The Role of Probiotics in Inflammatory Bowel Disease

Excerpt

The human intestine contains 300–500 different bacterial species. Concentrations of living bacteria in the large intestine may reach 10¹¹–10¹² cells/g of luminal contents [1]. Some of these bacteria are protective, some neutral and others pathogenic [2]. This dynamic community of intestinal microflora plays a critical role in maintaining intestinal health. Metabolic and digestive functions include fermentation of nondigestible dietary residue and mucous, salvage of energy from this residue, production of vitamin K, and absorption of ions. Trophic functions include control of proliferation and differentiation of intestinal epithelial cells, and development and balance of the immune system. These bacteria also protect against pathogens and maintain the epithelial barrier [1]. Probiotics, originally derived from cultured foods and milk products, are viable microorganisms with beneficial physiologic or therapeutic properties [2]. Although the definition of a probiotic has changed many times, a consensus definition term was issued a few years ago. This definition states that “oral probiotics are living microorganisms that, upon ingestion in specific numbers, exert health benefits beyond those of basic nutrition” [3]. Examples of bacteria demonstrated to have beneficial effects include lactic acid bacilli, Lactobacillus, bifidobacterium, Escherichia coli Nissle 1917, Clostridium butyricium, Streptococcus salivarius thermophilus, and a nonpathogenic yeast Saccharomyces boulardii [2, 4]. Mechanisms by which probiotics exert their therapeutic effects include (1) modulation of barrier function, (2) mucosal trophic action, (3) inhibition of pathogenic bacteria, (4) blockade of epithelial attachment and invasion by pathogenic bacteria, (5) modulation of intestinal cytokine production, (6) anti-inflammatory properties, and (7) enhancement of digestion and absorption of food [4, 5]. Properties of an ideal probiotic should include total host safety, resistance to gastric acidity and pancreatic secretions, adherence to epithelial cells, antimicrobial activity, inhibition of pathogenic bacteria, resistance to antibiotics, tolerance to food additives, and stability in food matrix [4]. …