Isolation of virulent Rhodococcus equi from native Japanese horses

R. equi was isolated from soil samples obtained from the environment of sev en native Japanese horse breeds (Hokkaido, Kiso, Noma, Misaki, Tokara, Miya ko and Yonaguni) and from fecal samples collected from three native horse b reeds (Hokkaido, Kiso and Misaki). Virulent R. equi at various levels (rang ing from 0.5 to 12.9%) was isolated from the feces or soil environment of H okkaido, Kiso and Misaki horses. Isolates were investigated both for the pr esence of 15- to 17-kDa antigens (virulence-associated protein antigens; Va pA) by colony blotting, using the monoclonal antibody 10G5, and the gene of VapA by PCR. Plasmid DNAs extracted from positive isolates were digested w ith restriction endonucleases, and the digestion patterns of the plasmids o f virulent isolates were divided into three types. Two of the three types ( 87-kb type II and 90-kb type I) had already been reported in Japanese isola tes, and a new type (tentatively designated as 90-kb type II) had been foun d in isolates from Kiso horses, Six virulent R. equi isolates from the Hokk aido horses contained an 87-kb type II plasmid. Eight of 24 isolates from t he Kiso horses contained an 87-kb type II plasmid, and the remaining 16 con tained a 90-kb type II (a new type) plasmid. Two isolates from the Misaki h orses contained a 90-kb type I plasmid. These results demonstrate the geogr aphic difference in the distribution of virulence plasmids in R. equi isola tes among native Japanese horses. (C) 2001 Elsevier Science Ltd. All rights reserved.