Melioidosis

Melioidosis is an infection caused by Burkholderia pseudomallei, a Gram negative soil and water saprophyte endemic in northern Australia, South-East Asia (Thailand, Vietnam), India, and increasingly Africa and the Americas.

• Acquired by inhalation of contaminated aerosols, percutaneous inoculation, or ingestion; peaks in the rainy season.
• Risk factors: diabetes (about 50% of cases), alcohol excess, chronic kidney and lung disease, and thalassaemia; HIV is not a major risk.
• About 165,000 cases and 89,000 deaths estimated per year; mortality 10 to 40%.
• Known as the "great mimicker".

• Pneumonia (most common, may be severe or abscess forming), bacteraemia, sepsis, and septic shock.
• Localised abscesses: liver, spleen, prostate, parotid (children in Thailand), skin, and soft tissue.
• Neurological melioidosis (brainstem encephalitis, myelitis), bone and joint infection, and genitourinary disease.
• Chronic form mimicking tuberculosis, with relapse after incomplete treatment.

• Culture of blood, sputum, urine, throat swab, or pus (gold standard; selective media such as Ashdown agar); laboratory alert needed because of occupational infection risk.
• Latex agglutination and PCR for rapid identification; serology has limited use.
• CT chest and abdomen for abscesses.
• Check glucose and HbA1c, renal function, and CD4 if indicated.
• Exclude TB, other bacterial pneumonia, typhoid, and Gram negative sepsis.

• Intensive phase (at least 10 to 14 days; 4 to 8 weeks for neurological, bone, deep abscess, or prostatic disease): ceftazidime 2 g IV every 6 hours (or 50 mg/kg up to 2 g) or meropenem 1 g IV every 8 hours (2 g every 8 hours in CNS disease and septic shock); imipenem is an alternative.
• Eradication phase (3 to 6 months): trimethoprim-sulfamethoxazole according to weight (under 40 kg: 160/800 mg twice daily; 40 to 60 kg: 240/1200 mg twice daily; over 60 kg: 320/1600 mg twice daily) plus folic acid 5 mg daily; alternative amoxicillin clavulanate or doxycycline 100 mg twice daily.
• Drain abscesses; manage septic shock in ICU; G-CSF has been used in septic shock.
• Glycaemic control and avoidance of environmental exposure (boots, gloves, masks in endemic areas).
• Follow up for relapse for at least 1 year.