Optochin test

two strains of viridans streptococci (optochin-resistant)

Detail of two strains of alpha-hemolytic streptococci on blood agar. Cultivation 24 hours in an aerobic atmosphere, 37°C, 5% CO₂. On the surface of agar are placed two disks impregnated with optochin. Optochin (ethylhydrocupreine) is a chemical used for the presumptive identification of Streptococcus pneumoniae, which is optochin-sensitive, from other alpha-hemolytic streptococci.