The purpose of the Growth Promotion Test is to determine the suitability of culture media. The medium is challenged with a small number of microorganisms to assure the nutritive properties. The test is described in USP Chapter : Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests, USP Chapter : Microbiological Examination of Nonsterile Products: Tests for Specified Substances and USP Chapter : Sterility Tests.