Nocardia

Snapshot

• A 25-year-old woman with a history of HIV presents to the emergency room for months of fever, night sweats, and cough. She has not had any treatments for her HIV-positive status. On physical exam, she is dyspneic with bilateral rhonchi. A PPD test is negative for tuberculosis. Chest radiograph reveals bilateral pulmonary cavitary lesions. Sputum analysis shows partially acid-fast gram + filamentous rods.

Introduction

• Classification 
  • Nocardia
    • an aerobic gram + bacteria with branching filaments
    • weakly acid fast
    • urease + and catalase +
  • transmission
    • inhalation
    • direct contact with skin break
• Epidemiology
  • demographics
    • mainly in immunocompromised patients
  • location
    • pulmonary (most common)
    • may spread to central nervous system
  • risk factors
    • immunocompromised status
    • chronic steroid use
    • HIV infection
    • trauma
• Pathogenesis
  • Nocardia can inhibit phagolysosome fusion
  • immunocompromised patients, especially those with defective cell-mediated immunity, are at higher risk
• Associated conditions
  • pulmonary nocardiosis
    • in immunocompromised patients
  • cutaneous nocardiosis
• can happen in immunocompetent patients

Presentation

• Symptoms
  • constitutional symptoms
    • weight loss
    • night sweats
• Physical exam
  • fever
  • pulmonary nocardiosis
    • cough
    • dyspnea
    • sputum production
    • chest pain
    • pleural effusion
  • neurologic nocardiosis
    • focal neurologic defects based on location of abscess
    • altered mental status
  • cutaneous nocardiosis
    • nodular lymphangitis
      • painful lymphadenopathy with drainage
• cellulitis

Imaging

• Chest radiography 
  • indication
    • pulmonary nocardiosis
  • findings
    • multifocal consolidation
    • cavitary lesions
• Computed tomography (CT) of the brain
  • indication
    • suspected central nervous system involvement
  • findings
• abscesses appear as rim-enhancing lesions

Studies

• Labs 
  • gram + staining with multi-branching beaded filamentous bacteria
  • Ziehl-Neelsen stain 
    • weakly acid fast
  • culture
• Making the diagnosis
• based on clinical presentation and isolation of organism

Differential

• Actinomyces infection
  • distinguishing factors
    • although Actinomyces is also gram + and forms branching filaments, it is not acid fast and causes oral/facial abscesses associated with dental procedures
    • SNAP treatment
      • Sulfa for Nocardia; Actinomyces uses Penicillin
• Tuberculosis
  • distinguishing factor
• negative PPD

Treatment

• Medical
  • trimethoprim-sulfamethoxazole (TMP-SMX) 
    • indication
      • all patients
  • carbapenems
    • indication
• patients contraindicated to TMP-SMX

Complications

• Disseminated infection