The pathogenesis of Shigella diarrhea. I. Enterotoxin production by Shigella dysenteriae I.

A strain of Shigella dysenteriae 1, freshly isolated from a patient with dysentery in Guatemala in August 1969, was found to elaborate an enterotoxin into the liquid of broth cultures. Partial purification of the enterotoxin by ultrafiltration on graded polymeric membranes and Sephadex gel filtration (Pharmacia Fine Chemicals, Inc., Piscataway, N. J.) suggested an approximate molecular weight of 55,000-60,000. The partially purified toxin was heat-labile, pronase sensitive, and activated by alkaline pH, and it elicited fluid production in ligated rabbit ileal segments; it failed, however, to cause increased vascular permeability in skin. When the activities of equal weights of identically prepared Vibrio cholerae and S. dysenteriae enterotoxins were compared in the rabbit ileum the latter caused a significantly smaller volume response with increased concentrations of potassium, chloride, and protein. The previously described neurotoxic (mouse lethal) factor was also present and eluted from Sephadex G-150 with the enterotoxin. If these biological activities prove to be possessed by a single molecular species, it is suggested that it be renamed Shigella enterotoxin in recognition of the physiologically more relevant biological action.