A COMBINED PCR AND SELECTIVE ENRICHMENT METHOD FOR RAPID DETECTION OF LISTERIA-MONOCYTOGENES

Development of a routine detection assay for Listeria monocytogenes in foods that uses the polymerase chain reaction (PCR) and enrichment cultures was investigated. Oligonucleotide primers were chosen to amplify a 3' region of L. monocytogenes hlyA gene spanning a conserved HindIII site. PCR detection sensitivity for L. monocytogenes in dilutions of pure enrichment cultures was between 50 and 500 colony forming units. A short enrichment period before PCR amplification allowed detection of the organisms in a range of complex foods contaminated with 10(4) cfu/g. Detection sensitivity for the assay in the presence of chicken skin and soft cheese was determined at 10-100 cfu/g. Utilization of enrichment cultures and PCR allowed identification of the organism within 24 h or 2 days.