与 诊 史
1. The only pathogenic amoeba among
all of the intestinal amoebae
2. Infecting perhaps 10% of the world's
3. Lead to invasive amoebiasis.
– world-wide distribution (10%)
– 5% in some developed countries
– 100 deaths in Chicago 1930
Trophozoite & Cyst
– oral-faecal transmission
Pay your attention to stages that have
Parasites stained with hematoxylin is
Trophozoite (active form)
(1) Size: 10-40 micrometers in diameter, some
are above 60 micrometers.
(2) Pseudopodium(ectopalsmic protrusion):
A. broad or finger-like in form
B. thrust out quickly
C. firstly, formed with ectoplasm, secondly,
endoplasm flows slowly into it.
D. motility is progressive and directional.
Trophozoite (active form)
(3) Endoplasm: red blood cells may be found in
(4) Nucleus (vesicular type)
It is not visible in an unstained specimen;
but its clear structure can be seen when
stained with hematoxylin.
A: membrane: distinct line
B: chromatin granules: fine and uniformly
arranged in the inner surface of the
C: karyosome: small and centrally located.
Phase contrast photomicrograph of cultured
Entamoeba histolytica trophozoites.
Charcot Leyden Crystal
These diamond shaped
crystals are often seen
in amoebic dysentery
faeces and may also be
present in other
They are absent in
×400. Enlarged by 9.6
Movement of E. histolytica
progressive and directional
(1) 10-20 mocrometers in size
(2) spherical in shape
(3) 1-2 nuclei (immature cyst); 4 nuclei (mature
(4) inclusions:(become smaller and smaller as the
glycogen vacuole appears as a clear space; food
chromatoid body dark blue rods or dots; its
function is not known
The single nucleus
with its central
visible. The dark
"rods" in the
cytoplasm are the
approximate size = 18
This is a mature
cyst and contains
only two nuclei are
visible in this plane
of focus, and a
chromatoid bar is
approximate size =
Trophozoite & cyst
Slow “lazy” movement
E. histolytica v E. coli
– 10-40um – 15-30um
– delicate nuclear – coarse nuclear
– 9.5-15.5um – 10-30um
– 4 nuclei – 8 nuclei
– Broad, blunt chromatid – thin, sharp chromatid
1 infective stage: mature cyst
2 access: mouth
3 ecological niches: large intestine; liver,
lung and other organs.
4 pathogenic stage: trophozoite
5 diagnostic stage: cyst; trophozoites
1. Toxicity of parasites pathogenic-
2. Symbiotic bacteria
3. Defence barrier immunity
event is a result of
the host cell
membrane of an
This protein forms ion channels in lipid cell membranes and results in cell
death within minutes of cell contact with the ameba. Amoebapore has been
isolated, synthesized and well characterized. Non-pathogenic strains of E.
histolytica can also produce amoebapore but are much less efficient at its
production and the molecule is not exactly similar to that produced by virulent
Pinpoint lesion on mucous membrane
Flask-shaped crateriform ulcers
Asymptomatic infection (carrier) >90%
cases (E. dispar?)
Sympomatic cases <10%
– 8-10% dysentery, colitis, etc
– 2% invasive amoebiasis
– 0.1% deaths
A. Intestinal amoebiasis
a. dysentery: dysenteric stools (pus and blood
without feces). fever, dehydration, and electrolyte
abnormalities. Tenesmus and abdominal
b. non-dysenteric colitis
d. amoeboma:may become the leading point of
an intussusception or may cause intestinal
Histopathology of a typical flask-
shaped ulcer of intestinal amebiasis
A Micro Abscess in the
Containing a large
number of E.
at the periphery .H
and E. ×400.
Enlarged by 5.4.
(1) acute non-suppurative
(2) liver abscess: right upper quadrant
pain, referred to the right shoulder. tender.
d. Skin, perianal infection
e. Other extra-intestinal amoebiasis
Amoebic Liver Abscess
Gross pathology of liver containing
Gross pathology of amebic abscess of liver. Tube of
"chocolate" pus from abscess.
An Amoebic Liver Abscess
Note the reddish
brown color of the pus
This color is due to the
breakdown of liver
cells. Enlarged by 5.4
X-ray of a Large Amoebic Liver
A fluid level
due to entry of
method direct smear with normal direct smear with iodine
diseases chronic intestinal
amoebiasis or carriers
1.container must clean
2.examined soon after they 4.keep specimen warm.
have been passed.
3.select bloody and 5.drug using histry.
2. Serologic studies: indirect
hemagglutination, skin tests, ELISA and
3. Tissue examination: sigmoidoscopic
4. DNA probe
Distribution: all climates, arctic to tropical.
Media: flies; black beetles etc.
Treatment and Prevention
Metronidazole-dysentery, liver abscess
Human feces should not be used as fertilizer
Food and drinks must be protected from
Personal hygiene: wash hands after
defecation and before meals.