B.C.G.-Dextrose Agar (Snyder test Agar) M106
B.C.G. Dextrose Agar (Snyder Test Agar) is recommended for the estimation of Lactobacilli and indication of caries activity.
Ingredients Gms / Litre Peptic digest of animal tissue 20.000 Dextrose 20.000 Sodium chloride 5.000 Bromocresol green 0.020 Agar 20.000 Final pH ( at 25°C) 4.8±0.2 **Formula adjusted, standardized to suit performance parameters
Suspend 65.02 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Dispense in 10 ml amounts into test tubes and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Allow the tubes to cool in an upright position. DO NOT OVERHEAT the medium.
Principle And Interpretation
Dental caries results from microbial acid and plaque formation. Plaque sets the stage for caries because it collects the acid forming bacteria on the tooth surface, supplies an anaerobic environment for fermentation, traps the acids and excludes the protective saliva. Caries lesions are basically the outcome of chemical attack on the enamel and dentin. Demineralization of the tooth alternates with periods of re-mineralization. If demineralization exceeds re-mineralization, a subsurface carious lesion becomes a clinical cavity with extension of the decay into the dentine (1). For determining the rate and amount of acid produced by microorganisms in saliva, Snyder (2, 3) described a colorimetric method. The procedure makes use of an agar medium that is known as Snyder Test Agar. Later on Alban (4) modified the procedure and reported it to be more accurate than the original procedure. This is a differential medium based on the rate of acid production from dextrose, by oral acidogenic microorganisms from buccal cavity and is evidenced by a change in colour of the indicator - bromo cresol green from blue-green to yellow (3). Peptic digest of animal tissue provides carbon, nitrogen, vitamins and minerals. Dextrose is the carbohydrate source and bromo cresol green is the pH indicator.
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 label.
1. Lewis and Ismail, 1995, Can. Med. Assoc. J., 152:836. 2. Snyder, 1941, J. Dent. Res., 20:189. 3. Snyder, 1941, J. Am. Dent. Assoc., 28:44. 4. Alban, 1970, J. Dent. Res., 49:641. 5. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. I, Williams & Wilkins, Baltimore, Md.