Field evaluation of the membrane filter-disc immunoimmobilization technique in the detection of salmonellae in egg products

Comparison of an LPS-specific competitive ELISA with a motility enrichment culture method (MSRV) for detection of Salmonella typhimurium and S. enteritidis in chickens

We report here evaluation of a competitive enzyme-linked immunosorbent assay (c-ELISA) for detection of Salmonella spp. in chicken organs and faeces. The c-ELISA used a monoclonal antibody (MAb), specific for a genus-specific epitope of the outer core oligosaccharide of salmonellae. Salmonella lipopolysaccharide (LPS) in samples competed with Salmonella LPS coated on microtitre plates, for binding to the MAb. Competition reduced binding of the MAb to the LPS on the plate and of the secondary antibody to the MAb hence reducing the chromogenic signal. Stable coating and minimal false positive were achieved by conjugating LPS to poly-L-lysine. The c-ELISA was compared with motility enrichment culture using modified semisolid Rappaport Vassiliadis (MSRV) medium, which detected less than 10(2) CFU/g, and did not allow migration of non-salmonella species. The c-ELISA detected 10(6) CFU of enriched culture or 10(2)-10(3) CFU of Salmonella/g of faeces. Its limit of detection was thus higher than that of MSRV culture and it had a sensitivity of 92.9% and a specificity of 96.7%.

Collaborative study on the use of motility enrichment on modified semisolid Rappaport-Vassiliadis medium for the detection of Salmonella from foods

A collaborative study was performed in 15 laboratories to evaluate the use of motility enrichment on modified semisolid Rappaport-Vassiliadis (MSRV) medium for rapid Salmonella detection in a variety of food products. The results of this procedure were compared with those obtained by the cultural procedure using Rappaport-Vassiliadis (RV) broth as selective enrichment and modified brilliant green agar for selective plating. The tests were performed with Salmonella reference samples (SRS) as well as with naturally contaminated food products. When SRS were used without added food the productivity of both MSRV and RV was 96%. When SRS were combined with reference samples containing competitive bacteria the productivity was 98% for MSRV and 95% for RV. In the tests with food samples the productivity of MSRV was 92% with SRS added to food and 96% with naturally contaminated samples, while the productivity of RV was 88% and 90%, respectively. Statistical analysis showed that there was no significant difference between the procedures.