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Melioidosis

(Whitmore Disease)

by Larry M. Bush, MD, Maria T. Perez, MD

Melioidosis is an infection caused by Burkholderia (formerly Pseudomonas) pseudomallei. Manifestations include pneumonia, septicemia, and localized infection in various organs. Diagnosis is by staining or culture. Treatment with antibiotics, such as ceftazidime, is prolonged.

The organism can be isolated from soil and water and is endemic in Southeast Asia; Australia; Central, West, and East Africa; India; the Middle East; and China. Humans may contract melioidosis by contamination of skin abrasions or burns, ingestion, or inhalation but not directly from infected animals or other humans. In endemic areas, melioidosis is likely to occur in patients with diabetes, alcoholism, chronic renal disease, or immunocompromise including AIDS. Melioidosis is also a potential agent of bioterrorism (see Biological Agents as Weapons).

Symptoms and Signs

Infection may manifest acutely or remain latent for years after an inapparent primary infection. Mortality is < 10%, except in acute septicemic melioidosis, which is frequently fatal.

Acute pulmonary infection is the most common form. It varies from mild to overwhelming necrotizing pneumonia. Onset may be abrupt or gradual, with headache, anorexia, pleuritic or dull aching chest pain, and generalized myalgia. Fever is usually > 39° C. Cough, tachypnea, and rales are characteristic. Sputum may be blood-tinged. Chest x-rays usually show upper lobe consolidation, frequently cavitating and resembling TB. Nodular lesions, thin-walled cysts, and pleural effusion may also occur. The WBC count ranges from normal to 20,000/μL.

Acute septicemic infection begins abruptly, with septic shock and multiple organ involvement manifested by disorientation, extreme dyspnea, severe headache, pharyngitis, upper abdominal colic, diarrhea, and pustular skin lesions. High fever, hypotension, tachypnea, a bright erythematous flush, and cyanosis are present. Muscle tenderness may be striking. Signs of arthritis or meningitis sometimes occur. Pulmonary signs may be absent or may include rales, rhonchi, and pleural rubs.

Localized suppurative infection can occur in almost any organ but is most common at the site of inoculation in the skin (or lungs) and associated lymph nodes. Typical metastatic sites of infection include the liver, spleen, kidneys, prostate, bone, and skeletal muscle. Acute suppurative parotiditis is common among children in Thailand. Patients may be afebrile.

Diagnosis

  • Staining and culture

B. pseudomallei can be identified in exudates by methylene blue or Gram stain and by culture. Blood cultures often remain negative except when there is marked bacteremia (eg, in septicemia). Serologic assays are often unreliable in endemic areas because positive results may be due to previous infection. Chest x-rays usually show irregular, nodular (4 to 10 mm) densities but may also show lobar infiltrates, bilateral bronchopneumonia, or cavitary lesions. Ultrasonography or CT of the abdomen and pelvis should probably be done to detect abscesses, which may be present regardless of the clinical presentation. The liver and spleen may be palpable. Liver function tests, AST, and bilirubin are often abnormal. Renal insufficiency and coagulopathy may be present in severe cases. The WBC count is normal or slightly increased.

Treatment

  • Sometimes trimethoprim/sulfamethoxazole (TMP/SMX) or ceftazidime

Asymptomatic infection needs no treatment. Mildly ill patients are given TMP/SMX, one double-strength tablet po bid for a minimum of 30 days. Moderately or seriously ill patients are given ceftazidime 30 mg/kg IV q 6 h for 2 to 4 wk (imipenem, meropenem, and piperacillin are acceptable substitutes), then oral TMP/SMX plus either doxycycline 100 mg bid or, in children < 8 yr and pregnant women, amoxicillin/clavulanate for 3 mo.

Key Points

  • Melioidosis is acquired by skin contact, ingestion, or inhalation; it is not acquired directly from infected animals or people.

  • The most common manifestation is an acute pulmonary infection (occasionally severe), but suppurative lesions may occur in the skin and/or many other organs; septicemia, which has high mortality, may result.

  • Diagnose using staining and culture; blood cultures are done but often are negative except in severe septicemia.

  • Treat mildly ill patients with TMP/SMX and seriously ill patients with IV ceftazidime followed by a prolonged course of oral TMP/SMX and either doxycycline or, in children < 8 yr and pregnant women, amoxicillin/clavulanate.

Drugs Mentioned In This Article

  • Drug Name
    Select Trade
  • FORTAZ, TAZICEF
  • PERIOSTAT, VIBRAMYCIN
  • MERREM
  • AMOXIL
  • No US brand name

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