tailieunhanh - International journal of food microbiology

Any one of the media evaluated can interchangeably be used as an obligatory isolation medium for the detection and enumeration of L. monocytogenes in foods, and for the detection in feed-stuffs. The L. monocytogenes specific plating media that were evaluated shorten the time of analysis and significantly reduce the work load. The detection of positive samples mostly after Half-Fraser enrichment, reduces the analysis time further, and makes it possible to skip the secondary enrichment. However, secondary enrichment cannot be totally left out, because samples with low levels of L. monocytogenes, with high levels of competing flora, and with injured L. monocytogenes, do need secondary enrichment. | International Journal of Food Microbiology 124 2008 154-163 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage locate ijfoodmicro Validation of NMKL method No. 136 Listeria monocytogenes detection and enumeration in foods and feed S. Loncarevic a M. 0klanda E. Sehica . Norlia T. Johansson b a Section for feed and food microbiology National Veterinary Institute 750 Sentrum 0106 Oslo Norway b Department of Animal Diseases and Food Safety Research Microbiology Research Unit Finnish Food Safety Authority Evira Mustialankatu 3 00790 Helsinki Finland ARTICLE INFO ABSTRACT Article history Received 20 December 2007 Received in revised form 17 March 2008 Accepted 17 March 2008 Keywords Listeria monocytogenes Validation Detection Enumeration A collaborative study was organised to define the performance characteristics of the revised NMKL Method Listeria monocytogenes. Detection and enumeration in foods . Chromogenic L. monocytogenes specific plating medium Agar Listeria according to Ottaviani and Agosti ALOA was introduced in the revised method in order to improve the sensitivity and specificity of the method and to shorten the analysis time. Efficacy of ALOA One Day from AES ready-to-use agar in bottles Listeria Chromogenic Agar Agosti and Ottaviani Listeria agar from Lab M LCA dehydrated powder Chromogenic Listeria Agar Plates from Oxoid OCLA ready-to-use plates and L. monocytogenes blood agar medium LMBA from Lab M dehydrated powder were tested. Three types of food matrices vacuum-packed hot-smoked salmon soft cheese and cooked ham and one feed matrix wheat grain inoculated with two levels of L. monocytogenes with or without L. innocua were used in the study. A total of 24 samples were analysed both in the detection and enumeration part of the study by 18 and 17 Nordic laboratories respectively. The sensitivities of ALOA LCA OCLA and LMBA in the detection of L. monocytogenes in food .