Melioidosis — DTM&H MCQ

Correct answer: B — Melioidosis

The correct answer is B, Melioidosis. This is caused by Burkholderia pseudomallei, a gram-negative bacillus endemic in the soil and water of Southeast Asia, with rice farming in Thailand being a classic occupational and geographic risk factor. The combination of fever, bilateral upper lobe cavitating pneumonia, blood-stained sputum, and subcutaneous abscesses reflects the organism's tendency to cause multifocal abscess formation and haematogenous dissemination, mimicking tuberculosis. A key laboratory clue is intrinsic resistance to aminoglycosides (and also to colistin and early beta-lactams), a feature used clinically to distinguish B. pseudomallei from other gram-negative organisms and to guide empirical therapy toward ceftazidime or a carbapenem rather than gentamicin-based regimens. Why the other options are wrong: E. Pulmonary tuberculosis: TB causes upper lobe cavitation and haemoptysis but is caused by an acid-fast bacillus, not a culturable gram-negative bacillus, and does not typically produce multiple subcutaneous abscesses. D. Leptospirosis: This spirochaete causes fever, jaundice and renal impairment after freshwater exposure but does not cause cavitating lung disease or abscesses, and is not a gram-negative bacillus on culture. A. Nocardiosis: Nocardia causes cavitating pneumonia and abscesses but is a gram-positive, branching, filamentous, partially acid-fast organism, not a gram-negative bacillus. C. Klebsiella lung abscess: Klebsiella pneumoniae is a gram-negative bacillus causing cavitating pneumonia, but it is not intrinsically resistant to aminoglycosides and does not typically cause disseminated subcutaneous abscesses. Key point: In a Southeast Asian rice farmer with cavitating pneumonia, skin abscesses, and an aminoglycoside-resistant gram-negative bacillus, think melioidosis (Burkholderia pseudomallei), not tuberculosis.

Reference: Journal of Travel Medicine, 'Travel-associated melioidosis: a narrative review', 2023, https://academic.oup.com/jtm/article/30/3/taad039/7087080