Melioidosis is an infection caused by the gram-negative bacterium Burkholderia pseudomallei (formerly Pseudomonas pseudomallei
Burkholderia pseudomallei 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. Sporadic cases are increasingly being identified in the Caribbean, Mexico, and Central and South America. The organism has been found in soil in the southern United States, but nearly all cases in the United States occur after travel to endemic areas. The risk of contracting melioidosis is highest for adventure travelers, ecotourists, military personnel, construction workers, miners, and other people whose contact with contaminated soil or water may expose them to the bacteria in an endemic area.
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
Chronic kidney disease or chronic lung disease
Immunocompromise including HIV/AIDS
Melioidosis is also a potential agent of bioterrorism.
Symptoms and Signs of Melioidosis
Melioidosis may manifest acutely or remain latent for years after an inapparent primary infection. Mortality is < 10% (1), 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 radiographs 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 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.
Symptoms and signs reference
1. Currie BJ, Mayo M, Ward LM, et al. The Darwin Prospective Melioidosis Study: a 30-year prospective, observational investigation. Lancet Infect Dis. 2021;21(12):1737-1746. doi:10.1016/S1473-3099(21)00022-0
Diagnosis of Melioidosis
Staining and culture
B. pseudomallei
Chest radiographs usually show irregular, nodular (4 to 10 mm) densities but may also show lobar infiltrates, bilateral bronchopneumonia, effusions, or cavitary lesions.
Ultrasonography or CT of the liver, spleen, and prostate should probably be done to detect abscesses, which often have a honeycomb-like appearance and 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 to 20,000/mcL (20 × 109/L).
Treatment of Melioidosis
For symptomatic patients, several weeks of IV antibiotics followed by a prolonged course of an oral antibiotic
Asymptomatic melioidosis needs no treatment.
B. pseudomallei than ceftriaxone and cefotaximedoxycycline.
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.
doxycycline.
