Detection of Salmonella Typhimurium from Artificially Contaminated Poultry Feed and Animal By-Products

Abstract

Feed and animal by-products were artificially contaminated at different levels by adding measured amounts of S. typhimurium broth culture to 100-g quantities of feedstuff. The use of a nonselective pre-enrich-ment broth generally did not increase the number of Salmonella recoveries over the number obtained when the feedstuff was sampled directly into the enrichment medium. Selenite brilliant green sulfapyri-dine (SBG sulfa), selenite cystine, tetrathionate brilliant green, and tetrathionate were generally more effective than selenite and SBG enrichments for the recovery of S. typhimurium from artificially contaminated feedstuffs. Brilliant green agar was superior to BG sulfa, S-S, and bismuth sulfite agars as a plating medium. Streak plates were more satisfactory than those prepared by the spread-plate method. The 10 and 20% dilutions of feedstuff to enrichment medium yielded more recoveries of the test organism than the 2 and 6% dilutions. The use of multiple samples increased the chance of recovering the organism. S. typhimurium was recovered for a longer time from feedstuffs stored at 4[degree]C than from those stored at 21-29[degree]C, especially when the initial contamination was fewer than 10 organisms per gram.