Shigella flexneri 2a is an invasive enteric pathogen that may produce
diarrhea when ingested by human beings and subhuman primates. We have previously shown that shigella
diarrhea correlates with water and
electrolyte transport abnormalities in the jejunum and colon.
Dysentery alone is associated only with colonic transport abnormalities. To define the relationship between invasion and
inflammation of the colon and the occurrence of jejunal transport abnormalities, we studied water and
electrolyte transport, histology, and bacteriology in rhesus monkeys that were infected by introducing S. flexneri 2a directly into the cecum. In contrast to the pattern of disease seen after
oral administration, cecal inoculation resulted in clinical disease in 64% of animals, of which 94% manifested
dysentery alone, rarely preceded by mild
diarrhea. Histologically, invasion and
inflammation was limited to the colon. Secretion of water and
sodium occurred in the colon of infected monkeys when compared with controls, whereas transport was normal in the jejunum and ileum. These data further demonstrate that severe
dysentery can result from cecal injection of shigellae, but also suggest that the occurrence of watery
diarrhea requires and may result from an undefined interaction between the jejunal mucosa and the organisms during transit through the small intestine.