Yeast Identification and Mycology Lecture Notes

Comprehensive vocabulary-style flashcards covering the characteristics, culture media, and various biochemical and serological identification methods for yeasts, specifically focused on Candida and Cryptococcus species.

Yeast

Eukaryotic, unicellular fungi that reproduce exclusively through blastoconidium formation via budding or fission.

Chitin

The primary component of the yeast cell wall, which may also include glucans and mannans depending on the species.

Ergosterol

A component of the cell membrane that serves as an identifying characteristic for most fungi.

Sabouraud Dextrose Agar (SDA)

The primary isolation medium for yeasts, which has an acidic pH of $5.0$ to inhibit bacteria and contains a high concentration of sugar.

Mycosel Agar (MSA)

A selective medium for fungi consisting of SDA supplemented with Chloramphenicol to inhibit bacteria and Cycloheximide to inhibit saprobes.

Germ Tube Test

A screening test used to differentiate $Candida\,albicans$ and $Candida\,dubliniensis$ from other yeasts by observing tube-like projections in serum after $2-3$ hours of incubation at $37^\circ\text{C}$.

Dalmau Plate Method

A technique used for microscopic differentiation of yeast species using corn meal, rice meal, or rice extract with T80 agar.

Polysorbate (Tween) 80

An additive used in cornmeal agar to reduce surface tension, allowing for the development of pseudohyphal, hyphal, blastoconidial growth, chlamydospores, and arthroconidia.

$Candida\,albicans$ (Microscopic Structures)

A yeast species identified by the presence of blastoconidia, pseudohyphae, and $1-2$ cell terminal chlamydospores.

$Candida\,dubliniensis$ (Microscopic Structures)

A yeast species similar to $C.\,albicans$ but characterized by producing terminal chlamydospores in pairs or groups of $4$.

$$Candida\,auris$$

Characterized as the most pathogenic yeast, appearing as yeast cells only under morphological study.

Urease Test

An identification test utilizing Christensen’s Urea Agar, particularly used for the identification of $Cryptococcus$ species.

Carbohydrate Assimilation Test

A test that determines the ability of a yeast isolate to use a specific carbohydrate substrate as its sole carbon source.

API 20 C AUX

A semi-automated system containing $20$ cupules for $19$ assimilation tests, incubated at $29^\circ\text{C} \pm 2^\circ\text{C}$ for $48-72$ hours.

Carbohydrate Fermentation Test

A test used to determine a yeast's ability to degrade carbohydrates, demonstrated by the production of gas or acid.

Chromogenic Agar

A selective and differential medium used to identify clinically significant $Candida$ species based on macroscopic color production.

CGB Agar

L-canavanine glycine bromthymol blue agar used to differentiate $Cryptococcus\,gattii$ (positive/blue) from $Cryptococcus\,neoformans$ (negative).

India Ink

A staining method used to detect capsules; both $C.\,gattii$ and $C.\,neoformans$ are positive for this test.

Latex Agglutination System

A serological test where anti-cryptococcal antibody-coated particles agglutinate with specimens containing cryptococcal capsular polysaccharide antigens.

Pronase

An enzyme used to pre-treat serum samples in latex agglutination to reduce non-specific interference and enhance antigen detection.

Lateral Flow Assay

An immunochromatographic dipstick assay with a $10$ minute running time that is FDA-cleared for detecting both $C.\,neoformans$ and $C.\,gattii$.