In vitro production of cholera toxin-like activity by Plesiomonas shigelloides

Although Plesiomonas shigelloides is considered to cause diarrhea in humans, the mechanisms by which it might do so are not known. Enteric pathogens such as Vibrio cholerae and some strains of Escherichia coli produce enterotoxins that activate adenylate cyclase, increase production of cyclic AMP, and thereby cause elongation of Chinese hamster ovary (CHO) cells in tissue culture. We grew 28 strains of P. shigelloides and the type strain in an iron-depleted medium, and sterile filtrates were examined in CHO cell culture. Filtrates from 24 of the 29 strains produced elongation of CHO cells. These changes could be prevented by heating or by preincubation of the filtrate with cholera antitoxin. These data indicate that P. shigelloides elaborates a cholera-like toxin; such a substance might be important in the pathogenesis of P. shigelloides-associated diarrhea.