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Hypervirulent K. pneumoniae — SCE Infectious Diseases MCQ

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HardHealthcare-Associated InfectionsHypervirulent K. pneumoniaeSCE Infectious Diseases

A 55-year-old woman is hospitalised with severe community-acquired pneumonia. Sputum culture grows Klebsiella pneumoniae with a mucoid (hypermucoviscous) phenotype. The organism is sensitive to all antibiotics tested. She develops liver abscess on day 5. What is the significance of the hypermucoviscous phenotype?

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Correct answer: C — It indicates a hypervirulent K. pneumoniae strain (HvKp) capable of causing metastatic infections in otherwise healthy individuals

Hypervirulent Klebsiella pneumoniae (HvKp) is characterised by a hypermucoviscous capsule (positive string test: a mucoviscous string >5 mm is formed when a colony is stretched with a loop). HvKp causes invasive community-acquired infections in otherwise healthy individuals, particularly liver abscess (often cryptogenic) with metastatic spread to lungs, eyes (endophthalmitis), and CNS. It is classically associated with K1 and K2 capsular serotypes, prevalent in East/South-East Asia. Despite being fully antibiotic-susceptible, HvKp causes aggressive disease.

Reference: Lancet ID 2022 – Hypervirulent K. pneumoniae; BSAC 2023 – Gram-negative virulence