Comparison of DNA hybridization and PCR assays for detection of putative pathogenic enteroadherent Escherichia coli.

The correlation of the different adherence patterns with DNA probes and PCR primers for the identification of Escherichia coli was analyzed in isolates from children, less than 2 years of age with or without diarrhea, from different regions of Brazil. A total of 1,428 isolates obtained from 338 patients and 322 control children were studied. The enteropathogenic E. coli (EPEC) adherence factor (EAF) probe was shown to be as good as the HEp-2 adhesion assay for the detection of typical EPEC strains. The DNA probes used to detect diffusely adhering E. coli and enteroaggregative E. coli (EAEC) showed low sensitivities (64 and 50%, respectively), and the best method of identifying these organisms in clinical research remains the HEp-2 adherence assay. The "bundle-forming pilus" (BFP) and the EAEC PCR assays could be used instead of the DNA probes as a screening method for typical EPEC and EAEC carrying the EAEC probe sequence in the clinical laboratory. In our study, only typical EPEC strains that carried EAF and BFP were associated with acute diarrhea.