Probiotic impact on microbial flora, inflammation and tumour development in IL-10 knockout mice

Background: The enteric bacterial flora has been implicated in the pathogen esis of enterocolitis and colon cancer in C57BL/6 IL-10 knockout mice. Prob iotic Lactobacilli modify the enteric flora and are thought to have a benef icial effect on enterocolitis. We conducted a controlled feeding trial in I L-10 knockout mice using the probiotic Lactobacillus salivarius ssp. saliva rius UCC118. Aim: To determine the effect of probiotic consumption on the gastrointestin al microflora, tumour development and colitis in IL-10 knockout mice. Methods: Twenty IL-10 knockout mice were studied (10 consumed probiotic org anisms in milk and 10 consumed unmodified milk) for 16 weeks. Faecal microb ial analysis was performed weekly to enumerate excretion of the probiotic U CC118, total lactobacilli, Clostridium perfringens, bacteroides, coliforms, bifidobacteria and enterococci. At sacrifice, the small and large bowel we re microbiologically and histologically assessed. Results: L. salivarius UCC118 was detected in faeces from all mice in the p robiotic fed group, but not the control group. Faecal coliform and enteroco cci levels were significantly reduced in probiotic fed animals compared to the controls (P < 0.05). At sacrifice, a significant reduction in C. perfri ngens numbers was observed in the test mice (P < 0.05). There were no fatal ities in the test group compared to two deaths from fulminant colitis in th e control group. Only one test mouse developed colonic adenocarcinoma compa red to five in the control group. Test animal mucosal inflammation consiste ntly scored lower than that of the control mice. Conclusion: In this placebo controlled trial, modification of enteric flora in IL-10 knockout mice by probiotic lactobacilli was associated with reduc ed prevalence of colon cancer and mucosal inflammatory activity.