Performance of the Microplate BacTrace™ ELISA Technique for Detection of Foodborne Salmonella

Abstract

The developmental BacTrace™ ELISA system which recognizes a common structural antigen (CSA-1) in the cell wall of target microorganisms was tested with pure cultures and naturally contaminated foods. The system readily detected all of the 104 Salmonella test strains but produced 38 (52.1%) false-positive reactions upon examination of 73 nonsalmonellae cultures. Citrobacter freundii, Escherichia coli, and Proteus mirabilis were primarily responsible for erroneous results. Of 119 foods tested, 37 (31.1%) were found to contain Salmonella by a standard cultural procedure. Parallel BacTrace™ testing of the nutrient broth (NB), tetrathionate brilliant green (TBG43), and selenite cystine (SC35) broth cultures arising from standard cultural analyses identified 24 (64.9%), 25 (67.6%), and 31 (83.8%) Salmonella contaminated foods, respectively. Maximum sensitivity of the test system (89.2%) could be attained through combination of ELISA results from both TBG43 and SC35. False-positive reactions were particularly prominent with high moisture foods.