal digestion, results showed that, compared with the LM M7 group, the LM 10403S group had significantly lower budding rate and significantly higher mortality of organoids. Also, the significantly increased LDH release and inflammatory factors (TNF-alpha and IL-1 beta) in the LM 10403S group were observed, and the main virulence genes (iap, inlA, inlB, actA, hly, plcA, and plcB) of 10403S were significantly highly expressed than LM M7 during the cell infection. These results reflected that the reason for the different pathogenicity between LM 10403S and M7 may be due to the high tolerance and the expression of virulence genes than LM M7 during gastrointestinal digestion and cell infection, which would be expected to provide a better understanding of the infection mechanisms among different pathogenic strains of L. monocytogenes in food.