Relationship between sample weight, homogeneity, and sensitivity of fecal culture for Salmonella enterica

Office of the Chief Veterinary Officer, Agriculture, Fisheries, and Forestry-Australia, PO Box 858, Canberra ACT 2601, Australia.

When testing for organisms such as Salmonella enterica in an aliquot taken from a sample of feces, the sensitivity of the procedure is considerably higher if the organisms are randomly distributed in the feces than if the same concentration of organisms is in random clusters. However, dispersing the clusters (by homogenizing the sample before taking the aliquot) increases the sensitivity. The increase depends on the weight of the fecal sample taken.