Use of inexpensive O antisera as the detecting antibodies for Salmonella antigens in the polymyxin-cloth enzyme immunoassay.

The application of O antigen-specific antisera to the detection of Salmonella lipopolysaccharide (LPS) antigens was examined in an enzyme immunoassay using polymyxin-coated polyester cloth. The LPS antigens were extracted with deoxycholate and captured on polymyxin-cloth. A mixture of rabbit antisera to Salmonella O antigens was allowed to react with the captured antigens, and the reacted antibodies were detected by an anti-rabbit IgG-peroxidase conjugate. The assay gave positive results with 40 different Salmonella serotypes which represented more than 99.9% of the serogroups isolated from over 122,000 food, feed and environmental samples analysed at Laboratory Services Division, Agriculture Canada, from 1975 to 1990. Strong cross-reactivity with Staphylococcus aureus was eliminated by pregrowth of the organisms in the presence of sodium deoxycholate. The O antisera were commercially available and are more economical than monoclonal or affinity purified polyclonal antibodies.