Shigellosis and Escherichia coli diarrhea: relative importance of invasive and toxigenic mechanisms.

Shigellae and dysentery-like Escherichia coli must invade the epithelium of the colon to cause disease which can present as dysentery, diarrhea, or both. This paper addresses the possible role of a Shigella dysenteriae-like (Shiga-like) toxin in the pathogenesis of shigellosis and E. coli diarrheal diseases. The possibility for such a role is suggested by the following observations: 1) diarrhea, considered to be a result of secretion of water by the small bowel, is frequently observed in shigellosis, a large bowel disease. 2) Even though shigellae do not invade the jejunum of monkeys fed Shigella flexneri, jejunal secretion is seen in animals with diarrhea. 3) The Shiga toxin of S. dysenteriae has enterotoxic activity and other serotypes of shigellae produce Shiga-like toxins. 4) E. coli 015 RDEC-1 causes a diarrheal disease and frequently death in young rabbits. This organism neither produces E. coli enterotoxins nor is it invasive, but it may produce low levels of a Shiga-like toxin.