Reference material for the evaluation of a standard method for the detection of salmonellas in foods and feeding stuffs.

To evaluate a standard salmonella isolation method a reference material consisting of 0.2 g spray-dried milk inoculated with Salmonella typhimurium and contained in gelatin capsules was prepared. The organisms were distributed homogeneously between capsules, and their numbers were stable for 120 d when the capsules were stored in dry conditions at 4 degrees C. Addition of these capsules with or without food samples to pre-enrichment broth gave low and reproducible levels of Salm. typhimurium contamination without altering the pre-enrichment and without influencing the other bacterial flora present. As a result of an interlaboratory trial, the reference material indicated that the food and/or its competitive flora may have a negative influence on the detection of salmonellas.