Is it acceptable to perform microdilution sensitivity test to evaluate antimicrobial activity of synthetic compounds without using indicator as MTT or Resazurin or other reagents for detection of MIC. and depend only on ELISA reader results of changes in optical density at wave length 620nm before and after incubation to detect the MIC?
With noting that compounds under investigation as antimicrobial agents are water insoluble.
If no indicator is added, one can reincubate either: 10 uL culture frome each well, or perform a plate count with 100 uL culture. This would yield minimal bactericidal concentration, though.
Thank you a lot for your help, I will consider trying your suggestions, specially culturing 10uL from each well.
The standard broth microdilution MIC assay measures antibacterial activity as the lowest concentration at which no growth of the culture is observed. This can be evaluated by eye as a lack of turbidity in the well of the microdilution plate, or read using an absorbance plate reader to measure OD600.
Compounds are usually dissolved and serially diluted in DMSO and added to the assay plate before the bacterial culture is added. If the compound precipitates in growth medium, its turbidity might be mistaken for growth of the culture, so it is a good practice to prepare duplicate wells in which bacteria-free medium is added as a test for compound precipitation.
I agree with Adam... but you should consider that DMSO may affect bacterial growth, so the proper controls must be performed. Usually 1% of DMSO is employed since not adverse effects on bacterial growth are observed at this concentration. GOOD LUCK!
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