Molecular Variability of the Adhesin-Encoding Gene pvpA among Mycoplasma gallisepticum Strains and Its Application in Diagnosis

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Abstract
Mycoplasma gallisepticum is an important pathogen of chickens and turkeys that 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. gallisepticum in game and free-flying song birds has strengthened the need for molecular diagnostic and strain differentiation tests. Molecular techniques, including restriction fragment length polymorphism of genomic DNA (RFLP) and PCR-based random amplification of polymorphic DNA (RAPD), have already been utilized as powerful tools to detect intraspecies variation. However, certain intrinsic drawbacks constrain the application of these methods. The main goal of this study was to determine the feasibility of using an M. gallisepticum -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 of the C-terminus-encoding region of the pvpA gene were the basis for strain differentiation. This method can be used for rapid differentiation of vaccine strains from field isolates by amplification directly from clinical samples without the need for isolation by culture. Moreover, molecular epidemiology of M. gallisepticum outbreaks can be performed using RFLP and/or sequence analysis of the pvpA gene.