Study of Serological Differences of Ornithobacterium Rhinotracheale Isolates

The present study was conducted to evaluate the antigenic diversity of five ORT (Ornithobacterium rhinotracheale) isolates (7,32,71,63,65) from a few provinces. 48 birds from 14-day-old SPF chicken were randomly divided into 6 separate groups and were kept in separate cages with free access to food and water. Each of the groups were inoculated with formalin inactivated antigens of each isolates containing a  1 × 10 8 CFU, per dose of bacteria along with incomplete fraud’s adjuvant twice within three weeks. The sixth group was injected with saline phosphate buffer. Two weeks post inoculation, all birds were bleeded for the preparation of serum samples. Evaluation of induced humoral immune response and differentiation of antigen diversity among isolates were done using commercial ORT ELISA kit and Agar Gel Precipitation (AGP) tests. Differences in titer were observed by ELISA with the highest serum level for isolates 7 and 32 (P<0.05) and the lowest titer for the 63 isolate.  AGP test showed one common antigen between most isolates (except for isolate 71). In addition, a similar reaction was detected by all the antigens against the serum of SPF chickens previously immunized with a commercial ORT (serotype A) vaccine. Overall this study showed the most isolates were serologically identical (except 71) and associated to the serotype A of ORT in addition to possible variable induction of the immune response by isolates in chickens. The results of this study could help researcher in choosing an ORT candidate for producing a more effective local vaccine.