Epidemiology

• Predisposing Factors:
  • Impaired Cell-Mediated Immunity:
    • Steroids
    • HIV
    • Solid Organ Transplantation
  • Animal Exposure: reported in most, but not all, patients

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Etiology

• Rhodococcus equi infection
• Gram-Positive Coccus or Rod: may stain weakly acid-fast (due to mycolic acid in cell wall), but is much smaller than AFB
  • Varies in shape from cocci to curved club shape (frequently misinterpreted as a diphtheroid or bacillus)

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Physiology

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Diagnosis

• Sputum GS/Cult+Sens:
  • Gram-Positive Coccus or Rod: may stain weakly acid-fast (due to mycolic acid in cell wall), but is much smaller than AFB
    • Varies in shape from cocci to curved club shape (frequently misinterpreted as a diphtheroid or bacillus)
• FOB:
• CXR/Chest CT Pattern:
  • Nodular Infiltrates: gradually cavitate
  • Lung Abscess:
  • Empyema: may occur

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Clinical

• Subacute Onset of Disease (resembling fungal or mycobacterial disease):

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Treatment

• Vanco or Erythromycin: agents of choice (as Rhodococcus is intracellular and these agents get into cells readily)
  • Addition of Rifampin: may be synergistic
  • Prolonged therapy is necessary to prevent relapse
• Alternatives: resistance has been reported to occur while receiving ß-lactams
  • Rifampin:
  • Chloramphenicol:

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References

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