Comparative genomic analyses reveal a lack of a substantial signature of host adaptation in Rhodococcus equi (‘Prescottella equi’)

Rhodococcus equi (‘Prescottella equi’) is a pathogenic actinomycete primarily infecting horses but has emerged as an opportunistic human pathogen. We have sequenced the genome of the type strain of this species, R. equi strain C7T, and compared the genome with that of another foal isolate 103S and of a human isolate ATCC 33707. The R. equi strains are closely related to each other and yet distantly related to other rhodococci and Nocardia brasiliensis. The comparison of gene contents among R. equi strains revealed minor differences that could be associated with host adaptation from foals to humans, including the presence of a paa operon in the human isolate, which is potentially involved in pathogenesis.