We have tested a compound for its antibacterial activity. here we found 75% inhibition of growth but no MIC was found. Can anyone help me with answering this query?
All bioactive compounds are not possessed antimicrobial properties. The MIC is the lowest concentration of a chemical that prevents the complete growth of a bacterium. you have varied the concentration of your bioactive compound, for eg: 1,2,3,4,5&6 mg/ml. from this concentration which concentration showed complete inhibition of bacterial growth, you choose as a MIC of your bioactive compound. eg: 1 shows 30%, 2 shows 60%, 3 shows 9%, 4 mg/ml shows 100%, 5 mg/ml shows 100% and 6 mg/ml shows 100%. so 4 mg/ml is MIC of your bioactive compound.
If your bioactive substance had antimicrobial activity, it should have MIC. You have to try more concentrations lower than you actually tested in narrow range or even in very narrow range to catch the MICs.
Enhance your concentrations, if its possess an antibacterial activity, you can theorically determine MICs
Thank you for your help. but we have tested in a varied range upto 500microgram . in that range we have found 75% inhibition of growth to be highest.
Which combinations of bacteria and antimicrobials did you test. To me, it looks, as if you had a mixed bacterial culture (with resistant and susceptible strains). Check genotypic or biochemical purity of your isolates.
we have tested Pseudomonas aeruginosa MTCC 424 starin against a napthoquinone.
I believe that If your bioactive substance had antimicrobial activity, it should have MIC. You have to try more lower concentrations and to control your solvant. .
i think the MIC value would be in the range higher than the ones we have tested. thank you to every one for their help.
In my opinion that much high amount of compound to determine MIC is not worth for drug discovery related process. Because there are limitation to achieve these concentrations inside the invivo systems. Nowadays people are looking for nanomolar activities with biologicaly safe molecules, So I suggest you to look for active molecule having fractional MIC in micrograms.
yes. that is why we tested upto 500micrograms of the compound. so may be the compound has an MIC above the tested value. but due to the limitation that high doses of the compound will not mimic the same thing invivo we have not tested beyond that
If you can't get a MIC in the range you use but still like to compare different compounds, then you can use IC50 instead (if you see growth inhibition but not a full killing).
than you for the suggestion actually we got an inhibition of 75% which was the highest. in that range.
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