Bacitracin

Bacitracin Susceptibility Test
The Bacitracin test exists typically to separate Group A Streptococcus from the rest of the genus. This Group is actually just one organism Streptococcus pyogenes. The compound is produced by Bacillus licheniformis and inhibits the creation of bacterial Cell walls. The practical point is that it will cause a zone of clearing around it's application site (usually with an impregnated paper disk) on a plate when applied before incubation, but after inoculation.