Streptococcus thermophilus NCIMB 41856 ameliorates signs of colitis in an animal model of inflammatory bowel disease

Background: Treatment of inflammatorybowel disease (IBD) is mainly based on suppression of symptoms, often withnumerous side effects. Trials of probiotics in IBD have frequently produceddisappointing results. The majority of probiotics are unusual, since they donot require iron for growth, unlike many bacteria resident in the intestine.The IBD intestine is iron-rich due to bleeding and use of oral iron supplements;conventional probiotics would be rapidly outcompeted. We have evaluated aniron-responsive Streptococcusthermophilus strain for its potential to reduce signs of colitis.

Methods: Efficacy of S. thermophilus was evaluated in the dextran sodium sulphate (DSS)mouse model of colitis. Treated animals were given 1x10⁸ cfu S. thermophilus per day and clinicalobservations were taken daily. At termination, gross and histopathologicalsigns of disease, cellular infiltration, location of bacteria, and cytokineexpression in the intestine were determined.

Results: S. thermophilus delayed onset of colitis and reduced clinical signsof disease, including bodyweight loss and gastrointestinal bleeding. It reducedbacterial translocation into the colonic tissue. Increased numbers of CD8⁺intraepithelial lymphocytes were seen in control animals treated with S. thermophilus. S. thermophilus had no effect on gross pathology, histopathology orcytokine production in either colitic or control animals.

Conclusions: We propose that S. thermophilus promotes maintenance of mucosalbarrier function which reduces bacterial translocation, thereby reducing immunestimulation and associated inflammation. This allows mucosal healing, reducinggastrointestinal bleeding and weight loss. This could be studied as alocally-acting adjunct or alternative to current IBD treatments.