Purpose: The purpose of this study was to validate under AOAC-Research Institute guidelines, a new lateral flow test strip-based method for the detection of Listeria spp. in RTE foods.
Methods: For each food type, a set of 5 non-spiked, 5 high-level spiked, and 20 low-level spiked samples were tested by the new lateral flow test strip method at 27 and 48 h and the respective cultural reference method. Low level spike levels ranged from 0.5 to 1.575 CFU per analytical unit (25 or 125 g).
Results: A total of 260 low-level spiked RTE food samples were tested by both methods. The number of confirmed positives for the RapidChek method tested at 27 h and 48 h, was 160 and 169, respectively, and 158 for the cultural reference method. All non-spiked samples were negative for Listeria spp. by all methods. The overall Chi-square was 0.032 (P = 0.858) and 0.995 (P = 0.316) after a 27 h and 48 h enrichment, respectively. Probability of Detection (POD) analysis showed no significant differences between the test method tested at either 27 or 48 h and the respective cultural reference method. These results indicated that the test method was equivalent in performance to the cultural reference method at both enrichment times.
Significance: The new test method should provide the end user with a rapid and reliable tool for monitoring and controlling Listeria species in Ready-to-Eat foods and minimize the introduction of Listeria monocytogenes-contaminated food products into commerce.