title: Use of the polymerase chain reaction for direct detection of Listeria monocytogenes in soft cheese.
abstract: The polymerase chain reaction (PCR) amplification technique was investigated as a tool for direct detection of Listeria monocytogenes in soft cheeses. Different sets of oligonucleotide primers were used, and parts of the L. monocytogenes Dth 18-gene could be amplified specifically when either a plasmid vector carrying the cloned gene or chromosomal DNA was used a template. The detection limit for L. monocytogenes in dilutions of pure cultures was between 1 and 10 colony-forming units. In extracts from soft cheeses containing L. monocytogenes DNA, the amplification was strongly inhibited. This inhibition could be reduced by an additional purification step. Despite this the detection limit showed a large variation, depending on the brand of cheese used. In some cheeses 10(3) cfu/0.5g could be visualized whereas in others the presence of 10(8) cfu/0.5 g did not yield a detectable quantity of amplified product.
authors.affiliation: National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Wernars
authors.forename: C J
authors.initials: CJ
authors.lastname: Heuvelman
authors.forename: T
authors.initials: T
authors.lastname: Chakraborty
authors.forename: S H
authors.initials: SH
authors.lastname: Notermans
mesh_terms: D001483:Base Sequence; D002611:Cheese; D004269:DNA, Bacterial / Q000032:analysis* / Q000737:chemistry; D005516:Food Microbiology; D005784:Gene Amplification; D008089:Listeria monocytogenes / Q000235:genetics / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests
chemical_list: D004269:DNA, Bacterial; D009841:Oligonucleotides