I have determined MIC at > 90 % cellular inhibition using 1 x 10^5 CFU/ml for MTB. I would like to predict how much of my antimicrobial peptide I would require to achieve the same inhibition using 1 x 10^7 CFU/ml.
My idea is to calculate the amount of molecules I have present and determine the ratio of molecules to the amount of cells inhibited at 1 x 10^5 CFU/ml. I would then apply this ratio for 1 x 10^7 CFU/ml and determine the amount of drug required.
Could this work?
Can an I test this with OD readings? I know my drug is bacteriostatic.
thanks.
You got 90% growth inhibition, did you try with more concentration compound to see 100% inhibition. If you have 100% inhibition data then prediction might be easy. Another issue with OD is, since it is an indirect method, sometimes there may be chance of 5% error, use plate count method (plate the sample after the antimicrobial assay) for confirmation and you can also compare the OD % results with the plate count results.
I would like to use a method that will by pass plate counting etc. Something that can just give an idea that it is working?
I thought using OD readings, I could show a difference in control vs treated. I don't need to determine exactly what the MIC.
I don't understand your first sentence. MIC is determined as the minimum antibiotic conc. that results in a reduction in 3log10 with a starting cell no. of 1x10^5 cfu/ml.
At this cell no. the OD is already very low so when you have a reduction to 10^2 cfu/ml I doubt you will get OD readings which are accurate. Therefore I do not recommend using a spectrophotometer for this analysis.
However, the question you pose about stoichiometry between antibiotic conc. and starting cell no. is interesting. Please let me know your results after you carry out the experiments.
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