RAPID DETECTION OF SALMONELLA SPP, IN FOODS BY COMBINATION OF A NEW SELECTIVE ENRICHMENT AND A SANDWICH ELISA USING 2 MONOCLONAL-ANTIBODIESAGAINST DULCITOL 1-PHOSPHATE DEHYDROGENASE

A rapid-detection method was developed for food-borne dulcitol-positiv e Salmonella spp. in foods that involves a new preenrichment and selec tive enrichment system and a sandwich ELISA using two monoclonal antib odies against dulcitol l-phosphate dehydrogenase. Preenrichment and se lective enrichment were in Enterobacteriaceae enrichment mannitol (EEM ) broth at 42 degrees C for 6 h and in a new dulcitol-magnesium chlori de-pyridinesulfonic acid-brilliant green-novobiocin (DMPBN) medium at 42 degrees C for 27 h, respectively. The cells were collected from the selective enrichment culture and suspended in 0.1 ml of 1 N NaOH for 2 min. The solution was neutralized with 0.1 ml of 2 M Tris-HCl buffer (pH 7.5) and the mixture was used as a sample for ELISA. The detectio n sensitivity of the ELISA was 10(5) CFU of Salmonella spp. per mi of culture. Competing non-Salmonella organisms in raw food did not interf ere with the detection of Salmonella cells even when present at 10(7): 1 (non-Salmonella: Salmonella ratio) in food. Nonmotile Salmonella gal linarum was detected by the ELISA. The minimum detectable number of in itial inoculum of Salmonella typhimurium was 0.69 CFU/25 g of raw chic ken after the preenrichment in EEM broth and the selective enrichment in DMPBN medium. The present ELISA method required a total analysis ti me of 36 h including the preenrichment and selective enrichment period s. The ELISA method was compared with a conventional cultural method f or the detection of Salmonella cells in 130 samples of raw foods. Of t he samples tested, 16 were Salmonella-positive and 114 samples were ne gative by both methods. False-positive and false-negative results were not encountered.