Yeast (Exam 3)

What are the general characteristics of yeast?

- Unicellular

- Rapid growers

- Reproduce via budding

Yeast colonies are ...

Creamy, pasty, smooth, wrinkly, pigmented

Yeast colonies have _____ that develop at the border of the colonies.

feet

Yeast can be found as normal flora in the ...

Mouth, skin, vaginal tract, GI tract/stool)

Yeast are ______ organisms.

opportunistic

What clinical diseases are caused by Candida albicans?

- Intertriginous candidiasis

- Paronychia

- Onychomycosis

- Vulvovaginitis

- Thrush

- Pulmonary, ocular, endocarditis, UTI, meningitis, fungemia, disseminated

Risk factors of Candida albicans infection

- Broad-spectrum antibiotics

- Previous ICU stays

- Central venous catheters

- Immunocompromised/suppressed

Candida spp. (not albicans) are normal flora of ______ and ______ surfaces, rarely pathogenic.

mucocutaneous, cutaneous

Candida spp. (not albicans) causes ______ infections.

nosocomial

Cryptococcus neoformans affects the ...

Brian, lungs

Yeast specimen sources can be ______ or ______.

sterile, non-sterile

Yeast can be identified via ...

- Direct exam

- Germ tube test

- CHROMagar

- Biochemical tests

- Microscopy

CHROMagar

What biochemical tests can be used to identify yeast?

- Assimilation

- Fermentation

- Urease

- Nitrate assimilation

______ is used for microscopy of yeast.

RIOT (Cornmeal, rice, potato dextrose)

Describe the procedure of the germ tube test

- Tube with pooled human serum

- Inoculate with yeast

- Incubate at 37 C for 2.5-3 hours

- Put on a slide and observe

Germ tube positive

Candida albicans only

Germ tube negative

Constriction(s)

Candida albicans morphology

Pseudohyphae

Clusters of round blastoconidia

Terminal chlamydospores

Candida albicans assimilates ______.

sucrose

Candida albicans is nitrate and urease ______.

negative

Candida stellatoidea is similar to Candida albicans, but it does not assimilate _______.

sucrose

Candida tropicalis morphology

Ovoid or elongate blastoconidia, singly along pseudohyphae at junctions

May form true junctions

Birds on a wire

Candida tropicalis is nitrate and urease ______.

negative

Candida tropicalis causes ...

- Vaginitis

- Intestinal, bronchopulmonary, systemic complications

Candida parapsilosis morphology

Curved, delicate pseudohyphae with giant cells

Ovoid or elongate blastoconidia, singly or in short chains/clusters

Candida parapsilosis is nitrate and urease ______.

negative

Candida parapsilosis causes ...

UTI, pyelonephritis, endocarditis, paronychia, otitis externa, vaginitis, endophthalmitis

Candida guilliermondii morphology

Few, short pseudohyphae with small clusters of blastoconidia at the constrictions

Candida guilliermondii is nitrate and urease ______.

negative

Candida guilliermondii causes ...

- Eye and skin problems

- UTI, endocarditis, osteomyelitis, keratitis, cutaneous

Candida kefyr morphology

Elongated blastoconidia at junction

Log-jam clusters

Candid kefyr is urease and nitrate ______.

negative

Candida kefyr causes ...

UTIs, endocarditis, keratitis, onychomycosis

Candida krusei morphology

Crossed matchsticks, tree-like

Long branching pseudohyphae

Elongate blastoconidia form chains at junctions

Candida krusei is urease ______ and nitrate ______.

positive, negative

Candida krusei causes ...

Endocarditis, vaginits

Candida glabrata morphology

No pseudohyphae

Small blastoconidia with single terminal bud

Candida glabrata is urease and nitrate ______.

negative

Candida glabrata assimilates ______ and ______.

glucose, trehalose

Candida glabrata causes ...

Fungemia, endocarditis, meningitis, UTIs, lung issues

Cryptococcus neoformans morphology

No pseudohyphae

Round cells with small isthmus

Capsule

Cryptococcus neoformans is opportunistic, spread by ______.

pigeons

Cryptococcus neoformans is urease ______ and nitrate ______.

positive, negative

Cryptococcus neoformans causes ...

Chronic or subacute pulmonary disease

CNS and brain, bones, eyes, skin

Cryptococcus neoformans can be plates on ______ agar.

Birdseed

Saccharomyces cerevisiae colonies

Asci produced on ascospore media

Saccharomyces cerevisiae morphology

Short pseudohyphae with oval multi-budding blastoconidia

Saccharomyces cerevisiae is germ tube ______.

negative

Saccharomyces cerevisiae is urease and nitrate ______.

negative

Rhodotorula rubra colonies

Coral red/orange/golden yellow

Rhodotorula rubra morphology

Globose or oval blastoconidia

Rare pseudohyphae

Rhodotorula rubra is germ tube ______.

negative

Rhodotorula rubra is urease and nitrate ______.

positive

Geotrichum candidum colonies

Immature: Yeast-like

Mature: Mold-like

Geotrichum candidum morphology

Rectangular

Wide, septate, hyaline

True hyphae with lateral branching

Arthroconidia break off hyphae

Free arthroconidia germinate from one corner

No blastoconidia or pseudohyphae

Geotrichum candidum is germ tube test ______.

negative

Geotrichum candidum is nitrate and urease ______.

negative

Pneumocystis (carinii) jiroveci morphology

Troph, precyst, cyst

Pneumocystis (carinii) jiroveci is germ tube ______.

N/A, negative

Pneumocystis (carinii) jiroveci uses what identification methods?

- Brochopulmonary secretions with GMS

- Direct fluorescence Ab

- Giemsa stain

- PCR

Pneumocystis (carinii) jiroveci causes ______ disease.

PCP

Interstitial pneumonia

Frothy, honeycombed, foamy exudate

Candida auris colonies

Grows at 37-40(42) C

Candida auris morphology

No pseudohyphae

Candida auris is easy to misidentify and requires ______.

MALDI-TOF