GUM LISTERIA MEDIUM

Many media with agar have been developed to isolate and cultivate Listeria monocytogenes. But when the colonies are observed by special optical illumination, due to opaqueness of agar there is interference in the colour and characteristics of the colonies. Hence Martin et al experimented with various formulations and found replacing the agar with self-gelling gellan gum resulted in the formation of a transparent medium. This helped in colonial visualization and identification of Listeria using Henrys Oblique Light System. The Henrys oblique light system consists of a 6-volt lamp projected onto a concave mirror to the underside of the stage of a stereomicroscope at 45? angle, which provides the transmitted oblique light.

for the isolation of Listeria monocytogenes from clinical and non-clinical specimens