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For further information, see CMDT Part 33-34: Nocardiosis

Key Features

  • Nocardia species are an aerobic filamentous soil bacterium that can cause pulmonary and systemic nocardiosis

  • Commonly identified nocardia species include members of the Nocardia asteroides complex and Nocardia brasiliensis

  • Bronchopulmonary abnormalities (eg, alveolar proteinosis) predispose to colonization, but infection is unusual unless the patient is also receiving systemic corticosteroids or is otherwise immunosuppressed

  • Central nervous system (CNS) involvement commonly accompanies pulmonary infection

Clinical Findings

  • Pulmonary involvement usually begins with malaise, loss of weight, fever, and night sweats

  • Cough and production of purulent sputum are the chief complaints

  • Dissemination may involve any organ

    • Brain abscesses and subcutaneous nodules are most frequent

    • Dissemination is seen exclusively in immunocompromised patients

Diagnosis

  • N asteroides is a branching, filamentous gram-positive bacterium that is weakly acid-fast

  • Identification is made by culture

  • Chest radiograph

    • May show infiltrates accompanied by pleural effusion

    • Lesions may penetrate through the chest wall and invade the ribs

  • Brain imaging should be considered even in absence of clinical symptoms and signs of CNS infection to rule out occult abscess

Treatment

  • Trimethoprim-sulfamethoxazole (TMP-SMZ)

    • For isolated cutaneous infections

      • 5–10 mg/kg/day (based on TMP) as an oral or intravenous formulation

    • For disseminated or pulmonary infections: 15 mg/kg/day (based on TMP)

    • Resistance to TMP-SMZ is increasing and initiating treatment with two drugs should be considered while awaiting antibiotic susceptibilities in cases of disseminated or severe localized disease

  • Alternative agents or drugs that can be given in combination with TMP-SMZ

    • Imipenem, 500 mg intravenously every 6 hours

    • Amikacin, 7.5 mg/kg intravenously every 12 hours

    • Minocycline, 100–200 mg orally or intravenously twice daily

  • Surgical procedures such as drainage and resection may be needed as adjunctive therapy

  • Response may be slow, and therapy should be continued for at least 6 mo

  • The prognosis in systemic nocardiosis is poor when therapy is delayed

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