COMPETITIVE ENZYME IMMUNOASSAY FOR the DETECTION of SALMONELLA LIPOPOLYSACCHARIDE¹

Abstract

A competitive enzyme immunoassay for detection of Salmonella sp. was developed in order to provide a sensitive assay for same-day identifzcation of Salmonella sp. The assay could be performed in about 90 min and consisted of the following steps. Lipopolysaccharide derived from Salmonella typhimurium was used to passively coat polystyrene 96-well plates and tubes. A titrated amount of monoclonal antibody specijc for an outer lipopolysaccharide core epitope commonly found in Salmonella sp. was mixed with the prepared test sample prior to adding the mixture to the antigen coated matrix. Antibody bound to the immobilized antigen was detected with horseradish peroxidase labelled goat antimouse IgG (H&L chain).The analytical sensitivity of the assay was 3. I ng and 5.6 ng of lipopolysaccharide per ml for the plate and tube formats, respectively, if25% inhibition or less was considered negative. This cutof level was based on reactivity of unrelated monoclonal antibodies with S . typhimurium lipopolysaccharide and lipopolysaccharide from E. coli with the Salmonella specijc monoclonal antibody in the assay.

The detection of Salmonella using a combined immunomagnetic separation and ELISA end-detection procedure

“…However, there was no evidence of cross-reactivity with these non-Salmonella strains in the dot blot assays (Table 1). Therefore, the dot blot assay results con®rmed the genus speci®city of the M105 antibody and its potential in a rapid immunological presumptive Salmonella detection method (Tsang et al 1991;Nielsen et al 1993;. The M105 antibody was then used in a combined IMS-ELISA procedure using the same range of Salmonella and non-Salmonella strains.…”

“…Therefore, the dot blot assay results confirmed the genus specificity of the M105 antibody and its potential in a rapid immunological presumptive Salmonella detection method ( Tsang et al . 1991 ; Nielsen et al . 1993 ; Mansfield et al .…”

DEVELOPMENT OF AN INDIRECT WHOLE CELL ELISA FOR THE RAPID IDENTIFICATION OF SALMONELLA1

“…MAb M105 has been applied in a competitive ELISA for the detection of Salmonella LPS, and the rapid identification of this group of intestinal pathogens (Nielsen et a / . 1993;Tsang et al 1995).…”

“…Previously, we have produced and described a murine hybridoma monoclonal antibody (MAb), designated as M105, which is directed against a genus-specific epitope in the Salmonella lipopolysaccharide (LPS) antigen (Tsang et al 1991). A competitive enzyme-linked immunosorbent assay (ELISA) was also developed initially for the detection of Salmnella LPS antigen (Nielsen et al 1993). Later, the competitive ELISA was adapted for the rapid identification of Salmonella growing on agar media (Tsang et al 1995), and the method is proposed to have a role in the laboratory identification of this organism where resources for carrying out the elaborate biochemical and serological tests are not available.…”

Competitive Enzyme-Linked Immunosorbent Assay for Detection of Leptospira interrogans Serovar pomona Antibodies in Bovine Sera

“…The results of the assay were expressed as percent inhibition of the binding of the monoclonal antibody to the antigen (%I), which was calculated as described (11). Receiver operating characteristic (ROC) curve analysis (MedCalc Software, Mariakerke, Belgium) was performed on the ELISA results to determine the optimal cutoff point (at which the sum of the sensitivity and specificity values is highest) for distinguishing between positive and negative results.…”