الفهرس 
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Abstract
430 E.coli strains were isolated from broilers of different ages with white sticky diarrhoea, from Kafr EL Sheikh Agriculture Secondary School, Egypt. Serotypes of 260 isolates were O1, O8, O78, O128 ,O148, O166, and O199. PCR assay was used for detection of heat labile enterotoxin gene (elt) for 7 identified serotypes of E.coli. It was found that E.coli serotype O1, O8, O78, O128, and O166 contained 550 bp and 350 bp enterotoxin gene fragment by using multiplex primer HLT&PET. On the other hand, E.coli serotype O148 contained 300 bp enterotoxin gene fragment using HLT primer. Monovalent formalin inactivated vaccine was prepared from highly pathogenic E.coli serotypes O1. It was useful for control of E.coli infections in chicken. The tested isolates showed sensitivity to ciprofloxacine, lincospectin, colistin, amikacin, peflodad, while they showed resistant to oxalinic acid, spiramycin, cefobid, spectinomycin, penicillin, amoxicillin, ampicillin and Egy-doxien.