What does NCCLS recommend? Is the pre-diffusion step a recommended step in the disk diffusion assay? What is its rationale? To standardize the methodology, you do as suggested by the reference protocol, otherwise you make some improvisations here and there and tell us why. I have gone through the NCCLS protocol for disk diffusion for God-knows-how-many-times and I have not seen this pre-diffusion step
We kept plates at 4 degree in refrigerator so that the compound (antimicrobial agent) will easily diffuse into the agar medium and also no bacterial growth will occur at this temperature. But we do not invert the plates.
dear dr. first I dont understand your Q. so if you mean when putting antibiotic disk on agar so it should kept without inverting it but if you sure that the disk is matured and adhere to the agar surfaces by leaving the plats for about 10 min at room temp. then you should incubated it by inverting and after complete the incubation period you can preserve it in refrigerator