E3- Fungal and Parasitic CNS infections Flashcards
What is the habitat of Cryptococcus neoformans?
Natural reservoirs- soil, bird droppings
What is typically required for Cryptococcus neoformans to cause an infection?
Underlying immunodeficiency prior to infection
What type of disease does Cryptococcus neoformans cause?
Starts as a skin or pulmonary infection and can lead to meningoencephalitis (fatal)
What can be seen on india ink of Cryptococcus neoformans?
Encapsulated yeast
What are the 3 pathogenicity factors of Cryptococcus neoformans?
- Capsule
- Diphenol oxidase that forms melanin from phenol containing substrates
- Able to grow at 37 degrees C
How is Cryptococcus neoformans transmitted?
Inhalation of yeast cells
Is Cryptococcus neoformans communicable?
NO
What form of Cryptococcus can cause more extensive infections?
How can you differentiate this species from Cryptococcus neoformans.?
Cryptococcus gatti
Culture on canavanine glycine bromothymol blue medium (C. gatti will turn blue)
How can Cryptococcus neoformans be dx?
- Samples of CSF (examined w/ india ink)
- Culture on Bird Seed agar/Caffeic acid medium
- Serology (detection of capsule antigen in CSF/serum by latex agglutination)
What type of stain should be used to examine Cryptococcus neoformans?
India ink
What type of plates should be used to culture Cryptococcus neoformans?
Bird Seed agar/Caffeic acid medium
What is typically required for Toxoplasma gondii to cause an infection?
Underlying immunodeficiency prior to infection
What patient populations can Toxoplasma gondii cause severe complicattions?
- Immunocompromised
- Newly infected pregnant women
What is the infective form of Toxoplasma gondii?
Cysts
Which type of trophozoite form of Toxoplasma gondii is considered the actively replicating form?
Tachyzoite-acute disease
Which type of trophozoite form of Toxoplasma gondii is considered the slowly replicating form?
Bradyzoite-chronic disease
Which type of cyst form of Toxoplasma gondii contains bradyzoites?
Zoitocysts
Which type of cyst form of Toxoplasma gondii is seen in seen in cats and is the sexual stage of the parasites lifecycle?
Oocysts
What is the triad of congenital toxoplasmosis?
- Chorioretinitis
- Hydrocephalus
- Intracranial calcifications
How is Toxoplasma gondii transmitted?
- Food borne (usually zoitocysts)
- Zoonotic (oocysts)
- Congenital
What forms of Toxoplasma gondii are seen on dx?
Zoitocysts and trophozoite forms
How is Toxoplasma gondii dx?
- ELISA
- PCR
- Isolated from CSF
What is the habitat of Naegleria fowleri?
Soil and fresh water (facultative environmental protozoan)
What form of Naegleria fowleri is infectious?
Flagellate (trophozoite)
What form of Naegleria fowleri is reproductive and feeds on bacteria?
Amoeboid (trophozoite)
What form of Naegleria fowleri is formed in tissue, causing destruction and phagocytosis of RBCs and WBCs?
Amoeboid (trophozoite)
What is the life-cycle of Naegleria fowleri?
- Infective flagellate form enters the nasal passage and then transforms into the amoeboid form
- It migrates along the olfactory nerve to the brain
- Causes severe necrosis of the olfactory bulb and brain tissue through sucker apparatus
How is Naegleria fowleri transmitted?
Entry through the nasal passageway
What type of infection does Naegleria fowleri cause?
Primary Acute Meningoencephalitis
Does a Naegleria fowleri infection require an immunocompromised host?
No
Is Naegleria fowleri spread person-to-person or via contaminated drinking water?
No
There is increasing incidence of Naegleria fowleri infections via what?
Neti pots
How is Naegleria fowleri dx?
- Drop CSF on plate with E. coli
- Look for clearing zones
- Pick up amoeba and place in distilled water
- Look for flagellated form
Is chlorine effect in killing Naegleria fowleri?
No
What is the infective stage of Acanthamoeba?
Trophozoite
What is seen in the trophozoite form of Acanthamoeba?
Spiked pseudopodia
How is Acanthamoeba transmitted?
Enters through the lower respiratory tract or ulcerated/broken skin
What are the 3 clinical syndromes caused by Acanthamoeba?
- Granulomatous Amoebic Meningoencephalitis
- Ocular Acanthamoebiasis Keratitis and Uveitis
- Disseminated disease
How does Acanthamoeba cause a Granulomatous Amoebic Meningoencephalitis infection?
Hematogenous route to the brain
How does Acanthamoeba cause an Ocular Acanthamoebiasis Keratitis and Uveitis infection?
Introduced by trauma to the eye, followed by contamination with cysts
What form of Acanthamoeba can be seen in tissue?
Both trophozoite and cysts
How is Acanthamoeba dx?
- Tissue sample
- Keratitis cornea scrapings
- Postmortem brain biopsy
What is not efficient in dx Acanthamoeba?
Examining CSF
What type of infection can Balamuthia mandrillaris cause?
Granulomatous Amoebic Meningoencephalitis
What form of Balamuthia mandrillaris is infectious?
Both the trophozoite and cyst forms are infectious
What is seen in the trophozoite form of Balamuthia mandrillaris?
Binucleate
Flat pseudopodia
How is Balamuthia mandrillaris transmitted?
Enters through the lower respiratory tract or ulcerated/broken skin
What geographic location is Balamuthia mandrillaris most commonly found?
Southern states (California) Latin America
What does Balamuthia mandrillaris allow to replicate within it? Why?
Legionella pneumophilia
Increases its virulence
What form of Balamuthia mandrillaris can be seen in tissue?
Both trophozoite and cysts
How is Balamuthia mandrillaris dx?
Only co-cultured with primate hepatic cells or human brain cells
Why can Balamuthia mandrillaris not be cultured easily?
It does not feed on bacteria
