Optochin

Optochin (or ethylhydrocupreine) is a chemical used for the presumptive identification of Streptococcus pneumoniae, which is optochin-sensitive, from other α-haemolytic streptococci (such as Streptococcus viridans) which are resistant.

Bacteria that are optochin sensitive will be inhibited to grow around optonin disc, while bacteria that are optochin resistant will be unaffected.