Attenuation of Colitis by Lactobacillus casei BL23 Is Dependent on the Dairy Delivery Matrix

The role of the food delivery matrix in probiotic performance in the intestine is not well understood. Because probiotics are often provided to consumers in dairy products, we investigated the contributions of milk to the health-benefiting performance ofLactobacillus casei BL23 in a dextran sulfate sodium (DSS)-induced murine model of ulcerative colitis.L. casei BL23 protected against the development of colitis when ingested in milk but not in a nutrient-free buffer simulating consumption as a nutritional supplement. Consumption of (acidified) milk alone also provided some protection against weight loss and intestinal inflammation but was not as effective asL. casei and milk in combination. In contrast,L. casei mutants deficient in DltD (lipoteichoic acidd -alanine transfer protein) or RecA (recombinase A) were unable to protect against DSS-induced colitis, even when consumed in the presence of milk. Mice fed eitherL. casei or milk contained reduced quantities of colonic proinflammatory cytokines, indicating that theL. casei DltD− and RecA− mutants as well asL. casei BL23 in nutrient-free buffer were effective at modulating immune responses. However, there was not a direct correlation between colitis and quantities of these cytokines at the time of sacrifice. Identification of the cecal microbiota by 16S rRNA gene sequencing showed thatL. casei in milk enriched forComamonadaceae andBifidobacteriaceae ; however, the consumption of neitherL. casei nor milk resulted in the restoration of the microbiota to resemble that of healthy animals. These findings strongly indicate that probiotic strain efficacy can be influenced by the food/supplement delivery matrix.