Entamoeba

Definition

Entamoeba is a genus of single-celled parasitic protozoans that can infect the human intestinal tract and cause the disease amoebiasis. These eukaryotic pathogens possess various virulence factors that contribute to their ability to cause disease in human hosts.

5 Must Know Facts For Your Next Test

1. Entamoeba histolytica is the primary species that infects humans and is responsible for the majority of amoebiasis cases worldwide.
2. Entamoeba possesses a variety of virulence factors, including adhesins, proteases, and pore-forming toxins, that enable it to adhere to, invade, and destroy host intestinal epithelial cells.
3. The Gal/GalNAc lectin is a key adhesin that mediates Entamoeba's attachment to host cells and triggers signaling cascades that promote phagocytosis and cytotoxicity.
4. Entamoeba secretes cysteine proteases that degrade the extracellular matrix and tight junctions, facilitating tissue invasion and dissemination.
5. Pore-forming toxins, such as amoebapores, allow Entamoeba to lyse host cells and evade the immune system by inducing apoptosis.

Review Questions

• Describe the life cycle of Entamoeba and how it contributes to its virulence as a eukaryotic pathogen.
  • Entamoeba has a biphasic life cycle, transitioning between a dormant cyst stage and an actively feeding and dividing trophozoite stage. The cysts are the infectious form, able to survive in the environment and be transmitted to new hosts. Once ingested, the cysts excyst in the intestine, releasing trophozoites that can adhere to and invade the intestinal epithelium. The trophozoites secrete virulence factors, such as proteases and pore-forming toxins, that enable them to destroy host cells, evade the immune system, and disseminate to cause extraintestinal infections. This complex life cycle allows Entamoeba to persist in the host and spread to new individuals, contributing to its success as a eukaryotic pathogen.
• Explain the role of the Gal/GalNAc lectin in Entamoeba's pathogenesis and how it relates to the virulence factors of eukaryotic pathogens.
  • The Gal/GalNAc lectin is a key virulence factor of Entamoeba that mediates the parasite's adhesion to host intestinal epithelial cells. This adhesion triggers signaling cascades that promote phagocytosis of the trophozoites and the release of cytotoxic factors, such as amoebapores, that lyse host cells. The Gal/GalNAc lectin is considered a critical virulence factor because it enables Entamoeba to establish a foothold in the host and sets the stage for the deployment of other virulence factors, like proteases, that facilitate tissue invasion and destruction. This multifaceted role of the Gal/GalNAc lectin in mediating adhesion, signaling, and the subsequent release of cytotoxic factors is a hallmark of the virulence strategies employed by many eukaryotic pathogens.
• Analyze how the various virulence factors of Entamoeba, including adhesins, proteases, and pore-forming toxins, work in concert to enable this eukaryotic pathogen to cause disease in the human host.
  • Entamoeba utilizes a sophisticated arsenal of virulence factors to successfully infect and cause disease in the human host. The Gal/GalNAc lectin, a key adhesin, allows the trophozoites to attach to and gain a foothold in the intestinal epithelium. This adhesion triggers signaling cascades that promote phagocytosis and the release of cytotoxic factors, such as the pore-forming amoebapores, which lyse host cells. Entamoeba also secretes cysteine proteases that degrade the extracellular matrix and tight junctions, facilitating tissue invasion and dissemination. The combination of adhesins, proteases, and pore-forming toxins enables Entamoeba to adhere to, invade, and destroy host cells, evade the immune system, and ultimately cause the severe intestinal and extraintestinal manifestations of amoebiasis. This multifaceted approach to virulence is a hallmark of successful eukaryotic pathogens and highlights the importance of understanding the interplay between various virulence factors in the pathogenesis of diseases caused by these complex organisms.

Related terms

Amoebiasis:

A disease caused by infection with Entamoeba species, primarily Entamoeba histolytica, resulting in intestinal and extraintestinal manifestations.

Trophozoite:

The actively feeding and dividing stage of Entamoeba that can invade the intestinal mucosa and cause tissue damage.

Cyst:

The dormant, environmentally resistant stage of Entamoeba that can be transmitted between hosts and reactivate in the intestine.