Lecture 05 - Amoebae Flashcards
What genus of amoeba are potentially pathogenic to humans
acanthamoeba, naegleria, balamuthia, sappinia and hartmannella
What is the group name of amoebae
sarcodina
What infections can amoebae cause
eye, brain, and other tissues/organs
What are the two basic forms of amoebae
trophozoite and cyst
What is the purpose of encystment
occurs under adverse environmental conditions and allows for survival outside of a host
What are the key points about trophozoites
- adhesion essential for locomotion and feeding
- movement enhanced by higher temperatures
What are amoebastomes
no correlation with pathogenicity, can attach to surfaces, ingests bacteria and cell debris
What are the key points about the flagellated stage
- cell changes shape
- induced by nutritional deprivation, temperature, or osmotic shock
- lasts from 2 to several hours
What are the key points about the cyst stage
- environmentally hardy
- mucopolysaccharide double wall
- resistant to biocides
- ostioles sealed by mucus plugs
- cysts not formed in tissues, left behind when trophozoites emerge
What is a diphasic amoeba
exists in both ameboid and flagellate form
How do amoeba invade
via the nasal passages on contact with water, they then travel along olfactory nerves, cribriform plate to brain
What does virulence of amoeba depend on
- Nfa 1 protien
- feeding cups
- nitric oxide production
- pore-forming proteins
- cytolytic molecules (cysteine proteases, phospholipases, hospholipolytic enzymes)
What is primary amoebic meningoencephalitis
extensive cell necrosis leading to significant hemmorage, destruction of meninges, olfactory nerves and brain tissue. As well as inflammatory exudate, and edema leading to death
What is the epidemiology of amoeba
ubiquitous and found mostly in freshwater lakes, hot water springs, poorly chlorinated pools and thermally polluted water bodies worldwide
How does the lab diagnose amoeba
microscopy of brain biopsy, CSF
in vitro culture
PCR
What is acanthamoeba culbertsoni
a trophozoite that has a spine and thick psudopodia, can also exist as as double walled cyst
What is the pathogenesis of acanthamoeba culbertsoni
slow tissue invasion
adhesion via mannose binding proteins
destruction of corneal eithelium
breaching bowmans capsule and destruction of corneal stroma
What is the pathology of acanthamoeba culbertsoni
granulomatous amebic encephalitits, necrotizing lesions, eye lesions, granuloma formation
What is the clinical presentaion of acanthamoeba culbertsoni
granulomatous amoebic encephalitis, healthy host with compromised eye, acute/chronic infection of skin, lung, uterus, prostate in immunocompromised
What is the epidemiology of acanthamoeba culbertsoni
free living and widely distributed in natural waters as well as in dust and soil
also detected in bottled mineral water, jacuzzis, recreational pools, ventilation ducts, humidifiers, air-conditioning units, shower heads and taps
How does the lab diagnose acanthamoeba culbertsoni
CSF, corneal scrapings, brain skin and other biopsies, microscopy using permanent stain, in vitro culture, PCR
What separates balamuthia mandrillaris from acanthamoeba culbertsoni
disseminated infection
