Which organism is alpha-hemolytic and optochin resistant with bile solubility negative?

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 resistance and negative bile solubility points to viridans streptococci. The greenish halo from partial hemolysis on blood agar describes alpha-hemolysis. Optochin resistance means this organism does not offer the sensitivity pattern that distinguishes Streptococcus pneumoniae (which is optochin sensitive). Negative bile solubility means it does not dissolve in bile, unlike S. pneumoniae which is bile soluble. Together, these traits identify the viridans group of streptococci, common in the oral cavity and a frequent cause of subacute endocarditis after dental work. For context, Streptococcus gallolyticus (group D) is typically bile esculin positive and not optochin resistant, Actinomyces are not cocci and Clostridia tetani is an anaerobic rod, so they don’t fit this pattern.