Mycology Flashcards
Important component in fungal cytoplasmic membranes that is a target for antifungals
ergosterol
Basset hound, cocker spaniels, poodles, and west highland terriers are predisposed to infection with what yeast?
Malassezia
Associated with greasy lesions that are malordorous and pruritic
Malassezia pachydermatis
Prolonged/excessive antimicrobial therapy can predispose for these infections
Candidiasis
Aspergillosis
Associated with moist lesions that can be scabbed; “Bed sores”
candida albicans
Which of the cutaneous mycoses can disseminate?
Candida albicans
How can you confirm invasion by Candida albican?
microscope exam–>presence of pseudohyphae
isolation alone isn’t enough to confirm diagnosis
Organisms that most commonly cause dermatophytosis
Microsporum spp. (usually M. canis)
Trichophyton spp.
What type of cells are infected by Microsporum/Trichophyton
dead skin cells (i.e. stratum corneum, hair, claw)
T/F: Geophilic dermatophytosis can be transferred from dog to man
False; can affect both dog and man but they can only get it from soil
Infective portion of Microsporum/Trichophyton
arthroconidia
Where do horses usually get ring worm
in friction area (i.e. halter area)
Pseudomycetomas associated with dermatophytosis are common to which spp.? Prognosis?
Cats
Poor (needs surgery)
Onchomycosis?
infection of the nail/claw
Best way to diagnose dermatophytosis?
Culture! Most definitive and can be done in-house
Dermatophilosis is caused by a _______
gram positive bacteria
Dermatophilus zoospores are attracted to what
differing levels of CO2
“Paint brush lesions” are typical of infection with
Dermatophilus
Diagnostic feature of Dermatophilus?
double rows of spores!
Important virulence factors of aspergillus
aflatoxins
gliotoxins–immunosuppressant
In dogs, this disease can present as a respiratory disease with bloody discharge and necrosis of sinuses
Aspergillosis
Female german sherpherds are predisposed to what
disseminated aspergillosis
Does disseminated aspergillosis in dogs have nasal involvement?
not usually
This infection in cattle can cause a respiratory tract infection with abortion; there will be TB-like lesions on the placenta
Aspergillosis
Horses infected with _____ with usually have guttural pouch infection and keratitis
Aspergillosis
Though rare in cats, which breed is more commonly infected with Aspergillosis
Persians
Sino-orbital disease in cats is associated with
Aspergillosis
A microscopic exam of a sample containing Aspergillosis will show
septate hyphae
dichotomous branching
Which diagnostic tool is least useful for aspergillosis?
serology
- -many strains
- -host may not be making markers
Causative agents of Entomophthoramycosis and their primary mode of tramission
Basidiobolus spp. (percutaneous and ingestion)
Conidiobolus spp. (inhalation)
Ruminants and small ruminant presenting with a blocked nasal cavity are likely infected with
Conidiobolus
This fungus is usually associated with insect bites and rarely disseminates
Basidiobolus
When diagnosing Entomophthoramycosis, what should you not do with the sample
refrigerate (they don’t like cold)
On a microscope, this will present as gram positive branching filaments
Norcardia spp. (Nocardiosis)
3 disease forms of Nocardiosis
cutaneous to subcutaneous
pulmonary
systemic
A cow that presents with watery milk that contain white/yellow flakes and has an enlarged udder with nodules most likely has
Nocardiosis
Why isn’t systemic therapy enough to treat nocardiosis
they are intracellular
Unique feature of dematiaceous fungi?
contain melanin in cell wall
A dog presenting with a tumor-like lesion with draining tracts and granules.
Granules on evaluation are a mixture of necrotic debris and hyphae (with brown pigment). Dx?
Mycetoma
Chromoblastomycosis produces what unique feature?
sclerotic bodies
Dimorphic fungi are usually ________ dependent
temperature
Name the 5 systemic mycoses
Blastomyces Histoplasma Crytpococcus Sporothrix Coccidioides
Most commonly infected host of blastomycosis
dogs
An outdoor dog presents with harsh lung sounds, proliferative granulomatous lesions, chronic cough, and weight loss. Radiographs reveal a “snowstorm” appearance to the lungs. Likely Dx?
blastomycosis
Best way to diagnose blastomycosis? How will it look?
Microscope exam
broad-based budding yeast (diff-quick)
T/F: culture for blastomycosis is easy and can be done in house
False… IT’S VERY DANGEROUS
this fungus prefers dark locations and lives in close association with bird and bat excrement
histoplasma
Incubation period for histoplasma?
short (12-16 days)
Infection of the lower respiratory tract is more likely if this form of histoplasma is inhaled
microconidia (vs. macroconidia)
Where does histoplama replicate?
intracellularly (“halo” appearance)
A dog presents with weepy, ulcerative lesions, as well as large bowel diarrhea (mucous and blood). Likely Dx?
(based on GI involvement)
histoplasma
Why isn’t serology very useful for histoplasma?
can get false positive and negatives
also shares antigens with blasto (can be positive for both)
Which dimorphic mold is capsulated?
Cryptococcus
Cryptococcus favors what form?
yeast
Size of the capsule of cryptococcus determines what
if it will stay in the nasal cavity or reach the pulmonary tissue
3 important things cryptococcus’s capsule does in the host
interferes with leukocyte migration
depletes complement
inhibits t-cell response
Which spp. is most susceptible to cryptococcus
Cats
A dog presents with skin lesions, fever, and neurological signs. The CNS signs point to a potential cervical lesion, but based on the other clinical signs, it’s probably
cryptococcus
A use for serology with cryptococcus infections?
monitoring response to treatment (one dilution drop per month of treatment)
Sporothrix is usually found where
in moss and decaying matter
the mold form of sporothrix produces conidia that usually enter the host _________
cutaneously (but can also be inhaled)
Unique feature of Sporothrix?
Both the mold and yeast forms are infective
a cat presents with multiple lesions that have shallow ulcers and draining tracts; most notably the lesions are found mostly on mucosal surfaces (i.e. eye, nose, genitalia). Likely cause?
Sporothrix
Sporothrix rarely disseminates in what spp.
dogs (usually localized to nose and extremities)
A horse presents with lesions on the medial portion of the fetlock and up; the horse has access to the woods; you also are able to palpate the lymph nodes and feel cording of the lymphatics. that’s diagnostic for
Sporothrix
Coccidioides is endemic to the
southwest
What causes activation of Coccidioides in the host
the CO2 content
Dissemination with this organism can be rapid (10 days)
Coccidioides
Which dog breeds are more susceptible to dissemination with Coccidioides
boxers and doberman pinschers
Finding spherules with a KOH wet mount is diagnostic for
Coccidioides
This presents as a tumor-like polyp in the nasal cavity and grow so large it can occlude the airway
rhinosporidium
What is the only way to diagnose rhinosporidium
microscope (will not grow in lab)
Spp. most commonly infected with rhinosporidium
dogs and horses (rarely cats)
This organism is associated with slow moving water and has a tropism for well-vascularized tissues
Prototheca
T/F: hosts MUST be immuncompromised to be infected with prototheca?
True
An aquatic pathogen that can cause cutaneous or intestinal infarctions
Pythium
How is phythium different from fungus?
cell wall doesn’t contain ergosterol
Pythium is attracted to what types of tissue
damaged (plant or mammal)
A dog presents with lesions on his extremities and ventral abdomen; he is EXTREMELY pruritic; the owners says the lesions have tripled in size over the past week… Dx?
Pythium
Unique features that can be used to ID pythium with a microscope
1) irregular, random hyphae
2) will not stain with H&E
3) eosinophilic cuff
Kunkers are associated with infection with what organism?
Phythium insidiosum
This organism has broad, relatively nonseptate hyphae and will stain with H&E
Langenidium
