A molecular study of Mycoplasma gallisepticum field isolates from poultry in southern Africa

[摘要] English: Mycoplasma gallisepticum (MG) is an economically important pathogen of poultry worldwide, causing chronic respiratory disease in both chickens and turkeys. Little research has been done to characterize the MG field strains present in southern Africa. Field evidence however, suggested breaks in the vaccinations against MG, despite the proper cold chain and correct administration. Molecular methods were used to screen various poultry farms in South Africa and Zimbabwe for MG. Isolates were further characterized by gene-targeted sequencing (GTS). Portions of the cytadhesin pvpA, gapA, mgc2 genes and the uncharacterized surface lipoprotein gene designated MGA_0319 were sequenced and analysed. Three MG strains were identified in this study: a Ts-11-like strain; a strain showing closest percentage identity to the atypical MG RV-2 strain found in Israel, however with the lack of a large deletion within the pvpA region; and lastly an isolate from Zimbabwe, likely to be a novel MG strain. The latter contained a unique, large, in-frame nucleotide insertion in the mgc2 gene. Antigenically-significant variation (determined in silico) within the membrane surface proteins of this isolate was found compared to the MG Rlow strain used as an inactive vaccine on the poultry farm. It is thus postulated that by MG altering its antigenic profile, it allows effective avoidance of immune recognition and antibodies produced as a result of vaccination with inactivated and possibly live MG vaccines. Further research is however needed to substantiate this claim.

[发布机构] University of the Free State