Ornithobacterium rhinotracheale (ORT) and Mycoplasma gallisepticum (MG) are bacterial causes of respiratory diseases in chickens. The objective of this work was to investigate the possible interaction between ORT and MG in respiratory problem of broiler chickens. The experimental study confirmed that ORT infection alone could induced respiratory signs as (rales, nasal discharge), post mortem lesions (unilateral and bilateral pneumonia) and histopathological changes in tracheas, lungs and air sacs. Moreover, co-infection of ORT with MG induced severe respiratory signs like pneumonia, edema and severe inflammatory cell infilteration in lungs and air sacs than that observed in chickens infected with ORT or MG alone. ORT and MG were successfully detected by PCR from tracheal swabs at 3, 7 and 14 days post infection. The results showed the synergistic effect of mixed infection of ORT and MG in broiler chickens regarding clinical signs, PM lesions, mortality rate, body weight, re-isolation and histopathological examination.
Key words: Ornithobacterium rhinotracheale, Mycoplasma gallisepticum, PCR, Broiler chickens.