Entamoeba histolytica

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Class Lobosea Amebic Infections

• Entamoeba histolytica
• E. coli
• E. gingivalis

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Class Lobosea
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Intestinal Amebae

• Entamoeba
• E. histolytica (pathogen)
• E. coli
• E. gingivalis

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Entamoeba Morphology
Ingested RBC
Nucleus with central karyosome and finely divided
peripheral chromatin
Pseudopod
E. histolytica trophozoite
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Entamoeba Morphology
1-4 ring-like nucleiwith finely divided
peripheral chromatin
Cyst wall and round shape
Mature E. histolytica Cyst
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Morphologic Comparison
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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

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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

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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

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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

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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, ?)

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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

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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.

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Amebic abscess of liver

1. Gross pathology of liver containing amebic
   abscess
2. Gross pathology of amebic abscess of liver.

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Chronic Non-Dysenteric Amebiasis

• self-cured carrier state
• 37 symptomatic gt5 years
• Intermittent diarrhea, mucus, abdominal pain,
  flatulence and/or weight loss
• E. histolytica trophs (rarely cysts) in stools
• Positive serology

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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

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Entamoebasis
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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 gt trophozoites in
  sputum!
• Extension to other sites, including
• peritoneum, pericaridum, others
• Amebic Pulmonary Abscess
• Other sites brain, skin, urogenital system

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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

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Diagnosis of Intestinal Amebiasis

• Techniques
• Direct Fecal Smear (trophs and cysts)
• Fecal concentration techniques - (cysts)
• Permanent Stained Fecal Smear
• Serologic Tests (for chronic disease)

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E. histolytica Microscopy
1
2

• Entamoeba histolytica trophozoites in section of
  intestine
• Entamoeba histolytica cyst and trophozoite,
  haematoxylin stained

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Entamoeba
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Entamoeba
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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

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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

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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

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E. coli Morphologic Comparison
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Entamoeba gingivalis
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Entamoeba gingivalis

• lives in/on the teeth, gums, and sometimes
  tonsils.
• it measures 10-35 µm in length
• is present in all cases of active periodontitis
• does not produce the cysts

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Infections with Free Living Amebae

• Naegleria fowleri
• Acanthamoeba spp.

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Diseases caused by F.L.A.
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Free Living Amebae
Not seenin humans
Naegleria
Acanthamoeba cysts trophs are seen in humans
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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.

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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

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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

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Acanthamoeba spp.
Acanthamoeba trophozoites with acanthopodia
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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.

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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!!!

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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!

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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.