Yeast and dimorphic fungal infections

Question 1

Candida albicans stains gram positive or negative?

Answer 1

Gram positive staining

Question 2

T/F: C. albicans is a monomorphic yeast

Answer 2

False

it reversibly transitions from single cell to pseudohyphal and hyphal forms

Question 3

What fungus causes “thrush”?

Answer 3

Candida albicans

Question 4

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

Answer 4

Pigs - around and in the mouth/face

Diaper rash in humans

Question 5

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

Answer 5

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

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

Question 6

What will determine tx of infections of C. albicans?

Answer 6

Severity of infection

Local vs systemic antifungals

Question 7

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

Answer 7

They have an affinity for oily skin and sebaceous glands

Question 8

Malazzezia may cause what two conditions in canines?

Answer 8

Otitis externia

sebaceous dermatitis

Question 9

What animals are most susceptible to Cryptococcus?

Answer 9

CATS

**Immunocompromised are most susceptible

Question 10

How do cats get Cryptococcus infections?

Answer 10

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

Cryptococcus gattii is associated with eucalyptus trees

Question 11

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

Answer 11

India ink

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

Question 12

What is the capsule of Cryptococcus good for?

Answer 12

Evading the immune system

Question 13

T/F: Cryptococcus is zoonotic

Answer 13

FALSE

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

Question 14

What pathogenesis can Cryptococcus cause?

Answer 14

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

Question 15

What diagnostics can be performed if you suspect cryptococcosis?

Answer 15

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)

Question 16

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

Answer 16

FALSE

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

Drugs - Amphotericin B, flucytosine, Azoles

Question 17

Thermally dimorphic fungi take what shape at what temperatures?

Answer 17

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

Question 18

What fungus is the most common cause of systemic mycoses?

Answer 18

Blastomyces = Blastomycosis

Question 19

Blastomyces dermatitidis is endemic to what region in the US?

Answer 19

Ohio to Mississippi river valley

Question 20

Why is blastomyces dermatitidis becoming more prevelant?

Answer 20

GLOBAL WARMING!!! environmental fungus

Sorry Trumpys - this is REAL

Question 21

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

Answer 21

Large - broad based - buddying yeast

Surrounded with inflammatory cells if taken from a granulomatous lesion

Question 22

How do animals gets blastomycosis? Who gets it?

Answer 22

Inhalation

Dogs and humans (sometimes cats)

Question 23

What does Blastomycosis cause?

Answer 23

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

Question 24

Can blastomycosis be treated successfully?

Answer 24

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

Question 25

What will Histoplasma look like under the microscope?

Answer 25

Found IN macrophages - will have a "halo" of spores H = Halo = Histoplasma

Question 26

Where does Histoplasma grow in the environment?

Answer 26

Dark moist soil covered in bird and bat feces (where birds roost/bat caves) *Endemic in the Ohio, Missouri, and Mississippi river valleys

Question 27

T/F: Histoplasma is a BSL3 agent

Answer 27

TRUE

Question 28

What is the route of entry of Histoplasma?

Answer 28

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

Question 29

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

Answer 29

Chronic/active respiratory dz or disseminated dz **Intestinal dz is common in dogs** induces granulomatous inflammation

Question 30

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

Answer 30

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

Question 31

How do you diagnose histoplasma infections?

Answer 31

Microscopic detection of agen in tissue, Serology | ***Culture can be done, but since this is a BSL3 - special steps must take place

Question 32

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

Answer 32

False it is dimorphic - but does not produce yeast form. It forms a large thick walled spherule containing endospores

Question 33

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

Answer 33

BSL3 - causes valley fever but is geopgrahically limited to San Joaquin valley and surrounding southwestern regions of US

Question 34

What do coccidioes produce at environmental temperatures?

Answer 34

Hyphae | *these will break into arthroconidia = infections structure

Question 35

How do humans and animals get coccidioidomycosis?

Answer 35

inhalation of arthroconidia

Question 36

What dz conditions does coccidioidomycosis cause?

Answer 36

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

Question 37

What does coccidioides look like under the microscope?

Answer 37

Large spherules full of lots of small spores

Question 38

Why should you ask owners about travel history?

Answer 38

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

Question 39

Disseminated strangles could resemble what fungal infection?

Answer 39

coccidioidomycosis | can have abscesses around the neck/throat etc

Question 40

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

Answer 40

SQ nodule/cutaneous local legions along lymphatics granulomatous and Pyogranulomatous host response

Question 41

What does Sporothrix schenkii look like under the microscope?

Answer 41

cigar shaped years (oblong ovals)

Question 42

Where do Sporothrix schenkii live in the environment?

Answer 42

sphagnum moss, hay, plant materials, and soil called a "rose gardner's syndrome)

Question 43

What can be used to treat Sporothrix schenkii infections?

Answer 43

Azoles (ketoconazole etc), potassium iodide

Question 44

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

Answer 44

False positives and false negatives

Question 45

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

Answer 45

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