The detection of the haemolytic activity is fundamental to the identification of Listeria species (in particular L. monocytogenes and L. ivanovii).

The Microgen® Listeria ID system uses this test in combination with 11 additional carbohydrate utilization tests (based on ISO standard methods) for the identification of Listeria species.

The haemolysin test is simply performed by adding 1 drop of the specially stabilized sheep red blood cells comprising the haemolysin reagent to the last well (well 12) of the Microgen® Listeria ID test panel. If the organism being identified produces haemolysin, the red blood cells will rapidly be lysed and the cellular contents released into the suspending medium and the contents of the well will appear as a homogeneous red/ brown solution.

Alternatively, if the organism being identified does not produce haemolysin, the stabilized red blood cells will remain intact. These cells will settle to the bottom of the microwell forming a distinct red layer with a clear.

The haemolysin test has recently been improved resulting in a significant increase in its sensitivity and greater ease of interpretation.