[07.35] Entamoeba Intestinal Protozoans V2.pdf

Entamoeba histolytica

What specific gastrointestinal protozoan is the direct cause of amoebiasis?

Developing countries

In what specific type of geographic settings is the highest prevalence of amoebiasis found?

Inadequate barriers between human feces and food/water supply

What is the primary reason for high amoebiasis prevalence in developing countries?

Asymptomatic

In what clinical state do most cases of Entamoeba histolytica infection exist?

Humans and non-human primates

Which organisms are the only natural hosts of Entamoeba histolytica?

Trophozoite

Which specific form of E. histolytica is amorphous and possesses a pseudopod?

Pseudopod

What extension of the cytoplasm is used by E. histolytica to pull its body forward and move?

Thin nuclear membrane

Relative to other protozoans, what is the thickness of the nuclear membrane in E. histolytica?

Centrally located

What is the typical position of the nucleolus or endosome within the E. histolytica nucleus?

Ingested red blood cells

What visible dark spots serve as a good diagnostic clue that an organism is E. histolytica?

Cyst

Which form of E. histolytica is spherical and environmentally resistant?

Die in the environment

What happens to trophozoites once they are exposed outside the host?

Fecal-oral or oral-anal

What are the two primary modes of transmission for E. histolytica cysts?

Weeks to months

How long can cysts remain viable in the environment?

Cyst

Between the cyst and trophozoite, which is the infective stage?

Stomach acid or gastric exposure

What physiological factor would destroy a trophozoite if it were ingested?

Terminal ileum or ascending colon

In which specific locations of the GI tract does excystation occur?

Eight

Up to how many trophozoites can be released from a single cyst during excystation?

Trophozoite

Which specific form of E. histolytica is considered the invasive form?

Portal circulation

Through which circulatory system do trophozoites spread hematogenously to extra-intestinal organs?

Liver, lungs, and brain

Aside from the intestines, what are the three most common extra-intestinal sites of spread?

Luminal amoebiasis

What is the term for infection where the organism remains in the intestinal lumen without invading tissue?

Carrier-state

What is another name for luminal amoebiasis where trophozoites are shed without symptoms?

90%

What percentage of diagnosed amoebiasis cases are non-invasive/luminal?

Less than 10%

What percentage of luminal amoebiasis cases eventually progress to invasive disease?

Around 10%

Among those with invasive disease, what percentage develop extra-intestinal complications?

Amoebic colitis

What is the most common manifestation of invasive amoebiasis?

Amoebic dysentery

If amoebic colitis presents with diarrhea, what is it specifically called?

Amoebic liver abscess

What is the most common manifestation of extra-intestinal invasive amoebiasis?

Amoebiasis

How is gastrointestinal infection by E. histolytica officially defined?

Top ten

Where does intestinal amoebiasis rank globally as a cause of severe diarrhea in the developing world?

50,000

How many people are estimated to die annually from acute intestinal amoebiasis?

Mucosanguineous diarrhea

What is the official medical term for the bloody and mucoid diarrhea associated with E. histolytica?

Tenesmus

What is the term for the feeling of incomplete defecation or emptying seen in amoebic dysentery?

Potassium loss

Why might a patient with amoebic dysentery experience abdominal cramping?

Abdominal distention

What abdominal sign may accompany the 3-5 episodes of mucosanguineous stool?

Cecum, ascending colon, and sigmoid colon

What are the three specific parts of the large intestine usually involved in colitis?

Ameboma

What is the term for tumor-like masses that can form in the colon due to E. histolytica?

Small number

Can a large or small number of cysts cause amoebiasis?

Stomach acid

What specific trigger starts the process of excystation?

Intestinal mucous blanket

What is the first barrier that E. histolytica must penetrate to cause mucosal injury?

Proteases

What molecules are secreted by trophozoites in culture that irritate goblet cells?

Glandular hyperplasia

The stimulation of goblet cells by the organism leads to what histological change?

Mucoid dysentery

What specific type of diarrhea results from the overproduction of mucin?

Mucin depletion

What process must occur before trophozoites can adhere to naked colonic epithelial cells?

EhMIF (Macrophage migration inhibitory factor)

Which virulence factor recruits neutrophils but inhibits nitric oxide to help colonization?

EhCP5 (Cysteine protease 5)

Which cysteine protease is specifically mentioned as helping degrade the mucin layer?

Glycosidases

Besides mucin proteases, what other enzymes help the parasite degrade the mucin layer?

EhCPs (Cysteine proteases)

Which molecules are responsible for inactivating C3a and C5a of the complement cascade?

IgA and IgG

Which mucosal and systemic immunoglobulins are cleaved by EhCPs?

Gal-GalNAc-specific lectin

Adhesion to enterocytes is mediated by which specific molecule?

Fewer recurrent infections

What is the clinical significance of a mucosal IgA response against the Gal-GalNAc lectin?

Amoebapores

Which family of peptides is responsible for the rapid killing of enterocytes via focal cytolysis?

Amoebapores

Which peptides facilitate both the cytolytic and apoptotic pathways by forming pores in lipid bilayers?

CD59-like or Protectin-like molecules

What molecules on E. histolytica provide protection against the human membrane attack complex (MAC)?

ECM substrates and fibronectins

To what does the pseudopodium anchor during the invasion of GI tissue?

Metalloproteases

Which enzymes degrade collagen type I and III in the extracellular matrix?

Hemoglobinase

What is the specific protease designed to ingest red blood cells?

C5a, IL-1B, IL-8, and COX-2

Name four inflammatory mediators released by the host upon amoebic invasion.

Oxidative bursts

To what specific neutrophil/macrophage immune response is E. histolytica resistant?

3000:1

What is the maximum mentioned ratio of macrophages needed to kill a single amoeba?

Direct spread

How is spread to adjacent tissues outside the muscularis interna classified?

Submucosa

Hematogenous spread typically begins via blood vessels located in which layer of the intestinal wall?

Mesenteric veins

Through which specific vessels does the parasite travel before draining into the portal vein?

Flask-shaped ulcer

What is the characteristic, non-pathognomonic histological lesion associated with E. histolytica?

Muscularis propria

What layer usually limits the spread of a flask-shaped ulcer?

HGL2

Which E. histolytica gene knock-off model lacks the Gal/GalNAc-specific lectin?

G3

Which E. histolytica gene knock-off model lacks amoebapores?

RBV

Which model lacks both the Gal/GalNAc-specific lectin and amoebapores?

RB8

Which model lacks both amoebapores and cysteine proteases?

EhCP-A5 (Cysteine protease A5)

Which specific enzyme is identified as the "key in the invasiveness" of E. histolytica?

Trophozoites remain only on the surface

What happens to the parasite if cysteine protease is removed?

40%

What percentage of extra-intestinal amoebiasis cases involve the liver?

Splanchnic and portal circulation

What are the two primary routes of circulation for liver abscess extension?

Anchovy sauce

How is the characteristic viscid, chocolate-brown pus of an amoebic liver abscess described?

Disorganized liver tissue and blood clots/streaks

What are the specific contents of "anchovy sauce" pus?

Sterile

Are the majority of the contents in an amoebic liver abscess infectious or sterile?

Walls or borders of the cavity

Where are trophozoites found in large numbers within an abscess?

Hepatomegaly, Abdominal Pain, and Fever

What is the clinical triad for suspecting an amoebic liver abscess?

RUQ abdominal pain

What is the most common symptom (found in 100% of cases) of ALA?

Acute ALA

High fever with chills and profuse perspiration is more characteristic of which ALA type?

Chronic ALA

Slowly developing fever without chills characterizes which ALA type?

Hepatomegaly

What is considered the "most important physical sign" in hepatic amoebiasis?

4-5 episodes per day of watery stool

How is diarrhea described when it occurs in the 2% of ALA cases?

Jaundice

Which physical feature suggests large/multiple abscesses or bacterial co-infection and indicates progressing disease?

Right lobe

Which specific lobe of the liver is the site of 87% of amoebic abscesses?

Portal vein drains there

Why is the right lobe the most common site for ALA?

Single cavitary lesion

Does ALA usually manifest as a single cavity or multiple small ones?

Rupture of abscess

What is a life-threatening complication found in 27% of ALA cases?

Avoid deep abdominal palpation

What clinical precaution should be taken before imaging if ALA is suspected?

Males

Which gender is 2.1 times more predisposed to amoebic liver abscess?

Younger age

Is younger or older age more predisposed to ALA according to the data?

Amoebic

Between amoebic and pyogenic liver abscess, which one is associated with higher albumin levels?

IHA titers > 1:256

What specific serological finding points specifically toward an amoebic etiology for an abscess?

Pleuropulmonary amoebiasis

Which complication accounts for 32% of all ALA complications?

Via the diaphragm

By what route does infection travel from the liver to the lungs?

Hepato-bronchial fistula

Through what structure does a lung abscess directly spread into the bronchial tree?

Empyema

Name a possible manifestation of pleuropulmonary spread.

Amoebic peritonitis

Which complication occurs secondary to the rupture of a lung or liver abscess and has high mortality?

Fulminant necrotizing colitis

What is the name of the high-mortality (~40%) progression of amoebic colitis?