blue, diameter less than 3 mm, regular and white halo
Listeria monocytogenes is a widespread bacteria, present in the soil, sewage or faecal matter. Its ability to form listerial biofilms on contact surfaces makes it difficult to eliminate. This pathogen can cause serious food poisoning and is therefore frequently a microbial Q.C. target in food processing facilities to avoid food contamination. Contamination can occur at all steps of the food manufacturing chain from raw materials to place of consumption.
CHROMagar™ has developed a rapid method for the detection of L. monocytogenes in food stuff, comprising the following simple steps (1) enrichement in half frazer broth for 24h, (2) isolation in CHROMagar™ Listeria, (3) confirmation of Listeria monocytogenes species in CHROMagar™ Identification Listeria.
1. Clear Reading : Since L. monocytogenes and L. innocua have similar biochemical properties, they cannot be differentiated on traditional media (Palcam, Oxford). CHROMagar™ Listeria helps to easily differentiate Listeria monocytogenes from other Listeria directly at the isolation step: the colonies are blue and surrounded by a white halo due to a specific phospholipase activity.