Which protozoan is known for tissue invasion and causes invasive amebiasis?

• A. Entamoeba histolytica
• B. Entamoeba coli
• C. Endolimax nana
• D. Iodamoeba butschlii

Answer: (A)

Tissue invasion by a pathogenic intestinal ameba underlies invasive amebiasis. Entamoeba histolytica is the one that not only lives in the gut but can penetrate the colonic mucosa, causing ulcers and dysentery, and it can spread through the bloodstream to form liver abscesses—hallmarks of invasive disease. Trophozoites that invade the tissue often ingest red blood cells, which reflects its damaging interaction with the mucosa. In contrast, the other amebae listed are typically luminal residents and do not invade tissue, so they do not cause invasive amebiasis. Thus, Entamoeba histolytica is the protozoan known for tissue invasion and invasive disease.