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RUSVM BacT Spring 2017 > Yeast and dimorphic fungal infections > Flashcards

Yeast and dimorphic fungal infections Flashcards

1
Q

Candida albicans stains gram positive or negative?

A

Gram positive staining

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2
Q

T/F: C. albicans is a monomorphic yeast

A

False

it reversibly transitions from single cell to pseudohyphal and hyphal forms

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3
Q

What fungus causes “thrush”?

A

Candida albicans

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4
Q

Where can you find thrush plaques caused by C. albicans in pigs? Humans?

A

Pigs - around and in the mouth/face

Diaper rash in humans

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5
Q

If C. albicans easy to diagnose? What test(s) might be performed?

A

YES.
Can perform in hospital gram stain or diff quick - will note budding yeast

**easy to grow in culture (aerobic or fungal)

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6
Q

What will determine tx of infections of C. albicans?

A

Severity of infection

Local vs systemic antifungals

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7
Q

Malazzezia pachydermatis are lipophilic yeast - this makes them have an affinity for what kind of cells/tissue?

A

They have an affinity for oily skin and sebaceous glands

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8
Q

Malazzezia may cause what two conditions in canines?

A

Otitis externia

sebaceous dermatitis

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9
Q

What animals are most susceptible to Cryptococcus?

A

CATS

**Immunocompromised are most susceptible

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10
Q

How do cats get Cryptococcus infections?

A

Cryptococcus is associated with pigeon droppings (C. neoformans) – cats will inhale this in the environment

Cryptococcus gattii is associated with eucalyptus trees

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11
Q

What stain is used for an impression smear of Cryptococcus and what will be seen under the microscope?

A

India ink

There will be a clear space around the spherical budding yeast = capsule

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12
Q

What is the capsule of Cryptococcus good for?

A

Evading the immune system

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13
Q

T/F: Cryptococcus is zoonotic

A

FALSE

Humans get infected - but from the environment (pigeon feces) not from infected animals

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14
Q

What pathogenesis can Cryptococcus cause?

A

Chronic granulomatous infection of the upper respiratory tract, CNS of cats and dogs, **when inhaled - granulomas of the nasal sinuses
sometimes skin, eye, LN
Rarley pneumonia

*Gelatinous masses and polyps with numerous organisms and minimal inflammation

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15
Q

What diagnostics can be performed if you suspect cryptococcosis?

A

Microscopic detection (encapsulated yeast)
Fungal culture - grows well
Test for capsular antigen in serum or CSF (ELISA) - CSF is more useful for CNS dz
(***tests for serum antibody are not as useful)

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16
Q

T/F: Cryptococcosis can be treated with a short course of antifungals

A

FALSE

Long term tx is required. Removal of masses can be a tx option.

Drugs - Amphotericin B, flucytosine, Azoles

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17
Q

Thermally dimorphic fungi take what shape at what temperatures?

A

Warm (mammalian body temps) = single cell yeast or spherical form
Ambient environmental temps (less than 30*C) = mold

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18
Q

What fungus is the most common cause of systemic mycoses?

A

Blastomyces = Blastomycosis

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19
Q

Blastomyces dermatitidis is endemic to what region in the US?

A

Ohio to Mississippi river valley

20
Q

Why is blastomyces dermatitidis becoming more prevelant?

A

GLOBAL WARMING!!! environmental fungus

Sorry Trumpys - this is REAL

21
Q

What characteristics will you note if looking at blastomyces under the microscope?

A

Large - broad based - buddying yeast

Surrounded with inflammatory cells if taken from a granulomatous lesion

22
Q

How do animals gets blastomycosis? Who gets it?

A

Inhalation

Dogs and humans (sometimes cats)

23
Q

What does Blastomycosis cause?

A

Disseminated dz is common - often pneumonia (will see a “snow showered” thorax on rads)
Infections can occur in other areas of the body - sometimes bone, eyes, cutaneous infection

24
Q

Can blastomycosis be treated successfully?

A

It depends on the severity of the infection. If caught early enough, yes.

25
Q

What will Histoplasma look like under the microscope?

A

Found IN macrophages - will have a “halo” of spores

H = Halo = Histoplasma

26
Q

Where does Histoplasma grow in the environment?

A

Dark moist soil covered in bird and bat feces (where birds roost/bat caves)

*Endemic in the Ohio, Missouri, and Mississippi river valleys

27
Q

T/F: Histoplasma is a BSL3 agent

A

TRUE

28
Q

What is the route of entry of Histoplasma?

A

inhalation

Transmission is favored by dry, dusty conditions and disturbance of soil

29
Q

Histoplasma has many similarities to tuberculosis - what clinical signs/pathogenesis will you see in a histoplasma infection?

A

Chronic/active respiratory dz or disseminated dz

Intestinal dz is common in dogs

induces granulomatous inflammation

30
Q

What clinical presentation of histoplasma infection will you see in dogs? And in cats?

A

Dogs = intestinal dz = HGE

Cats = granulomatous chorioretinitis (eye infection) ** second most common systemic fungal infection in cats

31
Q

How do you diagnose histoplasma infections?

A

Microscopic detection of agen in tissue, Serology

***Culture can be done, but since this is a BSL3 - special steps must take place

32
Q

T/F: Coccidioides immitis produces both a yeast and mold form

A

False

it is dimorphic - but does not produce yeast form.

It forms a large thick walled spherule containing endospores

33
Q

What level BSL agent is coccidioides immitis? What dz does is cause in humans?

A

BSL3 - causes valley fever

but is geopgrahically limited to San Joaquin valley and surrounding southwestern regions of US

34
Q

What do coccidioes produce at environmental temperatures?

A

Hyphae

*these will break into arthroconidia = infections structure

35
Q

How do humans and animals get coccidioidomycosis?

A

inhalation of arthroconidia

36
Q

What dz conditions does coccidioidomycosis cause?

A

Respiratory tract infection, disseminated infection in other organs, ***Osteomylitis, granulomatous host response

37
Q

What does coccidioides look like under the microscope?

A

Large spherules full of lots of small spores

38
Q

Why should you ask owners about travel history?

A

Helps you differentiate what infections/diseases animals may have based on exposure to endemic regions

39
Q

Disseminated strangles could resemble what fungal infection?

A

coccidioidomycosis

can have abscesses around the neck/throat etc

40
Q

Where do you often see Sporothrix schenkii infections in cats/horses (and other animals)?

A

SQ nodule/cutaneous local legions along lymphatics

granulomatous and Pyogranulomatous host response

41
Q

What does Sporothrix schenkii look like under the microscope?

A

cigar shaped years (oblong ovals)

42
Q

Where do Sporothrix schenkii live in the environment?

A

sphagnum moss, hay, plant materials, and soil

called a “rose gardner’s syndrome)

43
Q

What can be used to treat Sporothrix schenkii infections?

A

Azoles (ketoconazole etc), potassium iodide

44
Q

What is a common problem in testing when using fungal serology?

A

False positives and false negatives

45
Q

What is a specific in hospital test that can be performed to diagnose Cryptococcus neoformans?

A

Latex agglutination test

Qualitative and semi-quantitative test system for detection of capsular antigens - in serum or CSF

RUSVM BacT Spring 2017 (15 decks)

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