Working with Antibiotics

Antibiotic Information

Antibiotic	Abbreviation	Stock Solution Concentration	Solvent	Stock Concentration to Working Concentration	Notes
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 400 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	Use a final concentration of 800 ug/ml for S. pneumoniae
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 and 10ug/ml for S. mutans (just like E. coli).

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.