Intestinal and Commensal Amebae - Intestinal Amoeba (part 2)

E. histolytica pathogenesis

Mechanisms of virulence

• Enzyme/cytotoxic substance

• Contact-dependent cell killing

• Cytophagocytosis

E. histolytica pathogenesis

Pathogenic determinants

For receptor-mediated adherence of amoeba to its target cell

• Gal lectin

• Amoebaspores

• Cysteine proteinases

E. histolytica pathogenesis

Pathogenic determinants

Forms pores

• Gal lectin

• Amoebaspores

• Cysteine proteinases

E. histolytica pathogenesis

Pathogenic determinants

Breaks down mucin layer and extracellular matrix of mucosal cells before attachment of amoeba

• Gal lectin

• Amoebaspores

• Cysteine proteinases

E. histolytica pathogenesis

Proteolytic enzymes secreted by the amoeba causes tissue destruction forming flask-shaped amoebic ulcerations along the intestines (cecum, ascending colon, and sigmoid)

• Korek

• Mali

E. histolytica pathogenesis

After adherence to colonic mucosa through Gal lectin, the amoeba activates their _________ leading to apoptotic death and engulfment or phagocytosis of killed or viable target cells

• caspace-3

• caspace-4

• caspace-5

E. histolytica manifestations

- Majority of the cases

- Cysts are passed out in stools (cyst carrier state)

- Most cases in endemic communities

• Asymptomatic Infection

• Invasive Intestinal Amebiasis

• Invasive Extra-Intestinal Amebiasis

E. histolytica manifestations

Invasive Intestinal Amebiasis

- Present as gradual onset of extreme abdominal pain and diarrhea (with or without blood and mucus)

- Some patients have intermittent diarrhea alternating with constipation

- Fever is not common

• Amoebic colitis

• Ameboma

E. histolytica manifestations

Invasive Intestinal Amebiasis

- Children may develop fulminant colitis (sudden onset) with severe bloody diarrhea, fever, and abdominal pain

- Adults may also experience fulminant colitis if the patient

has been in a long period of asymptomatic cyst carrier state

or 8 to 10 days of incubation period

• Amoebic colitis

• Ameboma

E. histolytica manifestations

Invasive Intestinal Amebiasis

Serious complications: colonic perforation and secondary bacterial peritonitis

• Amoebic colitis

• Ameboma