Alpha-hemolytic streptococcus that is optochin susceptible and bile soluble. Which organism is this?

Prepare for the CAMLPR Microbiology Test. Utilize flashcards and engaging multiple-choice questions, each equipped with descriptions and explanations. Ready yourself for an excellent performance!

Alpha-hemolysis with optochin susceptibility and bile solubility points to Streptococcus pneumoniae. The greenish (partially hemolyzed) appearance on blood agar is typical of alpha-hemolysis, but among alpha-hemolytic streptococci, pneumococcus uniquely shows sensitivity to optochin and dissolves in bile. Optochin sensitivity helps separate it from the viridans group, which are optochin resistant. Bile solubility further distinguishes pneumococcus: bile salts activate its autolysin, causing the bacteria to lyse, so colonies disappear in bile, whereas most other alpha-hemolytic streptococci are bile insoluble. Thus this combination of tests best identifies Streptococcus pneumoniae.