Klebsiella pneumoniae type 1 (classical) pneumonia shows a specific radiographic pattern of 'bulging fissure sign'. The organism-specific virulence factor responsible for the characteristic mucoid and destructive nature of this pneumonia is:
- A Metallo-beta-lactamase (KPC) destroying all beta-lactams
- B Type III secretion system injecting effectors into alveolar macrophages
- C Pili (type 1 and type 3) binding uroepithelial cells and bronchial mucosa
- D Hypermucoviscous capsular polysaccharide (types K1/K2) resisting phagocytosis and complement ✓
Explanation
Hypervirulent Klebsiella pneumoniae (hvKP) strains with hypermucoviscous capsule (positive string test: mucoid strands >5mm) expressing K1/K2 capsular serotypes resist phagocytosis, complement killing, and serum bactericidal activity; the abundant capsule causes extensive tissue destruction, lobar consolidation, and the bulging fissure sign on CXR due to voluminous mucopurulent exudate. KPC and other beta-lactamases cause antibiotic resistance but not pathological phenotype. T3SS is primarily a feature of Pseudomonas and Salmonella. Klebsiella pili mediate urinary and respiratory adhesion but not the destructive pneumonia phenotype.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.