Use of colony pools for diagnosis of enterotoxigenic Escherichia coli diarrhea

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Abstract
Diagnosis of enterotoxigenic E. coli diarrhea was made in 109 adult [human] males with an acute dehydrating cholera-like syndrome in Dacca, Bangladesh, by testing 10 colonies isolated from admission stool specimens for production of heat-labile and heat-stable toxins. Toxin testing of 1 colony yielded a diagnosis in 92% of the cases, testing of 2 colonies yielded a diagnosis in 95% of the cases, testing of a pool of 5 colonies yielded a diagnosis in 95% of the cases and testing of a pool of 10 colonies yielded a diagnosis in 96% of the cases. From stool cultures obtained on subsequent days, toxin testing of individual colonies and pools revealed diminished efficacy of pooling with decreasing numbers of enterotoxin-positive isolates in the pool. To detect the presence of enterotoxigenic E. coli in stools, toxin testing of 5 individual isolates and a pool of 10 colonies was almost as effective as the testing of 10 individual isolates.