Rapid Test for Listeria

A new biochemical test differentiates Listeria monocytogenes from other nonpathogenic Listeria species in only 10 minutes, enabling doctors to test for the presence of a potentially fatal pathogen at a much earlier stage.

Infection with Listeria monocytogenes, called listeriosis, is rare, but the mortality rate is high. Those most at risk are immunocompromised individuals, the elderly, pregnant women and their unborn babies, and neonates. The diagnosis of listeriosis involves culturing the organism from blood, cerebrospinal fluid, or fecal specimens. After enrichment and culture on a Listera-selective medium, further steps are required to confirm the presence or absence of Listeria monocytogenes since other Listeria species have similar colonial appearance but do not cause human disease. This confirmation requires several days.

The new test provides an answer in only 10 minutes. Called O.B.I.S.mono, the test detects D-alanyl aminopeptidase (DALAase), an enzyme produced by all Listeria species with the exception of Listeria moncytogenes. D-alanyl's presence is indicated by a vivid color reaction. In the absence of that reaction, the suspect colonies are presumptive Listeria monocytogenes. The O.B.I.S. mono test demonstrated 100% sensitivity and 99% specificity in trials with naturally contaminated samples, and 100% sensitivity and 98% specificity with pure cultures compared to American Proficiency Institute (API) testing. The test is the product of Oxoid Limited (Basingstoke, UK).




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