Antibacterial activity was performed against gram positive and gram negative bacteria using 0.05M HCl as control. in gram positive bacteria control has not shown any significant activity whereas it has shown slight activity against gram negative bacteria . Pls suggest me how can i Calculate the % of inhibition in this case
Did you determine the antibacterial activity on agar ( by determining the diameter of zone) or in broth ( MIC)
It is not the usual practice to report % inhibition of growth of rapidly-growing bacteria. The usual practice is to report the minimal inhibitory concentration (MIC) of the substance. The reason for this is that it is usually easy to tell in a set of 2-fold serial dilutions of the inhibitor which was the lowest concentration that prevented growth.
In contrast, if you try to make a plot of growth (either by colony forming units or optical density) versus concentration, it will usually show a very steep transition from full growth to no growth within one or two dilutions, making it difficult to calculate the 50% inhibition concentration (IC50) accurately.
So, since you have already measured the MIC, the measurement is complete.
In your case the first question is why the control gave negative response?. This means that there was no growth of the bacteria under the normal conditions for bacterial growth if you add only water instead of the antibacterial agent. I suggest to do the experiment again under the "suitable environmental conditions" for the bacterial growth under test and then we can discuss the results.
Yes. My zone of inhibition is also not clear.
But by pixel from the pictures you can measure the ZOI if you like. All around the disc, you can measure different ZOI and then do average. I think it will help.
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