Melioidosis

Melioidosis may manifest acutely or remain latent for years after an inapparent primary infection. Case fatality 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 tuberculosis. Nodular lesions, thin-walled cysts, and pleural effusion may also occur. The white blood cell count ranges from normal to 20,000/mcL (20 × 10⁹/L).

Acute septicemic infection begins abruptly, with septic shock Sepsis and Septic Shock Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by a dysregulated response to infection. In septic shock, there is critical reduction in tissue perfusion; acute failure... read more 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.

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 tests, aspartate aminotransferase (AST), and bilirubin are often abnormal. Renal insufficiency and coagulopathy may be present in severe cases. The white blood cell count is normal or slightly increased.

Asymptomatic melioidosis needs no treatment.

Symptomatic patients are given ceftazidime 30 mg/kg IV every 6 hours for 2 to 4 weeks (imipenem, meropenem, and piperacillin are acceptable substitutes), then oral antibiotics (one double-strength tablet of trimethoprim/sulfamethoxazole [TMP/SMX] 2 times a day or doxycycline 100 mg 2 times a day) for 3 to 6 months. In children < 8 years and pregnant women, amoxicillin/clavulanate 25/5 mg/kg 3 times a day is used instead of doxycycline.