Entamoeba Histolytica Morphology Quiz

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Questions and Answers

What is the primary role of the trophozoite form of Entamoeba histolytica?

To reproduce in water

To remain non-pathogenic

To invade intestinal tissues (correct)

To undergo encystation

Which form of Entamoeba histolytica is characterized as small, spherical, and non-feeding?

Precystic (correct)

Cyst

Binucleate

Trophozoite

What happens to the precystic form of Entamoeba histolytica under conditions of compromised immunity?

It remains non-pathogenic

It undergoes division into smaller forms

It forms a thicker cyst wall

It becomes motile and pathogenic (correct)

Which of the following is NOT a characteristic of the cystic form of Entamoeba histolytica?

High motility and feeding Signup and view all the answers

How does Entamoeba histolytica typically enter the human body?

By ingestion of contaminated food or water Signup and view all the answers

In its cystic form, how many nuclei can a mature cyst of Entamoeba histolytica contain?

Four Signup and view all the answers

What is the diameter range of the trophozoite form of Entamoeba histolytica?

20 to 30μ Signup and view all the answers

What role do food handlers play in the transmission of Entamoeba histolytica?

They act as cyst passers Signup and view all the answers

What is the primary method by which trophozoites invade the intestinal wall?

By eating through the mucosa Signup and view all the answers

What triggers the excystation of cysts in the host's small intestine?

Digestion of the cyst wall by trypsin Signup and view all the answers

What leads to the formation of flask-shaped ulcers in the intestine?

Pathogenic transformation of amoebae and tissue necrosis Signup and view all the answers

How do houseflies and cockroaches contribute to the spread of infection?

They act as vectors, transporting viable cysts to food. Signup and view all the answers

What is the outcome when trophozoites do not invade the host tissues?

They continue living in the lumen of the intestine. Signup and view all the answers

What characterizes the stool of a person with amoebic dysentery?

It is usually acidic and contains entamoebae. Signup and view all the answers

What facilitates the penetration of trophozoites into the sub-mucosa?

Histolysis and cytolysis initiated by trophozoites' enzymes Signup and view all the answers

What happens to the cysts once they are ingested by a new host?

They protect the amoeba until excystation occurs. Signup and view all the answers

What is the primary symptom of amoebic dysentery?

Repeated blood-mixed, slimy and foul-smelling motions Signup and view all the answers

Which organ is NOT typically affected by trophozoites in amoebic dysentery?

Kidneys Signup and view all the answers

What diagnostic method is used to identify Entamoeba histolytica?

Microscopic finding of cysts and trophozoites in stool Signup and view all the answers

Which of the following is a common preventive measure for amoebic dysentery?

Washing hands after using toilet Signup and view all the answers

What symptom indicates the presence of abscesses in the liver caused by amoebic dysentery?

Enlargement and pain upon touch Signup and view all the answers

What is the recommended treatment for temporary relief of amoebic dysentery?

Emetine Signup and view all the answers

What type of sanitation efforts are municipalities responsible for to prevent amoebic dysentery?

Chemical treatment of human feces Signup and view all the answers

What is the significance of Charcot-Leyden crystals in stool analysis?

They suggest presence of E.histolytica Signup and view all the answers

Study Notes

Morphology

Entamoeba histolytica has three forms: trophozoite, precystic, and cyst.
Trophozoite: Active and motile form, measuring 20-30μ in diameter, characterized by a thin plasmalemma and a structured cytoplasm (ectoplasm and endoplasm).
Precystic form: Smaller (12-15μ), non-motile, non-feeding, resembles trophozoite without food vacuoles, can become pathogenic if host immunity is compromised.
Cysts: Rounded and encased in a resistant wall, measuring 10-20μ in diameter. Contains glycogen masses and chromatoid bodies. Nucleus divides from uninucleate to tetranucleate.

Transmission, Excystation, and Metacystic Development

Infection occurs via ingestion of contaminated food or water containing tetranucleate cysts.
Infected food handlers and feces in open areas contribute to contamination.
Houseflies and cockroaches can transfer cysts to uncovered food.
Cysts survive gastric juices and undergo excystation in the small intestine after 5-6 hours, releasing tetranucleate amoeba (metacyst).
Metacysts divide by binary fission to form 8 small uninucleate amoebulae, which can invade intestinal tissue or undergo encystation.

Clinical Features and Pathogenesis

E. histolytica resides harmlessly in the large intestine but can become pathogenic if gut resistance decreases.
Pathogenic magna forms invade the intestinal wall, creating flask-shaped ulcers filled with debris, lymphocytes, blood, and bacteria.
Tissue erosion occurs through histolysis and cytolysis caused by trophozoite-secreted proteolytic enzymes (histolysin).
Ruptured ulcers lead to blood and debris entering the intestinal lumen, causing amoebic dysentery characterized by acidic, foul-smelling stools mixed with blood.
Trophozoites can spread to other organs, leading to abscess formation and conditions like amoebic hepatitis, which can result in fatal complications.

Laboratory Diagnosis

Diagnosis of amoebiasis relies on microscopic examination of cysts in stool, trophozoites in fresh stool, or tissue.
Detection of antibodies against E. histolytica in blood can be performed using enzyme-linked immunosorbent assay (ELISA).
Presence of "Charcot-Leyden" crystals in stool suggests E. histolytica infection.

Prevention (Prophylaxis) and Treatment

Prevention: Hygiene practices are essential, including handwashing, food protection from pests, avoiding open defecation, and ensuring safe water supply.
Municipal hygiene efforts include monitoring food handlers, covering food articles, treating human waste, and maintaining sanitation.
Treatment: Emetine is effective for temporary relief of amoebic dysentery. Dehydroemetine, a synthetic derivative, can also be used for treatment, though achieving permanent cure may require ongoing management due to potential relapses.

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Description

Test your knowledge about the morphology of Entamoeba histolytica, focusing on its three distinct forms: trophozoite, precystic, and cystic. Understand the characteristics and significance of each form in relation to human health.