A 9-year-old indoor-outdoor cat was presented for a 6-month history of cutaneous nodules. Histologic examination of biopsy specimens revealed pyogranulomatous miliary nodular inflammation with giant cells. Bacteriologic culture revealed rapid growth of rough, nonpigmented bacteria. The organism was acid-fast. PCR testing identified the organism as M alvei. This was the first report of this rapidly growing mycobacterium in cats.

COMMENTARY: Mycobacteria are divided into 2 groups: slow-growing and rapid-growing. They are opportunistic organisms and are usually introduced into the host via some type of trauma. In dogs and cats, these organisms can cause granulomas, pyogranulomas, pneumonia, and systemic disease. One of the most common presentations of rapidly growing mycobacterial infections is a nonhealing wound, especially in cats. Definitive diagnosis may require multiple concurrent diagnostic tests, including cytologic examination of exudates, impression smears of tissue sections, histologic examination of biopsy specimens, and culture. Tissue homogenates and pus are recommended for culture. Multiple cytologic specimens should be sent to the reference laboratory unstained; rapidly growing mycobacteria vary in their degree of acid fastness. Treatment involves antimicrobial therapy and surgical debridement.

Pyogranulomatous panniculitis caused by Mycobacterium alvei in a cat. Beccati M, Peano A, Gallo MG. J SMALL ANIM PRACT 48:664, 2007.