الفهرس 
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Abstract
Ornithobacterium rhinotracheale has recently been reported to be a pathogen that causes respiratory tract infections in chickens and other birds . In this study, investigation through isolation and identification by direct detection of that new bacterium in chickens using PCR assay . 595 samples were collected from chickens breeder and broiler of different age and sex. Samples were either tracheal swabs from living birds. Tracheas or lungs and air sacs from freshly dead or slaughtered ones suffering from respiratory manifestation, nasal discharge, sneezing, cough, sinusitis, gasping, weakness, reduction in feed consumption and reduction in water intake. On post mortem examination, there were tracheitis, lung enlargement, congestion, firmness either unilateral or bilateral consolidation with or without fibrinous exudates, Airsaculitis, foamy white, yoghurt-like exudate. seven ORT isolates were recovered from 595 samples collected from various organs with isolation rate 1.2% .The samples included 330 tracheal swabs, 103 tracheas,150 lungs and 12 air sacs. Isolation rate was 3.9% (4 isolates out of 103 samples) and 2% (3 isolates out of 150 samples) and 0% in tracheal swabs and air sacs . All of ORT isolates were grown on 10% sheep blood agar at 37oC , under microaerophilic condition for 24-48 hr. No growth on MacConkey agar. ORT colonies were pin point after 24 hr. The colonies were pin headed (1-3 mm) after 48 hr. and became more uniform in size on subculture. It was convex, grey to grayish white. Opaque, non pigmented, non hemolytic with smooth surface and entire edges. The colonies had butyric acid like odour and with poor adherence. Morphological identification using gram’s stained bacterial film revealed Gram-negative pleomorphic rods, non-spore formers and non-capsulated bacteria. It revealed more polymorphism when cultured on liquid media. Biochemical identification detected that all ORT isolates were positive oxidase and negative catalase, indole , Simmon’s citrate. Direct detection of ORT by PCR assay using primer combination OR16S-F1 (5`-GAG AAT TAA TTT ACG GAT TAA G) and OR16S-R1 (5`-TTC GCT TGG TCT CCG AAG AT) revealed positive results . Seven isolates gave specific band which results in amplification of a 784 bp fragment on the 16SrRNA gene of ORT.