Corynebacterium mustelae Endocarditis in a Dog

A 7-year-old male neutered Labrador Retriever dog presented with acute-onset fever, shifting limb lameness and anorexia, with development of acute respiratory distress. At necropsy, there was vegetative endocarditis, which effaced the aortic valve. Gram staining of impression smears from the aortic valve and kidney revealed numerous gram-positive rods with some coryneform bacteria. Similar coryneform bacteria were isolated on aerobic culture of the aortic valve. Identification was attempted by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and 16S sequencing, the latter of which indicated Corynebacterium mustelae. This is the second reported case of endocarditis in a dog involving C. mustelae and the first with a description of post-mortem pathology. This case is an example of the utility of various modalities to identify facultative anaerobic bacterial pathogens that may be difficult to culture and may be more widespread than previously diagnosed.