Medic Notes: Myelodosis

Overview

• Myelodosis is an infectious disease caused by the gram-negative bacteria Bacchodura pseudomallei.
• It is often a fulminant and fatal disease.
• Endemic regions: Southeast Asia, the Caribbean, Northern Australia.
• Transmission: Direct contact with contaminated water and soil.
• Incubation period: 2 days to several years.

Predisposing Factors

• Immunosuppressed individuals:
  • Diabetes mellitus
  • Chronic renal failure
  • Retroviral infections
  • Hematological malignancies
  • Connective tissue disease
  • Long-term steroid therapy
  • Alcoholism
  • Trauma
• High-risk occupations: Farmers, cattle handlers.

Clinical Features

• Range of presentations:
  • Localized abscess
  • Severe community-acquired pneumonia
  • Acute fulminant septicemia
• Presentation groups:
  1. Acute Localized Infection
     • Symptoms: Nodule with acute lymphangitis/lymphadenitis, fever, general malaise.
  2. Pulmonary Infection
     • Symptoms: High-grade fever, headache, anorexia, myalgia, chest pain, cough.
     • Radiological findings: Bilateral disseminated nodules, diffuse fluffy alveolar infiltrates.
  3. Acute Septicemia
     • Common in patients with comorbidities.
     • Symptoms: Sudden onset, rapidly progressing to disseminated bacteremia, septicemic shock.
  4. Chronic Suppurative Infection
     • Typically involves joints, viscera, and other areas.

Diagnosis

• Always consider myelodosis if the patient presents with fever or signs of infection.
• Diagnosis through culturing B. pseudomallei from:
  • Blood, urine, sputum, skin lesions, abscess pus
  • Tissue biopsy (gold standard)
  • Non-sterile sites require special incubation methods or ashdowns medium.
• Serological tests:
  • Indirect Hemagglutination Test (IHAT)
  • Immunofluorescent Antibody Test (IFAT)
  • IgG and IgM ELISA
  • Rapid immunochromatographic tests
• IFAT is the most rapid, sensitive, and specific test in endemic areas.

Treatment

• Main treatment: Antibiotics
• Sensitive antibiotics include:
  • Doxycycline
  • Chloramphenicol
  • Chlortrimoxazole
  • Ceftazidime
  • Amoxicillin clavulanic acid
  • Imipenem
  • Meropenem
• Treatment is divided into:
  • Intensive Therapy (at least 2 weeks)
    • Severe myelodosis: Ceftazidime, Imipenem, Meropenem (with or without Coltrimoxazole)
    • Localized myelodosis: Coltrimoxazole + Doxycycline
  • Maintenance Therapy (at least 3 months)
    • Drugs: Coltrimoxazole, Amoxicillin clavulanic acid
    • Prevents relapse of myelodosis.