Cytotoxicity and suckling mouse reactivity of Aeromonas hydrophila isolated from human sources.

Human isolates of Aeromonas hydrophila and Plesiomonas shigelloides were tested for their ability to produce cytotoxins and (or) enterotoxins. The incidence of cytotoxin production by A. hydrophila was 81% for isolates from stool and 44% for extraintestinal isolates. Chinese hamster ovary (CHO) cells were more sensitive to A. hydrophila cytotoxin than either Vero or Y-1 mouse adrenal tumor cells (y-1). There was no evidence of cytotonic enterotoxin production by any of the isolates tested. Cytotoxin-containing filtrates from A. hydrophila were found to provoke a positive reaction in suckling mice. The response in mice was heat labile, and data supporting correlation of this activity with the cytotoxin produced by these organisms are presented. Following concentration, cytotoxin and material reactive in suckling mice were found to coelute from Sephadex G-25 and dose-response was demonstrated in mice. Antitoxin prepared to this material effectively neutralized cytotoxin, mouse reactivity, and rabbit ileal loop response. No evidence was obtained for either cytotoxin or enterotoxin production by P. shigelloides strains tested in this study.