The N-Light™ Listeria spp. test is based on the detection of an enzyme which may also occur in some other bacteria which can grow in the NEMIS broth. Therefore, there is a certain likelihood of false positive test results. In field trials conducted in food factories, 30 to 60% of the positive N-Light™ Listeria spp. tests could be confirmed in follow-up analyses by cultural and molecular methods as Listeria spp. Other species found in positive tests were Vagococcus fluvialis, Bacillus saprophyticus, Niallia circulans, Mammalicoccus sciuri and Enterococcus thailandicus. The fraction of false positives obtained with the N-Light™ Listeria spp. test is lower than that of other rapid on-site tests which mostly detect beta-glucosidase activity, an enzyme frequently occurring in a broad range Gram positive bacteria. For a screening assay intended for fast and easy monitoring of the Listeria risk in a factory, the accuracy is considered as good.
