The Amoeba Flashcards
What are Ameba?
Single-celled parasite that moves by means of cytoplasm extensions called pseudopods (false feet)
Trophozoite
Motile feeding stage of amebas that multiply by binary fission
Cyst
Non-motile, non-feeding stage of amebas that are capable of survival outside their hosts and initiating human infection
Karysome
Central mass of chromatin inside select amebic nuclei
Peripheral chromatin
Ring of chromatin that surrounds the nuclei of select amebas
Chromatid bar
Oblong structures containing condensed RNA material in the cytoplasm of amebic cysts
Excystation
The transformation of amebic cysts into amebic trophozoites
Encystation
The transformation of amebic trophozoites into amebic cysts
What are the two amebic morphologic forms?
Trophozoites and Cysts
What is the infective stage?
Ingestion of cysts in the human intestinal tract
How do trophozoites multiply in the intestinal tract?
Asexual binary fission
What is the diagnostic stage?
When cysts and/or trophozoites do not make the conversion in time.
- Usually found in the stool
Can trophozoites live in outside environment?
No in the outside environment they disintegrate.
Can cysts live in outside environment?
Yes they continue to develop in the outside world for subsequent entry into unsuspecting human.
True or False:
Most intestinal amebic infections are asymptomatic.
True
What intestinal ameba is pathogenic?
Entamoeba Histolytica
What is the sample of choice for recovering intestinal amoeba?
Stool
What is the sample of choice for recovering extraintestinal amoebae?
CSF/brain tissue or corneal scrapings.
What are the 3 intenstinal species?
Entamoeba histolytica
Entamoeba hartmanni
Endolimax nana
What are the 2 extraintestinal species?
Naegleria fowleri
Acanthoamoeba species
Where can you find E. histolytica?
Tropic,subtropic, and cold climates.
How is E. histolytica transmitted?
Via contaminated food/water, hand-to-mouth, unprotected sex (anal/oral)
Circulating flies and cockroaches.
What are the symptoms of an E. histolytica infection?
Diarrhea, dysentery, abdominal pain/cramping, weight loss.
Prevention and control of E. histolytica
- Proper water treatment and food/handling preparation
- Protected sex
- Protection of food from insects
- Avoidance of human stool
Laboratory diagnosis of E. histolytica
- Stool
- evidence of RBCs within cytoplasm
What are the two non-pathogenic ameba?
Entamoeba hartmanni and endolimax nana
How can you disninguish E. histolytica vs. Endolimax hartmanni in diagnosis?
Major difference is SIZE
Transmission for Endolimax hartmanni
- Consumption of contaminated food/water
- Via insects
What are the two extraintestinal species of amoeba?
Naegleria fowleri and acanthamoeba species
Where is Naegleria fowleri found?
Warm bodies of water including lakes, streams, ponds, and swimming pools and contaminated dust
What severe disease does Naegleria fowleri cause?
Primary amebic meningoencephalitis (PAM)
- trophozoites invade and cause rapid brain tissue destruction.
How do you diagnose Naegleria fowleri?
Saline/iodine wet preps of CSF are best for ameboid trophs, tissues, or nasal discharge
What are the 3 morphologic forms of naegleria fowleri?
- Ameboid trophozoite
- Flagellate form
- Cyst
True or false:
Entire life cycle of N. fowleri occurs in external environment.
True
What is the epidemiology of Acanthamoeba species?
Immunocompromised or debilitated individuals at greatest risk for CNS infections; or soft contact lens wearers.
What is Granulomatous amebic encaphalitis (GAE)?
Granulomatous lesions of the brain that result in ocular pain and vision problems.
How do humans contact Acanthamoeba species?
- Aspiration or nasal inhalation of the organisms through nasal mucousa and/or skin
- Direction invasion into the eye
What is the reservoir for E. histolytica?
Humans/accidental host
Describe the life cycle of E. histolytica in your own words.
What is the concern with untreated infections of E.histolytica?
Extraintestinal mybiosis.
