Pulmonary botryomycosis in a Scottish highland steer

Pertinent necropsy findings in a 5 1/2-year-old Scottish Highland steer wit h chronic intractable pneumonia and cough were limited to the pulmonary sys tem. The accessory lobe of the lung was collapsed, scarred, and multifocall y adhered to parietal pleura. A polypoid mass almost completely obstructed the lobar bronchus and protruded into the trachea; mucopurulent exudate dis tended more distal bronchi. Botryomycosis was diagnosed when histologic exa mination revealed pyogranulomatous pneumonia with eosinophilic granules and "club" formation surrounding colonies of gram-positive cocci. Staphylococc us aureus was cultured from the lung. Botryomycosis is an unusual response to infection with common bacteria and is characterized by pyogranulomatous inflammation with formation of eosinophilic granules surrounding colonies o f gram-positive cocci or gram-negative bacilli. Among domestic species, sta phylococcal botryomycosis is most common as a wound infection in horses or as mastitis in cows and sows. Pulmonary botryomycosis is rare in horses, hu mans, and guinea pigs and apparently has not been reported in cattle.