Application of monoclonal antibodies to dulcitol 1-phosphate dehydrogenase for rapid detection of salmonella

Monoclonal antibodies raised against dulcitol 1-phosphate dehydrogenase of Salmonella typhimurium IFO 12529 were screened against 20 serotypes of Salmonella and 13 non-Salmonella bacteria. A sandwich-capture, enzyme-linked immunosorbent assay (sandwich ELISA) was developed for detection of Salmonella in food. The assay utilizes two monoclonal antibodies (DU12 and DU28) which show no cross-reactions with nonSalmonella bacteria. The limit of detection of the sandwich ELISA was about 1 x 10⁷ CFU/ml. After cultivation in a medium containing dulcitol at 37 °C for 18 h followed by the sandwich ELISA, 1 CFU of Salmonella was detected. Although a high inoculum level of E. coli interfered with the detection of Salmonella, the interference was minimized by using a selective dulcitol-magnesium chloride-pyridinesulfonic acid medium for enrichment. The novel ELISA procedure detected Salmonella in chicken filtrates inoculated with 1.4 CFU/50 ml and 1.3 x 10⁷ CFU/50 ml of E. coli within 25 h.