Pneumonia-related Rhodococcus equi-induced infection harbouring pVAPA virulent type in an adult mule: First report

Abstract

Rhodococcus equi is an environmental bacterium related to pyogranulomatous infections in humans and animals. Horses, particularly foals, are the main domestic species susceptible; however, infections in adult equids are rare and usually linked to immunosuppression or debilitating conditions. The pathogenicity of R. equi is associated with plasmid-encoded virulence-associated proteins. Three host-adapted virulence-plasmid types (pVAPs) have been described: pVAPA, pVAPB and pVAPN, whose origin is associated with horses, pigs and ruminants, respectively. All types may infect humans, highlighting the zoonotic potential of the pathogen. However, data on virulence plasmids in R. equi isolates from mules are lacking. We report pneumonia-related R. equi harbouring the pVAPA-type plasmid in an adult mule presenting hepatic abnormalities, which may have favoured the infection. To our knowledge, this is the first report of pneumonia caused by R. equi in an adult mule, whose virulence-plasmid pattern was identified as the pVAPA type. Moreover, the identification of R. equi harbouring pVAPA in a mule with pneumonia is relevant to human health because this virulent type has also been described in people with clinical rhodococcosis. Our report contributes to the understanding of the clinical and epidemiological aspects and virulence-plasmid patterns of R. equi infections in mules.