Relative Effectiveness of Selenite Cystine Broth, Tetrathionate Broth, and Rappaport-Vassiliadis Medium for the Recovery of Salmonella spp. from Foods with a Low Microbial Load

Abstract

The relative effectiveness of Rappaport-Vassiliadis (RV) medium, selenite cystine (SC) broth, and tetrathionate (TT) broth for the recovery of Salmonella spp. from foods with a low microbial load was determined. RV medium made from its individual ingredients and incubated at 42°C was compared with a commercial preparation of SC broth, incubated at 35°C, and TT broth incubated at 35 and 43°C, for the recovery of Salmonella spp. Twenty-one artificially contaminated food types that included dairy foods, spices, and egg products, as well as other low-microbial-load foods, were analyzed. The foods were inoculated with single Salmonella serovars at target levels ranging from 0.04 to 0.4 CFU/g. No significant differences (P ≤ 0.05) among the selective enrichment broths for the recovery of Salmonella spp. from 18 of the foods were observed. Significantly fewer Salmonella-positive test portions of gelatin, guar gum, and nonfat dry milk were recovered with RV medium than with SC broth incubated at 35°C and TT broth incubated at 35 and 43°C. TT broth incubated at 35°C recovered the greatest number of Salmonella-positive test portions. For the recovery of Salmonella spp. from foods with a low microbial load, it is recommended that TT broth incubated at 35°C and RV medium incubated at 42°C be used.