Abstract
A method that stimulates cholera toxin (CT) production by Vibrio cholerae Ol biotype El Tor (El Tor vibrios) to the level of several micrograms per ml in the culture fluid was established. Such a large amount of CT was obtained by the following method: El Tor vibrios were cultured in AKI medium (1.5% Bacto peptone, 0.4% yeast extract-Difco, 0.5% NaCl, 0.3% NaHCO3) at 37C for 4hr in a stationary test tube and then for 16hr in a shaken flask, with inoculum sizes of 105 to 107/ml. With this method, 35 strains out of 60 examined produced 2 to 16μg/ml of CT as determined by the reversed passive latex agglutination test (RPLA). Thirty-three randomly selected strains out of the 60 produced reasonable amounts of rabbit skin vascular permeability factor, reflecting the amount of CT titrated with RPLA.
