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:

Hypertext updated by rim/kwg 2000-OCT-05