Isolation Techniques and Selective Media, A Photographic Atlas for the Microbiology Laboratory, Bismuth Sulfite Glucose Glycine Yeast (BiGGY) Agar
Purpose
BiGGY Agar is a selective and differential medium used to isolate species of the yeast Candida. Presumptive identification of Candida spp. is also possible because of the differential results. Candida
albicans is a common inhabitant of the normal flora of the oral cavity, gastrointestinal tract, and vagina, but it is also an opportunistic pathogen, especially in immunocompromised individuals. For more information, please refer to page 183.
Principle
Carbon, nitrogen, and other nutrients are supplied by yeast extract and dextrose, whereas glycine stimulates growth. During autoclaving, sodium sulfite and bismuth ammonium citrate react to form bismuth sulfite, which is inhibitory to most bacteria, but not Candida species. Candida species reduce the bismuth sulfite (at slightly acidic or neutral pH) and produce a brown pigment within, and sometimes around, the colonies (Figure 2-5).
2-5 BIGGY AGAR The ability to grow combined with the brown color (due to bismuth sulfite reduction) provides provisional identification of Candida albicans.
Suggested Reading
- Michael J. Leboffe & Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
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