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 of Lactobacillus 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 as L. casei and milk in combination. In contrast, L. casei mutants deficient in DltD (lipoteichoic acid D-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 either L. casei or milk contained reduced quantities of colonic proinflammatory cytokines, indicating that the L. casei DltD ؊ and RecA ؊ mutants as well as L. 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 that L. casei in milk enriched for Comamonadaceae and Bifidobacteriaceae; however, the consumption of neither L. 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. C ertain strains of Lactobacillus and Bifidobacterium are used extensively as probiotics intended to confer health benefits upon delivery to the digestive tract in foods, beverages, or dietary supplements. Dairy products are the most popular food matrices for probiotic strains, and numerous clinical trials examining probiotic efficacy have used yogurt or (fermented) milks as carriers of probiotics to the intestine (1-3). Comparisons of data from human studies have indicated that probiotic delivery matrices, including dairy products, can influence probiotic intestinal survival and persistence (1). Remarkably, however, only a single human study and a few animal studies have compared the impacts of different carrier matrices or food product formulations on the capacity of probiotics to influence health (1, 2). Evidence from preclinical animal studies indicates that fermented milks might augment probiotic efficacy, although this has yet to be systematically investigated.Probiotics are useful for the prevention and treatment of a variety of acute and chronic diseases (4-6). Prevention and reduction of symptoms of inflammatory bowel diseases (IBDs) are among the most extensively evaluated benefits (7). Although the pathogenesis of IBDs is unclear, these diseases are characterized by chronic intestinal inflammation and excessive accumulation of reactive ox...

We investigated the effects of host diet on the intestinal persistence and gene expression of Lactobacillus plantarum WCFS1 in healthy and health-compromised, 2,4,6-trinitrobenzene sulfonic acid (TNBS)-treated mice. Mice fed either a low-fat chow diet (CD) or high fat and sucrose Western diet (WD) received 10(9) L. plantarum WCFS1 cells for five consecutive days. Lactobacillus plantarum persistence was 10- to 100-fold greater in the intestines of WD-fed compared with CD-fed mice. TNBS, an intestinal irritant that induces the development of inflammatory bowel disease-like symptoms, resulted in up to a 10(4) -fold increase in L. plantarum survival in the digestive tract relative to healthy animals. Expression levels of 12 metabolic and gut-inducible L. plantarum genes were differentially affected by diet and TNBS administration. Pyrosequencing of 16S rRNA transcripts from the indigenous intestinal microbiota showed that WD resulted in significant reductions in proportions of metabolically active indigenous Lactobacillus species and increases in the Desulfovibrionaceae family. Feeding L. plantarum WCFS1 resulted in lower levels of colitis and higher concentrations of colonic IL-10 and IL-12 in WD and not CD-fed mice. Interactions between probiotics, nutritional components and the intestinal bacteria should be considered when examining for probiotic-mediated effects and elucidating mechanisms of probiotic function in the mammalian gut.

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BALB/c mice were fed milk or Lactobacillus casei BL23 in milk for 14d and fecal samples were collected at d 0, 4, and 7 as well as 1 and 8d after the last administration. According to high-throughput DNA sequencing of the 16S rRNA genes extracted from the fecal microbiota, the bacterial diversity in the fecal samples of all mice increased over time. After 14d of administration, the consumption of milk and milk containing L. casei BL23 resulted in distinct effects on the microbial composition in the intestine. Specifically, the proportions of bacteria in the Lactobacillaceae, Porphyromonadaceae, and Comamonadaceae were significantly higher in mice fed the L. casei BL23-milk culture compared with one or more of the other groups of mice. The relative amounts of Lachnospiraceae were higher and Streptococcaceae were lower in mice fed milk alone. The changes were not found at d 4 and 7 during milk and L. casei feeding and were no longer detected 8d after administration was stopped. This study shows that consumption of milk or probiotic L. casei-containing milk results in non-overlapping, taxa-specific effects on the bacteria in the distal murine intestine.