EVALUATION OF DNA-DNA HYBRIDIZATION FOR THE DIRECT-DETECTION OF ENTEROTOXIGENIC ESCHERICHIA-COLI IN STOOL BLOTS

The simplicity of enterotoxigenic Escherichia coli (ETEC) stool blot h ybridization, where the total bacterial growth of a fecal inoculum is examined directly for the presence of enterotoxin genes, has been marr ed by reports of unsatisfactory sensitivity and/or specificity. To ass ess the accuracy of stool blot hybridization and to study the effect o f varying proportions of ETEC among fecal E. coli (ETEC/E. coli) on te st performance, a detailed 'blind' study of 166 stool specimens from c hildren with diarrhea was performed. Oligonucleotide probes were found to be superior to polynucleotide probes, having a sensitivity of 80%, a specificity of 99%, a positive predictive value of 89% and a negati ve predictive value of 97%. The sensitivity was found to be 100% when ETEC/E. coli > 2/12, as compared with 20% when ETEC/E. coli less-than- or-equal-to 2/12 (p = 0.001), showing that the proportion of ETEC amon g fecal E. coli is of paramount importance for test sensitivity.