Hey guys, I need to prepare 400 mL MacConkey + 1.0 mg/L cefotaxime. However, I don't know how to make the stock solution for this antibiotics. Can someone help? Thanks
You need 0.4mg antibiotic.
You must prepare your medium as described by producer, when your medium be cool about 40-45 cilicious you must added your antibiotic.
But it is better that you dissolved your medium and antibiotic and then filter it with 0.22 micrometer filter.
Thanks for the answer. Yeah I know I need 0.4mg antibiotics. But do I have to dissolve it into distilled water? If so, how do I do it?
no it is not necessary be dissolved into water. you add it directly.
but as i say the best way is filtering no autoclave.
Hi,
If you want to prepare a media of MacConkey and 1.0mg/l cefotaxime, first you need to know whether you wanted the media in solid or liquid/broth state. If you require it in the former, then you need Agar and if you needed the later, you don’t need agar to prepare the media.
However, most preparations of media depend on the constituents manufacturers prescriptions.
Anyway, this can be helpful:
MACCONKEY AGAR
Weigh 52g of MacConkey agar Power and dissolve in 1 litre of distilled water in a conical flask. After which you autoclave at 121 degrees Centigrade for 15 minutes to sterilize the medium. Allow to cool for about 47oC before dispensing aseptically into sterile Petri-dishes. After which you can add your antibiotics, 1.0mg/l cefotaxime.
MACCONKEY BROTH
Dissolve 35g of commercially obtained MacConkey broth powder in 1 litre of distilled water. Then sterilize the medium by autoclaving at 121 oC for 15 minutes. Allow to cool for about 47oC before dispensing aseptically into sterile Petri-dishes. After which you can add your antibiotics, 1.0mg/l cefotaxime.
Note: Addition of the antibiotics before autoclaving can denature the drug.
1.0mg/l cefotaxime is already in liquid form. But if it is in the solid form, what it means is that you take 0.001g (i.e. 1mg) of the antibiotics and mix with 1 litre of distilled water which is already the distilled water used in the preparation of the medium. Just add 0.001g to the medium.
Dear Wesley,
I would normally recommend to prepare an antibiotic stock solution first so you can filter it and add a homogeneous solution to your MacConkey.
You can first prepare the concentration you’d like, to make it easier for you to calculate volumes.
Let’s say you prepare 10 ml of stock solution of 1000 mg/L of antibiotic (0.01g of cefotaxime on 10 ml distilled water), you filter your solution with a 0.22 micrometer filter and you can save it to use every time you need it.
Now you just need to take 0.4 ml of your stock solution and add it to your 400 ml of Mac Conkey sterile medium at 45°C.
I hope it helps.
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