Melioidosis

Burkholderia pseudomallei is a motile, aerobic, gram-negative bacillus that stains bipolar ('safety pin' appearance) and is intrinsically resistant to many antibiotics including aminoglycosides and early-generation cephalosporins. Transmission occurs via inoculation through skin abrasions, inhalation, or ingestion of contaminated water/soil, particularly in endemic regions (Southeast Asia, especially Thailand, and Northern Australia). Risk factors include diabetes mellitus (the strongest risk factor), chronic renal disease, alcoholism, thalassemia, and other causes of immunosuppression. Clinical presentations are highly variable, earning it the moniker 'the great mimicker': it can present as localized skin/soft tissue infection, pneumonia (often with cavitation resembling TB), abscesses in multiple organs (liver, spleen, prostate - parotid abscesses classic in children), or fulminant septicemia with high mortality. A hallmark feature is the capacity for latency, with reactivation occurring months to decades after initial exposure, historically noted in Vietnam War veterans ('Vietnamese time bomb'). Diagnosis relies on culture (definitive), as serology has limited utility in endemic areas due to high background seropositivity; PCR and biochemical identification are also used. Treatment requires a prolonged two-phase approach: an intensive intravenous phase (ceftazidime or meropenem for 10-14+ days) followed by an eradication phase with oral trimethoprim-sulfamethoxazole for 3-6 months to prevent relapse. Untreated septicemic melioidosis carries high mortality. It is considered a potential biothreat agent due to its virulence and environmental persistence.