Effective Enrichment-Plating Conditions for Detection of Salmonella in Foods.

The performance of tetrathionate brilliant green (TBG) and selenite cystine (SC) enrichments, and bismuth sulfite (BSA) and brilliant green sulfa (BGS) plating media was assessed on the basis of data on 2085 Salmonella -contaminated low and high moisture foods that were collected during a 6-year (1977 to 1983) study involving 22 laboratories. None of the eight enrichment- plating combinations considered identified all positive samples. TBG was markedly more sensitive than SC for detection of salmonellae in high moisture foods, where enrichment in TBG and plating on both BSA and BGS identified 92% of contaminated samples. Plating of SC enrichment cultures on the two agar media was substantially less productive (63%). With low moisture foods, TBG and SC rates of isolation varied by less than 10% under homologous conditions. Plating media did not affect method sensitivity. Identification of numerous contaminated samples by TBG or SC enrichment alone underlines the value of using multiple enrichment and plating media in standard methods.