Mycobacteria infection in a Cat

History: 2-year-old Domestic Long Hair cat, neutered male, showing a 1 cm diameter erythematous mass on the right upper lip. Unknown duration.

Cytological description: The images contain numerous large macrophages, neutrophils in good morphological condition, and several multinucleated giant macrophages. There is a large number of negatively stained rod-shaped bacteria within and between the macrophages.

Comments: Mycobacteria are environmentally resistant, non-spore-forming acid-fast bacteria. Because of their structural properties and ability to survive intracellularly, mycobacteria produce granulomatous inflammation in the host. Group IV atypical mycobacteria (M. fortuitum and M. chelonei) are the most frequently isolated from cutaneous lesions. Several cases of M. avium infections have also been reported in the cat. Treatment should be based on antibiotic sensitivity test results although the organisms are difficult if not impossible to grow. Surgical debridation should be a consideration in poorly responsive cases.

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