Listeria confirmations are struck to selective and differential agar types. If typical colonies are present then the confirmation is positive. If there is no growth or only atypical growth present, the confirmation is negative.
Listeria speciations can be requested independently or they can be carried on from a positive Listeria confirmation by customer request. Listeria speciations start by being struck to the same selective and differential agar types. Typical colonies are carried on for additional confirmatory testing and resulting in a bacterial identification which will provide the species of Listeria.