Lecture 24 - Fungal Respiratory Parasites Flashcards
describe yeast
- unicellular
- round to ovoid
- reproduce by budding
describe mold
- multicellular
- branching filaments (hyphae)
- forms mycelium
dimorphic fungus characteristics
- inhalation, inoculation, ingestion
- systemic
- mold (25-30) and yeast (35-37)
which of the following is dimorphic fungus?
a. candida
b. malassezia
c. aspergillus
d. blastomyces
d. blastomyces
what is the most common/important Blastomyces species
B. dermatitidis
describe Blastomyces in the parasitic stage
yeast form, 5- 20 um, with broad-based budding
what species is most commonly affected by Blastomyces
dogs (working/sporting breeds during hunting seasons)
describe the pathogenesis of blastomycosis in 6 steps
- inhalation of spores
- conversion to yeast
- express Bad 1 (adhesin) that aids in uptake by phagocytic cells in the respiratory tract
- minimal respiratory burst response and downregulation of TNF
- delayed CMI response
- pyogranulomatous inflammation
will Blastomyces disseminate? if yes, where to?
yes - vascular and lymph routes
how is blastomycosis diagnosed
- direct microscopy - broad base, single budding yeast
- PCR
- ELISA
- AGID (soluble exoantigen)
- culture
what is a differential for blastomycosis
cryptococcus
what is the treatment of blastomycosis
systemic antifungal therapy (itraconazole is preferred) for 2 months
describe histoplasmosis
dimorphic
mold and yeast (parasitic; 2-5 um, narrow-based budding)
what species are commonly affected by histoplasmosis
cats and dogs
summarize the pathogenesis of histoplasmosis in 5 steps
- inhalation of pathogen
- attach and phagocytosed by lung macrophages
- differentiate to yeast and multiply
- release of yeast on cell death
- intracellular replication continued
histoplasmosis causes _______ inflammation
pyogranulomatous
what are the virulence factors of histoplasmosis that allows survival in phagolysosome
- calcium-binding protein
- resistant to acidification
- M antigen
- iron acquisition
- melanin production
how is histoplasmosis diagnosed
- direct examination
- tissue biopsy/histology
- dimorphic fungal culture
- quantitative antigen ELISA
T/F: relapses of histoplasmosis are uncommon
FALSE
how should histoplasmosis be treated
4-6 month course of systemic antifungal therapy (itraconazole)
what two species of coccidiodes are pathogenic
- C. immitis
- C. posadasii
describe Coccidiodes morphology
dimorphic fungi
mold = bulging, barrel-shaped hyphae in soil
fungus = spherules containing endospores in tissue
what species are affected by coccidioidomycosis
dogs and horses
describe the pathogenesis of coccidioidomycosis in 5 steps
- inhalation or inoculation
- conidia differentiate into spherules
- engulfed by macrophages and survive
- inadequate Th1 cell-mediated immunity
- systemic dissemination
what is the important virulence factor of coccidioidomycosis? what is its job?
SOWgp
adhesin that causes Th2 immunomodulation to reduce CMI
how is coccidioidomycosis diagnosed
- direct microscopy
- dimorphic fungal culture
- complement fixation
- quantitative antigen immunodiffusion
- PCR
treatment for coccidioidomycosis
4-6 month course of systemic antifungal (fluconazole)
T/F: treatment of coccidioidomycosis in horses is typically unsuccessful
TRUE
a 4y/o Gordon setter died following mild fever, visual deficit, anorexia, and weight loss, non-healing draining skin lesion, and persistent cough over 4 weeks
On necropsy, lungs indicate interstitial pneumonia. histology reveals broad-based budding organisms with central granular protoplasm. what is your diagnosis?
B. dermatitidis
how many serotypes of C. neoformans is there
5 (A through D + AD)
describe the morphology of cryptococcus
dimorphic fungi with round to oval yeast cells that have thick capsular walls and narrow-based budding
what species is commonly affected by cryptococcosis
cats
where is C. gatti endemic
pacific northwest - associated with native plants
summarize cryptococcosis pathogenesis in 4 steps
- inhalation from environment
- thick capsule around yeast provides resistance to immune recognition and phagocytosis
- little to no inflammation
- spreads from nasopharynx to CNS
what are the virulence factors of cryptococcosis
- capsule
- phospholipase
- melanin production
what are the clinical symptoms of cryptococcosis
*usually self-limiting and opportunistic
- lesions in URT, granulomas in lungs, and secondary sites
- mastitis in cattle
- rare resp. disease in horse
how is cryptococcosis diagnosed
- specimen
- direct examination (yeast with narrow-based budding)
- culture
- ELISA
- PCR
how is cryptococcosis treated
surgical removal +/- 2-month antifungal treatment
T/F: cryptococcus infections are not contagious
TRUE
what are the 3 forms of candida
- budding
- pseudohypha
- true septate hyphae
T/F: candida is a normal commensal fungus of the digestive and urogenital tract
TRUE
what is the pathogenesis of candida
increase in concentration or failure to eliminate due to concurrent disturbance (immunosuppression or abx overuse)
the transition of candida from yeast to hyphal form provides what
- avoid phagocytosis
- enhanced invasiveness
what are candida virulence factors
- adhesion molecules
- surface structures bind fibrinogen and complement
- protease
- phospholipase
how is candida diagnosed
- yeast/hyphae under microscopy
- culture-based methods
- molecular/serological tests
treatment for candida
- correction of underlying condition
- copper sulfate/nystatin in feed/water
- fluconazole
describe pneumocystis
6 species
saprophyte, yeast-like organism causing subclinical/latent infection due to opportunistic disease
describe the pathogenesis of pneumocystosis in 4 steps
- inhalation of organism into the respiratory tract
- colonize at low numbers
- increased number in immunocompromised host (low CMI)
- obstruct alveolar spaces and disrupt gas exchange
how is pneumocystosis diagnosed
- specimen
- direct examination
- PCR
how is pneumocystosis treated
response to antibiotic and antiprotozoal drugs (clindamycin, atovaquone, etc.0
T/F: pneumocystosis is contagious within the same species but not zoonotic
TRUE
describe aspergillus
septate hyphae with unbranched conidiophores that rapidly grows and is thermotolerant and aerobuc
what 4 virulence properties are known for aspergillosis
- adhere to collagen, fibrinogen, laminin
- proteases
- growth at 37
- gilotoxin
summarize the pathogenesis of aspergillosis
- spore inhalation
- germination and hyphal invasion (no true virulence known)
what does gilotoxin do
inhibit cilia and phagocytosis
what is the clinical disease manifestation of aspergillosis
- immune competence
- vasculitis
- thrombus formation
- mycotic granulomas
what species is most susceptible to aspergillosis
birds
match the species to its aspergillosis manifestation
a. birds
b. dogs
c. horse
- guttural pouch mycosis
- pneumonia
- nasal aspergillosisis
a. 2
b. 3
c. 1
how is aspergillosis diagnosed
- presence of tissue invasion
- biopsy and histology
- routine fungal culture
- ELISA
how is aspergillosis treated
6-8week course of antifungal therapy and developing good hygiene procedures
