A 45-year-old chronic alcoholic presents with a productive cough, blood-tinged 'currant jelly' sputum, and lobar consolidation on chest X-ray. Gram stain shows Gram-negative, mucoid rods in short chains. The organism is urease positive and shows a positive string test. Which organism is the most likely causative agent?
- A Streptococcus pneumoniae
- B Klebsiella pneumoniae ✓
- C Pseudomonas aeruginosa
- D Acinetobacter baumannii
Correct answer: B. Klebsiella pneumoniae
Explanation
Klebsiella pneumoniae is a classic cause of severe lobar pneumonia in chronic alcoholics, characterised by thick, blood-tinged 'currant jelly' sputum due to blood mixed with mucus. It is a Gram-negative encapsulated bacillus that is urease positive and shows a positive string test (colonies form a viscous string when lifted with a loop) due to abundant polysaccharide capsule. S. pneumoniae is Gram-positive, and Pseudomonas and Acinetobacter are more associated with nosocomial infections.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.