( Nikolaj Schmolker Finta...)Use of the DCode System to Detect the Food-Borne Bacterial Pathogen Listeria monocytogenes

Nikolaj Schmolker, Fintan van Ommen Kloeke and Gill Geesey, Department of Microbiology and Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717-3980

Abstract
Amplification of a region of the 16S rRNA gene of L. monocytogenes, Listeria innocua, and Listeria seeligeri by the polymerase chain reaction (PCR)* using primers that anneal to conserved sequences, yielded multiple copies of gene fragments that, when evaluated by density gradient gel electrophoresis (DGGE), produced banding patterns that distinguished L. monocytogenes from the other two species. One set of primers yielded fragments from the 16S rRNA gene(s) of L. monocytogenes that gave rise to two distinct DGGE bands: one of which co-migrated with the single bands produced from the other two species, and another not produced by the other two species, which migrated to a location higher on the gel than the other band.

Introduction
Detection and quantification of food-borne pathogenic bacteria such as Listeria monocytogenes have historically depended on culture techniques that require an incubation period of several days. Use of procedures that involve culture and incubation for positive identification of causative agents of disease delays implementation of preventive action to control the spread of disease. New molecular techniques that provide positive identification of the causative agent of disease without the need to culture the suspect microorganism(s) facilitate a more rapid response to the problem. Using the polymerase chain reaction (PCR), positive identification of L. monocytogenes can be established within 1248 h of sample collection.^1-3

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