Development of an improved synthetic medium for a better production of the new cholera toxin and its immunological relationship with the toxin produced by Vibrio cholerae O139 strains.

An improved synthetic medium (M4) comprising syncase medium supplemented with sodium chloride (1%) and sucrose (0.5%) pH adjusted to 7.4 was developed for a better production of the new cholera toxin (NCT). The culture filtrates prepared in the M4 medium caused significantly (P > 0.05) more fluid accumulation than that in syncase medium. Crude toxin, prepared in the M4 medium with V. cholerae O1 strains (X-392 and 2740-80) caused a reaction similar to that of the same amount of NCT (32 micrograms) prepared in the syncase medium. The neutralization of the optimal loop reacting dose of the NCT prepared in the M4 medium by anti-NCT raised against syncase prepared toxin indicates the release of the same kind of toxin in both media. These observations indicate that the modified M4 medium may be used for NCT preparation and further characterization. All the strains of Vibro cholerae O139 used in this study produced a toxin antigenically similar to NCT.