Inadequacy of Selective Plating Media in Field Detection of Salmonella

The laboratory isolation of Salmonella began approxhately a century ago. Since that time there have been numerous reports in the scientific literature comparing the efficacy of various media and incubation conditions. An important part of the Salmonella laboratory procedure is the selective plating agar. Many of the currently used media were developed for the clinical microbiologist, and clinical samples have been used for the initial evaluations of these media [l]. Although these plating media were not initially developed for isolating Salmonella from environmental sources (and more specifically, poultry sources), several published reports have evaluated selective plating media efficacy with poultry samples [2, 3, 4, 51. However, the conflicting results of these past studies render them of limited value to theSalmonella researcher. It is rare to find any two papers that recommend the same plating medium on the basis of efficacy. One report may indicate that a certain plating medium is best, and another will report that the same plating medium was the poorest performer of those tested. Therefore, the objective of this paper is not to compare media, but rather to demonstrate the inability of many commonly