PREVALENCE OF ATTACHING AND EFFACING ESCHERICHIA-COLI IN STOOL SAMPLES FROM PATIENTS AND CONTROLS

Enteropathogenic E. coil (EPEC) and enterohemorrhagic E. coli (EHEC) h ave the ability to cause 'attaching and effacing' (AE) lesions; the ge nes necessary to cause AE in both of these pathogroups have been ident ified and termed eae. Using colony hybridization, we screened 237 stoo l samples from patients with diarrhea, and 237 stool samples from age- matched controls for the presence of E. coil carrying eae. Individual colonies harbouring ene could be recovered from 7 (2.9%) of the patien t stools, as well as from 6 (2.5%) of the control stools. All these E. coil isolates were positive in the fluorescence actin staining (FAS) test. In addition, all the samples were also probed for Shiga-like tox in (slt) genes and the EPEC adherence factor (EAF) to evaluate whether testing for ene identified all EHEC and class I EPEC. Of the 7 patien t samples harbouring E. coil with eae, 4 had E. coli with eae and sir genes, and 2 had E. coil with eae and EAF sequences. In 2 of the 237 p atient stools, E. coil which were eae and EAF negative but sit probe p ositive could be recovered. These 2 E. coil strains were non-reactive in the FAS test. Of the control samples, none of the E. coli strains, including the 6 samples containing eae positive strains, possessed EAF or sit-sequences. In concrete terms, the similar ene incidence found in both E. coil isolates from patients and controls is currently of li mited clinical diagnostic value and more importantly, the ene probe co uld not identify all slt-harbouring E. coil. On the basis of these res ults, the use of the ene-probe cannot be recommended in preference to the sit probes for the detection of EHEC.