Question

The stage of Entamoeba histolytica that causes intestinal ulceration is
A. Trophozoite
B. Metacystic trophozoite
C. Binucleate stage
D. Tetranucleate stage

Answer 1

Hint: Entamoeba histolytica is a member of the genus Entamoeba, is an anaerobic parasitic amoebozoa infecting primarily humans and other amoebiasis-causing primates. It is estimated that histolytica infects between 35-50 million individuals worldwide.

Complete answer: Entamoeba histolytica is an anaerobic parasite that causes proteolysis as well as tissue lysis. In its life cycle, three stages are found; (1) the trophozoite stage, (2) the precystic stage, and (3) the cystic stage. Infection in humans occurs when food infected with cysts (tetranucleated) is swallowed. They enter the small intestine after the cysts are swallowed, where trypsin ruptures the cyst in the digestive juices and releases the tetranuclear amoeba stage called the metacyst. Eventually, the four nuclei undergo mitotic separation, resulting in 8 metacystic trophozoites. The intestinal epithelium feeds on these metacystic trophozoites and develops into mature trophozoites. The method of feeding entails the production of dissolving tissue secretions (histolysis) responsible for intestinal ulcers. E. histolytica can modulate many human viruses' virulence and is itself a host of its own viruses. AIDS, for instance, accentuates the harm and pathogenicity of E. histolytica. Cells infected with HIV, on the other hand, are also eaten by E. histolytica. Infective HIV remains viable inside the amoeba, but no evidence of human reinfection from the amoeba that carries this virus has been identified.
So, the correct answer is option B.

Note: E. histolytica induces the degradation of tissues that contribute to serious illness. Three key activities mediated tissue destruction by histolytica: direct death of the host cell, inflammation, and invasion of parasites.