Paenibacillus amylolyticus osteomyelitis in a Poodle dog: case report and literature review

Abstract

Paenibacilli are gram-variable, endospore-forming bacteria that occupy various ecologic niches. These microorganisms have been known to infect humans occasionally at various anatomic sites. However, in humans, as well as in other vertebrate animals, the relationship between disease and isolation of Paenibacillus spp. remains poorly understood. We report here a case of infection in an adult Poodle dog. The animal had nodules in the lungs and multifocal osteolytic expansile bone lesions. From bone, Paenibacillus amylolyticus was recovered by culture and identified by MALDI-TOF mass spectroscopy and 16S rDNA sequencing; pyogranulomatous inflammation was observed in lung and bone specimens. The microorganism was resistant to clindamycin and imipenem. Four-month treatment with amoxicillin-clavulanate resulted in clinical resolution of disease in this dog. Nevertheless, therapy for more prolonged periods should be considered because recurrent infections can occur as a result of the transition of Paenibacillus spores to vegetative cells. Disease caused by a Paenibacillus species has not been reported previously in dogs, to our knowledge.

Keywords: Paenibacillus; bone; computed tomography; dogs; histopathology; lung; recurrent infection; spores.

Figure 1.

Radiography and computed tomography (CT) of Paenibacillus lesions in a dog. A. Expanding osteolytic lesion in the proximal end of the right tibia (arrowhead). B. Lysis of cancellous bone and rarefaction of cortical bone of the T12 vertebral body (asterisk). CT. C. Lung nodules (asterisks). CT.

Figure 2.

Cytologic sample of lung and biopsy of tibial bone. A. Neutrophils and epithelioid macrophages in lung aspirate. B. Neutrophils and macrophages with a small number of lymphocytes and plasma cells in a tibial biopsy.

Figure 3.

Microscopic images of Paenibacillus amylolyticus from culture plate. A. Gram-variable rods. Gram stain. B. Green endospores and red vegetative cells. Schaeffer–Fulton method.