Monoclonal antibody-based cross-reactive sandwich ELISA for the detection of Salmonella spp. in milk samples

An immunogen consisting of Salmonella lipopolysaccharide and bovine serum albumin was prepared by periodate oxidation. Mice sera cross-reacted with strains of the genus Salmonella. Monoclonal antibodies (mAbs) against the Salmonella lipopolysaccharide core structure were obtained after cell fusion. Based on mAb 6E8, a cross-reactive sandwich enzyme-linked immunosorbent assay was developed. The detection limit of different strains in the genus Salmonella ranged from 1.56 × 10⁶ to 1.25 × 10⁷ colony-forming units ml⁻¹. No cross-reactivity was observed with other bacterial strains tested, including Cronobacter sakazakii, Escherichia coli O6, E. coli strain O157 : H7, Campylobacter jejuni and Listeria monocytogenes. Samples of bovine milk spiked with 1 colony-forming unit ml⁻¹Salmonella spp. were analysed following enrichment for 24 h.