Opportunistic Mycoses-Kozel Flashcards by michelle granstrom

What are the important opportunistic mycoses?

Candidiasis.-most common
Aspergillosis
Mucormycosis
Cryptococcosis 
Pneumocystosis

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What is the morphology of candida?

primarily yeasts
also pseudohyphae & true hyphae (less common)
forms germ tubes

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What are germ tubes?

take yeast & put it in serum & throw it in an incubator.
makes a hyphae that is called a germ tube
a way to identify candida in the lab

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Where is candida normally found?

totally normally found in humans
skin–esp of health care workers
GI tract
female GU

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What are the different species of candida? Which is most common?

Most common: C. albicans
w/ the wide use of fluconazole starting to see disease form from other types.
C. glabrata
C. parapsilosis
C. tropicalis
C. krusei
C. lusitaniae
C. guilliermondii
C. dublinensis

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When candidiasis is a mucous membrane infection–how does it present?

takes normal flora & makes an opportunistic infection
mucous-membrane:
thrush in the oral cavity
candida esophagitis-AIDS
vaginitis (75% women)

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There can also be cutaneous candidiasis syndromes. What do these involve?

involve moist tissues

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When candidiasis has deep organ involvement–which organs does it involve? Which of these is the biggest concern?

CNS
pneumonia
endocarditis
urinary tract
abdominal
bone & joint
hematogenous disseminated candidiasis (invasive-biggest concern b/c the organism gets into the blood of a sick person)

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Describe how invasive candidiasis is a major nosocomial infection.

3rd most common blood stream infection
seen in hospitals
this type of infection costs a lot!!

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What are the general risk factors for invasive candidiasis?

hematologic malignancy
neutropenia
GI surgery
premature infants
patients older than 70 yrs

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What are some specific risk factors for invasive candidiasis?

Time spent in ICU
Central venous catheter
Colonization at multiple sites-if it is at more parts of your body
Number of antibiotics given-b/c antibiotics knock down normal flora

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What is involved in the direct examination of candidiasis?

Scrapings of mucosal or cutaneous lesions - KOH mount
Histopathology
Budding yeast-like forms and pseudohyphae

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How do you take a culture for diagnosis of candidiasis?

samples include scrapings, blood, or tissue. BUT blood is only pos 50% of the time & tissue is difficult to do in a sick patient.
grow it on standard mycologic media
use selective chromogenic medium–different species grow different colors
**confirmed by germ tube formation when grown in serum

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So…you have a pt in the ICU with a fever of unknown origin. You culture & put them on antibiotics. They don’t respond & culture is neg. Then what?

might be a fungal infection
don’t biopsy
it won’t show up in blood culture
maybe just put them on antifungals

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How do you treat oral thrush-mucocutaneous candidiasis?

topical creams w/ nystatin or clotrimazole
oral systemic therapy w/ azoles
If you have AIDS: prophylactic fluconazole

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What is nystatin similar to?

similar to amphotericin B. It is a polyene.

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HOw do you treat esophagitis-mucocutaneous candidiasis?

topic therapy won’t work

oral systemic therapy-fluconazole

How do you treat uncomplicated candida vaginitis-mucocutaneous candidiasis?

OTC topical azoles

oral azoles

How do you treat recurrent candida vaginitis?

treat causal factor if present-HIV, uncontrolled diabetes, antibacterials, hormone replacement therapy
use strong azole & maintenance azole, like fluconazole

How do you prevent deep-seated candidiasis?

avoid broad spectrum antibiotics
be meticulous with your catheter
infection control!

If you have deep-seated candidiasis what do you do?

remove the source of the infection, the catheter, drain abscesses
use anti fungal agents
Polyene-amphotericin B. Don’t forget about nephrotoxicity, tho!
Triazole-fluconazole
Echinocandin-caspofungin

What is the morphology of aspergillus?

branched septate hyphae

conidial heads with spheric conidia

Where do you find aspergillus?

everywhere in air, soil, decaying vegetation
esp in hospitals
constantly inhaled
worldwide

There are 19 disease producing species of aspergillus. What are the 4 most common? List in order of most to least common.

A. fumigatus
A. flavus
A. niger
A. terreus

What are some diseases caused by aspergillum?

allergic bronchopulmonary aspergillosis-th2 response aspergilloma-fungus ball in lung invasive syndromes--begin in lungs, angioinvasive...happens with immunosuppression-->causes: invasive pulmonary aspergillosis or disseminated infection

Which toxin does aspergillus release in food etc?

aflatoxin

Is aspergillosis an issue with people who receive bone marrow transplants?

YES | 7% of BT recipients develop invasive aspergillosis. 1/3 of those die.

How do you diagnose aspergillosis?

histopath showing invasion with hyphae (includes special stains) culture of biopsy, but can be risky in sick pt blood cultures not really helpful **Note: difficult to interpret cultures from non-sterile sites b/c these things are everywhere! radiology with halo sign biomarkers

Which biomarkers are helpful in diagnosing aspergillosis?

beta glucan-nonspecific fungal marker | immunoassay for galactomannan in serum

How do you prevent aspergillosis?

patient isolation HEPA filters pozaconazole prophylaxis for high risk pts

How do you treat aspergillosis?

voriconazole-1ry therapy | can also use amphotericin B, other triazoles, echinocandins

WHat is the morphology of mucorales?

coenocytic hyphae, few septa, multinucleated | saclike fruiting structures-called sporangia w/ internal sporangiospores

Where do you find mucorales?

everywhere in the environment, esp in decaying organic substrates like food & soil

Is infection w/ mucorales common? What are the 4 most important genera (most common-->least common)?

``` infection is rare. acquired by inhalation or cutaneous or percutaneous inoculation of spores Rhizopus Mucor Cunninghamella absidia ```

T/F Mucormycosis involves an angioinvasive mucorales.

True. It invades blood vessels & causes necrosis of vessel walls.

WHat are risk factors for mucormycosis?

Neutropenia Solid organ/hematopoietic stem cell transplant Diabetes or metabolic acidosis Deferoxamine (chelation) therapy to remove excess iron – fungus uses deferoxamine as a xenosiderophore **mucor actually feeds off of the chelator!

What are some clinical diseases that can result from mucormycosis?

Rhinocerebral – associated with diabetes mellitus Pulmonary infection Cutaneous Disseminated mucormycosis

How do you diagnose mucormycosis?

samples--biopsy, swabs, not really blood cultures | histopath will show broad, empty, thin walled, mostly aseptate hyphae

What would a culture of mucormycosis show?

rapidly grown in standard mycologic media | see sporangium & sporangiospores

What are the biomarkers that can be sued to check for mucormycosis?

there aren't any! | beta glucan & galactomannan will both come up negative.

How do you treat mucormycosis?

resistant to antifungals surgical resection of infected area amphotericin B **sometimes the bad forms of this begins as a sinus tract infection

The patient is a 28-year-old who presents with vaginitis that is accompanied by a thick, curdlike discharge. Physical exam showed edema and pruritis of the vulva. Microscopy showed epithelial cells and masses of hyphae. She was given a topical antifungal that is widely available over the counter. What is the mechanism of action of the antifungal? ``` A. Blocks ergosterol synthesis B. Inhibits DNA and RNA synthesis C. Inhibits squaline epoxidase D. Inhibits folic acid synthesis E. Inhibits glucan synthesis ```

This pt has vaginal candidiasis. The topical treatment will be an azole. Inhibit lanosterol demethylase. A.