Abstract
The large and heterogeneous microbial population colonising the human intestinal tract includes a number of aerobic and anaerobic bacteria that produce one or more toxins. While exhibiting very different physico-chemical properties these exotoxins share the ability to penetrate intestinal cells after their binding to a specific surface receptor, thus reaching a subcellular target at membrane or cytoskeleton level. The most relevant in vitro and in vivo data, reported in the literature, on the mode of action of the major enterotoxins and cytotoxins produced by bacteria belonging to the human gut microflora are reviewed in the light of our recent knowledge on bacteria-host cell interactions.