Role of the mucosal barrier in toxin/microbial attachment to the gastrointestinal tract.

An important component of bacterial infection of the gastrointestinal tract, particularly when enterotoxin disruption of gut function occurs, relates to the interaction of the bacterium and toxin with the intestinal surface. Adherence or attachment of bacteria lead to colonization and toxic/invasive diarrhoeal states. The purpose of this review is to consider the intestinal mucosal barrier as a deterrent to microbial/toxin attachment, particularly emphasizing the mucosal surface itself, which includes the mucus coat and microvillous membrane. Consequences of mucosal barrier deficiency, particularly the incomplete development of the mucosal barrier, result in bacterially induced diarrhoeal states such as toxigenic diarrhoea and necrotizing enterocolitis. To illustrate the importance of the mucosal barrier as a factor in controlling the external environment containing bacteria and bacterial toxins, recent research in our laboratory on the development of the mucosal barrier is presented. This compares mucosal surface functional control of antigen/toxin attachment and penetration with mucosal surface compositional changes. Finally, evidence of a preliminary nature will be provided to suggest that modifications of the underdeveloped mucosal barrier of the immature intestine by the ingestion of breast milk may act to prevent pathological interactions between the gut and microbes/toxins.