Oral Administration of Heat-Killed Lactobacillus plantarum Strain b240 Protected Mice against Salmonella enterica Serovar Typhimurium

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The purpose of this study was to investigate the effects of heat-killed Lactobacillus plantarum strain b240 (b240) on systemic infection by Salmonella enterica serovar Typhimurium (S. Typhimurium) and to determine the mechanism by which b240 protects against infection. Mice were administered either b240 or saline orally for 3 weeks, and then inoculated with S. Typhimurium. The mice treated with b240 were significantly protected against S. Typhimurium as compared to those fed saline. Moreover, translocation of S. Typhimurium into each organ tested in the mice that received b240 tended to be less than in the control mice. An important mechanism of protection against infection was demonstrated by the ability of b240 to inhibit both binding by and invasion of S. Typhimurium into cells. These results indicate that nonviable lactic acid bacteria also play important roles in preventing infection by enteric pathogens.