Entamoeba histolytica

Entamoeba histolytica is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

Protozoan species, genus Entamoeba.
- E. histolytica is morphologically similar to E. dispar, E. moshkovskii, and E. bangladeshi.
- Histolytic - histo + lyein (Greek) to loosen, trophozoites contain cytolytic and proteolytic enzymes, including collagenase and proteinases, and lyze neutrophils and macrophages.
Cysts are ingested and excystation occurs in the distal ileum and cecum. Motile trophozoites are released and migrate to the large intestine. Trophozoite surface protein and key virulence factor, Gal/GalNAc lectin, mediates adherence to host cells.
- Fecal anti-Gal/GalNAc lectin IgA protective against infection.[4]
- Disease occurs in minority (10%) of infections.[1]
Cysts found in contaminated water or food. Cysts remain viable outside host in water, soil, and sewage for weeks or months.
- Infecting dose is fewer than 10 cysts.[7]
- Occurs primarily in developing countries, also seen in immigrants from and travelers to endemic areas and those with oral-anal or oral-fecal contact.

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