Protozoa: Amebea

Question 1

What are the intestinal amebae? (3)

Answer 1

• Entamoeba
• Endolimax
• Iodamoeba

Question 2

Entamoeba histolytica:

-Morphologically indistinguishable from?

Answer 2

E. dispar

*nonpathogenic

Question 3

Entamoeba histolytica:

-Morphologically similar to?

Answer 3

• E. coli

- E. hartmanni

Question 4

What is the only feature that can differentiate E. histolytica from E. dispar?

Answer 4

Erythrophagocytosis (E. histolytica)

Question 5

Entamoeba histolytica - Trophozoites:

• Size
• Nucleus (2)
• Cytoplasm
• Motility

Answer 5

-15-20 um
Nucleus:
-small, central karyosome
-fine peripheral chromati
Cytoplasm:
-"ground glass" appearance (+/- ingested RBCs)
Motility:
-Unidirectional*

*E. coli/E.hartmanni are NONdirectional

Question 6

Entamoeba histolytica - Cysts:

-Characteristics (2)

Answer 6

• Cysts have up to 4 nuclei

- Chromatoidal bodies w. smooth rounded ends

Question 7

Entamoeba histolytica:

-Diagnosis method

Answer 7

Stool EIA > Stool microscopy

Question 8

Entamoeba histolytica:

• Transmission
• geographic distribution

Answer 8

Ingestion of Cysts in fecally contaminated food or water

-Worldwide distribution

Question 9

Entamoeba histolytica - Clinical features:

• S/S
• Histological findings/location
• Complications (2)

Answer 9

• Asymptomatic–Protracted diarrhea
• “flask shaped” ulcer (cecum MC)
• Invades intestinal wall and disseminates to liver
• Amebic abscesses (Anchovy Pastelike)

Question 10

Entamoeba Coli Vs. E. histolytica - Trophozoites:

• Size
• Karyosome
• Chromatin

Answer 10

• Larger than E. histolytica (20-25 um)
• Large, Eccentric karyosome
• Clumped, peripheral chromatin

Question 11

Entamoeba Coli Vs. E. histolytica - Cysts:

• Nuclei
• Chromatoidal bars

Answer 11

• Up to 8 nuclei (E. histolytica/hartmanni Never >4)

- Frayed (splintered) chromatoidal bodies

Question 12

Entamoeba hartmanni Vs. E. histolytica - Trophozoites:

-Most distinguishing characteristic

Answer 12

SMALL

• Trophozoite (5-10 um)
• Cyst (5-8 um)

Question 13

Endolimax nana.

-Characteristic feature (1)

Answer 13

Large, knobby “ball and socket” central karyosome

Question 14

Iodamoeba butschlii.

-Characteristic features (2)

Answer 14

• Prominent iodine staining vacuole

- Large “ball and socket” central karyosome

Question 15

Free living amebae are found widely in the environment, what are the species that are opportunistic human pathogens? (3)

Answer 15

• Naegleria fowleri
• Acanthamoeba spp.
• Balamuthia mandrillaris

Question 16

Naegleria fowleri:

• Causes
• Transmission
• Pathophysiology

Answer 16

• Primary amebic menignoencephalitis (PAM)
• Warm stagnant fresh water
• Enters through nasal cavity - frontal lobe via olfactory nerve (running through cribriform plate)

Question 17

Naegleria fowleri:

-Where are trophozoites found?

Answer 17

CSF or meninges and surrounding brain tissue

Question 18

Naegleria fowleri - Trophozoites:

• Size
• Nucleus/karyosome

Answer 18

• 10-35 um

- Small nucleus with a large, dense central karyosome

Question 19

Naegleria fowleri:

-Culture

Answer 19

Lawn of bacteria (E. coli)

Question 20

Naegleria fowleri:

-CSF handling

Answer 20

Do NOT refrigerate

Question 21

Acanthamoeba spp. and Balamuthia mandrillaris both cause what?

Answer 21

Granulomatous Amebic Encephalitis (GAE)

Question 22

Granulomatous Amebic Encephalitis (GAE):

• Source
• Brain involvement

Answer 22

-Cutaneous or Pulmonary source
Hematogenous dissemination to brain
-Organisms found in perivascular spaces

Question 23

What organism is responsible for amebic keratitis in contact lens wearers?

Answer 23

Acanthomeba spp.

Question 24

Acanthamoeba spp./Balamuthia mandrillaris - Identication:

-Cysts (3)

Answer 24

• 2 walls
• 1 nucleus
• Large karyosome

Question 25

Acanthamoeba spp./Balamuthia mandrillaris - Identication: | -Trophozoites (3)

Answer 25

- Pleomorphic - Small nucleus - Large central karyosome