NIH Thioglycollate Broth (USP Alternative Thioglycollate Medium) NIH Thioglycollate BD Difco™ 500 g. Broth and Sterility Test Broth, which are the USP Alternative Thioglycollate Medium, are Fluid Thioglycollate Medium without the agar or indicator components. They are used for the same sterility test procedures except that anaerobic incubation is recommended rather than aerobic incubation. They also meet the requirements of the USP growth promotion test.