Pleuropneumonia and mediastinitis caused by Rhodococcus equi in a dog: a case report.

Rhodococcus equi is a cosmopolitan bacterium found in the feces of several animals, and it is recognized as a major cause of bronchopneumonia in foals, as well as an opportunistic pathogen causing infections in humans and, rarely, in other species. This report describes a rare and atypical infection by Rhodococcus equi in a mixed-breed dog, associated with a pyogranulomatous pleuropneumonia and mediastinitis with abundant intralesional Gram-positive coccobacilli. The bacterium was isolated and identified as Rhodococcus hoagii (R. equi) using matrix-assisted laser desorption ionization-time of flight (MALDI-ToF), followed by whole-genomic sequencing that detected the vapN virulence-associated gene and identified a new sequence type (ST), designated as ST111.