Disseminated Nocardia farcinica: literature review and fatal outcome in an immunocompetent patient

Abstract

Background: Nocardia farcinica is a gram-positive, partially acid-fast, methenamine silver-positive aerobic actinomycete. Nocardia spp. are opportunistic pathogens, and N. farcinica is the least common species of clinical importance.

Methods: Review of the recent literature and description of a immunocompetent patient with no known risk factors who contracted fatal N. farcinica sepsis.

Results: Positive pre-mortem and post-mortem cultures from the lung and synovium correlated with acute bronchopneumonia and synovitis at autopsy. Colonies of filamentous bacteria, which were not apparent in conventional hematoxylin and eosin-stained sections, were observed with gram and methenamine silver stains, but acid-fast stains were negative. A literature review revealed that disseminated N. farcinica often is associated with an underlying malignant tumor or autoimmune disease (88% of patients). Chemotherapy or corticosteroid treatments are additional risk factors.

Conclusions: Trimethoprim-sulfamethoxazole typically is the first-line therapy for N. farcinica; treatment with amikacin and imipenem-cilastatin is used less often (7% of patients). Despite aggressive therapy, we observed that the death rate (39%) associated with N. farcinica in recent publications was eight percentage points higher than reported in a review from 2000.

FIG. 1.

Chest CT scan demonstrates multiple subcentimeter nodules in both lungs.

FIG. 2.

Histologic views. (A) Acute fibrinous and chronic synovitis. No organisms are visible by hematoxylin and eosin stain. Insets show fibrinous exudates. Lower right: Gram stain demonstrating gram-positive thin, branching, filamentous forms. Lower left: Gomori methenamine silver (GMS) stain, similarly demonstrating organism morphology. (B) Lung nodule. Low-magnification view of lung with centrally necrotic nodule of organizing pneumonia, lower left. (C) Higher-magnification view of the nodule showing central necrotic focus and peripheral lymphoid infiltrate. Lower right: Gram stain of center of nodule demonstrating numerous gram-positive thin, branching, filamentous organisms. Lower left: GMS stain showing similar organisms. (D) Microscopic, non-necrotic granulomas were associated with nodular abscess.