ICMSF methods studies. IX. The influence of selective enrichment broths, differential planting media, and incubation temperatures on the detection of Salmonella in dried foods and feed ingredients

Abstract

Ninety-eight dried foods and feed ingredients were analyzed for Salmonella using tetrathionate brilliant green (T) and selenite cystine (S) broths incubated at 35.degree. and 43.degree. C. The 4 enrichment cultures for each sample were subcultured in duplicate onto brillant green (BG), Salmonella-Shigella (SS) and bismuth sulfite (BS) agars, 1 plate of each being incubated at 35.degree. C, the other at 43.degree. C. Salmonellae were isolated from 44 of the 98 samples. Differences in the Salmonella recovery rates from the 4 selective enrichment conditions were not significant. There was a trend toward a higher proportion of Salmonella colonies on the selective media when the enrichment broths were incubated at 43.degree. C, although the differences were significant only with BG and SS subcultured from T. While the 4 enrichment systems were not significantly different, the trend toward a higher proportion of Salmonella colonies on the differential media subcultured from 43.degree. C enrichment broths indicates an advantage to incubation at the elevated temperature. Incubation of selective agars at 35.degree. C was best because at 43.degree. C Salmonella recovery was significantly reduced. Detection of salmonellae on BS was significantly better than on BG or SS.