Lecture 4: 4/9/26 Yeasts: "Candida" & Cryptococcus

Which yeast is the most common invasive fungal opportunist?

Candida

What phylum does Candida belong to?

Ascomycete

Candida is endogenous and ubiquitous in the environment and infections usually come in from …

gastrointestinal tract (where it can reside normally) or the skin (such as with intravenous catheter or trauma)

What is the most common candida species, and can form true hyphae.

Candida albicans

Treatment for invasive infections: Until you know the sensitivities, start with

echinocandin

C. glabrata can be resistant to

fluconazole (inducible/acquired)

C. krusei is always resistant to

fluconazole (intrinsic)

Fluconazole is still good for most

C. albicans and C. parapsilosis

___is multi-drug resistant, especially to azoles and even amphotericin, so echinocandins should be used

C. auris

Candida location of infection

nvasive: From blood, likes to go particularly to eye and skin - can go basically any other area as well, except pneumonia are rare (because you do not inhale it to become infected) and urinary tract infections are also rare.

difference between pseudohyphae and hyphae (note: C.albicans forms both)

Pseudohyphae is “pinched” ay budding point shorter and more elliptical

True hyphae is parallel walls, apical elongation, longer & more cylindrical

Virulence factors for Candida:

biofilms, morphogenesis, adhesins

What is the diagnosis technique for Candida?

culture

B-D-glucan (antigen test) is

fairly good sensitivity, but specificity is lower (positive in pneumocystis and other fungal infections).

C. auris can be particularly difficult to

diagnose

What phylum is cryptococcus?

Basidiomycetes

cryptococcus is both primary and opportunistic pathogen. Give example of these two/

Primary: C. gattii

Opportunistic: C. neoformans

What is the major risk for C. neoformans?

HIV/AIDS

What cryptococcus species is associated with Australia (eucalyptus, koalas), New Zealand, and the Douglas Fir Zone around Vancouver, BC

C. gattii

cryptococcus is a yeast that has a

thick capsule in body, and has a sexual phase

What are two virulence attributes for cryptococcus?

polysaccharide capsule and melanin

polysaccharide capsule

small until gets into lungs than can grow thick - protects from phagocytosis. Mutants without capsule are not pathogenic

Melanin

Protects fungal cell from respiratory burst of human phagocytosis

Primary pulmonary infection after inhalation of the yeast – usually

self-limited, but can progress

Cryptococcus can go to the

brain (meningitis) frequently and the skin

cryptococcal antigen (CrAg)

can be measured in blood or spinal fluid – very sensitive and specific

Cryptococcus yeast description for diagnosis

Narrow-based budding yeast with thick capsule.

What is the tx for cryptococcus for the lungs?

No treatment for asymptomatic or minimal lung symptoms in immunocompetent host. Otherwise, use fluconazole.

What is the tx for cryptococcus for the Meningitis?

Amphotericin + 5-FC (Flucytosine) at first, then switch to fluconazole.

What antifungal drug doesn’t work for cryptococcus?

Echinocandins

Describe the complication for cryptococcus for meningitis?

Complication: Elevated intracranial pressure : Presents with fever, headache, nausea

• Lumbar puncture or surgical drain to remove CSF