Ornithobacterium rhinotracheale (ORT) is an important respiratory pathogen of chickens and turkeys. Isolation of the bacterium from diseased birds is necessary for serotyping, to determine the antimicrobial susceptibility for an effective therapy and to produce autogenous vaccines. A series of experiments was carried out to determine optimal conditions for storage of swabs soaked in ORT suspension. Swabs were immersed in viable ORT suspensions with different bacterial counts and then stored under different conditions. At several time points the viable ORT count in the swabs was determined. Dry cotton swabs as well as three transport media, namely Amies gel medium (AG), Amies gel medium with charcoal (AC), and Stuart gel medium (SG) were tested. ORT could be reisolated from dry swabs stored at room temperature for up to five days and from swabs stored in the media at room temperature for more than seven days. Differences among the transport media were minor. The minimal number of cfu in the ORT-suspension, in which the swabs were soaked, was 10⁵ cfu/ml for successful reisolation of ORT one day post immersion from swabs stored at room temperature in AC medium, and 10⁶ cfu/ml was successful for reisolation from dry swabs. Higher inoculation doses and storage at 4°C prolonged the period in which ORT could be reisolated. Storage of dry swabs at -20°C allowed reisolation of ORT at a constant level for at least 5 d.p.i. Inoculation of swabs with ORT and E. coli reduced the period for which ORT could be reisolated.

Key words: Diagnosis, ORT, Transport medium, Viability