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Mycology - Yeasts


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Where are yeasts normal flora?
-Oral cavity
So how do we often see yeasts in lab?
As Contaminants
As opportunistic infections
What specimens can yeast contaminate?
-Lower Resp tract
-Upper resp tract
-Genital culture
-Skin culture
-Urine culture
-Intestinal culture
Yeast isolated from what specimens would indicate a pathogenic infection?
-Blood, CSF, body fluids
-Tissues, abscess, urine, LRT
What is included in the lab workup of a yeast?
-Colonial morphology
-Microscopic morphology
-Germ tube
-Cornmeal agar
-API 20C/other automated
What types of agar are used to grow yeast?
-Blood agar
What is chromagar for?
Differentiating C. albicans
What chromagar colors are:
-C. tropicalis
-C. albicans
-C. glabrata/krusei
-C. parapsilosis
Tropic = blue
Albicans = aqua
Glabrata = pink
Parapsilosis = white
What are 4 methods for complete identification of yeasts?
-Assimilation sugars
-API 20C
-Automated systems
-Additional biochemicals
What 3 disease categories are associated w C. albicans?
1. Mucocutaneous
2. Cutaneuos
3. Systemic
What are 4 mucocutaneous infections of C. albicans?
1. Thrush
2. Vaginitis/balanitis
3. Bronchial/pulmonary
4. Intestinal
What causes intestinal mucocutaneous C. albicans infection?
Overuse of antibiotics
What temp is Corn meal agar incubated at?
MUST be 25'C; 30 can inhibit.
4 types of cutaneous C. albicans infections are:
1. Intertriginous
2. Diaper rash
3. Paronychia
4. Candida granuloma
What are 4 types of systemic C. albicans infections?
1. Urinary tract
2. Endocarditis
3. Meningitis
4. Septicemia
What is the more commonly isolated Candida sp from UTI?
C. albicans; then
What are some causes of disseminated candidiasis?
-Numerous intravasc. devices
-More immunocompromised pts
-Broadspectrum antibiotics
-Technology-assisted life support
What is a common oral thrush infection in AIDS patients?
What do ALL candida species produce on corn meal agar?
-Yeast cells
-True hyphae
What does C. albicans produce to differentiate it?
-Terminal chlamydospores
What are some risk factors for disseminated candidiasis?
-Organ transplants
-Severe systemic diseases
-Heroin addiction
-GI surgery
What 3 common Antifungals are used for Candidiasis?
-Amphotericin B deoxycholate
-Azoles (flucon/posaconazole)
What should be kept in mind regarding antifungals?
C. albicans is developing resistance to the azoles
What cornmeal characteristics are unique to C. glabrata?
-Yeast cells
-NO hyphae
How does C. glabrata look on the API 20C?
What infections does C. glabrata typically cause?
-Fungemia - esp in patients with solid tumors
What yeast is associatd with CNS disorders?
Cryptococcus neoformans
What other type of disease does it cause?
pulmonary cryptococcosis
What 4 methods are used for identifying c. neoformans?
-India ink prep
-Latex agglutionation
-Urea reaction
-Birdseed agar
What do the id methods show for c. neoformans?
India ink = capsule
Latex aggl = agglutination
Urea = pos
Birdseed = brown
What is the birdseed agar used to show again?
Caffeic acid in c. neoformans - it turns colonies brown on agar.
What is a common contaminant in research labs?
What is the identifying characteristic about Rhodotorula?
Red colonies, urea pos
When should amphotericin B be used as an antifungal?
only as a last resort; it's very hard on the kidneys.
how is c. neoformans transmitted?
What type of yeast is Blastoschizomyces?
Normal skin flora
What infections does Blastoschizomyces cause?
What type of morphology does blastoschizomyces have on agar?
-Short arial hyphae
What characteristics are used to differentiate Blastoschizomyces on agar?
-Arthroconidia (some)
-Urea NEG
What do we differentiate Blastoschizomyces from?
What are id characterisitcs of trichosporon?
-Psudohyphe and Hyphae
-NO annello
-UREA pos
What are id characteristics of geotrichum?
-NO pseudohyphae
-LOTS of arthrospores
-no blasto/annello
-Urea neg
what is trichosporon known to cause?
white piedra
what is the beer/bread yeast?
saccharomyces cerevisiae
What a unique characteristic of S. cereviseae?
-Ascospores - sexual spores that stain acid fast.
What mold is a common cause of pneumonia in AIDS pts?
-Pneumocystis jiroveci

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