Antibiotic Assay

Hi ,

I have been trying to develop an antibiotic assay for amphotericin B using saccharomyces cerevisiae. The problem I am facing is, I am not getting a full lawn of growth of Saccharomyces. (I get dot dot type of colonies in the plate)

As per USP, the inoculum has to be 25% T at 580 nm and I can only use 1ml of inoculum to 100ml of media.

What are you guys getting ? Is there any tips ?