Lecture 6: Amebas Flashcards
What is the current status of ameba taxonomy?
Unsettled
What are some important families of amebas?
Family Entamobidae – E. histolytica
Family Vahlkampfiidae
Genus Naegleria – N. fowleri
Family Acanthamoebidae
Family Entamoeba
Parasites or commensals of the digestive organs
of vertebrates and arthropods
What are the 3 genra of ameba organisms important to humans and animals?
- Genus Entamoeba – pathogenic, commensals
- Genus Endolimax - commensals
- Genus Iodamoeba - commensals
Entamoeba coli
An intestinal commensal similar to E. histolytica
Entamoeba gingivalis
A commensal found in the mouth, does not have have a cyst form
Entamoeba poleki
E spp found in pigs and monkeys
Is E. Histolytica reportable?
Yes
Where can E Histolytica be found in the world?
All over the world, but most commonly in the tropics
E. dispar
A non-invasive strand of E histolytica, but immunologically different
E. hartmanni
Identical to E histolytica but smaller in size and nonpathogenic in nature
E. Moshkovskii
Identical in morphology to E. histolytica, but not a symbiont
E. Coli
Morphologically similar to E. histolytica
What are E histolytica’s life cycle stages?
Trophozoite
Precyst
Cyst
Metacyclic trophozoite
What kind of life cycle does E histolytica have?
Direct
Amebic Dysentery?
Intestinal disease caused by E. histolytica that can be acute, chronic, or cause an ameboma
What can amebic dysentery result in?
Hepatic amebiasis
Pulmonary amebiasis
Cardiac lesions
How can we diagnose amebic dysentery? (diagnostic stage)
An exam of fresh fecal material for trophozoites or cysts.
Identification of trophozoites in infected organs
What is used to treat amebic dysentery?
Metronidazole
How can we prevent amebic dysentery?
Stopping fecal - oral transmission Water filtration/boiling Proper sewage disposal Wash/peel vegetables & fruits Treat infected dogs
Family Vahlkampfiidae characteristics
- Aerobic inhabitants of soil, water, sewage
- Mainly bacteriophagous - consume bacteria as diet
- Few species can be facultative parasites in vertebrates
- Diphasic amebas
Diphasic amebas
Amebas that possess both a flagellated stage and an ameboid form – ameboid stage predominates
Binary fissions only takes place in ameboid form
Naegleri Fowleri
Organism that is the major cause of a disease called Primary Amebic Meningoencephalitis (PAM)
What are the life cycle stages of Naegleri Fowleri?
Cyst
Flagellate
Trophozoite
What kind of life cycle does Naegleri Fowleri have?
Direct
Primary Amebic
Meningoencephalitis (PAM)
An acute and rapidly fatal disease
What is PAM’s prepatent period?
2-5 days
Dead in 5 - 7 days
Who is most affected by PAM?
Young healthy children or youths
What form is PAM’s infective agent in?
Believed to be in the flagellated form, though ameba free-living form may be found in CSF
How does Naegleri Fowleri cause disease?
It enters via the nasal passages, migrates along olfactory nerves into the cranium.
Where does Naegleri Fowleri replicate?
It proliferates rapidly in warm temperatures (thermal pools)
How is PAM diagnosed?
At autopsy by identifying the organism in the CSF
Acanthamoeba spp.
Facultative parasites of humans similar to Naegleria
How many Acanthamoeba spp have been identified in human tissues?
Four
What form do the Acanthamoeba spp take?
Free living, non-flagellated form
What do the Acanthamoeba spp cause?
A chronic infection of the skin or the CNS, or corneal ulcers and keratitis in immunocompromised individuals
What is the source of Acanthamoeba spp infections?
Public swimming pools
Where was Balamuthia mandrillaris first isolated?
rom the brain of a baboon which died from meningoencephalitis. It has been associated with primary amoebic meningoencephalitis
How are Balamuthia mandrillaris infections acquired?
By respiratory tract or skin lesions
What can occur in CNS tissues due to Balamuthia mandrillaris?
Trophozoites and cysts
What is another name for Balamuthia mandrillaris and why?
Granulomatous Amebic Encephalitis. The name comes from the organisms ability to induce a chronic granulomatous inflammatory response.
