A comparative study of enterotoxin gene probes and tests for toxin production to detect enterotoxigenic Escherichia coli.

Escherichia coli isolated from children with diarrhea were tested for enterotoxin production and for hybridization with gene probes for heat-labile (LT) and heat-stable (ST-H and ST-P) enterotoxin. Fecal specimens were also examined directly for genes coding for enterotoxins. E. coli that hybridized with the cloned enterotoxin gene probes was identified by colony hybridization from 46 children, by enterotoxin production from 38 children, and by specimen hybridization from 37 of 304 children examined. Eighty-six percent (473 of 550) of E. coli that hybridized with the cloned DNA probes produced enterotoxins. Four E. coli that hybridized with the LT and 73 E. coli that hybridized with the ST-H probes were nonenterotoxigenic. These isolates were subsequently shown not to hybridize with other constructions of the same probes and did not hybridize with synthetic single-stranded oligonucleotides directed against the LT or ST genes.