Recipe for DG-18 Agar

Fungal growth on DG-18 Agar

The primary organisms on these two DG-18 agar plates include Penicillium spp., Cladosporium spp., Aspergillus spp., and Wallemia spp. 

Our lab uses DG-18 or Dichloran Glycrol agar to grow culturable xerophilic (dry loving) fungi on indoor air and surface samples. This DG-18 agar grows mould or yeast at water activity (aw) less than .85).  The restricted colony growth and the inhibition of the zygomycete fungi on the plate allow for easier identification and counting of mould colonies on the plate. Some water loving moulds like Stachybotrys spp. and Aspergillus fumigatus do not grow well on this media. We often pair plates of MEA (Malt Extract Agar) with the DG-18 agar to capture organisms needing higher water activity.

DG-18 Media Recipe:

• 172 milliliters (ml) of glycerine
• 31.5 grams (g) of DG-18 dry powder agar
• 1000 ml of distilled water
• 0.1 g of chloramphenicol in 5 ml of 70% ethanol suspension (add after other ingredients are mixed) - This antibiotic limits bacterial growth on the culture plate.  Autoclave the culture plates after identification to limit problems with the development of antibiotic resistance. 

Directions:

1. Heat mixture to boiling using stir bar and a hot plate in a covered 2 liter flask. Make sure all media dissolves into solution.  Observe and modify the stir plate temperature to prevent it from boiling over. 
2. Use insulated gloves to transfer liquid agar solution to an autoclave.
3. Autoclave  for a 60 minute cycle at 121 C. 
4. Remove and keep warm in a 60 C incubator. 
5. Pour out 13.5 ml of agar onto a Rodac plate or 25 ml onto a 100 petri dish on a laminar flow clean bench.  Refrigerate covered in a plastic bag and store for up to 3 months.