The colonization of the gastrointestinal tract is a complex and multifactorial process characterized by the dynamic interaction of forces exerted by environmental, dietary, microbially associated and host-related factors. Colonization can be defined as the persistence of microorganisms in a particular bodily site without causing disease in healthy hosts under normal circumstances. This is in contrast to infection whereby the establishment and persistence of a microbial population in the body has the potential to cause disease.
The gastrointestinal (GI) tract is sterile at birth but rapidly becomes colonized by a wide variety of bacteria. It then becomes the primary site of the body’s exposure to microorganisms. Over 90% of all microbiological contact with the body occurs within it. The most remarkable aspect of the gut is its efficiency in performing its roles in nutrition and fluid balance yet normally succeeding in excluding harmful organisms and other noxious stimuli from damaging the host. In this review, we describe the basic components of the mucosal immune system and how the gut microflora interact with it and other aspects of gut function.
Acute gastroenteritis is a major cause of infant morbidity and mortality worldwide . In developing countries, an estimated overall incidence of acute gastroenteritis ranges from 6 to 12 episodes of diarrhoea per year in children under 5 years of age compared to 1.3 to 2.3 episodes in developed countries.
Probiotics have become a hot topic within the last decade, but was already suggested for therapeutic use many years ago . An often cited definition of probiotics was proposed by Fuller: “a live microbial feed supplement that beneficially affects the host by improving its intestinal microbial balance”.
As other organs of the human body, the gut flora is a complex mixture of cells that contributes to the execution of a number of essential functions, some of which act in concert with epithelial and immune cells of the intestinal mucosa. However, the consortium of gastrointestinal tract cells is in many ways unique compared to other organs. In human adults, it contains 10-fold more cells than the rest of the body.