Lecture 6: Amebas

Question 1

What is the current status of ameba taxonomy?

Answer 1

Unsettled

Question 2

What are some important families of amebas?

Answer 2

Family Entamobidae – E. histolytica
Family Vahlkampfiidae
Genus Naegleria – N. fowleri
Family Acanthamoebidae

Question 3

Family Entamoeba

Answer 3

Parasites or commensals of the digestive organs

of vertebrates and arthropods

Question 4

What are the 3 genra of ameba organisms important to humans and animals?

Answer 4

1. Genus Entamoeba – pathogenic, commensals
2. Genus Endolimax - commensals
3. Genus Iodamoeba - commensals

Question 5

Entamoeba coli

Answer 5

An intestinal commensal similar to E. histolytica

Question 6

Entamoeba gingivalis

Answer 6

A commensal found in the mouth, does not have have a cyst form

Question 7

Entamoeba poleki

Answer 7

E spp found in pigs and monkeys

Question 8

Is E. Histolytica reportable?

Answer 8

Yes

Question 9

Where can E Histolytica be found in the world?

Answer 9

All over the world, but most commonly in the tropics

Question 10

E. dispar

Answer 10

A non-invasive strand of E histolytica, but immunologically different

Question 11

E. hartmanni

Answer 11

Identical to E histolytica but smaller in size and nonpathogenic in nature

Question 12

E. Moshkovskii

Answer 12

Identical in morphology to E. histolytica, but not a symbiont

Question 13

E. Coli

Answer 13

Morphologically similar to E. histolytica

Question 14

What are E histolytica’s life cycle stages?

Answer 14

Trophozoite
Precyst
Cyst
Metacyclic trophozoite

Question 15

What kind of life cycle does E histolytica have?

Answer 15

Direct

Question 16

Amebic Dysentery?

Answer 16

Intestinal disease caused by E. histolytica that can be acute, chronic, or cause an ameboma

Question 17

What can amebic dysentery result in?

Answer 17

Hepatic amebiasis
Pulmonary amebiasis
Cardiac lesions

Question 18

How can we diagnose amebic dysentery? (diagnostic stage)

Answer 18

An exam of fresh fecal material for trophozoites or cysts.

Identification of trophozoites in infected organs

Question 19

What is used to treat amebic dysentery?

Answer 19

Metronidazole

Question 20

How can we prevent amebic dysentery?

Answer 20

Stopping fecal - oral transmission
Water filtration/boiling
Proper sewage disposal 
Wash/peel vegetables & fruits
Treat infected dogs

Question 21

Family Vahlkampfiidae characteristics

Answer 21

1. Aerobic inhabitants of soil, water, sewage
2. Mainly bacteriophagous - consume bacteria as diet
3. Few species can be facultative parasites in vertebrates
4. Diphasic amebas

Question 22

Diphasic amebas

Answer 22

Amebas that possess both a flagellated stage and an ameboid form – ameboid stage predominates

Binary fissions only takes place in ameboid form

Question 23

Naegleri Fowleri

Answer 23

Organism that is the major cause of a disease called Primary Amebic Meningoencephalitis (PAM)

Question 24

What are the life cycle stages of Naegleri Fowleri?

Answer 24

Cyst
Flagellate
Trophozoite

Question 25

What kind of life cycle does Naegleri Fowleri have?

Answer 25

Direct

Question 26

Primary Amebic | Meningoencephalitis (PAM)

Answer 26

An acute and rapidly fatal disease

Question 27

What is PAM's prepatent period?

Answer 27

2-5 days | Dead in 5 - 7 days

Question 28

Who is most affected by PAM?

Answer 28

Young healthy children or youths

Question 29

What form is PAM's infective agent in?

Answer 29

Believed to be in the flagellated form, though ameba free-living form may be found in CSF

Question 30

How does Naegleri Fowleri cause disease?

Answer 30

It enters via the nasal passages, migrates along olfactory nerves into the cranium.

Question 31

Where does Naegleri Fowleri replicate?

Answer 31

It proliferates rapidly in warm temperatures (thermal pools)

Question 32

How is PAM diagnosed?

Answer 32

At autopsy by identifying the organism in the CSF

Question 33

Acanthamoeba spp.

Answer 33

Facultative parasites of humans similar to Naegleria

Question 34

How many Acanthamoeba spp have been identified in human tissues?

Answer 34

Four

Question 35

What form do the Acanthamoeba spp take?

Answer 35

Free living, non-flagellated form

Question 36

What do the Acanthamoeba spp cause?

Answer 36

A chronic infection of the skin or the CNS, or corneal ulcers and keratitis in immunocompromised individuals

Question 37

What is the source of Acanthamoeba spp infections?

Answer 37

Public swimming pools

Question 38

Where was Balamuthia mandrillaris first isolated?

Answer 38

rom the brain of a baboon which died from meningoencephalitis. It has been associated with primary amoebic meningoencephalitis

Question 39

How are Balamuthia mandrillaris infections acquired?

Answer 39

By respiratory tract or skin lesions

Question 40

What can occur in CNS tissues due to Balamuthia mandrillaris?

Answer 40

Trophozoites and cysts

Question 41

What is another name for Balamuthia mandrillaris and why?

Answer 41

Granulomatous Amebic Encephalitis. The name comes from the organisms ability to induce a chronic granulomatous inflammatory response.