Molecular epidemiology of VapA-positive Rhodococcus equi in thoroughbred horses in Kagoshima, Japan.

The research examines the prevalence and genetic variation of the bacteria, Rhodococcus equi, carrying a specific antigen (VapA), in thoroughbreds and their mothers in Kagoshima, Japan. It also investigates the distinctive geographical character in the distribution of the bacteria.

Research Overview

• The study focused on Rhodococcus equi, a bacterium that can cause severe pneumonia in foals. Specifically it was looking at a variant of this bacterium that carries an antigen known as VapA.
• The research evaluated the occurrence of this bacteria in the feces of 13 thoroughbred foals and their dams (mothers) from five farms in Kagoshima, Japan.

Findings

• Out of 886 isolates from the foals’ feces, 218 (24.6%) showed a VapA-positive arrangement of R. equi.
• Similarly, amongst 104 isolates from the dams’ feces, 13 (12.5%) were identified as VapA-positive R. equi.
• The researchers used restriction enzyme digestion (a technique in molecular biology used to break down DNA molecules into smaller fragments) for further analysis on the plasmid DNA of these 231 virulent isolates.

Plasmid Diversity

• Three distinctive types of plasmids, Type I, III and IV, were identified, all of 90-kb in size.
• The Type I plasmid was found in 172 isolates, Type III in 57 isolates, and Type IV in two isolates. This suggests that the Type I and III plasmids are relatively more common while Type IV is rare.
• These findings offer insight into the genetic variation among the virulence plasmids of R. equi isolates in Japan.

Geographical Significance

• The study further concludes that there’s a geographical element in the distribution of virulence plasmids in VapA-positive isolates from thoroughbred foals in Kagoshima.
• This suggests that different regions might have a different prevalence and type distribution of VapA-positive R. equi.