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The prevalence of virulent R. equi having 15- to 17-kDa antigens (VapA) in fecal isolates from 13 thoroughbred foals and their dams on 5 farms in Kagoshima, Japan, and the plasmid profiles of VapA-positive isolates by restriction fragment digestion patterns were investigated to compare the genotypic variation among virulence plasmids of R. equi isolates from Japan. In total, 218 (24.6%) of 886 isolates from the feces of the 13 foals and 13 (12.5%) of 104 isolates from the feces of their dams demonstrated VapA-positive R. equi. Plasmid DNA preparations of 231 virulent isolates from foals and dams were analyzed by restriction enzyme digestion with endonucleases EcoRI, EcoT22I and HindIII and were divided into 3 types: 172 isolates contained a 90-kb type I plasmid, 57 contained a 90-kb type III plasmid and 2 contained a 90-kb type IV plasmid. This study demonstrates a geographic character in the distribution of virulence plasmids found in VapA-positive isolates from thoroughbred foals in Kagoshima.

Selective adhesion to only certain epithelia is particularly common among the bacterial members of the indigenous microflora of mammals. We have found that the stratified squamous epithelium of the nonsecreting area of horse stomach is colonized by gram-positive rods. The microscopic features of a dense layer of these bacteria on the epithelium were found to be similar to those reported in mice, rats, and swine. Adhering microorganisms were isolated and identified as Lactobacillus salivarius, L. crispatus, L. reuteri, and L. agilis by DNA-DNA hybridization and 16S rRNA gene sequencing techniques. These lactobacilli associated with the horse, except for L. reuteri, were found to adhere to horse epithelial cells in vitro but not to those of rats. A symbiotic relationship of these lactobacilli with the horse is suggested.