A 65-year-old man presents with high fever, rusty sputum, and lobar pneumonia. Sputum culture grows alpha-hemolytic, lancet-shaped diplococci. Which laboratory test best differentiates this organism from other alpha-hemolytic streptococci?
- A Bacitracin sensitivity
- B Optochin sensitivity ✓
- C Bile esculin hydrolysis
- D Hippurate hydrolysis
Correct answer: B. Optochin sensitivity
Explanation
Streptococcus pneumoniae is optochin sensitive and bile soluble, distinguishing it from viridans streptococci which are optochin resistant. Bacitracin sensitivity identifies Group A Streptococcus. Bile esculin hydrolysis and hippurate hydrolysis are tests for Group B Streptococcus and Enterococcus. Optochin is the standard bedside test for pneumococcal identification.
Reference: Ananthanarayan and Panicker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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