A fluorogenic assay for rapid detection of Salmonella was evaluated in various foods. The assay involves an enrichment culture of Salmonella in Dulcitol-Malachite green- Novobiocin medium (0.5% bactotryptone, 0.5% dulcitol, 0.16% KH_2PO_4, 0.8% NaCl, 4.0% MgCl_2*6H_2O, 0.01% malachite green, 1 /*g/ml novobiocin, pH 5.0) for 22 hr at 30℃ with shaking. After the cultivation, alanine-arylamidase activity of the bacteria was measured by fluorescence using the fluorogenic substrate alanine-‘i-aminomethylcoumarin. Forty two contaminated samples of 7 foods were examined for Salmonella by the fluorogenic assay. The results were then compared with those obtained by the conventional Deoxycholate-Hydrogen sulfide-Lactose agar plating assay. In the case of raw chicken, raw pork, autoclaved pork and frozen hamburg, Salmonella-cell number and the activity was correlated. The correlation coefficient was 0.77. However, the sensitivity of the assay was lower in samples such as raw egg, eggroll and smoked pork ham than in samples described above. The low sensitivity in raw egg seems to be caused by its low concentration of nutrients essential for the growth of Salmonella, but not by growth inhibitors such as lysozyme and conalbumin present in it. The present assay can detect 10 CFU of Salmonella per gram of sample after a 24 hr-total-detection time though the application of this assay is limited to several kinds of foods.
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