Microflora imbalance and gastrointestinal diseases

The human intestine lodges a large amount of microorganisms, with over 500 species of bacteria whose density increases through the small bowel reaching concentrations from 10⁹ to 10¹⁴ colony-forming unit/ml in the colon. More than 99% of the gut microbiota is composed of bacteria that can be divided into 4 main families: Firmicutes, Bacteroidetes, Proteobacteria and Actinobacteria. Numerous factors are involved in the control of gut microbiota stability such as intestinal pH, temperature, microbial interaction, peristalsis, bile acid, drug therapy and immune responses. When these mechanisms fail, imbalance of intestinal microflora can occur, resulting in the onset of both extra-intestinal (infectious and allergic) and intestinal (infectious, inflammatory, autoimmune and neoplastic) diseases.