Optochin test explained.

Susceptibility to optochin is a simple and reliable method of differentiating Streptococcus pneumoniae from other alpha-haemolytic streptococci.

Optochin is a chemical, ethylhydrocupreine hydrochloride and is completely soluble in water. The optochin test detects an organism’s susceptibility to the chemical optochin. The chemical tests the fragility of the bacterial cell membrane and causes S. pneumoniae to lyse due to changes in surface tension.

The optochin test is widely used in the form of filter paper discs, impregnated with ethylhydrocupreine hydrochloride, which are applied directly to inoculated plates before incubation.

The optochin test is less time-consuming than the bile solubility test.

In relation to the optochin test, Public Health England has issued a technical report, including safety information. The report can be accessed here.

Posted by Tim Sandle