Restriction fragment length polymorphisms of virulence plasmids in Rhodococcus equi

Virulent Rhodococcus equi, which is a well-known cause of pyogranulomatous pneumonia in foals, possesses a large plasmid encoding virulence-associated 15- to 17-kDa antigens, Foal and soil isolates from five countries-Argenti na, Australia, Canada, France, and Japan-were investigated for the presence of 15- to 17-kDa antigens by colony blotting, using the monoclonal antibod y 10G5, and the gene coding for 15- to 17-kDa antigens by PCR, Plasmid DNAs extracted from positive isolates were digested with restriction endonuclea ses BamHI, EcoRI, EcoT22I, and HindIII, and the digestion patterns that res ulted divided the plasmids of virulent isolates into five closely related t ypes. Three of the five types had already been reported in Canadian and Jap anese isolates, and the two new types had been found in French and Japanese isolates. Therefore, we tentatively designated these five types 85-kb type I (pREAT701), 85-kb type II (a new type), 87-kb type I (EcoRI and BamHI ty pe 2 [V. M. Nicholson and J. F. Prescott, J. Clin. Microbiol. 35:738-740, 1 997]), 87-kb type II (a new type), and 90-kb, (pREL1) plasmids, The 85-kb t ype I plasmid was found in isolates from Argentina, Australia, Canada, and France. Plasmid 87-kb type I was isolated in specimens from Argentina, Cana da, and France. The 85-kb type IT plasmid appeared in isolates from France. On the other hand, plasmids 87-kb type IT and 90-kb were found only in iso lates from Japan, These results revealed geographic differences in the dist ribution of the virulence plasmids found in the five countries and suggeste d that the restriction fragment length polymorphism of virulence plasmids m ight be useful to elucidate the molecular epidemiology of virulent R. equi in the world.