Biological Characterization of Locally Circulating Mycoplasma gallisepticum in Poultry

Mycoplasma gallisepticum (MG) is a pathogen of concern for poultry. Present study was conducted to determine the biological characteristics of a field isolate of MG, recovered from an MG-affected flock. This isolation was made through conventional method of MG cultivation, using modified Frey’s media after confirming the isolate by polymerase chain reaction (PCR). A total of 48 birds were segregated into experimental group (32 birds) and the control group (16 birds). To appraise primary site of infection, MG broth propagated culture containing 1x106 CFU/ml was inoculated intratracheally to each bird in the experimental group, whereas the control group was sham inoculated by uninoculated broth. The clinical signs and symptoms were recorded daily from day 1 to 21 post-infection (p.i.). Seroconversion monitoring was carried out, at day 5, 10, 15, 20 p.i. by Serum Plate Agglutination test (SPA) and Enzyme Linked Immunosorbent Assay (ELISA). To determine the dissemination pattern of MG, birds were sacrificed according to plan, swabbed from various organs and subjected to MG-specific PCR. Tracheal lesions and air sac lesions were scored after necropsy. Clinically, mild signs of respiratory discomfort were observed on day 5 p.i., which intensified on day 9 to 21 p.i. in the experimental group. PCR of tracheal swab samples was positive from day 7 to 21 p.i., and the swabs collected from lungs were positive for MG from day 9 to 21 p.i. The study concluded that, MG isolate from field showed limited dissemination pattern and is restricted to respiratory tract.