PARASITOLOGY 4.
3
LUMEN DWELLING PROTOZOA
Doctor Martyr
Date
GENUS ENTAMOEBA
- Vesicular nucleus
- Small central karyosome
- Peripheral chromatin granules attached to the distinct -
nuclear membrane
- Entamoeba histolytica complex
- E. histolytica, E. dispar, E. moshkovskii
GENUS ENDOLIMAX
- Vesicular nucleus
- Relatively large, irregularly shaped karyosome anchored
to the nucleus by achromatic fibrils
GENUS IODAMOEBA
- Large chromatin rich karyosome surrounded by a layer of
achromatic globules anchored to the nuclear membrane
by achromatic fibrils
o 12-60 μm
Amoebae o Pseudopodia
Cytoplasmic protrusions
Ectoplasm – hyaline, outer layer body
Endoplasm - granular
Progressive, directional mobility
o Phagocytic stomata
o Ingested RBC’s
Pale, greenish, refractile bodies
o Stains – hematoxylin , trichrome
Visualize and identify nuclear structures
o Nucleus
Nuclear membrane - distinct line
Peripheral chromatin – layer of uniformly small
granules
Entamoeba histolytica Karyosome – central, mass of chromatin
Fibrils of linin network
o Pseudopod forming, non-flagellated protozoan parasite
o 2-stage life cycle o Hematoxylin:
Invasive trophozoite Ingested RBC’s – bluish black
Infective cyst Gray cytoplasm
Quadri-nucleate Nuclear structures – bluish-black
Resistant to gastric acid o Trichrome:
and desiccation Green cytoplasm
o MOT: Nuclear structures – dark red
Ingestion of cyst from fecally contaminated Ingested RBC’s – cherry red or green
material
Others
Venereal transmission, direct colonic Cystic stage
inoculation Precyst
o Excysts in intestine Rounded form
o Large intestine – trophozoites Single round nucleus, absence of
Intraluminal ingested material, lacks cyst wall
Invade mucosal crypts and form ulcers Cysts
o Hematogenous spread to other organs Spherical
Liver abscess Hyaline cyst wall – refractile if
unstained
1-4 nuclei – often not visible,
unstained
Chromatoidal bars
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PARASITOLOGY
INTESTINAL FLAGELLATES
o Virulence factors – invasiveness
Cysteine proteinases
Cytopathic to host tissues
Thinning of mucin layer, shortening of
villi, matrix breakdown
Gal/Gal NAc lectin
Adherence to host cells
Amebaphores
Form pores in host cell membranes
Cell lysis
o Stained cysts: o Penetration of muscularis mucosa to submucosa
Peripheral chromatin ring Flask shaped ulcers
appear thicker and less uniform in Cecum, ascending colon and sigmoid
size Erosion of blood vessels – intraluminal bleeding
May form plaques o Normal appearing mucosa despite undermining by
Masses in crescent fashion on one coalescing ulcers
side o Necrosis and sloughing off of intestinal wall
Karyosome may appear eccentric o Sigmoidoscopy show grossly normal mucosa between
Chromatoidal bars ulcers
o Differentiates amoebic dysentery from bacillary
dysenterae
Diagnostic characteristics o Progression irregular trenches with hair-like remnants
o “Buffalo skin” or
o Unstained trophozoites o “Dyak hair” ulcers
Ingestion of RBC’s
o Stained trophozoites
Fine uniform granules of peripheral chromatin
and small central karyosome in nucleus, Comparison between Amebic and Bacillary Dysenterae
ingested RBC’s, average size over 12 μm
o Stained cyst
Typical nuclear structure, chromatoidal bars Bacillary dysenterae Amebic dysenterae
with rounded or squared ends, diameter >
10μm
May be epidemic Seldom epidemic
Pathogenesis
Acute onset Gradual onset
o Asymptomatic infections
Carrier state Prodromal fever and malaise No prodromal features
o Symptomatic infections common
Intestinal
Dysenteric Vomiting common No vomiting
Nondysenteric colitis
Extraintestinal Patient prostrate Patient usually ambulant
Hepatic
Watery bloody diarrhea Bloody diarrhea
∗ Acute nonsuppurative
∗ Liver abscess Odorless stool Fishy odor stool
Pulmonary
Other foci Stool microscopy: numerous Few bacilli, red cells,
lacks synthesis glutathione synthesis bacilli, pus cells, trophozoites with ingested
o Intestinal amoebiasis macrophages, red cells, no red cells, Charcot-Leyden
Most common Charcot-Leyden crystals crystals
Asymptomatic, vague, nonspecific
Amoebic colitis Abdominal cramps common Tenesmus uncommon
Diarrhea/dysentery, abdominal pain and severe
and cramping, flatulence, anorexia,
weight loss, chronic fatigue Natural history: spontaneous Lasts for weeks, dysentery
Fever – not seen in uncomplicated recovery in a few days, returns after remission;
cases weeks or more; no relapse infection persists for years
Mild leukocytosis up to 12,000/μL
Periods of constipation is common
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PARASITOLOGY
INTESTINAL FLAGELLATES
o Physical examination Diagnosis
Abdominal tenderness over cecum, transverse
colon and sigmoid o Best – stool antigen + serology
Hepatic enlargement, tenderness o Stool exam – nonspecific and insensitive
o Severely diseased colon Slow leakage into abdominal From sigmoidoscopy
cavity Direct fecal smears (DFS)
Distention, ileus, peritoneal gas Formalin-Ether concentration test (FECT)
o Acute perforation Merthiolate-Iodine Formalin Concentration test
Most serious complication of amebic colitis (MIFC)
Signs of peritoneal irritation and peritonitis o Culture
Board-like abdomen TYI-S-33 medium
o Amoeboma o Serology
1% of intestinal infections o differentiate from nonpathogenic
Chronic granulomatous lesion species (E dispar)
Cecum or rectosigmoid area IHA – more specific, positive for years
“napkin ring” deformity ELISA – E histolytica Gal/GalNAc lectin
Radiologic findings of inflammatory bowel EIA
disease but seldom involve the terminal ileum DNA hybridization probes
o Hepatomegaly and tenderness PCR
Toxic response to infection
o Hepatic infection o UTZ, CT scan, MRI
Reach the liver through the portal vein Non-invasive, sensitive for early ALA
Liver tenderness and enlargement, fever,
weight loss Epidemiology
Cough – RLL pneumonitis
o Hepatic abscess (Acute Liver o Prevalence varies with level of sanitation
Abscess-ALA) Higher in tropics and subtropics, developing
Most common extra-intestinal form of countries
amebiasis Crowded conditions
Composed of proteinaceous, necrotic debris of o Severity
lysed hepatocytes and inflammatory cells Greater in tropics
Symptoms Malnutrition
o Fever and RUQ pain – mc o Transmission
o Increased pain severity, radiation to by asymptomatic carriers – impt (eg. Food
right shoulder, night sweats, handlers)
increased WBC Contaminated water and food
o Sonography, MRI, CT scan o Cysts – relatively resistant
o Aspiration – reddish brown fluid Killed by drying, T>55oC, superchlorination,
o Complications of ALA adding iodine to drinking water
Rupture into pericardium – most serious
Rupture into pleura Treatment
Intra-peritoneal rupture o Treatment goals:
Cure invasive disease at both intestinal and
o Pulmonary amoebiasis extraintestinsl sites
Erosion of hepatic abscess through Eliminate the passage of cysts from intestinal
diaphragm lumen
Subdiaphragmatic abscess – pleurisy, right o Drug for invasive disease +/- luminal agent
lower lobe pneumonitis
Rupture through pleural cavity – effusion o Asymptomatic intestinal amoebiasis
ascending the major fissure May become symptomatic, nidus for extra-
Bronchial erosion – amoebas in sputum intestinal disease, transmission
Primary pulmonary amoebiasis – Paromomycin, diloxanide furoate or
hematogenous metronidazole/tinidazole/secnidazole
o Acute amoebic colitis
o Other organs Metronidazole/Tinidazole/secnidazole
Brain – amebic meningoencephalitis Followed by luminal agent
Amebiasis + abnormal mental status Eliminates intestinal colonization
Skin Prevents relapse
Genital/genito-urinary
o Hepatic abscess
Metronidazole/Tinidazole
Aspiration and drainage
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PARASITOLOGY
INTESTINAL FLAGELLATES
o Metronidazole Diagnostic characteristics
MOA: reduction by ferrodoxin reactive
radical o Stained trophozoites
SE: nausea, diarrhea, metallic taste, headache Nuclear structure as E. histolytica, ingested
Can be given during the last 2 trimesters of bacteria, diameter < 12 μm
pregnancy o Stained cysts
Precaution: abstinence from alcohol Typical nuclear structure, chromatoidal bars
o Tinidazole with squared or rounded ends, diameter <
Better tolerated and shorter treatment duration 10μm
Prevention
Entamoeba coli
o Break the chain of transmission
o Boiling, iodine o Slightly larger trophs
o Food handlers o Granular cytoplasm, many vacuoles
Treat and monitor o Doesn’t ingest RBC’s
o Sluggish movements, not progressive
o Pseudopodia – short and blunt, not hyaline, more for
food ingestion
o Cytoplasm not differentiated into endoplasm-ectoplasm
Stained trophs
o Peripheral chromatin
Irregular in size and arrangement, more
abundant
o Karyosome
Large, irregular, eccentric, surrounded by a
halo of non-staining material
E. coli cysts
o Unstained
Highly refractile cyst wall, granular cytoplasm,
absent food vacuoles
1-8 nuclei, eccentric karyosome
Chromatoidal bodies are less common
o Stained
Granular cytoplasm
Glycogen appear as dark-staining masses
surrounding the nuclei
1-8 nuclei
Splinter-shaped chromatoidal bodies
Diagnostic characteristics
o Stained trophozoites
Nucleus with irregular clumps of peripheral
Entamoeba dispar chromatin
large, irregular, eccentric karyosome
o More prevalent than E. histolytica o Stained cysts
o Doesn’t cause disease Typical nuclear structure
o Doesn’t elicit antibody production splinter-shaped or irregular chromatoidals
o Morphologically indistinguishable from E. histolytica
o Serology required
Entamoeba polecki
Entamoeba hartmanni o Occasionally infect humans
o As E. coli in motility, granularity, vacuolization and
o “small race” E. histolytica bacterial ingestion
o Differentiated only by size o Nuclear structure intermediate between E. histolytica and
E. coli
Troph ≤ 12μm
o Cysts
Cysts ≤ 10μm Single nucleus
o Ingests bacteria but NOT RBC’s Chromatoidals – angular or pointed, thread-like
o Sluggish movement (+) glycogen, “inclusion mass”
Large central karyosome – spherical or stellate
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PARASITOLOGY
INTESTINAL FLAGELLATES
Diagnostic characteristics
Diagnostic characteristics o Stained trophs
Large karyosome with little or no peripheral
o Stained cysts chromatin
Inclusion masses o Stained cysts
Chromatoidal bars with angular or pointed ends Four nuclei with large karyosome and little or
no peripheral chromatin
o Pathogenesis
Infection but rarely cause disease
Diarrhea
o Treatment
metronidazole followed by diloxanide furoate
Entamoeba gingivalis
o Pyorrheal pockets between teeth and gums and tonsillar
crypts
o Reported in bronchial mucus
o Cytoplasm filled with ingested leukocytes
o Doesn’t form cysts
Iodamoeba butschlii
o Prominent glycogen vacuoles
o Sluggishly progressive with hyaline pseudopodia
o No peripheral chromatin on the nuclear membrane
o Stained trophs
Delicate nuclear membrane
Large irregularly rounded central karyosome
surrounded by a small layer of granules
o Cysts
Irregular with refractile wall
Stained – large brown glycogen mass more
than half the diameter of the cyst
Highly refractile eccentric karyosome
Chromatin granules form a crescentic aggregate between
karyosome and nuclear membrane, with linin fibrils
“basket of flowers
Diagnostic characteristics
o Stained trophs
Nucleus with large central karyosome
surrounded by a ring of small chromatin
granules or nuclear structure as in a cyst
o Stained cysts
Basket nuclei or nuclei as in trophs, large
glycogen vacuole
Endolimax nana
o Most common of the smaller amoebae
o Pseudopodia – large, blunt, rapidly extruded but non-
directional
o Sluggish, random movement
o Large irregular karyosome
o Refractile cyst wall
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PARASITOLOGY
INTESTINAL FLAGELLATES
OPPORTUNISTIC FREE LIVING AMOEBAE
Pathogenesis
o Inhabits fresh, brackish, salt water, moist soil and
decaying vegetation o Fever and headache followed by nausea and vomiting
Naegleria – amoebo-flagellates o Meningitis with involvement of olfactory, frontal,
Acanthamoeba – never produce flagella temporal and cerebellar areas
Balamuthia mandrillaris o Meningeal irritation – stiff neck, generalized seizures
o Primary Amoebic Meningoencephalitis and Kernig’s Sign
o Olfactory lobe involvement is characteristic
Disturbance in taste and smell
o Rapid – coma and death
o Course of 3-6 days
Naegleria fowleri
o Amoebic and flagellar stage
o Only trophs are found in tissues CSF
o History of swimming in fresh or brackish water
Cloudy, purulent, serosanguinous
Increased intracranial pressure
Increased leukocytes, predominant
neutrophils with NO bacteria
Increased proteins, low sugar
o Meningoencephalitis on autopsy
Exudate in subarachnoid space
Hemorrhage and inflammatory exudate in
gray matter
Rounded amoebae prominent in Virchow-
Robin spaces
Demyelination
Epidemiology
o Rare disease
o More common in developing countries
o History of recent swimming in fresh water during hot
summer weather
Treatment
o No satisfactory treatment
o Amphotericin B
Drug of choice (Belizario)
Disrupts plasma membrane permeability
PAM causing leakage of cellular components
o Azithromycin
o Identification of amoebae in CSF o Predisposing factors
o “limax” shape and progressive movement Warm temperature
o Fully active at room temperature Adequate food supply
o Flagellate from induced by suspending amoebae in Minimal competition from other protozoans
distilled water at 37oC for 4-5 hours Optimal pH and oxygen levels
o Phase contrast microscopy (troph)
Lobose monopseudopodium
Prominent nucleus with centrally located
nucleolus
A pair of flagella originating from a pear
shaped body
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PARASITOLOGY
INTESTINAL FLAGELLATES
ACANTHAMOEBA SSP AND BALAMUTHIA
MANDRILLARIS
o Granulomatous amebic encephalitis (GAE)
chronic CNS infection
o Acanthamoeba keratitis –eye infection
o Skin infections
MC reported condition associated with
Acanthamoeba and Balamuthia among AIDS
patients
GAE
Not associated with swimming
Hematogenous spread to the brain
From respiratory tract, ulcers on
skin and mucosa
In debilitated/immunocompromised patients
Poorly defined disease
Insiduous onset with prolonged
course
Characterized by focal
granulomatous lesions in the brain
Diagnosis
Identification of trophozoites in CSF
or trophs and cysts in brain tissue
Acanthamoeba and balamuthia not
easily cultured from CSF
Treatment
No satisfactory treatment
o Keratitis
Affects healthy persons
Trauma to eyes, contact lenses
Severe ocular pain out of proportion with the
degree of inflammation
Chronic progressive keratitis loss of vision
Differential – herpes simplex keratitis
Diagnosis
Identification of amoeba from
cultured corneal scrapings
Histology of infected tissue
Acanthamoeba can be cultured
from corneal scrapings
Treatment
Surgery + medical treatment
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