Converging effects of a Bifidobacterium and Lactobacillus probiotic strain on mouse intestinal physiology

Evidence has grown to support the efficacy of probiotics in the management of gastrointestinal disorders, many of which are associated with dysregulated fluid and electrolyte transport. A growing body of evidence now suggests that the host microbiota and probiotics can influence intestinal ion transport and that these effects often occur in a straindependent manner. In this study, we sought to investigate the effects of two therapeutically relevant organisms, Bifidobacterium infantis 35624 and Lactobacillus salivarius UCC118, on small intestinal transit, fecal output and water content, transepithelial resistance (TER), and colonic secretomotor function. Mice fed either strain displayed significantly reduced small intestinal transit in vivo, though neither strain influenced fecal pellet output or water content. Colon from mice fed both organisms displayed increased colonic TER, without a concomitant change in the gene expression of the tight junction proteins claudin 1 and occludin. However, L. salivarius UCC118 selectively inhibited neurally evoked ion secretion in tissues from animals fed this particular probiotic. Consistent with this finding, the neurotoxin tetrodotoxin (TTx) significantly inhibited the shortcircuit current response induced by L. salivarius UCC118 following addition to colonic preparations in Ussing chambers. Responses to B. infantis 35624 also displayed sensitivity to TTx, although to a significantly lesser degree than L. salivarius UCC118. Both strains similarly inhibited cholinergic-induced ion transport after addition to Ussing chambers. Taken together, these data suggest that B. infantis 35624 and L. salivarius UCC118 may be indicated in disorders associated with increased small intestinal transit, and, in particular for L. salivarius UCC118, neurally mediated diarrhea.