Effect of sublethal heat stress on Salmonella Typhimurium virulence

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Abstract
Aims: To determine the virulence gene expression of Salmonella Typhimurium in response to sublethal heat stress and determine the adhesion and invasion pattern of heat‐stressed Salmonella in Caco‐2 intestinal epithelial cells. Methods and Results: Transcriptional profiling was employed to capture the virulence gene response of Salm. Typhimurium at 42°C sublethal heat stress. Data indicated an induction of SPI‐2 and SPI‐5 genes and a repression of SPI‐1‐encoded genes due to heat stress. Gene expression pattern also showed induced transcription of fimbriae genes and genes present within the stress‐associated Rpo regulon. Changes in adhesion and invasion pattern of heat‐stressed Salm. Typhimurium were tested in Caco‐2 cells. Heat‐stressed Salm. Typhimurium showed greater adhesion to Caco‐2 cells compared with nonstressed control cells. Conclusions: Salmonella Typhimurium exposed to sublethal heat stress responds by altered virulence gene expression, which further enhances the adhesion of bacterial cells to intestinal Caco‐2 cells. Results indicate a role of physiological stress in Salm. Typhimurium in promoting microbial virulence and host cell vulnerability to infection. Significance and Impact of the Study: Studying the Salmonella virulence genes expression in response to sublethal heat stress is crucial for the understanding of the virulence status of Salmonella in temperature‐abused foods. Results of this study provide information about the gene response and virulence status of Salmonella pathogenicity factors in response to sublethal heat stress towards host cells.

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