A 48-year-old diabetic man from Taiwan presents with fever, right upper quadrant pain, and a multiloculated liver abscess aspirated pus yielding a hypermucoviscous, non-encapsulated-string forming Klebsiella pneumoniae. The hypervirulence phenotype of this strain is attributed to which factor?

• A Type 3 fimbrial adhesin mrkD
• B O-antigen modification by the wzy gene
• C Plasmid-mediated SHV extended-spectrum beta-lactamase
• D K1 or K2 capsular serotype with hypermucoviscosity mediated by rmpA ✓

Explanation

Hypervirulent K. pneumoniae (hvKp) classically carries capsular serotypes K1 or K2 together with the rmpA plasmid gene, which upregulates capsule synthesis producing the hypermucoviscous phenotype detected by a positive string test. It causes metastatic community-acquired infections in healthy and diabetic hosts, notably pyogenic liver abscess with endophthalmitis risk. ESBL carriage characterizes classical hospital strains, not hypervirulence, and type 3 fimbriae contribute to biofilm rather than serum resistance and metastatic spread.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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