Fungal respiratory infections Flashcards
Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidiodes immitis: all these undergo _____ and are dimorphic
In the envirorment they exsists as -______
phenotype switching
free living molds
In the host, ____ and ______ convert to budding yeast while ____ converts to endosporulating spherule with lots of endospores
Histo and Blasto = budding yeats
Cocci = endosporulating spherule
Infection from blasto/histo/cocci occurs most often via the ____ route and the primary site of infection is the ____ although it can disseminate
The other common location for primary infection is ______
respiratory system (can localize and cause pneumonia)
lung
cutaneous lesions
***must distinguish the site of primary infection!!!
What is key in making a definitive diagnosis for the respiratory fungal infections?
Dx requires microscopic examination
What are they key differences between the three respiratory fungal infections?
Geographic distribution and endemic areas adn efficacy of antifungal drug therapies
Where is Histoplasmosis found?
in the environment? with an what animal? What region?
Acicid soil, associated with BIRDS (bats, chickens, pigeons)
Along Mississippi and ohio river with over 85% people in those areas testing + on skin test
Describe how you see Histoplasmosis on a slide when in the ENVIRONment
multinucleated branched hyphae, with microconidia and macroconidia
Describe histoblastosis culture when taken from a human
n host: conidia convert in 15-18 hours to uninucleated oval budding yeast (2-4 micrometers),
with narrow bud neck; found inside mononuclear phagocytes, and extracellularly.
Explain mechanism of primary infction of Histoplasmosis
Main infeciton likely microconidia because of their small size, ability to become airborne–>penetrate into the deep lung and deposit in the alveoli. Microconidia are engulfed by macrophages, wherein the microconidia convert to the yeast form within a few hours and then
begin to replicate
What is the most frequent result of infection with hitsoplasmosis in an immunocompetant individual?
asymptomatic infection or a non-specific flu-like syndrome (fever, chest pain, dry/non-productive cough, headache, joint/muscle pain), which resolves.
If symptoms occur, they start **3-17 days **
(mean: 10 days) after exposure. In the gen. pop. , clinically severe disease is relatively rare (<5%)
Indianapolis, soil disruption, working in construction, prisoners clearing roadside vegitaiton, near bird roosts
–all these are correlated with which fungal infection?
Histoplasmosis
What are the five concerning clinical syndromes we see with histoplasmosis?
Pulmonary: focal/nodular or diffuse disease~ resemble TB on xray
Acute pericarditis (only 5% pts) d/t host immune response
Disseminated: more common in immunocompromised
Ocular histoplasmosis syndrome: fibrosing inflammatory response to yeast~ vision loss
Firbrosing mediastinitis: abnormal immunologic response–> leads to fibrosis
What is our most common endemic mycosis in AIDS patients
Histoplasmosis: big issue in immunodeficient patients
In Histoplasmosis, microconidia have receptors for ______integrins on the surface of macrophages, which facilitate phagocytosis
CD2/CD18
Histoplasmosis treatement: Not all clinical manifestations require drug treatment. Called upon in severe or progressive disease,
anti-fungal drugs are considered
a therapeutic adjunct to assist the host’s immune system in clearing
or at least containing the pathogen until the protective host response has developed
What three challenges does Histoplasmosis present to the Clinician?
- DDx: blastomycosis, pneumonia, TB
- In endemic areas, skin test reactivity to histoplasmin doesn’t necessarily indicate ‘active’ disease bc most inhabitant have been exposed
- Organisms can be see in PAS and GMS stained specimens
What is special about this staining of histoplasmosis?
Silver stain, see histoplasmosis in INTRAcellular vacuoles
How does histoplasmosis present on chest Xray?
Presents as multiple calcified lesions (can be confused with TB)
What do we see on this HE of histoplasmosis?
Histo granuloma, host response to hole off infection
What bad thing can happen to the mediastinum from histoplasmosis?
Fibrosing mediastinitis; exagerated host response
What is the pathology of fibrosing mediastinitis from Histoplasma pericarditis?
Exaggerated infl. response to healed pulmonary Histoplasma lesion…
Primary infection–Lesion heals–> Secondary inflammation–> fibrosis:
can have obstruction of SVC, cor pulmonale, mitral stenosis
You see organism from lung of pt and it is described as a large budding year with a BROAD bud neck. Dx?
Blastomycosis (turns into yeast in human host)
Describe what blastomycosis looks like in the environment
Uninucleate hyphae producing microconidia
What characteristics do we see when growing Blastomycosis in culture?
Blasto is dimorphic
What do we see cutaenously in pt with blastomycosis?
In primary has these black speckles, in advanced, more extensive
How does Blastomycosis look on chest xray
you can have moderate or in this picture severe which grows a bit quicker
What does Cocciodes look like in enviroment?
septate multicellular hyphae, with alternate cells developing into barrel-shaped arthroconidia each of which is separated by a vacuolated non-viable cell. Arthroconidia readily separate at these “joints”
How does cocciodes present in the host?
arthroconidia convert to large spherules, which are round double-walled
structures measuring approximately 20-100 micrometers in diameter, comparable in size to host macrophages (30-60 micrometers). The spherules contain numerous small endospores
What do we see on xray in early and late stage of cocciodiodes
See cavitation… especially in the late phase, may be fluid filled and you can see fluid line
