Purpose: The purpose of this study was to verify the performance of a 44-48 h, test strip-based method for the detection of Listeria monocytogenesin several food types and environmental surfaces.
Methods: For each food or environmental surface type (14), a set of 5 non-spiked and 20 low level-spiked samples were tested by the new lateral flow test strip method at 44 to 48 h using RapidChek NextDay media incubated at 30°C. All samples were culturally confirmed. Low level spike levels ranged from 1 to 4 CFU per analytical unit (25 g).
Results: A total of 280 low-level spiked samples were tested by the test strip method followed by cultural confirmation. The test strip method gave 212 presumptive positive results and the cultural method gave 211. There were 2 false positives and 1 false negative by the test strip method. All non-spiked samples were negative for Listeria monocytogenes. The method gave a sensitivity of 99.5% and a specificity of 98.5%. The overall Chi square was 0.000 (P> 0.999). Probability of Detection (POD) analysis showed no significant differences between the test method and the cultural method.
Significance: This new test strip method should provide the end user with a rapid and reliable tool for monitoring and controlling Listeria monocytogenes in a variety of foods and environmental surfaces. Since it uses the same enrichment broth as the RapidChek Listeria spp. NextDay method, when used in combination with that method, it should provide valuable additional information to the end user for the control of Listeria monocytogenes in food and in the food processing environment.