Bronchitis and bronchiolitis in a cat with cilia-associated respiratory bacillus-like organisms.

A 10-year-old male domestic shorthair cat died during anesthesia. Grossly, the lungs had multiple nodules corresponding to inflamed airways (bronchitis and bronchiolitis). Microscopically, cuffs and nodular aggregates of lymphocytes and plasma cells surrounded airways. Peribronchiolar fibrosis was also common. Globule leukocytes infiltrated the respiratory epithelium of noninflamed or mildly inflamed bronchi. Argyrophilic and filamentous organisms, consistent with cilia-associated respiratory bacillus-like organisms (CLO), were intermixed with cilia of respiratory epithelium. Ultrastructurally, CLO were longer and thinner than cilia and had a distinct trilaminar membrane, central electron-lucent areas, and no specialized external structures. Silver stained lung sections from 18 additional feline airways revealed similar bacilli in 2/9 normal lungs, 1/7 lungs with bronchitis and bronchiolitis, and 1/2 lungs with pneumonia. The significance of CLO in the pulmonary lesions was not determined.