Detection of Low Levels of Salmonella Species in a Variety of Food Matrices Using the Rapidchek Select Salmonella Test Method

Introduction: Controlling the spread of Salmonella throughout the entire food supply chain has proven very complicated because of the many potential sources of contamination. Testing for the presence of Salmonellaspp. has become a necessity for the food industry which creates a need for a flexible method that provides results in a timely accurate fashion and that has been validated on a range of both raw and processed foods.

Purpose: To validate the use of a commercially available test system for the detection of Salmonella species in a wide variety of food matrices.

Methods: 25g and 375g samples of the different food matrices were inoculated with a low level of Salmonella(Enteritidis ATCC 13076, Typhimurium ATCC 14028, or Montevideo ATCC 8387). The inoculum was held for 24 hours at 2 - 8°C for refrigerated foods. Samples for the test method were enriched in primary media, transferred to secondary media, and evaluated with test strips. All samples were confirmed using BGS and XLD agars.

Results: One hundred and twenty samples were analyzed in total for the 25 gram sample size and sixty samples were analyzed in total for the 375 gram sample size. All negative control samples were reported as negative (100% specificity).

Of the 110 low-level inoculated samples for the 25g sample size, eighty-two samples were detected with the test method and confirmed positive on XLD and BGS agars. For the 375g sample size, thirty-nine of 50 low-level inoculated samples were detected with the method and confirmed on selective agar plates. There were no false positive or false negative test results reported (100% sensitivity). The Chi-square for the results obtained by the test strip method and the cultural method was 0.00 (p=1.000).

Significance: The test system has been validated for use in several diverse sample matrices at 25g and 375g sample sizes.