Melioidosis

Melioidosis is an infectious disease caused by the gram-negative bacterium Burkholderia pseudomallei. The disease is endemic in Southeast Asia and northern Australia, with cases often imported to other regions. The bacterium is typically found in soil and water, and humans are infected through contact with contaminated sources. It presents a wide range of symptoms from mild fever to severe pneumonia and septic shock.

Signs and Symptoms

The incubation period for melioidosis ranges from 1 to 21 days, with an average of 9 days. Symptoms can be acute or chronic and may include fever, pneumonia, and multiple abscesses in organs such as the liver, spleen, and lungs. Complications can include encephalomyelitis, septic shock, and osteomyelitis.

Diagnosis

Diagnosis of melioidosis is confirmed through bacterial culture, although this has a sensitivity of about 60%. Samples can be taken from blood, pus, sputum, or urine. Imaging techniques such as chest X-rays and CT scans can also be used to identify abscesses. Serological tests and antigen detection methods like ELISA and latex agglutination can aid in diagnosis but are less reliable in endemic areas.

Treatment

Treatment is divided into an intensive phase and an eradication phase. The intensive phase involves intravenous antibiotics such as ceftazidime or meropenem for at least 10 to 14 days. For severe cases like neurological melioidosis or septic shock, meropenem is preferred. The eradication phase involves oral antibiotics, typically co-trimoxazole for 3 months to prevent recurrence. Co-amoxiclav is an alternative for those intolerant to co-trimoxazole.

Prevention

Preventive measures include avoiding contact with contaminated soil and water, especially in endemic areas. Protective gear like boots and gloves should be worn when handling soil or water. In regions with limited resources, boiling water before consumption is recommended. There is no approved vaccine for melioidosis, and the use of antibiotic prophylaxis is limited to high-risk individuals.

Prognosis

The prognosis for melioidosis varies significantly based on the setting. In well-resourced environments, the mortality rate is about 10%, whereas in resource-poor settings, it can exceed 40%. Recurrence can occur due to re-infection or relapse, particularly in individuals with underlying conditions such as diabetes or chronic kidney disease.

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Self-assessment MCQs (single best answer)

What bacterium causes melioidosis?

In which regions is melioidosis endemic?

What is the average incubation period for melioidosis?

Which of the following symptoms is NOT commonly associated with melioidosis?

What is the sensitivity of bacterial culture in diagnosing melioidosis?

Which imaging technique is NOT used to identify abscesses in melioidosis?

Which antibiotic is preferred for severe cases of melioidosis during the intensive phase of treatment?

What is the duration of the eradication phase of treatment for melioidosis?

Which preventive measure is recommended in regions with limited resources?

What is the approximate mortality rate of melioidosis in well-resourced environments?