Reclassification of Rhodococcus equi into a novel genus, Prescottia gen. nov., as Prescottia equi comb. nov

Since the recognition of Corynebacterium equi as the causal agent of equine pneumonia by Magnusson in 1923, the taxonomic status of this microorganism has not been straight forward. Now known as Rhodococcus equi, this species represents one of three distinct subclades within the genus Rhodococcus, namely Rhodococcus equi, Rhodococcus erythropolis and Rhodococcus rhodochrous. It has become increasingly evident that the subclade R. equi deserves generic status. In the present study, thirty one R. equi isolates, including the type strains of all validly published Rhodococcus species, were the subject of 16S rRNA gene sequence studies along with establishing their chemotaxonomic, molecular fingerprinting and phenotypic profiles. The R. equi isolates, including the type strain of the species, formed two distinct groups based on the molecular fingerprinting and numerical taxonomic data. The results of the chemotaxonomic studies confirmed these data and also provided additional characters for the differentiation of the two groups. These data add weight to the view that the species R. equi should be given generic status as Prescottia gen. nov. with Prescottia equi comb. nov, as the type species.