Successful treatment of canine infective endocarditis caused by Bacillus amyloliquefaciens

Bacillus amyloliquefaciens is a gram-positive bacterial species that is utilised as a probiotic in humans and animals. There are no reports of infective endocarditis (IE) in dogs. An 8-year-old, spayed, female Maltese presented with a 1-month history of fever, depression, weight loss, and hindlimb lameness. Laboratory test results indicated non-regenerative anaemia, neutrophilia, hyperglobulinemia, and proteinuria. Echocardiography revealed vegetation on the septal leaflet of the mitral valve and thromboemboli in the left atrium. Consecutive blood culture results revealed that the blood samples were consistently positive for Bacillus amyloliquefaciens, which is generally considered a probiotic bacterial species for animals. Broad-spectrum antibiotics (amoxicillin-clavulanic acid and cefotaxime) and anticoagulants (clopidogrel and rivaroxaban) were administered for 4 months. The clinical signs were responsive to antibiotic treatment. After 4 months, the dog was no longer febrile and the size of the thromboemboli in the left atrium had decreased. Bacteria were no longer isolated in blood cultures after antibiotic therapy. To the best of our knowledge, this is the first case report of canine IE caused by bactaeremic infection with Bacillus amyloliquefaciens.