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General considerations for the identification of Yeasts

المؤلف:  Patricia M. Tille, PhD, MLS(ASCP)

المصدر:  Bailey & Scotts Diagnostic Microbiology

الجزء والصفحة:  13th Edition , p717-721

2025-11-15

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Most often yeasts are identified through the use of a combination of tests (Figure1). Identification factors and techniques include:

• Colonial morphologic features

 • Microscopic morphologic features

• Physiologic studies

• Rapid commercial yeast identification tests

Fig1. Identification of yeasts in clinical specimens.

Several key characteristics can be seen macroscopically. Colonies have a wide variety of colors, shapes, and textures. Chromogenic agar can be used to differentiate yeast presumptively. Wet preps and lactophenol cotton blue stain can aid microscopic identification by improving the visualization of spore structure. Sexual and asexual characteristics are very important. Often a genus can be determined by the microscopic and macroscopic characteristics alone. India ink stain is useful when Cryptococcus organisms are suspected. Because carbon and nitrogen source differences are the key to differentiating yeasts, many automated and semiautomated commercial systems have been designed with assimilation and fer mentation tests. Supplemental testing takes advantage of restriction of a limited set of characteristics to further aid identification.