Development of real-time polymerase chain reaction assay for detection of Ornithobacterium rhinotracheale in poultry.

Ornithobacterium rhinotracheale (ORT) is an emerging bacterium causing severe economic losses in poultry mostly due to respiratory and locomotory disturbances. Due to the fastidious nature of the organism, ORT is often overgrown by faster-growing commensal and pathogenic bacteria. In this study we developed a real-time polymerase chain reaction (qPCR) assay for rapid and sensitive detection of ORT in samples collected from chickens and turkeys. The qPCR assay developed was able to detect 17 reference strains of ORT (serotypes A to Q) tested in this study, and no false-positive results were obtained from other organisms associated with respiratory tract infections. The qPCR assay was 100 times more sensitive than the modified conventional PCR. Using tenfold serial dilutions of the recombinant plasmid DNA containing the target gene fragment, the detection limit of the qPCR was estimated to be > or = 100 plasmid copies per reaction. Out of 42 examined poultry flocks, 26 cases were tested positive by both assays. The qPCR assay reduces turnaround time to about 2 hr, two times faster than the modified conventional PCR.