Isolation and identification of Avibacterium paragallinarum, the causative agent of infectious coryza, is considered a challenging task in laboratories with limited specialties. In the present study, 14 commercial layer fowls showing the typical symptoms of infectious coryza were subjected to primary isolation followed by polymerase chain reaction confirmation of suspect colonies (culture-PCR). Direct PCR assays on infraorbital sinus swab samples were also carried out. Thirty-five suspected cases of infectious coryza in commercial broiler chickens were also screened using direct PCR on infraorbital sinus swabs. In culture-PCR, only 1 of the 4 suspected isolates was confirmed as Av. paragallinarum. In comparison, in direct PCR, 5 layer samples were shown to be positive for Av. paragallinarum. All of the broiler samples were negative in the direct PCR assay. Our findings indicate that primary isolation in combination with PCR can be a simple method for diagnosis of infectious coryza, although with a lower sensitivity than direct PCR. While direct PCR is comparably the more rapid and sensitive test, there will be instances in which the bacterial isolate is needed for further use. Hence, the culture-PCR method can be a practical and simple approach, especially in laboratories with limited specialty in identification of this fastidious organism.

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