الفهرس 
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Abstract
This investigation was targeted for studying the presence of E.coli O157:H7 in some infant’s diarrheal samples in Egypt and its role in causing diarrhea associated with complications as bloody diarrhea and hemolytic uremic syndrome. At the same time the role of raw milk in transmitting of E.coli O157:H7 to children taking into consideration that cattle are the predominant reservoir of E.coli O157:H7. The study also was done to detect the presence of Shiga toxins in E.coli O157:H7.
60 samples were collected from diarrheic infants and 42 raw milk samples were cultivated on MacConkey and EMB media and revealed that 43 from diarrhea and 16 from raw milk isolates were lactose fermenters on MacConkey media and appeared as green metallic sheen on EMB media.
All isolates were biochemically identified, 43 and 16 isolates from diarrhea and raw milk respectively were confirmed to be E.coli.
Serological examination revealed that 22 isolates from diarrheic samples and 7 from raw milk were confirmed to be O157. To detect the O157:H7 strains PCR was performed on O157 isolates using primers encoding intimin (eae O157:H7) gene. Only 3 strains isolated from diarrhea were intimin positive E.coli O157:H7.
Antibiogram assay for both types of O157 isolates was performed and it was obvious that 100% were sensitive to imipenem. In addition, a percentage of 100% of isolates recovered from raw milk samples were sensitive to levofloxacin and sensitive to gentamicin with a percentage of 57%.
72.7% of diarrheal E.coli O157 were multi drug resistant (MDR) while in raw milk isolates were 28.6%.
It could be concluded that E.coli O157:H7 play non significant role in causing diarrhea among Egyptian infants. The role of cattle as a reservoir for O157:H7 is of low or even no evidence. O157:H7 isolates in Egypt harbor the virulence factor intimin gene, but not Shiga toxins genes. There are not any cases of HUS complication was reported even in researches that isolated E.coli O157:H7 harboring Stx-1 or Stx-2 genes.