2. Basic Clinical Mycology (III) Flashcards by Arvee Perez

Microscopic morphology of molds used in its ID

Septate/aseptate hyphae
Conidiophore structure
Microconidia/macroconidia

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Rapid information of immunoidentity for mold ID

Exoantigen test

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Exoantigen test is read at

24 hours

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Fungi ID through exoantigen test

Blastomyces
Coccidioides
Histoplasma

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How to do exoantigen test?

extract soluble antigen from unknown isolate
concentrate
react with antiserum specific to known fungi
positive control necessary for definitive ID

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Principle used in DNA probe kits

Nucleic acid hybridization

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DNA probe can only be performed on

Cultured organisms

NOT on specimens

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Advanced technique for mold ID that can only be performed on cultured organisms

DNA probe

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DNA probe was developed for

Balastomyces
Coccidioides
Histoplasma

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Macroscopic morphology of yeasts used in its ID

Color

Texture

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Color of yeast colonies

White
Tan
Pink
Salmon

Can have dematiaceous yeasts

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Texture of yeast colonies

Mucoid
Butterlke
Velvety
Wrinkled

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Method for microscopic examination of yeasts

Wet preparation

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Microscopic morphology of yeasts used in its ID

Hyphae
Pseudohyphae
Blastoconidia

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Media for yeasts that encourage development of chlamydospores

Cornmeal Tween 80 agar

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Develops in Cornmeal Tween 80 agar

Chlamydospores

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Clear media that can be observed under a light microscope

Cornmeal Tween 80 agar

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Cornmeal agar morphology for yeasts is used in conjunction with

Carbohydrate usage

4 main morphology types in Cornmeal Tween 80 agar

Hyphae
Pseudohyphae
Arthroconidia
Chlamydoconidia/blastoconidia

Fungi with pseudohyphae and blastoconidia only on Cornmeal Tween 80 agar

C. krusei
C. parapsilosis
C. kefyr
C. tropicalis

Fungi with blastoconidia only on Cornmeal Tween 80 agar

C. glabrata

C. neoformans

Fungi with arthroconidia only on Cornmeal Tween 80 agar

Trichosporon beigelii

Physiologic tests for yeast ID

Germ tube test
Fermentation/assimilation
Urea hydrolysis

Most basic and easiest physiologic test for yeasts to perform

Germ tube test

Filamentous outgrowth from blastoconidia

Germ tube

The germ tube test for yeast ID requires

Serum or plasma Commercial boths will last longer

Biggest problems in performing germ tube test for yeast ID

Overincubation | Overinoculation

Germ tube test reading for yeast ID is not valid if read after

2 hours

Produces "true" germ tubes

C. albicans

Characteristics of a true germ tube

No constriction at the base where the tube attaches to the mother cell

Produces germ tubes with a constricted base

C. tropicalis

Other yeasts that produce germ tubes

C. stellatoidea | C. dubliniensis

How do you differentiate C. albicans from C. stellatoidea since both produce germ tubes?

Use sucrose assimilation

Differentiating characteristic of C. dubliniensis from other yeasts

No growth at 45°C

Yeast that does not grow at 45°C

C. dubliniensis

Physiologic test for yeast ID that determines carbohydrate use in absence of oxygen

Fermentation

Commercial products for fermentation/assimilation physiologic test for yeast ID

API 20C: strip test | Vitek: automated

Fungi differentiated using urea hydrolysis physiologic test for yeast ID

Cryptococcus | Rhodotorula

Positive result in urea hydrolysis physiologic test for yeast ID

Pink

Negative result in urea hydrolysis physiologic test for yeast ID

Little to no change

Temperature study of Cryptococcus spp.

35°C: weak growth | 42°C: no growth

Temperature study of Candia spp.

Several spp. can grow well exceeding 45°C

Order of events for yeast ID

- wet preparation - germ tube test - corn meal morphology - physiologic/biochemical tests - temperature

Advanced techniques for mold identification

Exoantigen test | DNA probe