Further study of strontium selenite and selenite F broths for the isolation of Salmonella typhi.

The efficiency of strontium selenite and selenite F broths in the isolation of S. typhi from 625 clinical stool specimens were compared. A total of 126 strains of S. typhi were detected. Of these, 96 (76%) were isolated with selenite F broth and 118 (94%) were isolated with strontium selenite broth. At the same time, the number of false positive isolates accruing to strontium selenite broth was less than that accruing to selenite F broth. The superiority of strontium selenite broth over selenite F broth was more obvious when relatively few typhoid bacilli were present in faeces, eg, after antibiotic therapy, or when stools had been left for prolonged periods at room termperature. In the isolation of S. typhi with strontium selenite broth, salmonella-shigella agar was found to be a better plating medium than xylose lysine desoxycholate agar.