Antibiotics

Preparation of stocks

Dry antibiotics are in the large upright -20 °C freezer.
See the table below for stock concentrations for each antibiotic; note that stock concentrations are calculated in mg/ml.
Prepare the stock at the concentration listed below, in the diluent listed below, in a 50 ml conical tube. Typical preparation is to make 20 ml of stock.
- For antibiotics dissolved in 100% ethanol (e.g., Erm), no sterilization is needed beyond the addition of the alcohol. Proceed to aliquot the stock into 20 x 1 ml aliquots in labeled 1.7 ml microfuge tubes.
- For antibiotics dissolved in water (e.g., Carb), sterilization with a 0.22 μm filter is required. See the instructions below for using the Steriflip (backup: syringe filter sterilization). After sterilization, proceed to aliquot the stock into 20 x 1 ml aliquots in labeled 1.7 ml microfuge tubes.
Store aliquots in the respective Antibiotics box at -20 °C (mini freezer).

Steriflips are individually sealed. Select one (drawer to the left of the media bench) and ensure that the seal is intact.
Take out the filter piece and screw it onto a new 50 ml conical tube, noting placement of your fingers to ensure sterility in the output tube.
Take your filter apparatus to a sink with a vacuum hose on it (the clear hoses attached to the faucet).
Turn on the sink and attach the hose to the spout on the filter. Then, invert the apparatus.
- At this point, you should see the liquid being filtered.
- Once all liquid has passed through the filter, break the seal from the spout while the faucet remains running.
- Turn off the sink only after the hose is disconnected. (If the sink is turned off while the hose is connected, there is a risk of backflow contaminating the output liquid.
Unscrew the filter unit and replace with the sterile cap. Discard the filter unit and proceed to aliquot the stock as described above.

Antibiotic	Color	Abbr	Concentration (mg/ml)	Solvent	Stock notes
Carbenicillin	ORANGE	Carb	100	dH₂0	Filter
Chloramphenicol	RED	Cam	25	100% ethanol
Erythromycin	GREEN	Erm	10	100% ethanol
Kanamycin	BLUE	Kan	50	dH₂0	Filter
Spectinomycin	LIME	Spc	50	dH₂0	Filter
Tetracycline	PURPLE	Tet	10	100% ethanol (dH₂0 if tetracycline HCl)	Filter if dissolved in dH₂0. Keep dark (foil wrap)

There is detailed information about making antibiotic-containing media in media.

Antibiotic	Color	Final concentration (μg / ml)	Stock to add per 1 L media
Carbenicillin	ORANGE	LB-Carb¹⁰⁰	1,000 μl
Chloramphenicol	RED	LB-Cam²⁵	1,000 μl
Erythromycin	GREEN	BHI-Erm¹⁵⁰	150 mg dissolved in 1 ml ethanol
Kanamycin	BLUE	LB-Kan⁵⁰	1,000 μl
Spectinomycin	LIME	LB-Spc⁵⁰	1,000 μl
Tetracycline	PURPLE	LB-Tet¹⁵	1,500 μl

Antibiotic	Color	Final concentration (μg / ml)	Stock to add per 1 L media
Carbenicillin	ORANGE	N/A
Chloramphenicol	RED	LBS-Cam⁵	200 μl
Erythromycin	GREEN	LBS-Erm⁵	500 μl
Kanamycin	BLUE	LBS-Kan¹⁰⁰	2,000 μl
Tetracycline	PURPLE	LBS-Tet⁵	500 μl