I am currently facing problem on determining the MIC of dosage form of antibiotics. I am using broth microdilution method for the determination of MIC. I have no problem with this method as I have been getting MIC using it. However, when I used the same method to evaluate the MIC of dosage form of antibiotics, if failed, all the dosage form antibiotics did not have antimicrobial activity. I have no experience in testing the antimicrobial activity of dosage form antibiotics, they are all in tablet form. Due to their form, I had to crush and grind them into powder form before dissolving them with solvents (as suggested by CLSI). After that, I diluted them to desired concentrations and performed broth microdilution in a two-fold manner to find the MIC. I had done this twice and I got negative result for the two independent experiments.
I have no idea what had gone wrong here and I seriously need some advice on this matter. Thanks.