To make a media with antibiotics first one needs to prepare the LB media (like dissolving/mixing the components, adjusting the pH, etc) and autoclave it. One must also have the antibiotic solution prepared and sterilized using appropriate syringe filters (0.22 µm is commonly used). After the autoclave is complete keep the media-containing vessel in a laminar flow cabinet and wait till the media cools down to around 50 degrees Celcius (the cooler the better). After mixing properly pour the media onto plates. If the media is intended for broth culture then one can wait till the media has cooled down to room temperature and add the proper concentration of the antibiotic stock solution.

Dear Rayan,

Thanks for your kind feed back. Actually I wanted to know the specific amount (concentration) of streptomycin antibiotic needed to prepare the mother stock and then required amount I need to mix with my broth or solid LA media after cooling it to room temperature. It will be helpful for me if anyone did make the solution and give his or her suggestions for me to follow.

You can make the mother stock with a concentration of 100 mg/ml. Then you can add 100 µl per 100 ml of media to get a final concentration of 100 mg/L. This way it gets very easy to calculate the proper volume of the stock to be added to the media according to the concentration required in the media. For example: If one requires 75 mg/L conc. of antibiotic then one can simply add 75 µl of stock to 100 ml media. If the volume of the media is 250 ml then one just needs to multiply the required volume for 100 ml by 2.5.

Thank you