Author(s): Oldfield C; Bonella H; Renwick L; Dodson HI; Alderson G; Goodfellow M
Notes: Equine Rhodococcus equi virulence is positively correlated with the expression of a gene, known as vap A, that is located on a circular plasmid. A variant of vap A, known as vap B has been detected in some R. equi isolates from pigs. A better understanding of the biology and epidemiology of R. equi infections is needed, including the distribution of vap A+ and vap B+ strains in animals and the environment. To this end, a polymerase strain reaction technique was developed which permits the selective amplification of vap A and vap B genes in R. equi strains. The technique can be used to accurately designate R. equi isolates as vap A+, vap B+ or vap -. Statistical analysis using the Fisher Exact Test confirmed that the high frequency of vap A+ amongst equine isolates is significant. The experiments were designed by Dr C Oldfield and the corresponding author who also wrote the paper.