An alpha-haemolytic Gram-positive diplococcus isolated from CSF must be distinguished from viridans streptococci. Which pair of tests best establishes the identity of the pathogen?

• A Bacitracin sensitivity and hippurate hydrolysis
• B Optochin susceptibility and bile solubility ✓
• C CAMP test and esculin hydrolysis in bile
• D Novobiocin resistance and coagulase production

Explanation

Streptococcus pneumoniae is lysed by optochin (ethylhydrocupreine hydrochloride) and dissolves in bile salts owing to its unusual membrane content of an autolytic enzyme, while viridans streptococci resist both. Bacitracin identifies group A streptococci, CAMP identifies group B streptococci, and the remaining options apply to staphylococci or enterococci, none of which are alpha-haemolytic diplococci.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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