Purpose: The purpose of this study was to validate the performance of a new 24-h lateral flow test strip-based method for the detection of Listeria spp. on environmental surfaces (stainless steel, plastic, rubber, and painted concrete) under AOAC-Research Institute guidelines.
Methods: For each surface type, 5 non-spiked, 5 high level-spiked, and 20 low level-spiked environmental surfaces were tested by the new lateral flow test strip method at 24 and 40h and the USDA-FSIS cultural reference method. One surface type (stainless steel) was also validated by an Independent Laboratory. Inclusivity/exclusivity studies evaluated 50 Listeria strains and 35 non-Listeria bacterial strains.
Results: A total of 100 low-level spiked surfaces were tested by both methods. The number of confirmed positives for the RapidChek method tested at 24h and 40h, was 58 and 61, respectively, and 63 for the USDA-FSIS cultural reference method. All non-spiked surfaces were negative for Listeria spp. by all methods. The overall Chi-square was 0.520 (P = 0.471) and 0.084 (P = 0.772) after a 24h and 40h enrichment, respectively. Probability of Detection (POD) analysis showed no significant differences between the test method tested at either 24 or 40h and the USDA cultural reference method. These results indicated that the test method was equivalent in performance to the reference method at both enrichment times. The method showed 100% sensitivity and 100% specificity for Listeria spp.
Significance: The new lateral flow test strip-based method should provide industry with a rapid and reliable tool for monitoring and controlling Listeria species in the food processing environment and minimize the contamination of food products by Listeria monocytogenes.