Community-acquired pneumonia in a 70-year-old resident of a nursing home shows lobar consolidation and blood cultures grow gram-negative rods with a mucoid 'string test' positive (mucoid string >5 mm). Sputum Gram stain shows encapsulated gram-negative rods with bipolar staining. The organism and its clinical significance are:

• A Pseudomonas aeruginosa; grapes-like odour and oxidase positive
• B E. coli; aspiration pneumonia in alcoholics
• C Haemophilus influenzae non-typeable; common in COPD exacerbations
• D Klebsiella pneumoniae; thick capsule (Friedländer's bacillus) causing 'currant jelly sputum', lobar or bulging fissure pneumonia; high mortality ✓

Explanation

Klebsiella pneumoniae (Friedländer's bacillus) has a thick polysaccharide capsule producing a 'string test' positive mucoid colony; it causes pneumonia classically in diabetics, alcoholics, and elderly — characteristically presenting with upper lobe consolidation, 'currant jelly sputum' (blood-stained mucoid secretions), bulging fissure sign on CXR, and high mortality. Pseudomonas is oxidase-positive and non-mucoid on standard media. E. coli rarely causes primary pneumonia. H. influenzae causes bronchitis-type exacerbations.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.