Rapid results from Listeria test

Earlier this week we reported on the online launch of a database containing 20 years of research on the food-borne pathogen Listeria​. Today, a new rapid Listeria​ test from UK company Oxoid claims to provide 'peace-of-mind' in food testing laboratories.

With the launch of O.B.I.S. mono, Oxoid has extended its O.B.I.S. (Oxoid Biochemical Identification Systems) range of rapid colourimetric tests. This new biochemical test differentiates Listeria monocytogenes​ from other Listeria​ species on standard diagnostic culture media, reports the company.

Due to their similar appearance on Listeria​ selective media, Gram-positive, catalase positive, oxidase negative colonies could be one of a number of Listeria​ species or even a different species altogether, relates the company. If the presence of Listeria monocytogenes​, one of the most significant food-borne pathogens, is suspected, further lengthy identification procedures are required. In the meantime, product release is delayed and plant-cleaning procedures may be initiated at considerable cost to the manufacturer.

O.B.I.S. mono aims ' to offer valuable peace-of-mind at this critical point'​, reports the company, by indicating rapidly whether suspect colonies are Listeria monocytogenes​ or not.

All Listeria​ species, with the notable exception of Listeria monocytogenes, possess D-alanyl aminopeptidase (DALAase) activity, writes Oxoid​. O.B.I.S. mono was developed to detect this enzyme using a non-carcinogenic substrate, D-alanyl-7-amido-4-methylcoumarin (DALA), in response to health concerns associated with b-naphthylamines (potent carcinogens traditionally used to detect aminopeptidase activity).

The company claims that in trials, O.B.I.S. mono demonstrated 100 per cent sensitivity and 99 per cent specificity with naturally contaminated samples, and 100 per cent sensitivity and 98 per cent specificity with pure cultures compared to the Gold Standard method.