| Marwan Mohammad Said Budair
Shiga toxinigenic h:scherichia coli (STEC) comprises a diverse group of organisms capable of causing severe gastrointestinal and systemic diseases in humans. Within the STEC family, certain strains appear to be of greater virulence for humans, for example, those belonging to serogroup 0157 and those with particular combinations of other putative virulence factors. One hundred seventy six Shiga toxigenic Escherichia coli (STEC) isolated from patients with either severe diarrhea or non-severe diarrhea in the northern Palestine in 1999 were characterized for virulence genes by multiplex PCR assay. Of the 176 STEC isolates, 124 (70.5%) belonged to the 0157: H7 serotype.
All of the STEC isolates were stxl+, 140 (79.5%) were stx2+. The eae locus was detected in 16 (9.1 %) and the hlyA-encoding gene was detected in 18 (10.2%) of these isolates. Sixty-six of the 79 (83.5%) isolates obtained from individual with severe diarrhea, carried both the stxl and stx2 toxin genes and 14 (17.7%) were eae+, while 74 (76.3 %) of 97 isolates from individuals with non-severe diarrhea were stxl + stx2+ and 2 (2.1%) carried eaeA encoding genes. The locus encoding the production of hemolysin was detected in 16 of 79 and 2 of 97 from severe diarrhea cases and non-severe diarrhea, respectively. Our results show a strong association between stxl, stx2, eaeA and hyIA genes combined together and disease severity.
The combination of ERIC-PCR and multiplex-PCR analysis of 80 STEC isolates allowed us to define 9 clones among the isolates. Three major clones were found among 81.2% of all STEC isolates. The remaining clones were considered as sporadic since they were found only in a small number of isolates. An observation of primary concern is the widespread of the major clones throughout northern Palestine. Thus STEC infection was most probably due to the consequence of clonal transmission.
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