Mycoplasma gallisepticumspecies and strain‐specific recombinant DNA probes

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Abstract
Genomic libraries of vaccine (F‐K810) and wild type (S6) Mycoplasma gallisepticum were constructed in Escherichia coli (strain JM83) using the plasmid vector pUC8. Recombinant clones were screened by colony, dot and Southern hybridisations using 32P‐labelled genomic DNA from M. gallisepticum strains K810 and S6. Eight clones were identified which contained DNA sequences specific to M. gallisepticum and one clone was identified which contained a DNA fragment unique to the vaccine strain (F‐K810) of M. gallisepticum. When labelled and used as a probe in dot hybridisation assays, one of the M. gallisepticum species‐specific recombinant plasmids differentiated standard reference cultures, atypical strains and wild type isolates of M. gallisepticum from other avian Mycoplasma species. In similar assays, the plasmid containing vaccine strain‐specific sequences differentiated vaccine strains of M. gallisepticum from several other wild type strains of M. gallisepticum. Recombinant DNA probes provided sensitive and specific detection of M. gallisepticum strains and the vaccine‐specific probe will be useful for determining if the vaccine strain can replace wild type M. gallisepticum in commercial layer facilities.