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The Amoebas

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Have a nucleus that is vesicular with small endosome at or near the ... PAM is gotten when swimming in infected water and is usually diagnosed at autopsy ... – PowerPoint PPT presentation

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Title: The Amoebas


1
The Amoebas
2
Order Amoebida
  • Family Endamoebidae
  • Parasitic or commensals of digestive system
  • Includes Entamoeba, Endolimax and Iodamoeba

3
Entamoeba
  • Have a nucleus that is vesicular with small
    endosome at or near the center (concentric)
  • Chromatin is around the periphery of the membrane
  • Cytoplasm is usually full of food vacuoles
  • Golgi and mitochondria are absent
  • Have helical bodies in some trophozoites
  • 40 distinct ribonucleoproteins
  • Crystalize into chromatoidal bodies or bars in
    the cyst forms
  • Blunt or splintered ends based on the species

4
Entamoeba histolytica
  • 3rd most common cause of parasitic deaths
  • Causes severe diarrhea
  • 2 sizes
  • Smaller sizes trophozoites and cysts are not
    associated with disease
  • E. hartmanni
  • Larger sized trophozoites and cysts are
    pathogenic
  • E. histolytica

5
Life Cycle
  • Trophozoite
  • Precyst
  • Troph release undigested food, secretes a hyaline
    cyst wall to become cyst
  • Cyst
  • Metacyst
  • Has 4 nuclei
  • Metacystic trophozoite
  • Metacyst divides into 8 small amebulas which are
    small trophs
  • Precyst, Cyst and Metacyst forms as stool
    dehydrates and dries, not in diarrhea or in the
    tissues
  • Trophozoite in large intestine ? cyst in feces ?
    ingested ? trophozoite in large intestine

6
E. histolytica Trophozoites
  • Found in loose stools mainly
  • Nucleus with a central endosome and a fine
    peripheral ring of chromatin distinguishes this
    parasite from E. coli
  • Charcot-Leyden crystals, representing the
    crystallized contents of granules from eosinophil
    leukocytes may also be found in a fecal smear
  • Capable of causing ulcerative colitis, resulting
    in severe dysentery, as well as extra-intestinal
    amebiasis, including fatal brain infections.

7
E. histolytica Trophs
8
E. histolytica Cysts
  • Stool smear
  • Cysts found mainly in formed stools
  • Infective stage
  • Chromatoidal bars (C), when present in immature
    cysts (precyst), usually have blunt ends, versus
    splintered ends in cysts of E. coli
  • Disappear as cyst becomes older

9
E. histolytica Cysts
  • Cysts have four or fewer nuclei
  • Although all four nuclei may not be visible in
    the same plane, they can be counted by carefully
    adjusting the fine focus control (N1-N4, second
    row).

10
E. histolytica Biology
  • Trophozoites
  • Live and multiple indefinitely in the crypts of
    the mucosa of the large intestine, eating
    bacteria
  • Can invade the tissue when proteolyze the mucosal
    cells pathogenic and non-pathogenic
  • Uses filopodia for endocytosis, pinocystosis,
    attachment, penetration of tissue, release of
    cytotoxic substance and contact cytolysis of host
    cells
  • Move in the blood to other organs such as liver,
    lung and skin once it penetrates the intestinal
    mucosa
  • Trophs are NOT infective
  • Cysts
  • Leave in large numbers, host is usually
    asymptomatic or infected with small numbers
  • Cysts are not resistant to drying and temperature
    fluctuations but can withstand the chlorine
    levels used in H2O purification
  • Can withstand the stomach acid but in alkaline
    small intestine, the metacyst activates and can
    tear through the cyst wall, divides into amebulas
    and is moved into the cecum
  • Metacystic troph needs to contact mucosa to
    survive and cause infection

11
Intestinal Lesions
  • Usually develop in cecum, appendix or upper large
    intestine
  • Connect to lumen but spread laterally
  • Late infection may be complicated by bacteria,
    erode through wall and get in the blood
  • Can form a granulomatous mass in the wall of the
    intestine called an Ameboma
  • Result of cellular response
  • Lesions in the liver may have necrosis but are
    bacterially sterile hepatic amebiasis
  • Lung amebiasis is 2nd most common
  • May be primary or metastatic from the liver by
    way of through the diaphragm

12
Symptoms
  • Intermitent diarrhea, cramps, vomitting, general
    malaise slowly developing
  • More severe infection with higher parasite load,
    pain in abdomen, fulminent diarrhea and
    dehydration chronic form that continues to get
    worse
  • Acute amebic dysentary has headache, fever,
    severe abdominal cramping with prolonged
    straining at the stool
  • Very liquid feces with bloody mucous
  • Possible death from peritonitis, cardiac failure
    and exhaustion

13
Diagnosis and Treatment
  • Diagnosis
  • See troph or cyst in the stool sample
  • May need to do several consecutive days
  • Need to rule out E. dispar, a non-pathigenic
    parasite
  • Treatment
  • Metronidazole

14
Epidemiology
  • Can be found everywhere
  • Clinical amebiasis is mostly tropical and
    subtropical
  • Transmitterd from anal to oral contact
  • Bas bathroom and handwashing techniques

15
Entamoeba coli
  • Co-exists with E histolytica
  • Troph hard to distinguish from E histolytica
  • Commensal with no tissue lysis must identify
    because presence indicates fecal-oral
    contamination
  • Important to make the correct diagnosis
  • This requires no treatment
  • Life cycle identical to histolytica

16
E. coli Trophs
  • Stool smear
  • Distinguish from E. histolytica by the usually
    eccentric location of the endosome and the
    relatively coarser, larger granules in the ring
    of peripheral chromatin
  • Found mainly in loose stools.

17
E. coli Cysts
  • Stool smear
  • Presence of more than four nuclei (actually,
    eight are present in mature cysts)
  • Chromatoidal bars (C) in immature cysts have
    splintered ends, versus blunt ends in cysts of E.
    histolytica
  • Found mainly in formed stools
  • Infective stage.

18
E. gingivalis
  • Found in human, dog, cat and monkey
  • Dwells only in the mouth
  • Found on the surface of teeth, gums and gingival
    packets, may also be in the tonsil crypts
  • 95 with unhealthy mouth and 50 with healthy
    mouth
  • Present in all populations and is a commensal
  • Found only as a troph, have blunt pseudopodia for
    rapid movement, small nucleus, nearly central
    endosome and chromatin on the inner surface of
    the membrane

19
Endolimax nana
  • Found in the large intestine near the cecum
  • Commensal must identify because presence
    indicates fecal-oral contamination
  • Has a thin layer of ectoplasm around the
    endoplasm, short blunt pseudopodia very slow
  • Small nucleus the a large endosome, centrally to
    eccentrally located
  • Often have large glycogen vacuoles
  • Life cycle is similar to other Entamoeba

20
E. nana Trophs
  • Stool smear
  • Small nuclear size and prominent endosome
  • Infection occurs when the cyst is ingested
  • Found mainly in loose stools

21
E. nana Cysts
  • Stool smear
  • Small size and presence of up to 4 nuclei with
    prominent endosomes
  • Found mainly in formed stools
  • Infective stage

22
Iodamoeba buetschlii
  • Only a single species
  • Infects humans, other primates and pigs
  • Life cycle is same as other amoebas
  • Nucleus has light staining granules between
    endosome and nuclear membrane as well as
    achromatic strands

23
I. buetschlii Troph
  • Stool smear
  • Prominent endosome and numerous cytoplasmic
    vacuoles
  • Considered to be harmless
  • Important to identify because it is an indicator
    of fecal-oral contamination
  • Found mainly in loose stools. Infection occurs
    when the cyst is ingested.

24
I. buetschlii Cysts
  • Stool smear
  • Found mainly in formed stools
  • Oval shape nucleus, prominent endosome and large,
    single, glycogen-filled vacuole
  • Cell is retracted from the cyst wall in one
    specimen (arrow)
  • Infection occurs when the cyst is ingested

25
Acanthamoeba culbertsoni Troph
  • Culture smear
  • Spike-like rhizopods near the apex of the
    organism
  • Some are found as opportunistic parasites of
    immunosuppressed individuals and in
    immunocompetent persons suffering trauma to the
    conjunctiva of the eye or using contaminated
    contact lens cleaning solutions
  • In immunosuppressed individuals, it forms slowly
    spreading granulomas in the visceral organs
  • Eye infection may require surgical removal of the
    eye
  • Cyst is the infective stage
  • Life cycle
  • trophozoite in soil?cyst in soil ?introduced into
    the eye ? trophozoite in tissues ?cyst in tissues

26
Nalgeria fowleri
  • Causes primary amebic meningoencephalitis (PAM)
  • Has a flagellate and amoeba form and it rapidly
    switches from one to the other
  • Flagellate stage 2 flagella, no pseudopodia,
    vesicular nucleus with large endosome and
    peripheral granules
  • Ameboid stage single blunt pseudopodium
  • PAM is gotten when swimming in infected water and
    is usually diagnosed at autopsy

27
N. fowleri Life Cycle
  • cyst in bottom mud ? trophozoite in bottom mud ?
    biflagellated cell ? inhaled into nasal cavity ?
    trophozoite in nasal cavity ? migrates along
    olfactory nerve ? trophozoite in brain

28
Brain Section
500 mm
10 mm
  • Individual trophozoites within necrotic zone,
    each with a prominent endosome
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