Intestinal Amoeba Overview
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Questions and Answers

What is the infective form of E.histolytica?

  • Fecal contaminants
  • Trophozoites
  • Mature quadrinucleated cysts (correct)
  • Cysts in tissues

Which route is the most common for the transmission of E.histolytica?

  • Vector transmission through insects
  • Fecal-oral route (correct)
  • Airborne transmission
  • Sexual contact

In which part of the body does excystation of E.histolytica occur?

  • In the lower small bowel (correct)
  • In the large intestine
  • In the upper small intestine
  • In the stomach

Which of the following groups is specifically noted for higher risk of transmission of E.histolytica through the fecal-oral route?

<p>Institutional groups such as day-care centers (D)</p> Signup and view all the answers

How do trophozoites of E.histolytica primarily obtain nutrients?

<p>Feeding on liquid nutrient and bacteria in the intestinal lumen (B)</p> Signup and view all the answers

What happens to cysts when they are exposed to desiccation?

<p>They can survive for several weeks in a moist environment (A)</p> Signup and view all the answers

What is the typical outcome for the majority of E.histolytica infections in humans?

<p>Asymptomatic carriers in the large intestine (B)</p> Signup and view all the answers

What is the size range of trophozoites of E. histolytica?

<p>12-60 µm (D)</p> Signup and view all the answers

What contributes to the rare sexual transmission of E.histolytica?

<p>Anogenital or orogenital contact (B)</p> Signup and view all the answers

What component is found in the endoplasm of the trophozoite?

<p>Nucleus and food vacuoles (B)</p> Signup and view all the answers

What is the main characteristic of the cyst of E. histolytica?

<p>Size: 10-20 µm, with 1-4 nuclei (A)</p> Signup and view all the answers

Which of the following statements is true regarding the mature cyst of E. histolytica?

<p>It has 4 nuclei and lacks chromatoid bars. (B)</p> Signup and view all the answers

During the transformation from trophozoite to cyst, which of the following occurs first?

<p>Extrusion of food vacuoles (B)</p> Signup and view all the answers

What shape are the chromatoid bodies found in immature cysts of E. histolytica?

<p>Cigar-shaped with rounded ends (B)</p> Signup and view all the answers

What feature primarily helps trophozoites of E. histolytica to move?

<p>Pseudopodia (C)</p> Signup and view all the answers

What happens to the glycogen mass in the mature cyst of E. histolytica?

<p>It disappears (A)</p> Signup and view all the answers

What is the most common site for an amoebic ulcer?

<p>Ileocecal region (A)</p> Signup and view all the answers

What is the primary organ of locomotion in amebas?

<p>Pseudopodium (D)</p> Signup and view all the answers

Which of the following is NOT a complication associated with intestinal amebiasis?

<p>Cholecystitis (B)</p> Signup and view all the answers

Which of the following is a non-pathogenic intestinal amoeba?

<p>Endolimax nana (A), Entamoeba dispar (B)</p> Signup and view all the answers

What characterizes a fulminant amoebic colitis?

<p>Generalized necrotic involvement of the entire large intestine (B)</p> Signup and view all the answers

What symptom is typically associated with amoebic infection?

<p>Severe abdominal cramps (A)</p> Signup and view all the answers

In which areas is Entamoeba histolytica more commonly found?

<p>Tropics and subtropics (B)</p> Signup and view all the answers

Which type of amoebic ulcer results in scar formation after healing?

<p>Deep ulcer (D)</p> Signup and view all the answers

What percentage of the world’s population is affected by the disease caused by Entamoeba histolytica?

<p>10% (D)</p> Signup and view all the answers

Which group has a higher prevalence of infection by Entamoeba histolytica?

<p>Families of infected persons (C)</p> Signup and view all the answers

What is a potential result of the confluence of ulcers in intestinal amebiasis?

<p>Sloughing of mucosa (D)</p> Signup and view all the answers

What is the habitat of Entamoeba histolytica in humans?

<p>Colon (D)</p> Signup and view all the answers

Which condition involves segment of intestine invaginating into an adjoining intestinal lumen?

<p>Intussusception (D)</p> Signup and view all the answers

Which of the following forms is NOT a morphology of Entamoeba histolytica?

<p>Sporozoite (A)</p> Signup and view all the answers

What indicates the presence of Entamoeba histolytica in histological examination?

<p>Both A and B (D)</p> Signup and view all the answers

Which demographic group is less likely to have severe cases of Entamoeba histolytica infections?

<p>Infants and young children (B)</p> Signup and view all the answers

What can influence the variable clinical response to amebiasis?

<p>Host factors, bacterial flora, and strain pathogenicity (D)</p> Signup and view all the answers

Which factor does NOT contribute to the virulence of certain E.histolytica strains?

<p>Presence of high intestinal cholesterol (D)</p> Signup and view all the answers

What is the characteristic form of lesions caused by E.histolytica invasion?

<p>Flask-shaped with a broad base and narrow neck (D)</p> Signup and view all the answers

What are common reasons for host susceptibility to E.histolytica infection?

<p>Malnutrition and alterations in flora (B)</p> Signup and view all the answers

What is a common symptom associated with severe amebiasis?

<p>Amoebic dysentery with bloody diarrhea (D)</p> Signup and view all the answers

Which of the following statements about E.histolytica is TRUE?

<p>Both males and females are equally affected. (A)</p> Signup and view all the answers

What role does stress play in the pathogenesis of amebiasis?

<p>It contributes to malnutrition and immune depression. (A)</p> Signup and view all the answers

Which term describes the phase of E.histolytica that invades the colonic mucosa?

<p>Trophozoite phase (C)</p> Signup and view all the answers

What characterizes an amoeboma?

<p>It is a diffuse pseudotumor-like mass of granulomatous tissue. (B)</p> Signup and view all the answers

Which cells are predominantly found in the granuloma of amoeboma?

<p>Eosinophils and amebae (D)</p> Signup and view all the answers

What complication can arise from chronic amoebiasis?

<p>Granulation tissue formation leading to strictures (B)</p> Signup and view all the answers

What is the most common site for extraintestinal amoebiasis?

<p>Liver (B)</p> Signup and view all the answers

What is an amebic liver abscess (ALA)?

<p>A rare but most common extraintestinal complication. (A)</p> Signup and view all the answers

How do amebae typically enter the liver in cases of amebic liver abscess?

<p>Through the portal vein (A)</p> Signup and view all the answers

What can cause liver damage in amebic infections?

<p>Cytokines from inflammatory cells (A)</p> Signup and view all the answers

Which of the following is NOT typically a result of amoebic intestinal infections?

<p>Development of pancreatic cysts (A)</p> Signup and view all the answers

Flashcards

Intestinal Amoeba

A type of protozoa found in the large intestine of humans and animals.

Entamoeba histolytica

A pathogenic amoeba causing amebiasis, a common diarrheal disease.

Entamoeba histolytica Habitat

Lives in the mucous and submucous layers of the large intestine.

Amoeba Morphology

Amoebas have three forms: trophozoite, precyst, and cyst.

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Trophozoite

The actively feeding and multiplying form of the amoeba, living inside the intestinal lining.

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Non-pathogenic Intestinal Amoebas

Species of amoeba found in the large intestine that do not cause disease

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Amebiasis Epidemiology

A worldwide disease, more common in the tropics and subtropics, due to hygiene and economic factors.

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High-risk groups for Amebiasis

Families exposed to an infected person, Aborigines, males, those in institutions (prisons, mental hospitals, etc.)

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Entamoeba histolytica: Life Cycle Stage

The actively feeding and motile form of Entamoeba histolytica. It's responsible for tissue damage and disease.

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Trophozoite Movement

Trophozoites move using pseudopodia – extensions of their cytoplasm that allow them to crawl and engulf food.

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Trophozoite Features

Trophozoites are irregular in shape, 12-60 µm in size, and have a distinct nucleus with a central karyosome.

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Precyst Formation

The transition stage before a trophozoite becomes a cyst. They round up, lose food vacuoles, and acquire a glycogen vacuole and chromatoid bars.

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Cyst Function

The resistant, inactive form of Entamoeba histolytica. They can survive outside the host and are the infectious stage.

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Cyst Characteristics

Cysts are round, 10-20 µm, and have a thick wall. They contain 1-4 nuclei and may have chromatoid bars.

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Infective Cyst

A mature cyst with 4 nuclei. This is the stage that causes infection when ingested.

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Cyst Formation: Food Vacuoles?

Trophozoites lose their food vacuoles during precyst formation to prepare for the dormant cyst stage.

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E. histolytica transmission

The spread of Entamoeba histolytica infection occurs primarily through the fecal-oral route, where contaminated food or water containing mature cysts is ingested.

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What is the infective form of E. histolytica?

The infective form of E. histolytica is the mature quadrinucleated cyst. This stage is resistant to harsh environments and can survive outside the host for weeks.

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How does E. histolytica spread in a community?

Asymptomatic cyst passers, individuals who carry the parasite without symptoms, are crucial in the spread of E. histolytica. They unknowingly shed cysts in their feces, contaminating the environment and perpetuating the infection cycle.

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How does E. histolytica enter the body?

Once ingested, the mature quadrinucleated cysts undergo excystation in the lower small intestine, releasing trophozoites that can then colonize the large intestine.

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What are the roles of trophozoites?

Trophozoites, the actively feeding and multiplying form of E. histolytica, live in the lumen and mucosal crypts of the colon, feeding on bacteria and nutrients.

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How does E. histolytica encyst?

As trophozoites move further down the intestine, they undergo encystation in the colon's lumen, transforming back into cysts that are then released in feces.

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What happens to most people infected with E. histolytica?

In most cases, E. histolytica remains commensal in the large intestine, meaning it lives in the body without causing disease. These individuals are called asymptomatic cyst passers.

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What conditions can lead to E. histolytica becoming pathogenic?

While most people remain asymptomatic, certain parasite and host factors can trigger E. histolytica to become pathogenic, leading to tissue invasion, amoebiasis, and potential complications like liver abscesses.

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Amoeba's Role

Entamoeba histolytica can be asymptomatic but becomes invasive under certain conditions, causing tissue damage.

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Factors Influencing Amoeba's Impact

Factors like host health, amoeba strain virulence, and bacterial flora determine the severity of E. histolytica infection.

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Virulent Strains

Certain E. histolytica strains are more aggressive due to their ability to produce enzymes that break down tissue and adhere to cells.

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Identifying Different Strains

Amoeba strains can be differentiated by their isoenzyme patterns, called zymodemes, helping to understand their virulence.

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Risk Factors for Invasive Amoeba

Malnutrition, stress, altered gut flora, and weakened immune systems increase the likelihood of aggressive E. histolytica infection.

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Amoeba's Path of Destruction

E. histolytica invades the colon, forming characteristic ulcerative lesions and causing bloody diarrhea.

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Amoeba's Characteristic Ulcers

E. histolytica ulcers consist of necrotic tissue with a flask shape, wider at the base and narrow at the opening.

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Gender Impact on Amoebiasis

Both males and females are infected with E. histolytica at a 1:1 ratio.

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Amoebic Ulcer Location

Amoebic ulcers are most commonly found in the ileocecal region, the junction of the small and large intestines. They can also be found in the sigmoidorectal region or along the entire length of the large intestine.

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Deep Amoebic Ulcer

A deep amoebic ulcer extends beyond the muscularis mucosa, the muscle layer of the intestinal wall, and can cause scarring of the intestine as it heals.

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Ulcer Confluence

When multiple amoebic ulcers merge together, it can lead to sloughing off of the intestinal lining, leaving a gaping wound. This makes the intestine more vulnerable to bacterial infections.

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Fulminant Amoebic Colitis

A severe and potentially life-threatening condition where the entire large intestine becomes necrotic (dying tissue) due to widespread amoebic ulcers. This is more common in people with weakened immune systems or during pregnancy.

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Amoebic Appendicitis

When the appendix becomes infected by Entamoeba histolytica, leading to inflammation and pain. It's often associated with severe colonic amoebiasis.

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Intestinal Perforation

A serious complication where the amoebic ulcer eats through the entire intestinal wall, causing a hole. Contents of the gut can leak into the abdominal cavity, leading to peritonitis (infection of the abdominal lining).

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Toxic Megacolon

A life-threatening condition where a segment of the large intestine becomes extremely dilated and inflamed, leading to bowel obstruction. This is a rare complication of severe amoebiasis.

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Intussusception

A segment of the intestine telescopes into itself, like a collapsible tube, causing a blockage. It can occur in various parts of the digestive system, but is more common in children.

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Amoeboma

A tumor-like mass of inflamed tissue in the rectum or sigmoid colon, caused by amoebic infection.

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Amoebic Stricture

A narrowing of the colon caused by scar tissue from healed amoebic ulcers.

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Chronic Amoebiasis

Persistent Entamoeba histolytica infection marked by lasting inflammation, scarring, and potential amoeboma formation.

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Amebic Liver Abscess

A pus-filled pocket in the liver caused by Entamoeba histolytica.

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Transmission of Extraintestinal Amebiasis

Amoebas can travel from the intestines to other organs, like the liver, through the bloodstream, primarily the portal vein.

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Liver Damage in Amoebiasis

Even without directly causing damage, Amoebas trigger the release of inflammatory substances that contribute to liver damage in amoebic liver abscess.

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What is an amoeboma?

A tumor-like mass in the colon caused by inflammatory tissue buildup due to Entamoeba histolytica infection.

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What is the cause of an amoebic stricture?

Scar tissue from healed amoebic ulcers in the colon can narrow the colon's lumen, causing an amoebic stricture.

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Study Notes

Intestinal Amoeba

  • Intestinal amoeba are single-celled protozoa that change shape constantly.
  • Their locomotion is aided by pseudopodia, which are cell extensions.
  • Amoeba are classified by habitat: intestinal or free-living.
  • Intestinal amoeba live in the large intestine of humans and animals.
  • Free-living amoebas are small, free-living organisms, and some are opportunistic pathogens.
  • Intestinal amoebas can be pathogenic (causing disease) or non-pathogenic.
  • Entamoeba histolytica is a pathogenic intestinal amoeba.
  • Entamoeba histolytica is found in the human colon's mucous and submucous layers of the large intestine.
  • Entamoeba histolytica commonly infects tropical and subtropical regions, where poor socioeconomic status, poor nutrition, hygiene, and sanitation are more common issues in developing countries.
  • Most Entamoeba histolytica infections are asymptomatic.
  • Entamoeba histolytica is a common diarrheal pathogen in long-term travelers ( >6 months).
  • The biggest burden of the disease is found in the tropics of China, Central and South America, and the Indian subcontinents, affecting 10% of the world's population.
  • Some groups are at a higher risk for Entamoeba histolytica infections, like families of infected individuals, aboriginal people, male homosexuals, people in mental hospitals, prisons, and institutions for children.

Classification of Amoeba

  • Amoebas are single-celled protozoa with constantly changing shapes.
  • The presence of locomotion organs called pseudopodia is a key differentiator in this diverse group.

Entamoeba histolytica

  • A worldwide distribution, more prevalent in the tropics and subtropics.
  • Has three morphological forms: trophozoite, precyst, and cyst.
  • Trophozoites are the vegetative form present in tissues. They are irregular in shape, averaging 20 µm in size and have pseudopodium for locomotion and containing cytoplasm made up of ectoplasm & endoplasm containing nucleus, food vacuoles and phagocytosed red blood cells.
  • Precysts are a stage before encystment. These amoeba round up, extrude food vacuoles, have a smaller size (10–20 µm), have a glycogen vacuole and chromatoid bars.
  • Cysts are a rigid, resistant form, measuring 10–20 µm, have a thick wall and are more resistant to gastric juice and unfavorable environmental conditions. They have 1–4 nuclei (mature cyst has four), chromatoid bars (aggregation of RNA), and glycogen mass.

Transmission

  • Entamoeba histolytica is transmitted primarily through the fecal-oral route.
  • Contaminated food or water containing mature cysts is a common source of infection.
  • Food handlers, children and institutionalized groups are at an increased risk.
  • Sexual contact is another possible route, especially among homosexual men in developed countries.

Life Cycle

  • Entamoeba histolytica completes its life cycle in a single host (humans).
  • The infectious form is the mature quadrinucleated cyst.
  • This cyst resists chlorination, gastric acid, and desiccation. It can survive in moist environments.
  • In the intestine, cysts excyst into trophozoites; these live in the gut lumen, mainly cecum, descending colon, and recto-sigmoid feeding on liquid substances and bacteria.
  • Trophozoites encyst in the colon, which are excreted in the feces.

Pathogenesis

  • Entamoeba histolytica infection is mostly asymptomatic.
  • Under specific conditions, amoebas become invasive, causing tissue lysis, usually with host and parasite factors.
  • Certain strains of E. histolytica have higher virulence; they produce proteolytic enzymes, cytotoxins, and cytolysins; often with surface adhesins.
  • Factors that can influence E. histolytica invasiveness include factors like poor nutrition, stress during pregnancy, alteration of colonic flora and low resistance or weakened immune systems from various factors (e.g., diseases, drugs, etc.)
  • Amoebic ulcers are a consequence of E. histolytica invasion.
  • These ulcers can be either superficial (confined to the mucosal layers with no scarring) or deep (penetrating muscular layers with scar formation).
  • The location of amoebic ulcers can vary in the ileocecal or sigmoid regions, or they can be widespread throughout the large intestine..
  • Ulcers can coalesce and lead to sloughing of the mucosa and secondary bacterial infection.
  • Severe complications, like fulminant colitis or perforation, also result from infection.
  • Extraintestinal amoebiasis involves trophozoite spread to other organs like the liver which causing abscesses (usually in the upper right lobe of the liver).

Diagnosis

  • Diagnosis of E. histolytica relies on various methods:
  • Microscopic examination of stool samples for cysts or trophozoites.
  • Molecular diagnostic tools like PCR.
  • Serological testing for antibodies is helpful for identifying invasive amoebiasis through the detection of cysts or trophozoites in stool or mucosal scrapings.
  • Sigmoidoscopy with mucosal scrapings for visualization and direct examination of the trophozoites.

Treatment

  • The primary treatments for amebiasis generally involve metronidazole or tinidazole.
  • Supportive care, including fluid and electrolyte replacement, is often necessary.

Prevention

  • Public health measures, including safe food handling, adequate sanitation and hygiene practices, are vital strategies for preventing transmission.

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Intestinal Amoeba PDF

Description

This quiz explores the characteristics and classifications of intestinal amoeba, focusing on their biological functions and the implications of specific species like Entamoeba histolytica. Understand their role as both pathogenic and non-pathogenic organisms, especially in human health. Key factors influencing infection rates in various regions are also considered.

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