|Potato infusion||200 g|
|Distilled water||1 liter|
To prepare potato infusion, boil 200 g sliced, unpeeled potatoes in 1 liter distilled water for 30 min. Filter through cheesecloth, saving effluent, which is potato infusion (or use commercial dehydrated form). Mix in other ingredients and boil to dissolve. Autoclave 15 min at 121°C. Dispense 20-25 ml portions into sterile 15 × 100 mm petri dishes. Final pH, 5.6 ± 0.2.
Medium should not be re-melted more than once. Medium powder is available commercially but may require supplementing with extra agar to a final concentration of 20 g/liter. To BBL or Difco dehydrated medium, add 5 g of agar.
For potato dextrose salt agar, prepare potato dextrose agar, as above, and add 75 g NaCl per liter.
For cosmetics, cool medium to 47-50°C after autoclaving. Add 40 ppm (final concentration) chlortetracycline. Mix thoroughly and dispense 20 ml portions into 15 × 100 mm petri dishes. Dispense 4 ml of stock filter-sterilized chlortetracycline HCl (1 g/100 ml) per liter of medium.
Original Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.