ENDOCARDITIS IN A DOG DUE TO INFECTION WITH A NOVEL BARTONELLA SUBSPECIES

Vegetative valvular endocarditis involving the aortic and, to a lesser extent, mitral valves was diagnosed echocardiographically in a 3-year -old spayed female Labrador retriever, Historically, the dog had been treated with tetracycline hydrochloride and prednisolone for positive seroreactivity to Ehrlichia canis and antinuclear antigens. Although t hree aerobic and anaerobic blood cultures failed to grow bacteria, blo od cultured simultaneously by the lysis centrifugation technique grew a fastidious, gram-negative organism. Despite an initial therapeutic r esponse, the owner elected euthanasia 17 days later, Necropsy confirme d aortic and miti al valvular endocarditis, Bacteria phenotypically si milar to Bartonella species were visualized in the heart valve by ligh t and electron microscopy, and Bartonella DNA from a frozen heart valv e was amplified by PCR. Subsequent phenotypic and genotypic characteri zation of the isolate, including biochemical testing, cellular fatty a cid analysis, DNA hybridization, and sequencing of the 16S rRNA gene i ndicated that this organism, which can induce endocarditis in dogs, is a novel Bartonella subspecies containing an insertion sequence unique among currently recognized Bartonella species. The name Bartonella vi nsonii subsp. berkoffii subsp, nov, sill be proposed for this organism ,