Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/10/2008
Publication Date: 9/1/2008
Citation: Evans, J.D., Leigh, S.A. 2008. Differentiation of Mycoplasma gallisepticum vaccine strains ts-11 and 6/85 from commonly used Mycoplasma gallisepticum challenge strains by PCR. Avian Dis. 52(3):491-497. Interpretive Summary: Mycoplasma gallisepticum (MG) is a major respiratory pathogen to poultry species (chickens and turkeys) worldwide. In the United States alone, economic losses associated with MG infections are significant and have exceeded $150 million annually. Current strategies to control against MG infections include the use of three attenuated strains of MG which are approved for use as vaccines in the egg layer industry. While the vaccines can reduce the impact of MG infections within this sector of the industry, the vaccines are not wholly protective necessitating further means of control. However, the development of novel control strategies is currently hampered by a lack of knowledge associated with MG and MG-induced pathogenesis and the availability of applicable tools. Even the means by which currently available vaccine strains impart protection to their host remains a subject of debate and an understanding of this process could aid in the development of novel control strategies. Toward this end, MG vaccine strain-specific primer sets applicable to simple one-step conventional and real-time PCR systems were developed which allow the identification of the MG vaccine strains ts-11 and 6/85 alone or in the presence of the commonly-utilized laboratory challenge MG strains R, Rlow, and S6. Application of these primer sets will allow for further characterization of the means of protection afforded by currently available attenuated vaccines and will provide information that may be utilized to develop further means of controlling MG.
Technical Abstract: Mycoplasma gallisepticum (MG) is an important avian pathogen causing significant economic losses within the poultry layer industry. In an effort to develop tools to aid in MG research and diagnostics, we have compared available sequences of the attenuated MG vaccine strain ts-11 to those of commonly-used pathogenic challenge strains in search of a simple means of differentiation. Via gapA sequence alignments and comparisons, we have identified and designed primers toward strain differentiation. When applied to conventional PCR assay at low annealing temperature, all of the primer sets consistently allow for the differentiation of MG attenuated vaccine strains ts-11 as well as the attenuated MG vaccine strain 6/85 from the commonly-utilized MG challenge strains Rlow, R, and S6. Conventional PCR differentiation is based on the visualization of sole products with the attenuated MG strains ts-11 and 6/85 and the lack of the corresponding products from MG strains Rlow, R, and S6. When applied to MG strain F, product visualization varies with the applied primer set. Research-associated primer sets are also applicable towards differentiation of MG strains ts-11 and 6/85 from the pathogenic challenge strains via real-time analyses and will aid in the further characterization of the means by which currently available live MG vaccines impart protection to their vaccinated hosts.