Factors influencing heat labile Escherichia coli enterotoxin activity

Abstract

In this study, conditions for production, detection, and storage of heat labile Escherichia coli enterotoxin (LT) in culture filtrates from E. coli H 10407 were defined by using the adrenal tumor cell assay system. An enriched medium containing 0.6% yeast extract, 2% Casamino Acids, and 0.25% glucose buffered at pH 8.5 produced the highest LT activity of the various test media. In E. coli strain H 10407, LT activity was markedly decreased if the initial pH of the culture media was reduced to pH 7.5 or less. In contrast to E. coli P 263, if strain H 10407 was grown in the presence of mitomycin C there was no increase in LT production. Crude culture filtrates containing LT can be stored at 4°C for several days without an appreciable loss of activity; however, for long term storage lyophilization or freezing at -70°C is recommended.