Detection of shiga toxin producing Escherichia coli isolated from children and cattle using PCR technique

  • H. N. A'aiz, and F. A. Abdulla A. H. Al- Hama Coll. of Vet. Med. / Univ. of Al-Qadisiyah


This study was undertaken to detect STEC isolates, gene(Stx2) in Escherichia coli isolates
and characterize them by biochemical tests , enterohemolysin production and PCR.During a
period of seven months (November 2007 to May 2008), a total of 280 fecal samples were
collected from 120 hospitalized children suffering from diarrhea and 160 cattle fecal samples .
Feces specimens were screened for the presence of NSF E. coli and STEC by cultured on
sorbitol MacConkey agar (SMAC).A total of 209 (74.6%) non-sorbitol fermenting (NSF)
bacterial isolates were obtained , 69 (57.5%) from children fecal samples and 140 (87.5%) from
cattle feces . Of which 5 (4.16%) NSF E. coli isolated from children fecal samples and 38
(23.75%) from cattle feces. NSF isolates were identified as Shiga toxin producing E. coli
(STEC), but only 16 (10%) isolates of cattle and 2 (1.6%)isolates of children were PCR-positive
for (Stx2) gene which gave amplification bands at 346 bp using DNA marker in the interpretation
of the results. Among 18 STEC studied, a total of 16 (88.8%) isolates expressed enterohemolysin
on washing sheep blood agar plates.On the other hand, the study was showed that the sensitivity
and specificity of PCR technique in diagnosis of STEC were 41.8% , 100% respectively, in
comparison with other tests like biochemical tests, sensitivity and specificity of these tests were
(100% , 86.9%) respectively.