High levels of heat labile Escherichia coli enterotoxin in bacterial cell sonicates of agar grown cultures.

Escherichia coli heat-labile enterotoxin from 5 strains of human and animal origin was detected in broth cultures and agar-plate culture sonicates by using CHO and Y-1 adrenal cells and rabbit intestinal loop assay. Cell sonicates possessed higher levels of heat-labile enterotoxin than supernatants of broth cultures. Highest levels of heat-labile (LT) enterotoxin were detected in the sonicates of cultures grown on blood agar, followed by those grown on MacConkey, and lactose agar respectively.