- Polymyxin B sulfate
- Distilled water, sterilized
- Filter paper disk blanks, 5-6 mm or 1/4 inch, sterilized
- Micropipettor, to deliver 10 µl
Sterilize filter paper disks in glass petri plates. Dissolve polymyxin B in sterile water to yield a final concentration of 5000 units/ml. Place 10 1 of the 5000 units/ml solution on each disk. Dry the disks. Store desiccated and protected from light in refrigerator.
Example: Polymyxin B is sold by activity in USP units per mg. Check reagent bottle for activity of the lot in use. For polymyxin B with antibiotic activity of 8090 USP units per mg, dissolve 0.618 mg in 1 ml sterile water.
|5000 Units/ml||= 0.618 mg/ml|
Hypertext Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.