Evaluation of a defined medium for the production of both thermolabile (LT) and thermostable (ST) enterotoxins of Escherichia coli

The production of thermolabile (LT) enterotoxin was compared in a defined medium reported by Staples et al. (SAG medium) for the production of thermostable (ST) enterotoxin and the Casamino acids-Yeast extract (CAYE) medium. Aliquots were drawn frum cultures of an enterotoxigenic (LT+, ST+) E. coli in both media at different times, growth curves were plotted, and culture filtrates tested for toxin activity. Levels of LT and ST and in the SAG showed that it is as suitable as CAYE for the production of LT. The addition of either glucose (1%) or lincomycin (90 microgram/ml) to SAG medium increased LT levels, but no synergistic effort could be observed if both substances were added concomitantly. Cultures in SAG medium incubated stationarily for 72 h at 37 degrees C yielded more LT than shaking cultures incubated similarly.