Effect of sublethal heat stress on Salmonella Typhimurium virulence

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 degrees 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.