Opportunistic mycoses 2 + Deep Mycoses Flashcards
___ is a heavily encapsulated, neutrotrophic yeast that primarily causes meningoencephalitis
Cryptococcus neoformans
(C in cryptococcus - for capsule; neo - neutrophils (sorta))
Describe the transmission/pathogenesis of Cryptococcus
Tx: spore inhalation
Pathogenesis: Inhalation of yeast >> replication in lung >> fungus crosses blood brain barrier via capsule expansion or zona occludans (tight junctions) or enters epithelial cells/macrophages which send it into the brain parenchyma
Describe the 2 main virulence factors of Cryptococcus neoformans
Heteropolysaccharide (glucuronoxylomannan) capsule - inhibits phagocytosis
Phenoloxidase - production of melanin; the bug’s cell wall has melanin that serves as an oxidative sink (visualized by the white dude Fontana Masson)
At what CD4 count are HIV+ patients at risk for Cryptococcus infections?
Name 2 other risk factors for Cryptococcus infection
100ul or less
High dose corticosteroids
Solid organ transplant recipients receiving immunosuppressive agents
Which organism is indicated below?
Cryptococcus neoformans (note that the clear space around the red yeast shows where the capsule is - it breaks down in this fixation which is why it doesn’t stain)
How does a patient with Cryptococcal meningoencephalitis present?
What happens in the brain that can lead to cortical blindness and herniation?
Headache, impaired concentration, memory loss, confusion, lethargy
Increased intracranial pressure due to capsule expansion >> cortical blindness, herniation
Why are inflammatory markers muted in Cryptococcus meningoencephalitis?
Capsule inhibits host immune response + this is likely happening in an immunocompromised host anyway
How do you Dx Cryptococcus infection?
Direct exam (easy to see in HIV+ pts)
Culture (also do wet mount with India ink - see clear halos around bug and aggregations of yeast forms)
Cryptococcal Ag test
PCR (some false negatives)
Rx for Cryptococcal infection
Ampho B + 5FC (just think of how the 2 rhyme) + fluconazole maintenance
**adjunctive Rx: relief of increased intracranial pressure**
(you treat Crypto C with amphoB and 5FC)
___ opportunistic pneumonia caused by an obligate parasite-fungus
Pneumocystic pneumonia
___ is the causative agent of Pneumocystic pneumonia
Pneumocystis jirovecii
An HIV infected patient presenting with tachypnea, dyspnea, alveolar interstitial pulmonary infiltrates + hypoxia has ___ until proven otherwise
An HIV infected patient presenting with tachypnea, dyspnea, alveolar interstitial pulmonary infiltrates + hypoxia has Pneumocystis until proven otherwise (pt also has non-productive cough)
Which organism causes the pathology below?
Pneumocystis jirovecii
**advanced stage diffuse alveolar-interstitial pneumonia (bat-wing appearance)
(most of the diffuse-ness is host protein)**
How do you Dx Pneumocystis infection?
Dx: bronchoalveolar lavage >> staining >> cysts with endospores and once released, become trophozoites
Trophs are obligate parasites and like to infect alveolar macrophages
(can visualize both cysts - GMS or calcoflour stain and trophs - Wright-Giemsa or immunoflourescence)
Also do PCR
What is the 1st line Rx for Pneumocystis pneumonia?
TMP-SMX (also used as Prx in high risk pts) - think Pneumocystis is almost a protozoan but not really so that’s why you ca treat it w/ antibiotics
Others:
Pentamidine
Primaquine/Clindamycin
Dapsone-trimethoprim
Atovaquone
The host defense hallmark of Histoplasmosis is ___
Which fungus is the causative agent of histoplasmosis?
Granuloma formation (non caseating or caseating)
Histoplasma capsulatum
In an immunocompetent host, what kind of granuloma is formed in response to Histoplasmosis infection?
Granuloma with NO necrosis (this is an immunocompetent host)
What kind of granuloma in response to Histoplasma infection forms in an immunocompromised host?
Poorly formed granulomas with histiocytosis and caseation occurs with many intracellular yeasts
Which set of lung xrays belongs to an immunocompetent vs immunocompromised host with Histoplasma infection? (what are the features of each)
Top panel: immunocompetent host - Solitary or scattered asymptomatic pulmonary nodules
Bottom panel: immunocompromised host - disseminated, multiple pulmonary nodular interstitial infiltrates
Which organism is this and what infection does it cause?
Histoplasma capsulatum
Which fungus is this and what infection does it cause?
Blastomyces dermatitidis yeast: broad based budding and double refractile wall
Causes blastomycosis
Blastomycosis typically affects 3 body systems/ organs. Name them.
Lung, skin and bone
(B - bone, L for lung and S for skin)
Which fungus is this and what infection does it cause?
Coccidiodes (causes coccidiodomycosis)
**the fungi live as arthroconidia in the environment tend to be joined together (easily wafted into the air and enter the body via inhalation)
**note that they exist as spherules in tissue. Spherules are loaded with endospores and those are responsible for causing disease (not eradicated by macrophages)
Describe how Coccidiodomycosis is transmitted
Organism grows in soil >> forms hyphae following rainfall (which makes the environment moist) >> hyphae become arthroconidia which are easily wafted into the air >> inhalation >> conversion to spherules in human host >> release of endospores that chew up lung tissue and further propagate infection
What is the difference between Histo and Coccidiodomycosis infection in the lungs (i.e. which one has lung cavities that calcify vs ones that don’t)?
Histo cavities calcify whereas Cocc won’t
