Hi,
I am used to preparing LB plates with antibiotic solution added to liquid medium and pour the mix into the plate.. I was wondering: is it the same if I spread the antibiotic solution on the LB agar plate when this is already solidified? I ask this because I think it is quicker..Do you have useful suggestions/hints to carry out this procedure?
Thank you
Hi, you have to add the antibiotic solution to liquid medium before it being solidified. It is not recommended to spread the antibiotic solution on the LB agar plate when this is already solidified, that will give you incorrect results.
Hi
I have done that but just when i don't have another choice. It is because you must try to calculate the volumen that the LB agar will absorve the antibiotic. In my case i disolved 40 µg of Amp in 100 µl of PBS and spreaded very well. I use 90 X 15 mm plates and I always include a negative control. I do not recomend do this routinely because if you not spread very well the antibiotic you could have anormal growth.
Good luck
I agree with Dr. Stefan. His comment is highly appreciable.
Hi, you have to add the antibiotic solution to liquid medium before it being solidified. It is not recommended to spread the antibiotic solution on the LB agar plate when this is already solidified, that will give you incorrect results.
I am interested in this question, i will perform an experiment in which i will mix the antibiotic with the agar medium, then i will spread the inoculum into agar surface to obtain resistant colonies that i will count!
My question is, is this experiment will be called viable count or spread plate method? but if i put the antibiotic in a hole in the agar medium, will it be called agar well diffusion method?
if i am going to use the antibiotic therapeutic concentration say (vancomycin 1 g), how many micro-leter should i add to the agar medium that will be mixed or in a a hole?
Adding the antibiotic to the molten media is obviously preferable but in a pinch, spreading a small volume (i.e., 100 ul on a 100 mm plate) on the surface and giving it adequate time to absorb, seems to work just fine. I did this just yesterday with ampicillin in two control transformations (pBS and pBX) and it worked as anticipated... I have always spread X-GAL and IPTG on plates for blue/white screening, which is a little different because concentration is not as important, but same idea...
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