Anyone who is familiar with Gramicidin (antibiotic) assay? I have been performing this test for quite a while, but I could not come up with a valid result. I am using USP as my reference for the procedure (Spectrophotometry). The problem is, the turbidity of my assay do not have a trend even if I increase the concentration of the antibiotic used for the Standard. I am working with a pure culture of Enterococcus hirae, and all the materials used was sterilized, so I am confident that my problem with turbidity is not caused by contamination. Any insight will be highly appreciated. Thanks in advance.
