الفهرس 
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Abstract
In this study, P. multocida the causative agent of FC was isolated from chicken layers and breeders. The isolation trials revealed 6 P. multocida positive cases with incidence rate of 10.9%. The suspected P. multocida isolates were identified morphologically and biochemically. Serotyping of the isolated strains revealed that the isolates were related to serotype A:1 and A:3. The isolates were tested genetically using PCR of universal and capsular specific primers of P. multocida, and the molecular testing revealed their relatedness to P. multocida capsular type A. Inactivated P. multocida vaccine consisted of serotype 1 and 3 was prepared and its efficacy in chickens was determined. ELISA test showed an increase in antibody titer after twice vaccination, the highest level was at 5 weeks after vaccination. The FC vaccine conferred 85% and 80% protection after challenge with P. multocida serotype A:1 and A:3, respectively, while the protection rate was 10% and 20% in non vaccinated challenged groups with P. multocida serotype A:1 and A:3, respectively. The mortality rate, clinicopathological findings, re-isolation of the organism and histopathological examination of organs from all groups was recorded. Antibiogram of isolated strains revealed that the strains were in vitro sensitive to several antibiotics as chloramphenicol, tetracycline, trimethoprim /sulphamethoxazole, ofloxacin, penicillin G, norfloxacin, azithromycin, and erythromycin and resistant to ampicillin and clindamycin.