Twenty-three strains of Rhodococcus equi from independent clinical cases were analyzed for the presence of virulence plasmid DNA. Of the clinical isolates, 19 contained an 85-kb plasmid and the remaining 4 contained a 90-kb plasmid. All of the isolates expressed 15to 17-kDa antigens and were virulent in mice. Restriction enzyme and Southern blot analyses showed large regions of DNA homology between the 85-and 90-kb virulence plasmids. It was concluded tentatively that there are at least two virulence plasmids in R. equi and that they have a common origin.

The prevalence of virulent Rhodococcus equi in environmental isolates from 31 horse-breeding farms in Hidaka, Hokkaido was investigated: isolates were tested for the presence of virulence plasmid DNA and 15-to 17-kDa antigens by immunoblotting. R. equi was isolated from almost all of the soil samples obtained from the 31 farms with 102 to 105 colony forming units per gram of soil. However, virulent R. equi at various levels (ranging 1.7 to 23.3 %) was isolated from 24 of the 31 farms and appeared in 6.5% of the isolates (121 of 1,865). The ratio of 85-kb and 90-kb virulence Plasmids in the 121 isolates was about 3:1, which was similar to that previously reported about clinical isolates from infected foals in Hidaka. The similarity between the amounts o f virulence Plasmids obtained from the environment and from infected foals indicates that soil-borne virulent R. equi, which is thought to be a major source of the infection, constitutes a great risk to foals in horse-breeding farms. This study shows that plasmid profiles are useful markers in epidemiological surveys of R. equi infection in foals.

One hundred and eight foals were necropsied and examined for Rhodococcus equi infection from 1992 to 1998 in Hokkaido and

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When a rough surface is irradiated by a laser light and a reflected light or a transmitted light is observed, a diffraction fringe with speckle is obtained at the observation plane. This diffraction fringe is called the speckle pattern. In the present study, the static states of woven fabric surfaces were obtained as the autocorrelation functions from the speckle patterns. The functions indicate the following facts. (1) By the reflection method, the surface configuration of a woven fabric can be known, on the other hand, by the transmission method, the state of plane arrangement of yarn can be known. (2) Three fundamental weaves, i.e. plane weave, twill weave, and satin weave, can be discriminated. (3) The presence of periodic defect in the woven fabric and its size can be detected.