1. Entamoeba histolytica E. coli E. gingivalis
Class Lobosea & Amebic Infections
Entamoeba histolytica
E. coli
E. gingivalis

2. Class Lobosea

3. Intestinal Amebae Entamoeba E. histolytica (pathogen) E. coli
E. gingivalis

4. Entamoeba Morphology Ingested RBC
Nucleus with central karyosome and finely divided peripheral chromatin
Pseudopod
E. histolytica trophozoite

5. Entamoeba Morphology
1-4 ring-like nuclei with finely divided peripheral chromatin
Cyst wall and round shape
Mature E. histolytica Cyst

6. Morphologic Comparison
Entamoeba histolytica
Cysts
Trophozoites
Thick wall
Plasmalemma (thin)
1-4 ring-like nuclei
1 ring-like nucleus
Chromatoidals
(blunt)
Lacking
Round, 14-20 µm
Irregular, 12-17
Concentratable
Labile

7. Life Cicle of E. histolytica
Amebiasis Transmission
Humans acquire E. histolytica by:
Ingesting cysts in fecally contaminated food or drink
Rarely by directly inoculating trophozoites into colon or other sites (anal sex?)
Fecal-Oral transmission (hand to mouth)
Infective cysts and trophozoites pass in feces

8. E. histolytica Stages - CYSTS
Usual Infective Stage for humans
Resistant walls maintain viability
If moist can last several weeks
Killed by desiccation or boiling
Usual Diagnostic Stage in formed stools
Can be concentrated and stained easily
Not seen in liquid (diarrheic) stools or tissues

9. E. histolytica Stages - TROPHOZOITES
Are the motile, feeding stages that:
Cause amebiasis (damage tissue)
Spread throughout the body, but ...
rarely transmit the infection to others
are labile in liquid stools or tissue, and
must be rapidly found or preserved (quick fixation & cold storage) for laboratory diagnosis

10. Pathogenesis of Amebiasis
Trophozoites ...
Attach to mucosal epithelial cells (MEC)
Lyse MEC
Ulcerate and invade mucosa
Cause dysentery (diarrhea + blood)
Metastasize via blood &/or lymph
Form abscesses in extraintestinal sites

11. Clinical Classification of Amebiasis (World Health Organization)
Asymptomatic (intestinal) Amebiasis "Cyst Passers”
Most common
Infection may continue without clinical symptoms for weeks to months ...
May spontaneously resolve (self cure)/or carrier state
Symptomatic Infection:
Intestinal Amebiasis: (colon and rectum)
Acute Dysenteric (dysentery)
Chronic Non-Dysenteric (“self-cured”)
Extra-Intestinal Amebiasis:
Amebic Liver Abscess (ALA)
Amebic Pulmonary Abscess
Other sites (brain, skin, GU, ?)

12. Acute Dysenteric Amebiasis:
Amebic Dysentery
Symptoms:
Bloody mucoid diarrhea
RBCs and few WBCs (pus) in stools
Abdominal pain
weight loss
bloating, tenesmus and cramps
Signs:
Fever (33%)
Diffuse abdominal tenderness
Tender (enlarged) liver
Stools positive for trophozoites +/- WBC
NOT cysts in loose stools

13. Pathology
Intestinal ulcers are due to enzymatic degradation of tissue.
The infection may result in appendicitis, perforation, stricture granuloma, pseudo-polyps, liver abscess
Sometimes brain, lung and spleen abscesses can also occur. Strictures and pseudo-polyps result from the host inflammatory response.

14. Amebic abscess of liver
Gross pathology of liver containing amebic abscess
Gross pathology of amebic abscess of liver.

15. Chronic Non-Dysenteric Amebiasis:
“self-cured” carrier state
37% symptomatic >5 years
Intermittent diarrhea, mucus, abdominal pain, flatulence and/or weight loss
E. histolytica trophs (rarely cysts) in stools
Positive serology

16. Intestinal Amebiasis Complications
Intestinal perforation and Peritonitis (a surgical emergency)
Ameboma
Palpable mass of granulation tissue that may obstruct colon
Toxic megacolon
complication of inappropriate steroid therapy

17. Entamoebasis injuries of lungs perforation of diaphragm
abscess in liver
injury of descending colon
injury of ascending colon
Entamoebasis

18. Extra-Intestinal Amebiasis:
Amebic Liver Abscess (ALA)
Symptoms
dysentery (1 yr), weight loss, abdominal pain, chest or shoulder pain
Complications
Pulmonary Abscess: by direct extension through the diaphragm into thorax
Rupture into the pleural cavity and/or hepatobronchial fistulas => trophozoites in sputum!
Extension to other sites, including
peritoneum, pericaridum, others
Amebic Pulmonary Abscess
Other sites: brain, skin, urogenital system

19. DX: Laboratory Diagnosis of Hepatic Amebiasis
Examine stools for trophs/cysts (suggestive)
Blood cell counts - leukocytosis?
Radiologic Studies
Serologic tests
Catheterize abscess and aspirate: Examine "anchovy paste" aspirate for trophozoites and do serologic testing for amebic antigens
Culture for other pathogens (sterile on first stick, then contaminants)
Chemotherapeutic Trial

20. Diagnosis of Intestinal Amebiasis
Techniques:
Direct Fecal Smear (trophs and cysts)
Fecal concentration techniques - (cysts)
Permanent Stained Fecal Smear
Serologic Tests (for chronic disease)

21. E. histolytica: Microscopy1 2
Entamoeba histolytica trophozoites in section of intestine
Entamoeba histolytica cyst and trophozoite, haematoxylin stained

22. Entamoeba

23. Entamoeba

24. Prevention/Control of Amebiasis
Individual measures
Diagnosis and treatment of E. histolytica patients
no animal reservoirs (other than humans) are known
Safe drinking water (boiling or 0.22 µm filtration)
Cleaning of uncooked fruits and vegetables
Prevention of contamination of food

25. Prevention/Control of Amebiasis
Community measures
Public services and utilities
Adequate disposal of human stools
Safe and adequate water supply
Primary health care systems
Health education (washing hands, cleaning and protecting food, controlling insects)
Specific surveillance programs and Control programs integrated into ongoing sanitation & diarrhea control
Health Regulations
Control of food vendors and food handlers
Control of flies and cockroaches

26. Entamoeba coli
It is a commensal of the human large intestine, but it looks much like E. histolytica
Cyst usually has 8 nuclei
Does not produce the protein-degrading [proteolytic] enzymes
nucleus
food
vacuole

27. E. coli: Morphologic Comparison

28. Entamoeba gingivalis
amoeba
Red blood
cells

29. Entamoeba gingivalis
lives in/on the teeth, gums, and sometimes tonsils.
it measures µm in length
is present in all cases of active periodontitis
does not produce the cysts

30. Infections with Free Living Amebae
Naegleria fowleri
Acanthamoeba spp.

31. Diseases caused by F.L.A.

32. Free Living Amebae Not seen in humans Naegleria
Acanthamoeba cysts & trophs are seen in humans

33. Life cycle of Naegleria fowleri
1 – cyst,
2 – amoeba makes it way into cranium,
3 – switches to flagellate in order to swim into mouth or nose.

34. Primary Amebic Meningoencephalitis PAM
An acute suppurative infection of the brain and meninges that is rapidly fatal and usually not diagnosed antemortum
Caused by Naegleria spp.
Headache, lethargy and olfactory problems
Sore throat, runny nose, severe headache, vomiting, stiff neck, confusion leading to ...
Coma and death

35. Primary Amebic Meningoencephalitis PAM
Thermophilic, chlorine tolerant trophozoites penetrate cribiform plate and follow olfactory nerves into brain ...
Acute inflammation and hemorrhagic necrosis
Sanguinopurulent exudate containing trophs is found in meninges & tissues
CSF: Glucose -, Protein +, Leukocytes +
NEG Gram stains and bacterial CSF cultures

36. Acanthamoeba spp.
Acanthamoeba trophozoites with acanthopodia

37. Acanthamoeba
are found in the soil and dust, in fresh water (lakes, rivers, and hot springs and in hot tubs.
may also be found in sea water
can also be found in contact lens paraphernalia
Acanthamoeba have been found in the nose and throat of healthy people as well as those with compromised immune systems.

38. Acanthamoeba
can enter the skin through a cut, wound, or through the nostrils
can travel to the lungs and through the bloodstream to other parts of the body, especially the central nervous system.
can enter the eye via contact lenses or through a corneal cut or sore. Infection, keratitis or a corneal ulcer results.
In addition, it can cause skin lesions and/or a systemic (whole body) infection!!!

39. Acanthamoeba Keratitis
Corneal infection with Acanthamoeba spp. trophozoites & cysts
Ulcerations & “Ring Infiltrate” of cornea
Induced by
trauma to eye, exposure to contaminated H2O
contact lens wear with tap water rinsing
Cavorting in hot tub wearing soft-contacts!

40. Granulomatous amebic encephalitis (GAE)
Acanthamoeba spp. cause a serious, most often deadly infection called GAE
Symptoms:
headaches, stiff neck, nausea and vomiting, tiredness, lack of attention to people and surroundings, loss of balance and bodily control, seizures, and hallucinations.
Signs and symptoms progresses over several weeks and death usually occurs.