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R64
Polymyxin B Disks, 50 Units
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.
Calculation:
5000 Units/ml | = 0.618 mg/ml |
8090 Units/mg |
Hypertext updated by rim/kwg 2000-OCT-05