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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; 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 AIDS.
Symptoms and Signs
Infection may be asymptomatic or remain latent for years. 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.
Disseminated 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.
Nondisseminated septicemic infection occurs when bacteremia involves only a single organ. It does not usually lead to shock.
Localized (chronic suppurative) infection causes secondary abscesses, most often in the skin, lymph nodes, or bone. Patients may be afebrile. An acute suppurative form is uncommon.
Diagnosis
B. pseudomallei can be identified in exudates by methylene blue or Gram stain and by culture. Chest x-rays usually show irregular, nodular (4 to 10 mm) densities. The liver and spleen may be palpable. Liver function tests, AST, and bilirubin are often abnormal. The WBC count is normal or slightly increased.
Treatment
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 or amoxicillin/clavulanate for 30 to 120 days.
Last full review/revision August 2009 by Burke A. Cunha, MD
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