Sabouraud Destrose Agar
SABOURAUD DEXTROSE AGAR AND SABOURAUD DEXTROSE AGAR WITH CHLORAMPHENICOL
INTENDED USE. Sabouraud Dextrose Agar is used in qualitative procedures for cultivation of pathogenic and nonpathogenic fungi, particularly dermatophytes. The medium is rendered more selective for fungi by the addition of chloramphenicol. The addition of chloramphenicol inhibits most bacteria making the dermatophytes easier to identify. Prepared plates of these media are deep-filled to reduce the effects of drying during prolonged incubation.
SUMMARY AND EXPLANATION OF THE TEST Sabouraud Dextrose Agar is a general-purpose medium devised by Sabouraud for the cultivation of dermatophytes. The low pH of approximately 5.6 is favorable for the growth of fungi, especially dermatophytes, and slightly inhibitory to contaminating bacteria in clinical specimens. The addition of chloramphenicol is a modification designed to increase bacterial inhibition.
PRINCIPLES OF THE PROCEDURE Sabouraud Dextrose Agar is a peptone medium supplemented with dextrose to support the growth of fungi. The peptones are sources of nitrogenous growth factors. Dextrose provides an energy source for the growth of microorganisms. Chloramphenicol is a broad-spectrum antibiotic which is inhibitory to a wide range of gram-negative and gram-positive bacteria when it is added to the formulation.
BIGGY AGAR
INTENDED USE: BIGGY (Bismuth Sulfite Glucose Glycine Yeast) Agar is a selective and differential medium used in the detection, isolation and presumptive identification of Candida species.
SUMMARY AND EXPLANATION OF THE TEST. BiGGY Agar is based on the formulation of Nickerson. Nickerson developed the medium in 1953 following a study of sulfite reduction by Candida species. Differentiation of Candida is based on growth patterns and pigmentation of isolated colonies. The bismuth sulfite acts as an inhibitory agent to suppress bacterial growth, which enables the recovery of isolated colonies of Candida. The Candida species reduce the bismuth sulfite, resulting in pigmentation of colonies and, with some species, pigmentation in the surrounding medium.
PRINCIPLES OF THE PROCEDURE. Candida species, through a process of substrate reduction, produce sulfide and bismuth which combine to produce brown to black pigmented colonies and zones of dark precipitate in the medium surrounding colonies of some species. Dextrose and yeast extract provide the nutrients in the formulation.
Sabouraud Dextrose Agar and Sabouraud Dextrose Agar with Chloramphenicol The addition of Chloramphenicol does a better job of inhibiting bacterial growth.
Microsporum canis
White fluffy middle area, golden yellow border, yellow undersurface view
Microsporum gypeseum
Light brown border- white rapidly spreading mycelium, cream to tan undersurface view
Trichophyton mentagrophytes
Granular white, sugar like appearance, variable under surface color
Trichophyton tonsures
Velvety texture with rugose folds. Reddish-brown undersurface
Trichophyton rubrum
White-fluffy downy appearance with dark red under surface
Epidermophyton floccosum
Restricted growth, olive green to pale yellow growth with brownish undersurface
Trichophyton terrestre
Buff yellow, powdery, may look like T. mentagrophytes, pale to light tan undersurface
Biggy Agar
C. albicans
Round or hemispherical colonies of medium-size black in color with no diffusion, slight mycelial fringe.
C. krusei
Large flat wrinkled colonies with a silvery-black edge and yellow halo, no diffusion.
C. psrakrusei
Medium-sized flat wrinkled colonies which exhibit a glistening reddish-brown color and an extensive mycelial fringe.
C stellatoidea
Medium-sized flat colonies with a deep dark negligible mycelial development.
C. tropicalis
Discrete medium-sized colonies, dark brown with black center, slight mycelial fringe, diffuse blackening frequently observed with this species after 72 hours of incubation.
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