ICMSF methods studies. II. Comparison of analytical schemes for detection of Salmonella in high-moisture foods

Twenty-one naturally contaminated high-moisture food samples were analyzed to compare the relative efficiency of using thirteen 25-g, three 108.3-g, one 325-g, and one 500-g subsamples in recovery of salmonellae. In addition, recovery by preenrichment in lactose broth was compared with direct selective enrichment in selenite cystine and tetrathionate brilliant green broths. Analysis of preenriched large lumped subsamples, prepared by combining multiple 25-g subsamples, detected positive samples as effectively as the analysis of individual 25-g subsamples. In the analysis of 25-g subsamples, direct enrichment detected as many positive "lots" as preenrichment, but in the analysis of lumped subsamples, direct enrichment gave dramatically reduced recovery. Nevertheless, directly enriched 25-g subsamples resulted in a significantly lower rate of recovery than preenriched subsamples. The results indicate that analysis of a single lumped 325-g preenriched subsample is as efficient in the recovery of salmonellae ...