Gut Microbial Diversity Is Reduced by the Probiotic VSL#3 and Correlates with Decreased TNBS-Induced Colitis

Background: Compositional changes within the normal intestinal microbiota have been associated with the development of various intestinal inflammatory disorders such as pouchitis and inflammatory bowel diseases (IBD). Therefore, it has been speculated that manipulation of a dysbiotic intestinal microbiota has the potential to restore microbial homeostasis and attenuate inflammation. Methods: We performed community composition analyses by terminal restriction fragment length polymorphism (T-RFLP) of the bacterial 16S ribosomal RNA gene to investigate the impact of the probiotic VSL#3 on colonic microbial community composition and development of trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. Results: TNBS-induced chronic colitis was significantly reduced in VSL#3-fed rats compared to controls (P < 0.05). T-RFLP analysis revealed distinct microbial communities at luminal versus mucosal sites. Within the luminal microbiota, chronic colitis was associated with an overall decrease in bacterial richness and diversity (Margalef's richness, P < 0.01; Shannon diversity, P < 0.01). This decrease in luminal microbial diversity was enhanced in TNBS-treated rats fed VSL#3 (Margalef's richness, P < 0.001; Shannon diversity, P < 0.001) and significantly correlated with reduced clinical colitis scores (Pearson correlation P < 0.05). Conclusions: Our data demonstrate that the probiotic VSL#3 alters the composition of the intestinal microbiota and these changes correlate with VSL#3-induced disease protection.