Rapid Enumeration of Listeria monocytogenes in Artificially Contaminated Cabbage Using Real-Time Polymerase Chain Reaction

Authors: Hough A.J.1; Harbison S-A.2; Savill M.G.1; Melton L.D.3; Fletcher G.4

Source: Journal of Food Protection®, Volume 65, Number 8, 1 August 2002 , pp. 1329-1332(4)

Publisher: International Association for Food Protection

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Abstract:

A quantitative real-time polymerase chain reaction (PCR) detection method specific for Listeria monocytogenes was developed, and studies involving pure culture showed that the response of the assay was linear over 7 log10 (log) cycles. The method was then applied to the detection of L. monocytogenes artificially inoculated onto cabbage, a vegetable chosen because it is a major component of coleslaw, which has been associated with an outbreak of listeriosis. After being allowed to attach to the food, cells were washed from the cabbage leaf surface and recovered by centrifugation. The DNA was purified by an organic solvent extraction technique and analyzed by real-time PCR. In this matrix, the method again produced a linear response over 7 log cycles from 1.4 × 102 to 1.4 × 109 CFU of L. monocytogenes in 25 g of cabbage, and analysis of the reproducibility of the system showed that log differences in L. monocytogenes numbers added to cabbage could be reliably distinguished. The system allowed quantitative results to be obtained within 8 h and was relatively inexpensive, showing good potential for routine analytical use.

Language: English

Document Type: Research article

Affiliations: 1: Christchurch Science Centre, Institute of Environmental Science and Research, P.O. Box 29 181, Christchurch, New Zealand 2: Mt. Albert Science Centre, Institute of Environmental Science and Research, Private Bag 92 021, Auckland, New Zealand 3: Food Science Programme, University of Auckland, Private Box 92 019, Auckland, New Zealand 4: New Zealand Institute for Crop and Food Research Limited, Private Bag 92 169, Auckland, New Zealand

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