Recovery of Salmonella from refrigerated preenrichment and refrigerated enrichment media

Abstract

The productivity of the standard cultural procedure for the isolation of Salmonella using preenrichment in buffered peptone water (BPW) followed by inoculation into Rappaport-Vassiliadis (RV), tetrathionate (TBG) (Difco) and selenite-cystine (SC) (Difco) enrichment broths, was compared with that using preenrichment and enrichment cultures which had been held under refrigeration (72 h at 5–10°C). Seventy-seven of 251 samples of food products were found to contain Salmonella. Refrigerated preenrichment cultures inoculated into RV medium (43°C), TBG broth (43°C) and SC broth (37°C) yielded salmonellae from 93.5, 85.7 and 54.5% contaminated samples, respectively. Refrigerated cultures in RV, TBG and SC broths, inoculated onto three selective plating media, identified 100, 87.0 and 41.6% of the contaminated samples, respectively. The selective plating medium brilliant green deoxycholate agar was at least as productive as brilliant green sulpha agar and bismuth sulphite agar, when streaked from RV and TBG broths, but was less effective when streaked from SC broth.