A 28-year-old man presents with sudden onset rusty sputum, high fever, and right-sided pleuritic chest pain. Chest X-ray shows homogeneous consolidation of the entire right upper lobe with air bronchograms. Which organism is the most likely cause?
- A Mycoplasma pneumoniae
- B Staphylococcus aureus
- C Streptococcus pneumoniae ✓
- D Klebsiella pneumoniae
Correct answer: C. Streptococcus pneumoniae
Explanation
Rusty sputum with lobar consolidation and air bronchograms is classic for pneumococcal (Streptococcus pneumoniae) lobar pneumonia in a young adult. Mycoplasma causes patchy interstitial infiltrates without rusty sputum. Klebsiella favors alcoholics and produces currant jelly sputum. Staphylococcus typically causes multifocal bronchopneumonia or cavitary lesions, especially post-viral.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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