Pulmonary botryomycosis in a cat.

Pulmonary botryomycosis is an extremely rare bacterial infection that has not been previously documented in cats. This report describes a case of pulmonary botryomycosis in a 10-year-old spayed female domestic shorthair cat with chronic pulmonary lesions refractory to long-term corticosteroid therapy. Surgical lobectomy of the right cranial and middle lung lobes was performed. Histopathological examination revealed extensive necrotizing and fibrosing pyogranulomatous inflammation with characteristic club colonies composed of Gram-positive cocci surrounded by eosinophilic Splendore-Hoeppli material. On molecular analysis of formalin-fixed, paraffin-embedded tissue, the highest 16S rDNA sequence homology was Staphylococcus spp. This case represents the first documented instance of pulmonary botryomycosis in a cat and highlights the diagnostic importance of combining histopathological and molecular approaches.