Molecular variability of the adhesin-encoding gene pvpA among Mycoplasma gallisepticum strains and its application in diagnosis

Mycoplasma gallisepticum is an important pathogen of chickens and turkeys t hat causes considerable economic losses to the poultry industry worldwide. The reemergence of M. gallisepticum outbreaks among poultry, the increased use of live M. gallisepticum vaccines, and the detection of M. gallisepticu m in game and free-flying song birds has strengthened the need for molecula r diagnostic and strain differentiation tests. Molecular techniques, includ ing restriction fragment length polymorphism of genomic DNA (RFLP) and PCR based random amplification of polymorphic DNA (RAPD), have already been uti lized as powerful tools to detect intraspecies variation. However, certain intrinsic drawbacks constrain the application of these methods. The main go al of this study was to determine the feasibility of using an M. gallisepti cum-specific gene encoding a phase-variable putative adhesin protein (PvpA) as the target for molecular typing. This was accomplished using a pvpA PCR -RFLP assay. Size variations among PCR products and nucleotide divergence o f the C-terminus-encoding region of the pvpA gene were the basis for strain differentiation. This method can be used for rapid differentiation of vacc ine strains from field isolates by amplification directly from clinical sam ples without the need for isolation by culture. Moreover, molecular epidemi ology of M. gallisepticum outbreaks can be performed using RFLP and/or sequ ence analysis of the pvpA gene.