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Ampicillin LB agar reheating and reusing - (Jan/26/2017 )

Hey everybody!

So that may be a dumb question, but I want to be really sure about that.

I've prepared 500ml LB agar medium yesterday and added ampicillin after the autoclave program, when the solution was at 50 degrees. I did not use all of the LB agar (containing Amp), so I'm currently storing it in the fridge.

Of course it's solidified and I know, that I can heat it up again in order to pour new plates.


My question is: Can I assume, that all of the ampicillin is degraded after 5 min of microwaving? I think it is not heat-stable at all, so I should be fine adding the amount of ampicillin, which I would normally add, if there was no antibiotic added before. Do you think I'm on the safe side with that or do you think there might still be some residual Amp present in the LB agar?


Your help is highly appreciated! :)




-Mirco G-

I tend to err on the side of compulsiveness....while it may work to just reheat, or reheat and add additional amp, I just wouldn't be willing to risk a week's worth of downstream work on the hope that you are working with what you think you should be...especially given the somewhat sensitive nature of amp compared to other antibiotics.


LB, agar and amp and relatively cheap as far as lab reagents go. I would make fresh new media and be sure that any colonies I work with later are legit.


Other's may have differing opinion though.


I agree with Labtastic. I would also be concerned about the potential of adding minor inhibitory compounds from the break-down of the ampicillin.