Studies on a Cytotoxic Principle of Non-0 1 Vibrio Cholerae

The purpose of this study was to characterize the role of a cytotoxic principle in diarrhea due to cholera-like-enterotoxin-negative non-O1 V. cholerae. The highest cytotoxic activity was observed when non-O1 Virbrio cholerae strains were grown in Brain Heart Infusion Broth (Difco) without shaking and Vero cells were used as target cells. This cytotoxic principle was different from that found in a fluid accumulating factor (FAF) of non-O1 V. cholerae, strain 79-9-2, for its instability to heat, for its hemolytic activity and for the toxicity to Vero cells, and designated as cytotoxin V. A fraction of cytotoxin V obtained from culture filtrate of Strain 6-17-80 by ammonium sulfate precipitation, followed by gel filtration with Sephadex G-200 and Hydroxyapatite column chromatography, was hemolytic, lethal to mice and positive in ligated rabbit ileal loop test (RIL). Antiserum against this fraction neutralized cytotoxicity and hemolytic activity in culture supernatants of many other non-O1 V. cholerae strains irrespective of their biological characteristics, as well as those from V. mimicus and O1 V. cholerae strains. There seemed to be a close correlation between the level of cytotoxin V and that of hemolysin or lethal toxin in each individual strain of non-O1 V. cholerae, but not between the level of cytotoxin V or hemolysin and fluid accumulation in the RIL with whole culture. Concentrated culture filtrates containing high levels of cytotoxin V or hemolysin was shown to cause fluid accumulation in the RIL.These results indicate that the cytotoxin V of non-O1 V. cholerae is an entity closely correlated with hemolysin, and that it could possibly cause diarrhea, if a large amount would be accumulated in the intestine. Cytotoxin V alone, however, does not seem to explain the major enteropathogenic mechanism of non-O1 V. cholerae strains which do not produce cholera-like enterotoxin.