Pathogenic and Non-pathogenic Amoeba

Question 1

What are the intestinal amoeba?

Answer 1

• Entamoeba histolytica
• Entamoeba dispar
• Entamoeba coli
• Entamoeba polecki
• Entamoeba hartmanni
• Entamoeba gingivalis
  *Endolimax nana
• Iodamoeba butschlii

Question 2

What are the non-pathogenic amoeba?

Answer 2

• Entamoeba dispar
• Entamoeba coli
• Entamoeba polecki
• Entamoeba hartmanni
• Entamoeba gingivalis
• Endolimax nana
• Iodamoeba butschlii

Question 3

What are the pathogenic amoeba?

Answer 3

• Entamoeba histolytica

Question 4

Pathogenic intestinal amoeba that can cause amoebic dysentery and amoebic liver abscess

Answer 4

Entamoeba histolytica

Question 5

Treatment for Entamoeba histolytica

Answer 5

Metronidazole or tinidazole

Question 6

Non-pathogenic intestinal amoeba that is morphologically indistinguishable from E. histolytica.

Answer 6

Entamoeba dispar

Question 7

Non-pathogenic intestinal amoeba that is commonly found in the human intestine.

Answer 7

Entamoeba coli

Question 8

Non-pathogenic intestinal amoeba that is similar to E. coli, but has a smaller nucleus.

Answer 8

Entamoeba polecki

Question 9

Non-pathogenic intestinal amoeba that is similar to E. coli, but has a larger nucleus.

Answer 9

Entamoeba hartmanni

Question 10

Non-pathogenic amoeba that is commonly found in the human mouth.

Answer 10

Entamoeba gingivalis

Question 11

Entamoeba gingivalis

Answer 11

Endolimax nana

Question 12

Non-pathogenic intestinal amoeba that is commonly found in the human intestine.

Answer 12

Iodamoeba butschli

Question 13

What are the free-living amoeba?

Answer 13

• Naegleria fowleri
• Acanthamoeba spp.
• Balamuthia mandrillaris

Question 14

Treatment for Naegleria fowleri

Answer 14

• Amphotericin B
• Fluconazole
• Miltefosine
• Azithromycin
• Surgery (to remove infected brain tissue)

Question 15

Treatment for Acanthamoeba spp.

Answer 15

• Chlorhexidine
• Propamidine isethionate
• Fluconazole
• Miltefosine
• Azithromycin
• Surgery (to remove infected tissue)

Question 16

Treatment for Balamuthia mandrillaris

Answer 16

• Fluconazole
• Miltefosine
• Azithromycin
• Surgery (to remove infected brain tissue)

Question 17

Free-living amoeba that can cause primary amebic meningoencephalitis (PAM).

Answer 17

Naegleria fowleri

Question 18

Free-living amoebae that can cause granulomatous amebic encephalitis (GAE) and chronic amebic keratitis (CAK).

Answer 18

Acanthamoeba spp

Question 19

Free-living amoeba that can cause granulomatous amebic encephalitis (GAE).

Answer 19

Balamuthia mandrillaris

Question 20

What are the three forms of E. histolytica?

Answer 20

• trophozoite
• precyst
• cyst.

Question 21

What is the trophozoite stage of E. histolytica?

Answer 21

The trophozoite stage is the vegetative or growing stage of E. histolytica. It is irregular in shape, varying in size from 12-60 µm, with an average size of 20 µm. It is large and actively motile in freshly-passed dysenteric stool but smaller in convalescents and carriers. The trophozoite has clear, transparent, and refractile outer ectoplasm and finely granular inner endoplasm.

Question 22

How does the trophozoite of E. histolytica move?

Answer 22

The trophozoite of E. histolytica moves through crawling or gliding movements, not through free swimming. It forms finger-like projections called pseudopodia by sudden jerky movements of the ectoplasm in one direction, followed by the streaming in of the whole endoplasm. The direction of movement can change suddenly with the formation of a new pseudopodium.

Question 23

What is the structure and appearance of the nucleus in the trophozoite stage?

Answer 23

The nucleus in the trophozoite stage is spherical, 4-6 µm in size. It contains a central karyosome surrounded by a clear halo and is anchored to the nuclear membrane by fine radiating fibrils called the Linin network, giving it a cartwheel appearance. The nuclear membrane is lined by a rim of chromatin distributed evenly as small granules.

Question 24

What distinguishes the trophozoites of E. histolytica from other intestinal amoebae?

Answer 24

The trophozoites of E. histolytica, especially those from acute dysenteric stools, often contain phagocytosed erythrocytes. This feature is diagnostic, as phagocytosed red cells are not found in any other commensal intestinal amoebae.

Question 25

What is the precystic stage of E. histolytica?

Answer 25

The precystic stage occurs when the trophozoite of E. histolytica extrudes its food vacuoles, becomes round or oval in shape, and measures about 10-20 µm in size. It contains a large glycogen vacuole and two chromatid bars.

Question 26

Describe the cystic stage of E. histolytica.

Answer 26

The cystic stage of E. histolytica is spherical in shape, about 10-20 µm in size. The early cyst contains a single nucleus, a mass of glycogen, and 1-4 cigar-shaped refractile rods called chromatoid bodies or chromidial bars. As the cyst matures, the glycogen mass and chromidial bars disappear, and the nucleus undergoes two successive mitotic divisions, resulting in a quadrinucleate cyst. The cyst wall is highly refractile and resistant to gastric juice and unfavorable environmental conditions.

Question 27

What is the host for the life cycle of E. histolytica?

Answer 27

The life cycle of E. histolytica occurs exclusively in one host, which is humans.

Question 28

What is the infective form of E. histolytica?

Answer 28

The infective form of E. histolytica is the mature quadrinucleate cyst, which is passed in the feces of convalescents and carriers. The cysts can remain viable for about 10 days under moist conditions.

Question 29

How is E. histolytica transmitted?

Answer 29

Infection with E. histolytica occurs when a person swallows food and water contaminated with cysts. The cysts are resistant to the action of gastric juice and can pass through the stomach undamaged to reach the small intestine.

Question 29

What happens during excystation of E. histolytica?

Answer 29

Excystation of E. histolytica occurs when the cyst reaches the cecum or the lower part of the ileum, where the alkaline medium and the action of trypsin damage the cyst wall. As a result, the cytoplasm of the cyst detaches from the cyst wall, and ameboid movements lead to the liberation of the quadrinucleate ameba, which is referred to as the metacyst.

Question 30

What is the fate of the metacystic trophozoites of E. histolytica?

Answer 30

The nuclei in the metacyst of E. histolytica immediately divide to form eight nuclei. Each nucleus is surrounded by its own cytoplasm, resulting in the formation of eight small amebulae or metacystic trophozoites. If excystation takes place in the small intestine, these trophozoites do not colonize there but are carried to the cecum. The optimal habitat for the metacystic trophozoites is the submucosal tissue of the cecum and colon, where they lodge in the glandular crypts and grow by binary fission.

Question 31

How is the life cycle of E. histolytica completed?

Answer 31

Some of the metacystic trophozoites of E. histolytica develop into precystic forms and cysts, which are then passed in feces to repeat the cycle. The entire life cycle of E. histolytica, including excystation, colonization, and cyst formation, is completed within one host.

Question 32

What is the role of carriers in the spread of E. histolytica?

Answer 32

In most cases, E. histolytica remains as a commensal in the large intestine without causing any ill effects. These individuals become carriers or asymptomatic cyst passers and are responsible for the maintenance and spread of infection in the community. However, in some cases, the infection may become activated, and clinical disease, known as amebiasis, ensues. Latency and reactivation are characteristic features of amebiasis.

Question 33

What are the two main forms of amebiasis caused by E. histolytica?

Answer 33

The two main forms of amebiasis caused by E. histolytica are intestinal amebiasis and extraintestinal amebiasis.

Question 34

What is the incubation period for amebiasis caused by E. histolytica?

Answer 34

The incubation period for amebiasis caused by E. histolytica can range from 4 days to 4 months, with significant variability.

Question 35

What are the symptoms of intestinal amebiasis?

Answer 35

Symptoms of intestinal amebiasis include diarrhea (which may be bloody), abdominal pain, cramping, and occasionally fever. In severe cases, it can lead to dysentery.

Question 36

Which organ is most commonly affected by extraintestinal amebiasis?

Answer 36

The liver is the most commonly affected organ in extraintestinal amebiasis caused by E. histolytica, leading to the formation of amebic liver abscesses.

Question 37

What are the symptoms of amebic liver abscesses?

Answer 37

Symptoms of amebic liver abscesses include fever, right upper quadrant abdominal pain, and hepatomegaly (enlargement of the liver).

Question 38

Can E. histolytica trophozoites invade tissues beyond the intestine?

Answer 38

Yes, E. histolytica trophozoites have the ability to invade tissues beyond the intestine, leading to extraintestinal amebiasis.

Question 39

What factors contribute to the severity of amebiasis?

Answer 39

The severity of amebiasis depends on the organ affected and the extent of tissue damage caused by the invasion of E. histolytica trophozoites.

Question 40

an individuals infected with E. histolytica remain asymptomatic?

Answer 40

Yes, many individuals infected with E. histolytica remain asymptomatic and act as carriers, passing cysts in their feces without experiencing any symptoms.

Question 41

What are some complications of extraintestinal amebiasis?

Answer 41

Complications of extraintestinal amebiasis can include pulmonary, cerebral, or other forms of organ-specific involvement beyond the liver.