Rapid Confirmation of L. mono from Presumptives on Chromogenic Media

Fast identification of Listeria colonies

The Rap-ID L. mono™ is a simple, inexpensive and rapid confirmation test for L. monocytogenes isolated on chromogenic agar. The new Rap-ID L. mono allows the identification of colonies of L. monocytogenes isolated on chromogenic agar within 4 hours.

The introduction of chromogenic media for the isolation of Listeria spp. from food samples has improved the screening of colonies for the presence of L. monocytogenes. However, these media will not differentiate between colonies of L. monocytogenes and L. ivanovii both of which produce colonies on chromogenic media such as ALOA which are blue – green in colour with a surrounding halo. Standard methods therefore require the performance of additional testing to confirm that isolates grown on these media are L.monocytogenes.

Methods currently available to confirm the identification of these isolates include full biochemical identification which is expensive and requires 24 hours incubation, fermentation of the sugar rhamnose which also requires 24 hours incubation, or alternatively, molecular methods which will provide same day results, but are expensive and not available to all laboratories.

The Rap-ID L. mono provides a simple, rapid and inexpensive single tube test that offers an alternative to the above methods. The Rap-ID L. mono utilizes a chromogenic substrate that uniquely differentiates between L. monocytogenes and L. ivanovii.

Inoculated with a single colony, the Rap-ID L. mono produces a characteristic yellow coloured reaction with L. monocytogenes within a 4 hour incubation period, while colonies of L. ivanovii do not produce any colour change.

Procedure for using Rap ID L. mono


The Rap-ID L. mono should only be used from chromogenic agar media where confirmation of L. monocytogenes is required. In situations where either non chromogenic media are used, or the full identification of all Listeria species is required, it is recommended that the Microgen Listeria ID (MID 67) is used.

Listeria Identification


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Tags: Listeria, Environmental Monitoring, Identification, Listeria monocytogenes

Date Published: April 3, 2018

Source article link: Microgen Bioproducts Ltd. » company contact details

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