title: Comparative study of colorimetric and fully automated enzyme-linked immunoassay system for rapid screening of Listeria spp. in foods.
abstract: Two enzyme-linked immunoassay (ELISA) systems for rapid screening of Listeria spp. were compared for their use in analysis of spiked foods regulated by the U.S. Food and Drug Administration. The Tecra Listeria kit is a 48 h visual ELISA that detects Listeria spp. through colorimetry. It has been approved for first action by AOAC INTERNATIONAL. The Vitek immunodiagnostic assay system for Listeria (VIDAS LIS) is a fully automated 48 h ELISA that detects Listeria spp. by immunofluorescence. Fifty-two food samples were artificially contaminated with high (11-42 colony-forming units [cfu]/25 g food) and low (2-8 cfu/25 g food) levels of L. monocytogenes and screened by the 2 protocols. Unspiked samples were also assayed as negative controls. Six unspiked samples were found positive for Listeria spp. by both methods: 3 were identified as L. monocytogenes and 3 as L. innocua by official methods. Both ELISA methods detected all spiked samples. One unspiked sample was assayed positive by Tecra and negative by VIDAS LIS. No Listeria spp. were recovered when the sample was tested by the conventional method. No interference due to background fluorescence of food matrixes was observed in the VIDAS LIS method. Results suggest a modified VIDAS LIS preenrichment medium may be used in place of the VIDAS standard medium in the protocol.
authors.affiliation: U.S. Food and Drug Administration, Brooklyn, New York 11232, USA.
authors.forename: K F
authors.initials: KF
authors.lastname: Kerdahi
authors.forename: P F
authors.initials: PF
authors.lastname: Istafanos
mesh_terms: D001322:Autoanalysis; D003124:Colorimetry; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D005516:Food Microbiology; D008087:Listeria / Q000302:isolation & purification*; D013997:Time Factors