A 52-year-old diabetic man presents with fever, right upper quadrant pain and a solitary pyogenic liver abscess. Aspirated pus grows a mucoid gram-negative rod. On culture plate, a loop dragged through the colony pulls out a viscous string longer than 5 mm. This string test positivity identifies:
- A Hypervirulent Klebsiella pneumoniae with hypermucoviscosity ✓
- B ESBL-producing Klebsiella pneumoniae
- C Carbapenem-resistant Klebsiella pneumoniae carrying KPC
- D Klebsiella ozaenae subspecies causing atrophic rhinitis
Correct answer: A. Hypervirulent Klebsiella pneumoniae with hypermucoviscosity
Explanation
The string test detects hypermucoviscosity caused by overproduction of capsular polysaccharide, regulated by genes such as rmpA, and defines hypervirulent K. pneumoniae. This phenotype explains the classic syndrome of community-acquired pyogenic liver abscess with metastatic spread to eye, lung or meninges, seen especially in diabetic men of Asian origin. String positivity is a phenotypic marker of hypervirulence, not of ESBL or carbapenemase production, which are separate resistance mechanisms.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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