Nocardia is a genus of aerobic, Gram-positive, weakly acid-fast, filamentous bacteria found in soil, decaying organic matter, and water. It can cause opportunistic infections, particularly in people with weakened immune systems.
Genus: Nocardia
Type: Gram-positive, branching filamentous rods
Staining: Weakly acid-fast (due to mycolic acids in their cell wall)
Oxygen requirement: Obligate aerobes
Habitat: Soil, organic material
Nocardia asteroides (most common human pathogen)
Nocardia brasiliensis (common in skin infections)
Nocardia farcinica, N. otitidiscaviarum, etc.
Seen in immunocompromised patients (e.g., transplant recipients, chronic steroid users)
Symptoms: cough, fever, dyspnea, chest pain
Can mimic tuberculosis or malignancy on imaging
Can disseminate to the brain (abscesses) or other organs
More common in healthy individuals, especially with N. brasiliensis
Follows traumatic inoculation
Forms localized abscesses or actinomycetoma (chronic subcutaneous infection with draining sinuses)
Brain abscesses, especially in disseminated disease
Microscopy and culture from infected tissue or sputum
Modified acid-fast stain (e.g., Fite-Faraco or Kinyoun stain)
Slow-growing, may require prolonged culture (up to 2 weeks)
Imaging (e.g., CT or MRI for pulmonary or CNS involvement)
First-line: Trimethoprim-sulfamethoxazole (TMP-SMX)
Severe or disseminated disease may require combination therapy (e.g., imipenem, amikacin)
Treatment is often prolonged (6–12 months), especially with CNS involvement
Nocardia is a soil-borne, weakly acid-fast, filamentous bacterium that causes chronic, often severe infections primarily in immunocompromised individuals, affecting the lungs, skin, or brain. Early diagnosis and prolonged antibiotic therapy are key to management.