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Material Safety Data Sheet

Organisms

Organisms in the Clinical sector this product works with:

Dehydrated Culture Media

Sector: Clinical

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BiGGY AGAR

Code: CM0589

For the isolation and presumptive identification of Candida species

Typical Formula*

gm/litre

Yeast extract

1.0

Glycine

10.0

Glucose

10.0

Sodium sulphite

3.0

Bismuth ammonium citrate

5.0

Agar

13.0

pH 6.8 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards 

Directions
Suspend 42g in 1 litre of distilled water and bring gently to the boil to dissolve the agar. Allow to cool to 50-55°C. Mix gently to disperse the flocculant precipitate and pour into sterile Petri dishes.
DO NOT AUTOCLAVE THE MEDIUM.

Description
BiGGY, Bismuth Sulphite Glucose Glycine Yeast Agar, is based on the formulation developed by Nickerson1 and may be used for the isolation and presumptive identification of Candida species.

In a study of sulphite reduction by yeasts, the ability of many yeasts to reduce a bismuthyl hydroxy polysulphite was noted. This was demonstrated to be most evident in Candida species. but strong reducing ability was confined to Candida albicans, Candida krusei and Candida tropicalis. Growth on an acidic or neutral medium containing bismuth sulphite produced black colonies because of the extra-cellular reduction of the bismuth sulphite, to bismuth sulphide.

The bismuth sulphite complex confers a high degree of selectivity to the medium, and most strains of bacteria are inhibited on BIGGY Agar.
Barr and Collins2 described the addition of neomycin sulphate to the medium at 2mg per litre to improve inhibition of accompanying bacterial flora.

The medium may be used for the isolation and presumptive identification of Candida albicans and Candida tropicalis from sputum2,3 and vaginal smears4. It is a recommended medium for the quality assessment of pharmaceutical and cosmetic products5.

Technique
Reconstitute the medium as directed and pour into sterile Petri dishes to contain approximately 20ml of medium.
Freshly prepared plates should be used. Reactions on slant cultures are unsatisfactory1.
Incubate the plates at 28-30°C and examine daily for evidence of sulphite reduction.

Colony appearance on BiGGY Agar (48 hours)

 
Colony morphology
Candida albicans
Smooth, circular brown-black, slight mycelial fringe;
no colour diffusion into surrounding medium; no sheen
Candida tropicalis
Smooth, dark brown with black centres; slight mycelial fringe;
diffuse blackening of medium after 72 hours; sheen
Candida krusei
Large, flat, wrinkled silvery brown-black with brown peripheries;
yellow halo diffused into medium
Candida pseudotropicalis
Medium size, flat, dark reddish-brown glistening;
slight mycelial fringe; no diffusion
Candida parakrusei
Medium size, flat, wrinkled, glistening dark reddish-brown with lighter periphery;
extensive yellow mycelial fringe
Candida stellatoidea

Medium size, flat, dark brown;
very light mycelial fringe

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Medium should be freshly prepared just prior to use.

Quality control

Positive controls:

Expected results

Candida albicans ATCC® 10231 *

Good growth; brown coloured colonies

Candida tropicalis ATCC® 750 *Good growth; brown coloured colonies

Negative control:

 
Escherichia coli ATCC® 25922 *No growth
* This organism is available as a Culti-Loop®

Precautions
Carry out further tests to confirm identity of isolated yeasts.
Do not use slants of medium because the reactions are unsatisfactory.
The flocculent precipitate present in the molten medium must be evenly suspended whilst dispensing the agar.

References
1. Nickerson W. J. (1953) J. Inf. Dis. 93. 43-56.
2. Barr F. S. and Collins G. F. (1966) South. Med. J. 59. 694-697.
3. Haley L. D. (1959) Trans. N. Y. Academy Sci. Series 11.
4. Mendel E. B., Naberman S. and Hall D. K. (1960) Obstet. & Gynec. 16. 180-184.
5. Code of Good Practice for the Toiletry and Cosmetic Industry (1975). Recommended Microbiological Limits and Guidelines to Microbiological Quality Control.

 
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