Rice Extract Agar

Rice Extract Agar is recommended for differentiation of yeasts by means of their typical chlamydospores and on basis of micromorphological criteria.

Composition**

Final pH (at 25°C): 5.8±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 15.0 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well and pour into sterile Petri plates to give a thin layer of medium (1-2 mm).

Principle And Interpretation

Rice Extract Agar was developed by Taschdjian to aid in the identification of chlamydospore producing species of Candida (1).This medium can be used for culturing yeasts and differentiating them on basis of micromorphological characteristics particularly for differentiation of C.albicans and C. stellatoidea on basis of formation of chlamydospores. Rieth had demonstrated that this medium can be used for mycological diagnostic procedures (2). Rice extract in the medium serves as sole nutrient source. A small inoculum of suspected Candida colony can be inoculated by streaking (very thinly) on the surface of rice extract agar in 3-4 broad zig zag lines and covered with cover glass This oxygen deficient condition favours chlamydospore formation and pseudomycelial growth of yeasts. If the specimen is heavily infected with Candida it can be streaked directly on agar. On incubation for approximately 96 hours at 22-25°C culture can be directly examined under microscope through cover glass.

Culture may be confirmed further as suggested by Ajello et.al (3).Typical morphologies can be revealed as under:

Quality Control

Appearance Off-white to light yellow coloured homogeneous free flowing powder

Gelling Firm, comparable with 1.43% Agar gel.

Colour and Clarity of prepared medium White-light yellow coloured clear to slightly opalescent gel forms in Petri plates.

Reaction Reaction of 1.5% aqueous solution is pH 5.8 ± 0.2 at 25°C. pH : 5.8±0.2

pH 5.60-6.00

Cultural Response

M1026A: Cultural characteristics observed after an incubation of 96 hours at 22-25°C.

Storage and Shelf Life

Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label.

Reference

1. Taschdjian. 1953. Mycologia 45 : 474.
2. Reith, H., Hansen,P. El-Fikl, A.Y., u ITO, K. Hefedifferenzierung auf Reisagar-Bill.Pharm.Res., Inst., (Osaka) 19; 13-(1959).
3. Ajello, L., Georg,L.K., Kaplan,W.A., Kaufman, L. :Laboratory AManual for medical Mycology Communicable Disease Center, Atalanta, Georgia, USA, 1966.