Comparison of the synthetic oligonucleotide gene probe and infant mouse bioassay for detection of enterotoxigenic Escherichia coli.

A commercial DNA/DNA hybridisation kit for the detection of Escherichia coli heat stable enterotoxin gene sequences was compared to the suckling mouse bioassay using 183 isolates of Escherichia coli from clinical specimens. The gene probe assay had a specificity of 99% and a sensitivity of 90.4% compared to the infant mouse method. Using the colony blot method of preparing the bacterial DNA and a hybridisation temperature of 50 degrees C optimal results were obtained. The gene probe method is not affected by the incubation conditions of the test organisms. It is technically straightforward and can be applied to large numbers of specimens with fewer logistic difficulties than with the bioassay.