The development of a formulation for radiation-sterilizable urea broth.

Urea broth, a medium used for the identification of the genus Proteus, was sterilized by gamma radiation, using radiation doses of 1-1.5 Mrad. The radiation-sterilized medium, modified by adding sodium ascorbate and increasing its phenol red and yeast extract content, performed as well as the commercial formulation prepared aseptically, when tested with different Proteus and non-Proteus species. Gamma-irradiation appears to be an attractive and economical method for sterilizing nutrient media in sealed tubes, avoiding the risk of contamination during processing.