Intestinal and Commensal Amoebae Flashcards
What is the main pathogenic amoeba responsible for intestinal infections?
Entamoeba histolytica.
How is Entamoeba histolytica transmitted?
transmitted through the ingestion of cysts via contaminated food or water.
What are the two forms of Entamoeba histolytica in its life cycle?
The trophozoite (active feeding form) and cyst (dormant, infectious form).
Which amoeba is often mistaken for Entamoeba histolytica but is non-pathogenic?
Entamoeba dispar.
What is the primary symptom of an infection with Entamoeba histolytica?
Dysentery, which includes severe diarrhea, often with blood and mucus
Which intestinal amoeba is considered non-pathogenic and commensal, often found in human intestines?
Entamoeba coli.
What is the method of diagnosing amoebic infections?
Microscopic examination of stool samples or serological tests in cases of extraintestinal amoebiasis.
What is the key difference in the appearance of cysts between Entamoeba histolytica and Entamoeba coli?
E. histolytica cysts typically have 1-4 nuclei, while E. coli cysts have up to 8 nuclei.
Which amoeba can cause liver abscesses in severe cases?
Entamoeba histolytica.
Which species of amoeba is typically non-pathogenic but can cause infections in immunocompromised individuals?
Entamoeba dispar.
How does Entamoeba histolytica cause damage in the host’s intestine?
trophozoites invade and destroy the intestinal mucosa, leading to ulcers and tissue destruction.
What are the two diagnostic techniques used to differentiate E. histolytica from E. dispar?
Serological tests and molecular diagnostic techniques like PCR.
What is the reservoir of infection for Entamoeba histolytica?
Humans are the primary reservoir of infection.
What drug is commonly used to treat infections caused by Entamoeba histolytica?
Metronidazole
How does the transmission of Entamoeba histolytica differ from that of commensal amoebae?
Both are transmitted through ingestion of cysts in contaminated food or water, but E. histolytica has a higher risk of causing disease, while commensal amoebae generally do not cause symptoms.
Why are cysts vital for the survival and transmission of intestinal amoebas?
Cysts are resistant forms that can survive outside the host in harsh environmental conditions.
What are the clinical differences between amoebiasis caused by Entamoeba histolytica and infections by commensal amoebae?
E. histolytica causes amoebic dysentery, with symptoms like bloody diarrhea, while infections by commensal amoebae, such as Entamoeba dispar, are typically asymptomatic.
Why is it challenging to differentiate between Entamoeba histolytica and Entamoeba dispar?
They are morphologically identical, so molecular or antigen detection methods are required to distinguish between the pathogenic E. histolytica and the non-pathogenic E. dispar.
Why is proper sanitation needed in preventing amoebic infections?
Poor sanitation leads to fecal contamination of water and food, increasing the risk of cyst ingestion and spread of amoebic infections.
Why are cysts more likely to be found in formed stools while trophozoites are found in liquid stools?
Cysts are the infective form that is passed in formed stools, while trophozoites, which are active and fragile, are more commonly found in liquid stools due to diarrhea.
What diagnostic techniques can distinguish between amoebic dysentery and bacillary dysentery?
Stool microscopy, antigen detection, and PCR can help identify amoebic dysentery, while culture and identification of bacteria like Shigella are used for bacillary dysentery.
What is the role of cysteine proteases in the pathogenicity of Entamoeba histolytica?
Cysteine proteases degrade host tissues and aid in the invasion of the intestinal lining, contributing to tissue damage and symptoms.
Why is PCR considered a more reliable diagnostic tool for Entamoeba histolytica infections?
PCR can specifically detect E. histolytica DNA, differentiating it from non-pathogenic amoebae and offering high sensitivity and specificity.
How does the epidemiology of E. histolytica differ between developing and developed countries?
In developing countries, poor sanitation and water quality contribute to higher transmission rates, whereas in developed countries, cases are usually imported.
