|2,4-Diamino-6,7-diisopropyl pteridine (O/129) or phosphate salt|
|Distilled water, sterilized|
|Filter paper disk blanks, 5-6 mm or 1/4 inch, sterilized|
|Micropipettor, calibrated to deliver 10 1|
Mark disks to differentiate 10 g from 150 g disks. Sterilize filter paper disks in glass petri plates. Dissolve O/129 or O/129-PO4 (the phosphate salt dissolves more easily) in sterile water. For 150 g disks, place 10 1 of 15 mg/ml O/129 or 20.8 mg/ml O/129-PO4 on each disk. For 10 g disks, make l:l5 dilutions of the O/129 solutions and place 10 1 l of 1.O mg/ml O/129 or 1.4 mg/ml O/129-PO4 on each disk. Dry disks and store desiccated and protected from light in refrigerator. O/129 disks are commercially available.
Original Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.