Working with Antibiotics

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Antibiotic Information

Antibiotic Abbreviation Stock Solution


Solvent Stock Concentration to

Working Concentration

Ampicillin Amp 100mg/ml H2O 1000x Plates only last 2 weeks
Carbenicillin Crb 100mg/ml 50% Ethanol 1000x
Chloramphenicol Cam 20mg/ml 100% Ethanol 1000x Use a final volume of 5 ug/ml for S. pneumoniae (stock is a 4000x solution for this purpose)
Cycloheximide Chx 100mg/ml DMSO 1000x Toxic to fungi and animals (including humans)

Use protective gear; work in chemical hood.

Erythromycin Ery 250mg/ml 100% Ethanol 1000x There are 2 different concentrations in the -20 freezer. Use final concentration of 0.25ug/ml for S. pneumoniae. Precipitates in the freezer; before use, put in dry heating block at 37° for 2 hours before use. Vortex occasionally during this incubation. It will come out of solution as soon as it is added to media; stir media gently and continue to use.
Gentamicin Gen 20mg/ml Water 1000x
Kanamycin Kan 50mg/ml H2O 1000x Plates only last 2 weeks; Use a final concentration of 250 ug/ml for S. pneumoniae (stock is a 200x solution for this purpose)
Spectinomycin Spec 60mg/ml H2O 1000x
Streptomycin Str 100mg/ml H2O 1000x
Tetracycline Tet 10mg/ml 70% Ethanol 1000x Light sensitive

Wrap tubes and plates in aluminum foil; Use a final concentration of 1 ug/ml for S. pneumoniae.

Preparing Antibiotics

Prepare 10mL of antibiotics at a time (less, for antibiotics that degrade quickly, like Ampicillin, Kanamycin, and Tetracycline).

If the solvent is not water, we can assume that the antibiotics will be sterilized by the solvent. After creating the appropriate concentration, they should be aliquoted into sterile microcentrifuge tubes by 500µl and put in the -20 freezer.

If the solvent is in water, prepare the solution in a 50ml conical tube. Filter sterilize the solution through a 0.22µm filter and a 10mL syringe, all in the biological hood using sterile technique. Aliquote into microcentrifuge tubes by 500µl and put in the -20 freezer

Be sure to label the aliquots with the antibiotic, concentration, and date. Please wrap Tetracycline aliquots in foil.