The GMS-stained cytospins contained numerous clumps of branching, filamentous organisms. The original acid-fast stain was negative. A modified acid-fast stain was requested.
The organisms stain positively under the modified procedure.
The cytologic features are consistent with Nocardia.
Culture of BAL fluid confirmed the presence of Nocardia asteroides.
Discussion: Nocardia species are aerobic gram-positive bacilli commonly found in soil and decaying plant matter. N. asteroides may be a saprophytic constituent of respiratory flora in patients with no clinical evidence of disease, or may colonize the respiratory tract in individuals with other pulmonary disorders such as tuberculosis, cystic fibrosis or neoplasms. Immunocompromised patients, especially those who have received kidney or heart transplants or who are receiving long-term corticosteroid therapy are particularly susceptible to infection. Primary pulmonary disease commonly manifests with fever and productive cough. The radiologic picture is varied and may include a diffuse infiltrate or marked consolidation. Bloodborne dissemination to the brain or other organs occurs in about half of patients.
The delicate, beaded branching filaments are gram-positive or gram-variable and stain with GMS and Giemsa. A modified Kinyoun acid-fast stain gives good results on smears and cytospins; this stain is useful in differentiating Nocardia from Actinomyces, which is not acid-fast. Actinomyces, while also forming clumps of filamentous organisms, frequently also demonstrates a "sulfur granule" morphology with a densely staining core. Culture provides definitive identification of Nocardia and other aerobic actinomycetes.
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