Background: Infectious endocarditis is an uncommon disease in dogs; however, its incidence and survival rates have increased owing to advances in the understanding of the disease and diagnostic techniques. For diagnosis, it is necessary to determine whether a dog suspected of being infected has any abnormalities that meet the modified Duke criteria. Staphylococcus spp., Streptococcus spp., and Escherichia coli are the most commonly isolated bacteria causing infective endocarditis in dogs, whereas the less commonly isolated bacteria include Pseudomonas spp. and Proteus spp.
Case presentation: A 5-year-old neutered male Maltese presented with lethargy, anorexia, anaemia, and pyrexia. A vegetative mass in the aortic valve was identified on echocardiography, and the possibility of endocarditis was considered. The dog's fever, anorexia, and lethargy rapidly improved in response to the initial antibiotics and prednisolone, which was prescribed for a possible immune-mediated disorder. However, the dog's condition deteriorated again after discontinuing antibiotics and tapering the prednisolone dose. During this period, Paenibacillus spp. was isolated from blood cultures. After prescribing antibiotics based on the sensitivity results and adding hydralazine to reduce afterload, the dog survived without recurrence of symptoms to date.
Conclusions: Paenibacillus spp. was identified as the causative agent of infectious endocarditis. A favourable prognosis can be expected if appropriate antibiotics in combination with medications that address the blood flow changes due to valve damage are used.
Keywords: Paenibacillus lautus; Blood culture; Canine; Heart failure; Infectious endocarditis.
© 2025. The Author(s).