الفهرس 
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Abstract
This work was carried out to detect Shiga toxin Producing Escherichia coli O157:H7 as causative agents of acute diarrhea in Mansoura university Children Hospital (MUCH), with special focusing on its phenotypic character, serotyping and Shiga toxin production. Twenty E. coli O157 strains were isolated from 570 stool samples and no strains were isolated from the control group. E. coli O157 were identified using colonial morphology and Gram stained smears after culturing stool on SMAC.E. coli O157 were confirmed using biochemical reactions followed by serotyping and Shiga toxin detection was done by PCR. All the E.coli isolates of serotype O157:H7 carried Stx2 gene and were negative for the stx1 gene. 12 out of 15 (80%) of the serotype O157:HNM carried stx2 gene and were negative for the stx1 gene. Three strains of serotype O 157:HNM did not posses stx2 gene .In the present study E. coli accounted for 3.5 % of acute diarrhea cases. E. coli O157 was isolated from both watery diarrhea (80%) and bloody diarrhea (20%). All confirmed E. coli O157:H7 strains in the present study were significantly associated with bloody diarrhea. In this current study, monthly variation revealed that the isolation of E. coli O157 were highest in summer and early autumn than other seasons of the year. In the current Study, it was observed that diarrhea was a constant clinical symptoms in all cases of E. coli O157 infection followed by abdominal pain (90%), dehydration (75%), fever (80%) and vomiting in 60% among the isolated cases infected with E.coli O157. Children below 5 years, Drinking raw/unpasteruized milk and contact with animal were considered as risk factors in our work. Conclusion <U+F0A7> E. coli O157 was responsible for 3.5% of all the studied cases presented with acute diarrhea in MUCH <U+F0A7> A considerable percentage of E.coli other than serotype O157 fails to ferment sorbitol and reliable on SMAC for detection of STEC of other serotypes is not specific <U+F0A7> Serotype E. coli O157:H7 is strongly associated with bloody diarrhea <U+F0A7> E. coli O157 is more prevalent in young age<5 years and in warm months <U+F0A7> Drinking raw/unpasteruized milk and contact with animal( farm) are considered as risk factors in our work. <U+F0A7> stx2 was detected in 80 % of the isolated stains (O157:NM) and 100 % of the isolated strain (O157:H7), while stx1 was not detected in any of them.