Detection of Listeria monocytogenes in foods using a hydrophobic grid membrane filter and chromogen-labelled DNA probe method.
1995
Yan W. | Matik N. | Peterkin P.I.
The conventional HPB method for identifying Listeria monocytogenes from foods involves lengthy enrichment, selection and biochemical tests. In this study, the efficacy of a more rapid DNA hybridization protocol in combination with electronic data detection system using hydrophobic grid membrane filters (HGMFs) for the detection of L. monocytogenes for different foods was determined and compared to that of the conventional HPB method. A 3.1 Kb BamHl restriction fragment, containing the coding sequence of the listeriolysin 0 gene, was labelled with digoxigenin dUTP by random priming and used as probe in hybridization studies. A total of 200 food samples encompassing 8 high-risk food groups (pate, ground poultry, ground beef, ground pork, soft and semi-soft cheese, packaged vegetable, frozen cooked shrimp and jellied meat products) were screened for the presence of L. monocytogene by the two methods. Results showed that the 3.1 kb probe was highly specific in discriminating L. monocytogene for other Listeria sp. present in many of the samples tested. Overall, approximately 16 percent of the 200 samples tested positive for L. monocytogenes. Results obtained showed a food effect with the HGMF DDA probe method on any of the food groups tested. The HGMF chromogen-labelled DNA probe method was shown to be an efficient and reliable alternative to the conventional HPB protocol for detecting L. monocytogenes in foods.
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