Yeast and dimorphic fungal infections Flashcards
Candida albicans stains gram positive or negative?
Gram positive staining
T/F: C. albicans is a monomorphic yeast
False
it reversibly transitions from single cell to pseudohyphal and hyphal forms
What fungus causes “thrush”?
Candida albicans
Where can you find thrush plaques caused by C. albicans in pigs? Humans?
Pigs - around and in the mouth/face
Diaper rash in humans
If C. albicans easy to diagnose? What test(s) might be performed?
YES.
Can perform in hospital gram stain or diff quick - will note budding yeast
**easy to grow in culture (aerobic or fungal)
What will determine tx of infections of C. albicans?
Severity of infection
Local vs systemic antifungals
Malazzezia pachydermatis are lipophilic yeast - this makes them have an affinity for what kind of cells/tissue?
They have an affinity for oily skin and sebaceous glands
Malazzezia may cause what two conditions in canines?
Otitis externia
sebaceous dermatitis
What animals are most susceptible to Cryptococcus?
CATS
**Immunocompromised are most susceptible
How do cats get Cryptococcus infections?
Cryptococcus is associated with pigeon droppings (C. neoformans) – cats will inhale this in the environment
Cryptococcus gattii is associated with eucalyptus trees
What stain is used for an impression smear of Cryptococcus and what will be seen under the microscope?
India ink
There will be a clear space around the spherical budding yeast = capsule
What is the capsule of Cryptococcus good for?
Evading the immune system
T/F: Cryptococcus is zoonotic
FALSE
Humans get infected - but from the environment (pigeon feces) not from infected animals
What pathogenesis can Cryptococcus cause?
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
What diagnostics can be performed if you suspect cryptococcosis?
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)
T/F: Cryptococcosis can be treated with a short course of antifungals
FALSE
Long term tx is required. Removal of masses can be a tx option.
Drugs - Amphotericin B, flucytosine, Azoles
Thermally dimorphic fungi take what shape at what temperatures?
Warm (mammalian body temps) = single cell yeast or spherical form
Ambient environmental temps (less than 30*C) = mold
What fungus is the most common cause of systemic mycoses?
Blastomyces = Blastomycosis
Blastomyces dermatitidis is endemic to what region in the US?
Ohio to Mississippi river valley
Why is blastomyces dermatitidis becoming more prevelant?
GLOBAL WARMING!!! environmental fungus
Sorry Trumpys - this is REAL
What characteristics will you note if looking at blastomyces under the microscope?
Large - broad based - buddying yeast
Surrounded with inflammatory cells if taken from a granulomatous lesion
How do animals gets blastomycosis? Who gets it?
Inhalation
Dogs and humans (sometimes cats)
What does Blastomycosis cause?
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
Can blastomycosis be treated successfully?
It depends on the severity of the infection. If caught early enough, yes.
What will Histoplasma look like under the microscope?
Found IN macrophages - will have a “halo” of spores
H = Halo = Histoplasma
Where does Histoplasma grow in the environment?
Dark moist soil covered in bird and bat feces (where birds roost/bat caves)
*Endemic in the Ohio, Missouri, and Mississippi river valleys
T/F: Histoplasma is a BSL3 agent
TRUE
What is the route of entry of Histoplasma?
inhalation
Transmission is favored by dry, dusty conditions and disturbance of soil
Histoplasma has many similarities to tuberculosis - what clinical signs/pathogenesis will you see in a histoplasma infection?
Chronic/active respiratory dz or disseminated dz
Intestinal dz is common in dogs
induces granulomatous inflammation
What clinical presentation of histoplasma infection will you see in dogs? And in cats?
Dogs = intestinal dz = HGE
Cats = granulomatous chorioretinitis (eye infection) ** second most common systemic fungal infection in cats
How do you diagnose histoplasma infections?
Microscopic detection of agen in tissue, Serology
***Culture can be done, but since this is a BSL3 - special steps must take place
T/F: Coccidioides immitis produces both a yeast and mold form
False
it is dimorphic - but does not produce yeast form.
It forms a large thick walled spherule containing endospores
What level BSL agent is coccidioides immitis? What dz does is cause in humans?
BSL3 - causes valley fever
but is geopgrahically limited to San Joaquin valley and surrounding southwestern regions of US
What do coccidioes produce at environmental temperatures?
Hyphae
*these will break into arthroconidia = infections structure
How do humans and animals get coccidioidomycosis?
inhalation of arthroconidia
What dz conditions does coccidioidomycosis cause?
Respiratory tract infection, disseminated infection in other organs, ***Osteomylitis, granulomatous host response
What does coccidioides look like under the microscope?
Large spherules full of lots of small spores
Why should you ask owners about travel history?
Helps you differentiate what infections/diseases animals may have based on exposure to endemic regions
Disseminated strangles could resemble what fungal infection?
coccidioidomycosis
can have abscesses around the neck/throat etc
Where do you often see Sporothrix schenkii infections in cats/horses (and other animals)?
SQ nodule/cutaneous local legions along lymphatics
granulomatous and Pyogranulomatous host response
What does Sporothrix schenkii look like under the microscope?
cigar shaped years (oblong ovals)
Where do Sporothrix schenkii live in the environment?
sphagnum moss, hay, plant materials, and soil
called a “rose gardner’s syndrome)
What can be used to treat Sporothrix schenkii infections?
Azoles (ketoconazole etc), potassium iodide
What is a common problem in testing when using fungal serology?
False positives and false negatives
What is a specific in hospital test that can be performed to diagnose Cryptococcus neoformans?
Latex agglutination test
Qualitative and semi-quantitative test system for detection of capsular antigens - in serum or CSF
