Subkingdom Protozoa
General Characteristics
• They are single-celled organisms which are
generally classified according to their
organelles of locomotion.
• Considered as the simplest forms of animals
• Nucleus
• Nucleolus
• Mitochondria
• Locomotory Apparatus
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Subkingdom
Protozoa
Phylum
Sarcomastigophora
Phylum Phylum
Ciliophora Apicomplexa
Subphylum Subphylum
Sarcodina Mastigophora
Class Class
Class Class Zoo- Kinetofragminophorea Sporozoa
Lobosea mastigophora
(amoebas) (flagellates)
Intestinal Species
Entamoeba histolytica
Entamoeba hartmanni
Entamoeba coli
Entamoeba polecki
Subphylum Class Endolimax nana
Sarcodina Lobosea Iodamoeba butschlii
Dientamoeba fragilis
Extaintestinal Species
Entamoeba gingivalis
Naegleria fowleri
Acanthamoeba species
Intestinal and Luminal Protozoa:
Stages of Development
• Cyst – infective stage
• Trophozoite – vegetative stage
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General Statements:
All amoebas are capable of producing cyst
and trophozoite except for Entamoeba
gingivalis.
All intestinal amoebas are commensals
except Entamoeba histolytica.
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E. histolytica trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 8 – 65 um, ave: 12-25 um
Motility Progressive, finger-like
pseudopodia
Number of nuclei One
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Finely granular
Cytoplasmic inclusions Ingested red blood cells (bluish
black color in IH)
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E. histolytica cyst:
Typical characteristics at a glance
Parameters Description
Size range 8-22 um, ave: 12 – 18 um
Shape Spherical to round
Number of nuclei One to four
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Finely granular
Cytoplasmic inclusions Chromatoid bars with rounded ends
in young cyst
Diffuse glycogen mass in young cyst
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• Entamoeba histolytica only tissue invader
• Cysts can survive weeks in moist environment
• Size of cyst: <10 micra – E.hartmanii
>10 micra – E. histolytica, E. dispar, E. moshkovskii
• needs micrometry
• when reporting :
• E. histolytica / E. Dispar / E. moshkovskii –
indistinguishable
• E. histolytica (pathogenic)
• E. dispar / E. moshkovskii
(nonpathogenic)
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Entamoeba histolytica
• Clinical Symptoms:
1. Asymptomatic Carrier State
2. Symptomatic Intestinal Amebiasis
3. Symptomatic Extraintestinal Amebiasis
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Entamoeba histolytica
• Asymptomatic Carrier State
1. the parasite is a low-virulence strain
2. the inoculation into the host is low
3. patient’s immune system is intact
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Entamoeba histolytica
• Symptomatic Intestinal Amebiasis
1. Amebic colitis – intestinal infection caused by the
presence of amebas exhibiting symptoms
2. Amebic dysentery – presence of blood and mucus
in the stool
3. Secondary bacterial infection – after formation of
flask-shaped ulcers in the colon, cecum, appendix
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Entamoeba histolytica
• Symptomatic Extraintestinal Amebiasis
1. Liver abscess
2. Amebic pneumonitis
3. Weakness, weight loss, sweating,
pronounced nausea, vomiting
4. Migrate and infect the lung, pericardium,
spleen, skin, and brain
5. Men: venereal amebiasis (penile amebiasis
from a woman with vaginal amebiasis)
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Virulence Factors
1) a surface galactose binding lectin
that mediates E. histolytica binding to
host cells and may contribute to
amebic resistance to complement
Virulence Factors
2) amebapores, small peptides
capable of lysing cells, which may play
a role in killing intestinal epithelial cells,
hepatocytes, and host defense cells.
Virulence Factors
3) a family of secreted cysteine
proteinases that play a key role in E.
histolytica tissue invasion, evasion of
host defenses, and parasite induction
of gut inflammation
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Entamoeba histolytica
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Mode of Transmission
• Transmission via fecal-oral route
• Food preparation contaminated
by poor hygiene
• Human waste used for crop
fertilization
• Oral-anal sex
Laboratory Diagnosis
•Wet mount and permanent staining techniques
• Ova and parasite exam (3 samples required)
• Fresh stool exam with microscopy and gross exam
• Motile or encysted organisms
• Watery stool with mucus or blood
•Culture: TYI-33 supports the growth of amoeba
•Entamoeba histolytica stool antigen testing (preferred)
• Test Sensitivity: 87%
• Test Specificity: >90%
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Laboratory Diagnosis
• Other tests
• Fecal leukocytes positive
• Occult blood positive
• Fecal eosinophilia (presence of
Charcot-Leyden crystals)
• Antigen Tests:
• ELISA
• IHA
• GDP
• IIF
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Entamoeba histolytica
•Treatment:
• Paramomycin
• Diloxanide furoate
(Furamide)
• Metronidazole
(Flagyl)
• tetracycline with
diiodohydroxyquin
9/22/2015
Commensal
Amebae
9/22/2015
Commensal Amebae
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E. hartmanni trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 5-15 um, ave: 8 – 12 um
Motility Nonprogressive, finger-like
pseudopods
Number of nuclei One
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Finely granular
Cytoplasmic inclusions Ingested bacteria may be present
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E. hartmanni cyst:
Typical characteristics at a glance
Parameters Description
Size range 5-12 um, ave: 7 – 9 um
Shape Spherical
Number of nuclei Four (quadrinucleated)
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Finely granular
Cytoplasmic inclusions Chromatoid bars with rounded ends in young cyst
Diffuse glycogen mass in young cysts
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E. hartmanni
TROPHOZOITE CYST
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Entamoeba hartmanni
• Designated as “small race” E.
histolytica
• Px are generally asymptomatic
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E. coli trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 12-55 um, ave: 18 – 27 um
Motility Nonprogressive, blunt pseudopods
Number of nuclei One
Karyosome Large, irregular shape, eccentric
Peripheral chromatin Unevenly distributed
Cytoplasm Coarse and granulated
Cytoplasmic inclusions Vacuoles containing bacteria often visible
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E. coli cyst:
Typical characteristics at a glance
Parameters Description
Size range 8-35 um, ave: 12 – 25 um
Shape Round to spherical
Number of nuclei Eight
Karyosome Large, irregular shape, eccentric
Peripheral chromatin Unevenly distributed
Cytoplasm Coarse and granulated
Cytoplasmic inclusions Diffuse glycogen mass present in
young cysts, may displace nuclei
(often seen in cysts with 2 nuclei)
to opposite ends of the cyst.
Thin chromatoid bars with pointed
to splintered ends in young cysts
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E. polecki trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 8-25 um, ave: 12 – 20 um
Motility normal stools Sluggish, nonprogressive
Motility diarreic stools Progressive, unidirectional
Number of nuclei One (consistent)
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Granular and vacuolated
Cytoplasmic inclusions Ingested bacteria
Other food particles
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E. polecki cyst:
Typical characteristics at a glance
Parameters Description
Size range 10-20 um, ave: 12 – 18 um
Shape Spherical or oval
Number of nuclei One
Karyosome Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm Granular
Cytoplasmic inclusions Chromatoid bars, angular or
pointed ends in young cysts
Glycogen mass in young cysts
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Entamoeba polecki
TROPHOZOITE CYST
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Endolimax nana trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 5-12 um, ave: 7 – 10 um
Motility Sluggish, nonprogressive, blunt
pseudopods
Number of nuclei One
Karyosome Large, irregular, blotlike
Peripheral chromatin Absent
Cytoplasm Granular and vacuolated
Cytoplasmic inclusions Ingested bacteria
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Endolimax nana cyst:
Typical characteristics at a glance
Parameters Description
Size range 4-12 um, typically 7-10 um
Shape Spherical, ovoid, ellipsoid
Number of nuclei One to four; 4 most common
Karyosome Large, blotlike, usually central
Peripheral chromatin Absent
Cytoplasm Granular and vacuolated
Cytoplasmic inclusions Chromatin granules
Nondescript small mass sometimes
no glycogen mass visible
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Endolimax nana
TROPHOZOITE CYST
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Iodamoeba butschlii trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 8-22 um, ave: 12-18 um
Motility Sluggish, usually progressive
Number of nuclei One
Karyosome Large, usually central refractive
achromatic granules may or may
not be present
Peripheral chromatin Absent
Cytoplasm Coarsely granular and vacuolated
Cytoplasmic inclusions Ingested bacteria, yeast cells, and
other debris
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Iodamoeba butschlii cyst:
Typical characteristics at a glance
Parameters Description
Size range 4-12 um, typically 7-10 um
Shape Spherical, ovoid, ellipsoid
Number of nuclei One (uninucleated)
Karyosome Large, blotlike, usually central
Peripheral chromatin Absent
Cytoplasm Granular and vacuolated
Cytoplasmic inclusions Large glycogen body which stains
deeply with iodine
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Iodamoeba butschlii
TROPHOZOITE CYST
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Entamoeba gingivalis trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 8-20 um
Motility Active, varying pseudopod
appearance
Number of nuclei One
Karyosome Centrally located
Peripheral chromatin Fine and evenly distributed
Cytoplasm Finely granular
Cytoplasmic inclusions Epithelial cells
Bacteria
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Entamoeba gingivalis Transmission: _____________
Specimen: ________________
TROPHOZOITE TROPHOZOITE
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Prevention: __________________
9/22/2015
Free – Living
Pathogenic Amebae
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Naegleria fowleri
major cause of a disease called PAM
has 2 long flagella at one end
most cases are contracted in lakes and
swimming pools
probably the flagellated trophozoites are
forced deep into the nasal passages when the
victim dives in water
found in USA, Czechoslovakia, Mexico, Africa,
New Zealand, Australia
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Naegleria fowleri Ameboid trophozoite:
Typical characteristics at a glance
Parameters Description
Size range 8-22 um
Motility Directional, blunt pseudopods
Number of nuclei One
Karyosome Large and usually centally located
Peripheral chromatin Absent
Cytoplasm Granular and usually vacuolated
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Naegleria fowleri Flagellate form:
Typical characteristics at a glance
Parameters Description
Size range 7-15 um
Motility Jerky spinning movements due to
2 whiplike structures
Number of nuclei One
Karyosome Large and usually centally located
Peripheral chromatin Absent
Cytoplasm Granular and usually vacuolated
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Naegleria fowleri cyst:
Typical characteristics at a glance
Parameters Description
Size range 9-12 um
Shape Round with thick cell walls
Number of nuclei One
Karyosome Large, centally located
Peripheral chromatin Absent
Cytoplasm Granular and vacuolated
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Acanthamoeba culbertsoni
• cause chronic infection of the skin or
CNS in immunocompromised persons
• has small spiky acanthopodia
• causes amoebic keratitis
• Granulomatous Amoebic Encephalitis
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Acanthamoeba culbertsoni trophozoite*:
Typical characteristics at a glance
Parameters Description
Size range 12-45 um
Motility Sluggish, spinelike pseudopods
Number of nuclei One
Karyosome Large
Peripheral chromatin Absent
Cytoplasm Granular and usually vacuolated
* Trophozoites encyst when nutrients in the environment are depleted.
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Acanthamoeba culbertsoni cyst:
Typical characteristics at a glance
Parameters Description
Size range 8-25 um
Shape Round with ragged edges
Number of nuclei One
Karyosome Large, centrally located
Peripheral chromatin Absent
Cytoplasm Disorganized, granular, sometimes
vacuolated
Other features Double cell wall and outer jagged
cell wall
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Naegleria Acanthamoeba
Trophozoite with broad Trophozoite with
pseudopods filamentous pseudopods
Actively motile Sluggishly motile
Forms the flagellate stage Does not form flagellate
Single-walled cyst stage
Does not encyst in tissues Double-walled cyst
May encyst in tissues
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9/22/2015
Diagnosis / Treatment / Prevention
• Diagnosis of Acanthamoeba encephalitis is made only
after death in the majority of cases.
• Fatal outcome in 3 – 40 days.
• Previously, most cases required surgical excision of
infected cornea and corneal transplantation.
• Newer methods are being studied ; battery of drugs
• Boiling water is the best possible way of killing
trophozoites and cysts.
