RESUMEN
Shiga toxigenic Escherichia coli (STEC) isolates from symptomatic and asymptomatic patients in northern Palestine in 1999 were screened for serotype O157 and characterised for virulence genes by multiplex PCR assay. Of the 176 STEC isolates, 124 (70.5%) were of serotype O157. All these isolates carried the gene for Shiga toxin type 1 (stx,) and 112 (90.3%) carried stx2. The intimin encoding gene locus eae was detected in 16 isolates (12.9%) and the enterohaemolysin encoding gene, hlyA, in 18 (14.5%). Statistical analysis showed a significant association between the presence of eaeA and hlyA, either alone or combined with stx1 and stx2 genes in O157 isolates from symptomatic infection. ERIC-PCR analysis of DNA from 80 serotype O157 isolates revealed three major clonal populations.