Buffered charcoal yeast extract agar
Buffered charcoal yeast extract (BCYE) agar is a selective growth medium used to culture or grow certain types of bacteria, particularly the Gram-negative species Legionella pneumophila.[1] It has also been used for the laboratory diagnosis of Acanthamoeba keratitis,[2] Francisella and Nocardia. It contains L-Cystine amino acid and ferric pyrophosphate that assist in the growth of Legionnaire's species. The charcoal within the medium acts as a detoxicant because it decomposes hydrogen peroxide which is toxic to the Legionnaire's bacterium, the charcoal is also capable of changing the surface tension as well as collect carbon dioxide. The yeast extract in BCYE is the rich source of food(vitamins, nitrogen, and carbon) that the bacteria will use to grow. BCYE also has ACES buffer which maintains an optimal PH level for the bacteria to grow which is around 6.9.[1]
| Ingredient | Amount (g/L) | Purpose |
|---|---|---|
| Agar | 12.0 | Solidifying |
| Yeast extract | 10.0 | Vitamins, nitrogen, and carbon |
| ACES buffer | 10.0 | Buffer |
| Activated charcoal | 2.0 | Decomposes hydrogen peroxide, a toxic metabolite of Legionella |
| Potassium hydroxide | 2.8 | pH (target shall be 6.9±0.2) |
| Alpha-ketoglutarate | 1.0 | Stimulates oxygen-scavenging enzymes in Legionella |
| L-cysteine | 0.4 | Provide absolutely essential nutrients to Legionella |
| Ferric pyrophosphate | 0.2 |
Preparation of BCYE agar:[2]
1.Suspend 20gms in 500 ml of distilled water
2.Heat to boil so it can dissolve completely
3.Sterilize by autoclaving at 15 pounds of pressure at 150 degrees Celsius for 15 minutes
4. Cool to 50 degrees Celsius
5.Add Legionella Supplement
6.Mix and pour with constant stirring so charcoal contents are evenly dispersed
Results to expect:[3]
The Legionella bacteria that are smooth colorless to blue or grey will become more white and filamentous over time and appear green and yellow fluorescent under UV light. The colony surface is typically smooth but may look like it has strains that give it a fried egg type of appearance when looked at under a microscope.
Storing BCYE plates:[4]
BCYE plates should be stored in the dark at temperatures of 2-8 degree Celsius. Plates should not be frozen or overheated keep exposure to light minimal. BCYE along with most growth mediums should not be opened unless it is being used and should be at room temperature before inoculating anything onto the medium.
This culture is to be differentiated from regular yeast extract agar, which is not selective.
References
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 2012-06-12. Retrieved 2012-05-11.
{{cite web}}: CS1 maint: archived copy as title (link) - ^ Penland RL, Wilhelmus KR (October 1998). "Laboratory diagnosis of Acanthamoeba keratitis using buffered charcoal-yeast extract agar". Am. J. Ophthalmol. 126 (4): 590–2. doi:10.1016/S0002-9394(98)00125-1. PMID 9780107.
- ^ Aryal, Sagar (4 January 2022). "BCYE Agar- Composition, Principle, Preparation, Results, Uses". Microbe Notes.
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