Lect 18 Flashcards
Cryptococcosis from Cryptococcus neoformans affects what patient population
- immunocompromised
- AIDS, lymphoma
Cryptococcus gattii affects what patient population
found in immunocompetent hosts
Cryptococcus neoformans natural reservoir
- soil
- bird droppings
how does someone get infected with Cryptococcus neoformans
- inhalation of dessicated yeast cells
- most often starts as skin or pulmonary infection then progresses to CNS
- cryptoococcal disease are not communicable!
what critical condition can Cryptococcus neoformans cause
meningoencephalitis
- yeast form prefers CSF
Cryptococcus neoformans
- capsule?
- serotypes?
- encapsulated
- serotypes A-D (most frequently A)
Cryptococcus neoformans has what that allows them to form melanin from phenol containing substrates
Diphenol Oxidase (Laccase)
List virulence factors of Cryptococcus neoformans
- capsule
- Diphenol oxidase - form melanin
- ability to grow at 37 C
Name the two clinical manifestations of infection with Cryptococcus neoformans
- pulmonary
- asymptomatic/flu-like/cavitation
- Disseminated
- meningitis, skin lesions, cryptococcoma
how is cryptococcosis diagnosed
- samples: CSF, sputum, skin lesion -> india ink
- growth on CGB medium will differentiate between gattii and neoformans
tx of Cryptococcosis
- amphotericin B (+flucytosine)
- life long fluconazole prophylazid following primary tx in AIDS patients
Exserohilum rostratum is commonly found where
- black mold of the soil and plants
- found in warm, humid climates
what was the predominant pathogen in the multistate outbreak of fungal meningitis associated with contaminated steroids
Exserohilum rostratum
Toxoplasma gondii affects what patient populations
- asymptomatic in immunocompetent host
- severe complications in immunocompromised hosts and women newly infected in pregnancy
Toxoplasma gondii is present in what two distinct morphological forms? These forms also can be divded into subcategories. name this too.
-
Trophozoites
- Tachyzoite: acute disease; actively proliferating
- Bradyzoite: chronic disease; slowly replicating
-
Cysts
- Zoitocyst: tissue cytst that contains bradyzoites
- Oocyst: sexual stage in cats
what is the host for sexual stage of Toxoplasma gondii life cycle
cats
which form of Toxoplasma gondii is the infective stage
cysts
what are the triad of symptoms suggesting congenital toxoplasmosis
- chorioretinitis
- hydrocephalus
- intracranial calcifications
how does transmission of Toxoplasma gondii occur
- no person-to-person contact
- occurs through
- foodborne
- zoonotic
- congenital
- **pregnant women should not clean liter box or adopt new cats
What stages of Toxoplasma gondii life cycle are diagnostic
- Zoitocysts
- Trophozoites
how is Toxoplasma gondii diagnosed
- ELISA to measure parasite specific IgG or IgM in pregnant women
- PCR
- parasites can be isolated from CSF
Tx of Toxoplasma gondii
- not necessary in immunocompetent
- in immunocompromised
- pyrimethamine and sulfadiazine (does not completely remove parasite)
- AIDS patients require lifelong therapy
What is Naegleria fowleri? where is it normally found
- facultative environmental protozoan
- found in soil and fresh water
- swimming pools, streams, ponds
infection with Naegleria fowleri results in
Primary acute meningoencephalitis (PAM)
- rapidly fatal: death can occur within 2 days of becoming symptomatic
- fever, stiff neck, HA, AMS, confusion, hallucinations, sz
Naegleria fowleri has what two distinct morphological forms
- Cyst: single nucleate
- Trophozoites
- Flagellate (2 flagella)
- Amoeboid
which form of Naegleria fowleri is the reproductive form, the only form in tissue, phagocytoses RBC and WBC, and destroys tissue
- Trophozoites -> Amoeboid
in Naegleria fowleri, the cyst form arises from
arises from the amoeboid form in harsh conditions
in Naegleria fowleri, which form is the infective stage? how does it infect
- Trophozoites -> Flagellate form
- enters nasal passages, then transforms into amoeboid form
- migrates along olfactor nerve to brain
- consumes cells of brain
Naegleria fowleri can infect what patient populations
immunocompetent patients
how does someone become infected with Naegleria fowleri
- not spread person-to-person
- can’t be contracted from drinking contaminated water
-
HAS to go through nasal passages
- increased incidence through use of tap water in Neti pots
how is Naegleria fowleri diagnosed
- CSF
- wet mount for motile amoeba
-
clearing zones on E-coli covered agar plates
- plates coated with E-coli
- drop of CSF on plate
- look for clearing zones, pick up amoeba and place in distilled water
- if you see flagellated form => confirmation
DOC Naegleria fowleri
- combo
- Amohotericin B
- Rifampin
- Miconazole
prevention of Naegleria fowleri
- avoid swimming in stagnant ponds
- keep head above water
- use only distilled/purified water in Neti pots
- Salination occasionally works as a decontaminant, chlorine is ineffective
What are the two main causes of Acanthamoebiasis
- Acanthamoeba castellani
- Acanthamoeba culbertsoni
What are the two morphological forms of Acanthamoeba
- Trohozoite
- infective stage
- posses spiked pseudopodia
- Cyst
- 3 layered wall
how does someone become infected with Acanthamoeba
- enters through lower respiratory tract or through ulcerated or broken skin
Acanthamoeba causes what three clinical syndromes
- Granulomatous Amoebic Meningoencephalitis (GAM or GAE)
- Ocular Acanthamoebiasis Keratitis and Uveitis
- Disseminated disease
describe Ocular acanthamoebiasis keratitis
- introduced by trauma to the eye followed by contamination with cysts
- ulceration, intense pain, blurred vision
Acanthamoeba primarily affects what patient population
immunocompromised hosts
what does Acanthamoeba feed on in nature
- free living organism
- feeds on bacteria in nature
how is Acanthamoeba diagnosed
- both cysts and trophozoites can be observed in tissue sections
- keratitis: corneal scraping
- GAE: post mortem brain biospy
tx: Acanthamoeba keratitis
- oral itraconazole, topical miconazole and a corticosteroid
tx of Acanthamoeba GAE
- pentamidine and ketoconazole
Balamuthia mandrillaris exists in what 2 forms
- trophozoite: no flagella
- mostly binucleate
- flat pseudopodia for locomotion
- cyst: 3 layered wall
which form of Balamuthia mandrillaris is infectious
BOTH forms
how does Balamuthia mandrillaris enter the body
- inhalation of cysts or through wounds
- may form a skin lesion or migrate to the brain
clinical presentation
- facial paralysis
- difficulty swallowing
- sz
- paralysis
- double vision
Balamuthia mandrillaris
where is Balamuthia mandrillaris normally found
- soil
- preys on other amoeba
Balamuthia mandrillaris can affect what patient population
can infect healthy persons
Balamuthia mandrillaris allows what bacteria to replicate within it
- legionella pneuophila
- increases virulence of parasite
how is Balamuthia mandrillaris diagnosed
- cysts and trophozoites can be identified in tissue sections
- cannot be cultured easily
- only co-cultured with primate hepatic cells or human brain cells
tx Balamuthia mandrillaris
- combo x 2 weeks
- flucanazole
- sulfadiazine
- pentamidine
- then azithromycin for at least 3 weeks
