I am working on antimicrobial effect of CBD (Cannabidiol). As it is insoluble in water, I prepared a stock of 500 mg/ml (in DMSO). Now I have two problems:
1- I can not dissolve more than 500 mg in 1 ml of DMSO (It would become too dense and insoluble)
2-More important, When I pour 100 μl of the stock in the 100 μl of the culture media (Muller Hinton agar) it would shrink and would not dissolve.
A concentration of 50% DMSO would kill or inhibit the growth of most microbes on its own without any additional antimicrobial compounds, anyway. That's the case for the vast majority of solvents at such high concentrations (except water obviously).
Hello, I had the same problem when I was doing my bachelor degree thesis.
I would recommend switching from agar dilution method to microdilution method.
The advantages are quite useful: when you dilute the compound in DMSO, let's say to a 400 mg/mL, you could use this stock to evaluate lesser concentrations (i.e. 4, 8, 16, 32, 64 ug/mL)
In this way, you avoid the bactericidal effect of DMSO or ethanol.
I would also recommend you to read document M07-A10: Methods for Dilution Antimicrobial Susceptibility Tests for Aerobic bacteria. In this document you can find the techinical details for microdilution methods
Greetings from Mexico!!
Arturo Reyes-Gualito Dear Arturo,
Thanks a lot for your professional answer. I do perform broth microdilution.
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