Molecular studies on M.gallisepticum and avian pathogenic E. coli induced infections in broilers

摘要

Mycoplasma gallisepticum (MG) is a persistent, highly transmissible chicken pathogen. Of great importance is the ability of pathogenic strains of Escherichia coli to act synergistically with Mycoplasma gallisepticum leading to Chronic Respiratory Disease (CRD) in chickens. The aim of this study was to determine the role of MG and E.coli virulence genes in the occurrence of CRD in experimentally inoculated broilers and the histopathological lesions induced by the microorganisms under the study. Sixty specific pathogen free two weeks old broiler chicks were inoculated with virulent strains of M.gallisepticum and/or E.coli by intra-tracheal route. Specimens from lungs, tracheas and air sacs were collected weekly after necropsy for detection of any histopathological lesions and for re-isolation and identification of the inoculated bacteria. The results showed that the challenge with M.gallisepticum and E.coli together could induce CRD-like lesions (fibrinous pericarditis, perihepatitis and air saculitis) in chronic cases (5th and 6th weeks post inoculation), while the mildest lesions were observed in single infections. Conventional and real time PCR were applied to detect the most important virulence genes of the microorganisms causing the disease which were mgc2 gene for M.gallisepticum and iucD, iss and irp2 virulence genes for E.coli.