E. histolytica pathogenesis

Pathogenic determinants

For receptor-mediated adherence of amoeba to its target cell

E. histolytica pathogenesis

Pathogenic determinants

Forms pores

E. histolytica pathogenesis

Pathogenic determinants

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

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)

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

E. histolytica manifestations

- Majority of the cases

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

- Most cases in endemic communities

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

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

E. histolytica manifestations

Invasive Intestinal Amebiasis

Serious complications: colonic perforation and secondary bacterial peritonitis

E. histolytica manifestations

Invasive Intestinal Amebiasis

- Occurs <1% of intestinal infections

- Presents as a mass-like lesion with abdominal pain and history of dysentery

- Can be mistaken with carcinoma

- May also occur asymptomatically

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Most common extra-intestinal form of amebiasis

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

2nd most common extra-intestinal manifestation

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

In ALA, the commonly affected lobe of the liver is the _____

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Cardinal manifestations of ALA

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

In __________: patients experience tenderness of the liver and hepatomegaly (50% of cases)

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Usually manifested by older patients, it involves wasting with significant weight loss rather than fever

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Most serious complication of ALA, with 70% mortality

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Second most serious complication of ALA

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Caused by the perforation of the diaphragm

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

- Manifests among 1 to 2% of the patients infected

- Considered in cases with abnormal mental status

E. histolytica manifestations

Invasive Extra-intestinal Amebiasis

Other systems involved

E. histolytica manifestations

May be epidemic

Acute Onset

Prodromal fever and malaise common

Vomiting common

Patient is prostate

Watery, bloody diarrhea

Odorless Stool

E. histolytica manifestations

Seldom epidemic

Gradual Onset

No prodromal features

No vomiting

Patient usually ambulant

Bloody Diarrhea

Fishy odor stool

E. histolytica manifestations

Stool Microscopy: Numerous bacilli, pus cells, macrophages, RBCs, no Charcot-Leyden crystals

Abdominal cramps common and severe

Tenesmus common

Natural history: spontaneous recovery in a few days, weeks or more; no relapse

E. histolytica manifestations

Stool Microscopy: Few bacilli, RBCs, trophozoites with RBC ingested, Charcot-Leyden Crystals

Mild abdominal cramps

Tenesmus uncommon

Natural history: lasts for weeks; dysentery returns after remission; infection persists for years

Body Defense Against E. histolytica

1st line of defense

Body Defense Against E. histolytica

2nd line of defense

Body Defense Against E. histolytica

3rd line of defense

Body Defense Against E. histolytica

Which of the following component of adaptive immunity does not work against amebae?

E. histolytica diagnosis

- Standard method of parasitological diagnosis

- Minimum of three stool specimens are collected on different days

- To detect trophozoites, fresh stool should be examined within 30 minutes after defecation

E. histolytica diagnosis

Direct Fecal Smear (DFS)

Unidirectional trophozoite motility

E. histolytica diagnosis

Direct Fecal Smear (DFS)

- Entamoeba spp. will stain blue

- Differentiation from white blood cells

E. histolytica diagnosis

Direct Fecal Smear (DFS)

Nucleus and karyosome are observable to differentiate E. histolytica with other non-pathogenic amoebae

E. histolytica diagnosis

Direct Fecal Smear (DFS)

Trophozoites with ingested RBC is diagnostic of amebiasis

E. histolytica diagnosis

Concentration methods

Formalin Ether / Ethyl Acetate Concentration Test (FECT) and Merthiolate Iodine Formalin Concentration Test (MIFC) are more sensitive than DFS in detection of cysts

E. histolytica diagnosis

Stool culture

E. histolytica diagnosis

- Differentiates E. histolytica and E. dispar

- Expensive but accurate

E. histolytica diagnosis

- Non-invasive and sensitive methods

- Early detection of amebic liver abscess (ALA)

E. histolytica diagnosis

- Can be used in monitoring cysts carrier since antibodies have been demonstrated in asymptomatic intestinal infections

- Key in diagnosis of ALA

E. histolytica diagnosis

• DFS

• Concentration Techniques

• Stool Culture

• Serologic Testing (ELISA, IHAT, CIE, AGD, IFAT)

• Molecular testing (PCR)

E. histolytica diagnosis

• Serologic testing (ELISA IHAT, CIE, AGD, IFAT)

• Imaging (CT, MRI, Ultrasound)

• Abscess Aspiration

E. histolytica treatment

DOC for invasive amebiasis

E. histolytica treatment

DOC for asymptomatic cyst passers

E. histolytica treatment

Used for invasive amebiasis

E. histolytica prevention and control