الفهرس 
Material and methods;
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Abstract
The role played by Escherichia coli in producing diarrhoea in calves has received a great level of attention and investigation that hasn’t been directed to any other type of bacteria. In this study136 out of 183 faecal swabs collected from newborn Frisian cattle calves showing clinical signs of diarrhoea were found to be positive for bacteriological examination and harboured Escherichia coli with an incidence of (74.3%). All isolates proved to be Escherichia coli by culture method, morphological appearance and biochemical reactions from These isolates 24 isolate were selected randomly and submitted for serological identification using O antigen only and results obtained showed that the most predominant serovars were O111, O26, O55, O86, O125, and O119. Using PCR to detect the presence of Sta gene in tow groups (first group contains 7 serotyped isolates, second group contains 5 serotyped isolates. And the results revealed that 5 of 12 serotyped isolates . Also esting these serotyped isolates under various degrees of temperature (37 and 45.5) there found that all the isolates keep viable at these temperature degrees but with clear decline in their viable numbers.
All bacterial isolates showed growth after various treatments tested for biochemical and haemolytic activity and showed no changes.