In qualification testing for the USP <61> method on tablets containing HPMC, I've experienced inability to distinguish individual Ps aeruginosa colonies as early as Day 1 at 32°C on TSA.
The positive control plates show a range from 18-30 CFU, with colony sizes of 0.5mm to 1.5mm, while the test sample plates have instead a film of growth, sort of like one very large, irregular colony border ,with indistinguishable individual colony borders.
Has anyone ever had this experience before?
Thank you in advance,
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