Recovery of Salmonella spp. from refrigerated preenrichment cultures of dry food composites.

Refrigerated preenrichment 72 h and selective enrichment cultures arising from 25 g analytical units of dry foods can be used to increase the analytical flexibility and productivity of laboratories for the detection of foodborne Salmonella spp. by AOAC method 994.04. Results of this intralaboratory study using artificially contaminated dry foods validate the extended application of the refrigerated preenrichment approach to dry food composites (375 g). All samples found to be contaminated by AOAC/Bacteriological Analytical Manual methods were identified readily from the homologous, refrigerated preenrichment broth cultures. This extended application of the refrigeration approach was recently adopted First Action by AOAC and was included as a modification to method 994.04. In addition, ancillary work on the diagnostic value of prolonged (48 h) incubation of lysine iron (LI) agar as described in the AOAC Official Method 967.26 led to a recommendation that the 48 h period of incubation be revoked in favor of a 24 h incubation of inoculated LI medium.