MODULE 2 UNIT 2 Flashcards
It includes the amoebas, which have no permanent locomotory organs, but move about with the aid of temporary prolongations of the body called
It includes those protozoa which possess whip-like structures called
Two groups of amoebae are of medical importance.
- Parasitic amoebae; 2. Pathogenic free-living amebae
three genera of Parasitic amoebae
Entamoeba, Endolimax, and Iodamoeba
Parasitic amoebae include
Entamoeba histolytica, Entamoeba dispar, Entamoeba coli, Entamoeba hartmanni, Endolimax nana, and Iodamoeba butschlii which are all found in the intestinal lumen, and Entamoeba gingivalis which is found in the mouth
is the only pathogenic species which causes intestinal and extraintestinal amoebiasis.
E. histolytica
All the other amaebae species are commensals. They all exist in two forms in the life cycle, trophozoites and cysts, EXCEPT {?} which occurs in the trophozoite stage only
E. gingivalis
Several species of free-living amoebae are found in soil and water.
Pathogenic free-living amebae
are of clinical interest because they can cause fatal meningoencephalitis and eye infections.
(1) Naegleria and (2) Acanthamoeba
Trophozoite Size
10-60 µm (ave: 15-20 µm)
Trophozoite Motility and
Pseudopodia
Progressive, rapid, unidirectional motility; with hyaline, fingerlike pseudopodia formed rapidly
Trophozoite Nucleus
Number
1
Trophozoite Peripheral
chromatin
Fine granules, uniform in size and usually evenly distributed; may have beaded appearance
Trophozoite Karyosome
Small, compact, centrally located
Trophozoite Linin network
The space between the karyosome and the nuclear membrane is traversed by fine thread of linin network giving a radial spokeswheel or cartwheel appearance.
Trophozoite Cytoplasm
Appearance
Finely granular, “ground-glass” appearance; clear differentiation into a clear ectoplasm and more granular endoplasm; if present, vacuoles are usually very small
Trophozoite Inclusions
RBCs are diagnostic; few ingested bacteria or debris in vacuoles
Cyst Size
10-20 µm (12-15 µm)
Cyst Shape
Usually spherical
Cyst Nucleus
Number
1-4; mature cyst contains 4 nuclei
Cyst Peripheral chromatin
Similar to that seen in trophozoite
Cyst Karyosome
Similar to that seen in trophozoite
Cyst Cytoplasm
Chromatoidal bodies
May be present; usually elongate with blunt, rounded, smooth ends (cigarshaped); may be round or oval.
Cyst Glycogen vacuole
May be present, usually diffuse, stains reddish brown with iodine.
is morphologically indistinguishable from E. histolytica and should be reported as E. histolytica/E. dispar unless ingested red blood cells are seen, suggesting E. histolytica infection.
Entamoeba dispar
The DNA and ribosomal RNA , and isoenzyme pattern of (?) is different from that of E. histolytica.
E. dispar
Unlike E. histolytica, E. dispar is (?).
nonpathogenic.
The ratio of E. dispar to E. histolytica in most developing countries can be as high as (?) in a community setting.
10:1
The ratio of E. dispar to E. histolytica in most developing countries can be as high as (?) in a community setting.
10:1
E. histolytica passes its life cycle in one host and has the following successive stages:
cyst, metacyst, metacystic trophozoite, trophozoite, and precyst.
are passed in feces
Cysts and trophozoites
Infection with Entamoeba histolytica (and E.dispar) occurs via (?) from fecally contaminated
food, water, or hands.
ingestion of quadrinucleated mature cysts
(?) occurs in the cecum or lower part of the ileum, under the influence of neutral or slightly acidic digestive juices.
Excystation
A quadrinucleated (?) is liberated from the cyst wall. The nuclei in the metacyst immediately undergo division to form eight nuclei, each of which gets surrounded by its own cytoplasm. The cytoplasm divides into as may parts as there are nuclei.
metacyst
(?) are released, which migrate to the large intestine (cecum), their normal habitat.
Eight (8) metacystic trophozoites (or amoebulae)
t. In the glandular crypts, they feed and grow and develop into normal (?)
trophozoites
The trophozoite discharges undigested food and condenses into a spherical mass, called the (?)
precyst
There are 2 types of inclusions in unripe and ripening cysts:
chromatoidal bodies and glycogen mass
s. Ripening of cysts of E. histolytica consists of (?) consecutive mitotic divisions of the nucleus to produce (?) nuclei .
2; 4
During this process,(?) is expended and the chromatoidal bodies become less conspicuous or completely disappear
glycogen
(?) are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool.
Cysts
is used clinically to denote all conditions produced in human host by infection with E. histolytica at different areas of invasion.
Amoebiasis
E. hislolytica causes 2
(1) intestinal and (2) extraintestinal amoebiasis
Adapted by the WHO, intestinal amoebiasis is clinically classified into (a) asymptomatic, and (b) symptomatic infections.
Intestinal amoebiasis
intestinal amoebiasis is clinically classified into (?)
(a) asymptomatic, and (b) symptomatic infections.
The majority of infections with E. histolytica are
Asymptomatic infection
This occurs in approximately 90% of cases especially in endemic communities
Asymptomatic infection
There is NO evidence of tissue invasion.
Asymptomatic infection
Infected individual passes formed stool with cyst forms. But, there is concern that an infection with E. histolytica may become symptomatic in the intestinal tract or with subsequent extraintestinal invasion.
Asymptomatic infection
Only about 10% of amoebiasis are symptomatic
Symptomatic infection
(?) is defined as an intestinal infection caused by the presence of E. histolytica exhibiting symptoms occurs when the mucosa is invaded.
Amoebic colitis
(?) is defined as an intestinal infection caused by the presence of E. histolytica exhibiting symptoms occurs when the mucosa is invaded.
Amoebic colitis
(?) is characterized by gradual or sudden onset, dysentery with 6-10 or more bloodtinged, mucoid, foul-smelling stools per day.
Acute amoebic colitis or amoebic dysentery
(?) may resemble bacillary dysentery, but can be differentiated on clinical and laboratory grounds.
Amoebic dysentery
(?) does not always result in dysentery.
Intestinal amebiasis
(?) is uncommon (only if rectum is involved), low-grade fever or none at all, and mild leukocytosis.
Tenesmus
(?), aka nondysenteric amoebic colitis, is characterized by intermittent diarrhea and constipation. i.e., alternating diarrhea and constipation, or abdominal pain.
Chronic amoebic colitis
Cysts are found in formed stool while trophozoites are seen during times of diarrhea. This may last for years.
Chronic amoebic colitis
(?) got its name through its ability to lyze tissues, initiated by invasion of the colonic mucosa.
E. histolytica
There are three pathogenic processes, each of which is facilitated by the expression of virulence factor.
Cytoadherence; Cytolysis; Proteolysis
Trophozoite lectins, a group of proteins, bind to specific carbohydrate-containing receptors on host luminal surfaces and mediate adherence.
Cytoadherence
Amoebapores are proteins of amoeba capable of inserting into the host cell membrane and form pores causing lysis of the host cells. Trophozoites’ amoeboid movement also contributes to the lysis of mucosal cells.
Cytolysis.
Amoebapores are proteins of amoeba capable of inserting into the host cell membrane and form pores causing lysis of the host cells. Trophozoites’ amoeboid movement also contributes to the lysis of mucosal cells.
Cytolysis.
Cysteine proteinase enzymes are responsible for further tissue lysis
Proteolysis.
(?) by the trophozoites produces discrete ulcers with pinhead center and raised edges. Sometimes, the invasion remains superficial and heals spontaneously.
Mucosal penetration
More often, the trophozoites penetrate to submucosal layer and multiplies rapidly, and spread by lateral and downward extension producing a typical (?) in cross section, with mouth and neck being narrow and base large and rounded.
flask shaped (or tear drop-shaped) ulcer
The (?) are multiple and are confined to the colon, being most numerous in the cecum and next in the sigmoidorectal region.
ulcers
The ulcers generally do not extend deeper than submucosal layer.
Colonic perforation.
Occasionally, the ulcers may involve
the muscular and serous coats of the colon, causing perforation
and peritonitis. This occurs in about 60% of fulminant cases.
Blood vessel erosion may cause hemorrhage.
Colonic perforation.
Occasionally, a granulomatous mass may develop on the intestinal wall.
Amoeboma.
It is the result of cellular responses to a chronic ulcer and often still contains active trophozoites, usually in the cecum or rectosigmoid.
Amoeboma.
It produces wall thickening and or constriction of the lumen, the so-called “napkin ring” lesion and may obstruct the bowel.
Amoeboma.
This may be mistaken for colon cancer
Amoeboma.
Secondary amoebic infection occurs as a result of trophozoites entering portal circulation or by direct extension from the intestinal tissues and becoming lodged in the liver, and other extraintestinal organs such as the lungs, brain, spleen and cutaneous sites.
Extraintestinal amoebiasis
Hepatic involvement is the most common extraintestinal complication of amebiasis.
Hepatic amoebiasis
The dissemination from the primary site in the colon is primarily by the blood stream.
Hepatic amoebiasis
he trophozoites reach the liver through the portal vein.
Hepatic amoebiasis
At times, it may also occur through direct extension from the intestinal ulcer.
Hepatic amoebiasis
It covers both amoebic hepatitis and amoebic liver abscess (ALA).
Hepatic amoebiasis
In ALA, the trophozoites lyze liver cells and forms abscess filled with necrotic debris described as anchovy sauce or chocolate pus.
Hepatic amoebiasis
lt is bacteriologically sterile and free of amoeba.
Hepatic amoebiasis
At the periphery, there is almost normal liver tissue, which contains invading trophozoites.
Hepatic amoebiasis
(?) ranks next to liver abscess in rate of occurrence.
pulmonary amoebiasis
Primary amoebiasis of the lung occurs independently without the presence of hepatic involvement by (?) from the colon wall via the pulmonary circulation into the pulmonary arteries.
direct hematogenous spread
But most often it is secondary to hepatic abscess by direct extension through the diaphragm and therefore, the (?) is the usual area affected. The patient presents with pneumonia with
expectoration of anchovy sauce or chocolate sputum.
lower part of the right lung
Involvement of distant organs is by hematogenous spread and through lymphatics.
Metastatic amoebiasis
Abscesses in kidney, brain, spleen and adrenals have been noticed
Metastatic amoebiasis
Spread to brain leads to severe destruction of brain tissue and is fatal.
Metastatic amoebiasis
This is a result of damaged skin frequently brought in contact with trophozoites.
Cutaneous amoebiasis
It occurs commonly around the perineum or perianal region secondary to amoebic dysentery, also on the skin over the region adjoining the visceral lesion - as in hepatic abscess.
Cutaneous amoebiasis
The prepuce and glans are affected in penile amoebiasis which is acquired through anal intercourse.
Genitourinary amoebiasis
Similar lesions in females may occur on vulva, vagina, or cervix by spread from perineum.
Genitourinary amoebiasis
It is performed for diagnosis of intestinal amoebiasis.
Stool examination
It is not of value in the diagnosis of extraintestinal amoebiasis.
Stool examination
E. histolytica cyst can be detected in stool in less than 15% cases of amoebic hepatitis.
Stool examination
: This is a standard method for routine O & P exam. Trophozoites are primarily recovered from stools that are of soft, liquid, or loose consistency.
Direct fecal smear (DFS)
Formed stool specimens are more likely to contain cysts.
Direct fecal smear (DFS)
Saline mount of fresh unfixed stool demonstrates motile trophozoites, or cysts while iodine preparation primarily demonstrates the cysts only.
Direct fecal smear (DFS)
When patient is suspected of having intestinal amoebiasis, 6 specimens is recommended (however, is rarely requested) and collected on separate days within 14-day period: 3 specimens collected from normal bowel movement and 3 specimens collected after catharsis/purge.
Direct fecal smear (DFS)
Bacteria
Few, Numerous
Pus cells
Scanty, well-preserved; Numerous, degenerated
RBC
Often in rouleaux; Unaltered, scattered
Macrophage
NOT a feature; May be numerous (may have RBC)
Charcot-Leyden crystals
May be present; Absent
Trophozoite
Present; Absent
There are two types of concentration procedures:
flotation and sedimentation
Cysts may be seen and identified, but trophozoites are not likely to be seen. Therefore, this is recommended for isolation and identification of amoebae in non-diarrheic stool.
Stool concentration
It is considered the best practice in the diagnosis of protozoa because it allows examination and recognition of the detailed morphology of the trophozoites or cysts.
Permanent staining
It provides contrasting colors for the parasites and the background. The parasite is examined under high magnification by oil-immersion technique.
Permanent staining
The parasite is examined under high magnification by (?) technique.
oil-immersion
Blue-green, sometimes light pink or with a tinge of purple; Slightly more purple
TRICHROME
Blue-gray; Blue-gray
IRON HEMATOXYLIN
Red, sometimes with a tinge of purple
TRICHROME
Darker than cytoplasm, bluegray to black
IRON HEMATOXYLIN
Green, provides nice contrast with the protozoa
TRICHROME
Lighter shade of blue-gray
IRON HEMATOXYLIN
Scraping obtained by sigmoidoscopy is often contributory.
Examination of sigmoidoscopy specimen
Examination method includes a direct wet mount and permanent staining.
Examination of tissue aspirates/biopsy
Liver abscess material, may be processed and examined in the same manner. Microscopic examination of pus aspirated from liver abscess may demonstrate trophozoite of E. histolytica in less than 20% cases.
Examination of tissue aspirates/biopsy
In case of liver abscess, when diagnostic aspiration is done, the pus obtained from the center of the abscess may not contain amoeba as they are confined to the periphery.
Examination of tissue aspirates/biopsy
The fluid draining after a day or two is more likely to contain the trophozoite. Aspirates from the margins of the abscess would also show the trophozoites.
Examination of tissue aspirates/biopsy
Cysts are never seen in extraintestinal lesions. Trophozoite of E. histolytica may be demonstrated in liver biopsy specimen, in case of hepatic amoebiasis or amoebic hepatitis.
Examination of tissue aspirates/biopsy
It is a more sensitive method in diagnosing chronic and asymptomatic intestinal amoebiasis.
Stool Culture
(?) yields higher positivity for E. histolytica as compared to direct examination.
Culture of stools
Media used for polyxenic culture include:
- Boeck and Drbohlav’s biphasic medium - NIH polygenic medium - Craig’s medium - Nelson’s medium - Robinson’s medium - Balamuth’s medium.
Medium for axenic culture:
- Diamond’s medium
Amebic antibodies appear in serum only in late stages of intestinal amebiasis.
Antibody detection
Test for antibodies in serum help in the diagnosis of mainly extraintestinal infections.
ELISA-based assay
In reference diagnostic laboratories, molecular analysis by conventional PCR-based assays or real-time PCR is the method of choice for discriminating between E. histolytica and E. dispar
Molecular diagnosis
X-ray, ultrasonography (USG), computed tomography (CT) scan, or magnetic resonance imaging (MRI) of liver may be found useful in detection of amebic liver abscess.
Molecular diagnosis
X-ray, ultrasonography (USG), computed tomography (CT) scan, or magnetic resonance imaging (MRI) of liver may be found useful in detection of amebic liver abscess.
Radiologic examination
Cosmopolitan. Although clinical amoebiasis is more prevalent in the tropics and subtropics than in the temperate zone.
Geographical distribution
Approximately 1 to 5% worldwide. About 5% in the Philippines, but the true prevalence in not determined yet with the recent redescription of E. histolytica and E. dispar.
Prevalence
Human is the major reservoir. Dogs, pigs, and monkeys are also implicated.
Reservoir
Transmission
Fecal-oral route.
(?) contaminated with feces containing cysts are the most common source of infection.
Food and drinks
This is associated to poor sanitation particularly from open defecation or night soil practice, or careless plumbing in which sanitary drains were connected to freshwater pipes.
Polluted soil/water
Transmission of (?) by water is common when people depends on untreated wells, springs, streams, or storage tanks; or by soil when vegetables and fruits are eaten raw and not thoroughly washed.
E. histolytica
(?) may remain viable in water for 9-30 days and
are not killed by chlorination in strengths used for bacterial
decontamination of public water supply. However, they can be
killed in drinking water by hyperchlorination or by addition of iodine, or by boiling (thermal death point at 50-55 oC).
Cysts of E. histolytica
In moist soil conditions, they can survive for upto for
8 days at 28 to 34°C
40 days at 2 to 6°C
60 days at 0°C
Unclean handling of food by infected individuals who are cyst passers or cyst carriers appears to be a very common method.
Infected food handlers
There are contact carriers - so-called (?) who have never suffered from amoebic dysentery and whose health remains to be unimpaired, and the convalescent carriers who have recovered from a clinical attack of acute amoebic dysentery.
“healthy” carriers
These serve as mechanical vectors of E. histolytica from feces, then depositing infective cysts on unprotected food. Viable cysts and trophozoites may be recovered from the vomitus or excreta. Cysts remain viable in their excreta for as long as 48 hours after the insect has fed on contaminated feces.
Flies, cockroaches, and other insects
Ingestion of cyst occurs through hand-tomouth contamination which especially occurs among children and institutionalized individuals (in mental hospitals, prisons, orphanage, daycare).
Poor personal hygiene
This is related to sexual practices that foster transmission and ingestion of cyst.
Sexual transmission
Oral-anal contact is a common practice among homosexual men (men who have sex with men, MSM).
Sexual transmission
It can also occur during oral-genital sex after anal intercourse.
Sexual transmission
(?) was a medical term first used by Henry L Kazal and colleagues in 1976 to describe a complex of gastrointestinal symptoms associated with sexually transmitted GIT diseases, which had many gay patients.
Gay bowel syndrome
Accurate identification of commensal amoebae is crucial for the following reasons:
- They may be confused with Entamoeba histolytica in diagnostic investigations. These amoebae do not cause a disease, therefore treatment is not necessary. 2. Although nonpathogenic, they should still be reported when identified in stool specimens since their presence is an indication of ingestion of fecally contaminated food or water.
The three genera of amoeba can be distinguished from each other by the structure of nucleus.
Small compact karyosome; Large irregular karyosome; Large circular karyosome
(?) central or eccentrically located; nuclear membrane lined with peripheral chromatin.
Small compact karyosome
(?) attached to the nuclear membrane by fibrils radiating to the periphery; no peripheral chromatin.
Large irregular karyosome
(?) surrounded by refractile achromatic granules called periendosomes; no peripheral chromatin.
Large circular karyosome
5-12 µm (ave. 8-10 µm)
Entamoeba hartmanni
10-50 µm (ave. 20-25 µm)
Entamoeba coli
5-20 µm (ave. 10-15 µm)
Entamoeba gingivalis
6-15 µm (ave. 8-10 µm)
Endolimax nana
6-20 µm (ave.12-15 µm)
odamoeba butschlii
Less progressive motility; with hyaline, fingerlike pseudopodia formed rapidly
Entamoeba hartmanni
Nonprogressive, sluggish, nondirectional motility; with blunt, usually granular pseudopodia formed slowly
Entamoeba coli
Moderately active, progressive; with multiple pseudopodia , vary from long, and lobose to short and blunt, often formed rapidly
Entamoeba gingivalis
Sluggish, moderately progressive; with blunt, hyaline pseudopodia formed slowly
Endolimax nana
Sluggish, slightly progressive; with blunt or fingerlike, hyaline pseudopodia formed slowly
Iodamoeba butschlii
Fine granules, uniform in size and usually evenly distributed; may have beaded appearance
Entamoeba hartmanni
Usually clumped and unevenly arranged on the membrane; may also appear as solid, dark ring with no beads or clumps
Entamoeba coli
Fine granules, closely packed
Entamoeba gingivalis
NONE
Endolimax nana
Iodamoeba butschlii
Small, compact, centrally located, may be eccentric
Entamoeba hartmanni
Moderately large, not compact, usually eccentrically located
Entamoeba coli
Small, welldefined, usually centrally located
Entamoeba gingivalis
Large, irregularlyshaped,centrally or eccentrically located; may appear “blotlike”; many nuclear variations are common
Endolimax nana
Large, usually central, surrounded by refractile achromatic granules that are difficult to see
Iodamoeba butschlii
Finely granular, “ground-glass” appearance; clear differentiation into a clear ectoplasm and more granular endoplasm; if present, vacuoles are usually very small
Entamoeba hartmanni
Granular, with little differentiation between ectoplasm and endoplasm; with few to numerous vacuoles
Entamoeba coli
Finely granular, vacuolated
Entamoeba gingivalis
Granular, vacuolated
Endolimax nana
Coarsely granular, heavily vacuolated
odamoeba butschlii
Bacteria and debris; NO RBC
Entamoeba hartmanni
Bacteria, yeasts and other food materials in vacuoles
Entamoeba coli
Epithelial cells and leukocytes
Entamoeba gingivalis
Bacteria and debris
Endolimax nana
Bacteria and debris
Iodamoeba butschlii
5-10 µm (ave. 6-8 µm)
Entamoeba hartmanni
10-35 µm (ave. 15-25 µm)
Entamoeba coli
NO CYST STAGE
Entamoeba gingivalis
5-10 µm (ave. 6-8 µm)
Endolimax nana
5-20 µm (ave. 10-12 µm)
Iodamoeba butschlii
10-35 µm (ave. 15-25 µm)
Entamoeba hartmanni
Usually spherical; may be oval, triangular or other shapes
Entamoeba coli
NO CYST STAGE
Entamoeba gingivalis
Usually oval, may be spherical or ellipsoidal
Endolimax nana
May vary from oval to round; cyst may collapse because of large glycogen vacuole space
Iodamoeba butschlii
Nucleus: 1 to 4
Entamoeba hartmanni
Nucleus: 1 to 8
Entamoeba coli
NO CYST STAGE
Entamoeba gingivalis
Nucleus: 1 to 4
Endolimax nana
Nucleus: 1
Iodamoeba butschlii
Peripheral chromatin and Karyosome: Similar to that seen in trophozoite; Similar to that seen in trophozoite
Entamoeba hartmanni, Entamoeba coli
NO CYST STAGE
Entamoeba gingivalis
Peripheral chromatin: None
Endolimax nana, Iodamoeba butschlii
Karyosome: Smaller than karyosome seen in trophozoite, but generally larger than those of the genus Entamoeba
Endolimax nana
Karyosome: Larger, usually eccentric refractile achromatic granules may be on one side of the karyosome- “basket nucleus”
Iodamoeba butschlii
Chromatoidal bodies: May be present; usually elongate with blunt, rounded, smooth ends (cigarshaped); may be round or oval
Entamoeba hartmanni
Chromatoidal bodies: May be present (less frequently than in E. histolytica); splinter-shaped with rough, pointed ends
Entamoeba coli
Chromatoidal bodies: NO CYST STAGE
Entamoeba gingivalis
Chromatoidal bodies: Rarely present; occasionally, small spherical or elongated granules or inclusions seen
Endolimax nana
Chromatoidal bodies: NO chromatoidal bodies present; small granules occasionally present
Iodamoeba butschlii
Glycogen vacuole: May be present, usually diffuse, stains reddish brown with iodine
Entamoeba hartmanni, Entamoeba coli
Glycogen vacuole: NO CYST STAGE
Entamoeba gingivalis
Glycogen vacuole: Usually absent, diffuse, illdefined, brownish
Endolimax nana
Glycogen vacuole: Large, compact, well-defined mass, stains dark brown with iodine
Iodamoeba butschlii
was at one time designated as “small race” E. histolytica because of the many similarities between the two
Entamoeba hartmanni
differentiated from e. histolytica by its smaller size
Entamoeba hartmanni
Life cycle, epidemiology, and laboratory diagnosis of the intestinal commensal amoebae are similar to that of
E. histolytica
In single stool examinations of over 30,000 Filipinos, the prevalence of Entamoeba coli was
21%
In single stool examinations of over 30,000 Filipinos, the prevalence of Endolimax nana
9%
In single stool examinations of over 30,000 Filipinos, the prevalence of Iodamoeba butschlii
1%
s lives on the surface of gum and teeth, in gum pockets, and sometimes in the tonsillar crypts
Entamoeba gingivalis
They are abundant in cases of oral disease.
Entamoeba gingivalis
Transmission is most probably direct: through kissing, droplet spray, or by sharing utensils.
Entamoeba gingivalis
may best be made by examining mouth scrapings, particularly from the gingival area
Entamoeba gingivalis trophozoites
-Elongated with tapered end measuring 7-20 µm
Naegleria fowleri Trophozoite
-Lobose pseudopodia (lobopodia) are clear initially but fill with granular cytoplasm
Naegleria fowleri Trophozoite
-Prominent nucleus and dense central karyosome
Naegleria fowleri Trophozoite
-Finely granular cytoplasm contains a conspicuous clear Nuclear halo and numerous vacuoles (including contractile vacuoles)
Naegleria fowleri Trophozoite
-Spherical, 8-12 µm in diameter
Naegleria fowleri Cyst
-Smooth, single-layered wall is pierced by one or two flat, mucus-plugged pores
Naegleria fowleri Cyst
-Finely granular cytoplasm -Nucleus with a central karyosome
Naegleria fowleri Cyst
-Pear-shaped
Naegleria fowleri Flagellate
-Single nucleus
Naegleria fowleri Flagellate
-Biflagellated
Naegleria fowleri Flagellate
In their free-living state, trophozoites are found in bodies of warm freshwater, such as lakes, ponds, river, hot springs fresh warm water with temperatures from near 25°C up to 46°C (optimally at 42°C) and also in soil.
Naegleria fowleri
The trophozoites feed on bacteria.
Naegleria fowleri
The trophozoites replicate by binary division during which the nuclear membrane remains intact (a process called promitosis).
Naegleria fowleri
When trophozoites are exposed to a change in ionic concentration, they can turn into temporary non-feeding flagellated forms within a few minutes which usually revert back to the trophozoite stage.
Naegleria fowleri
Trophozoites encyst due to unfavorable conditions such as food deprivation, crowding, desiccation, accumulation of waste products, and cold temperatures.
Naegleria fowleri
Trophozoites infect humans or animals by penetrating the nasal tissue during waterrelated activities often in warm or hot freshwater (lakes, rivers, and hot springs) and migrating to the brain via the olfactory nerves causing primary amebic meningoencephalitis (PAM).
Naegleria fowleri
In tissues, trophozoites phagocytize red blood cells and white blood cells and destroy tissue.
Naegleria fowleri
PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM)
Naegleria fowleri
a rare, rapidly fatal disease with sudden onset (IP 1-7 d) of headache, fever, stiff neck, lethargy, and coma in otherwise healthy people. .
PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM)
After the start of symptoms, the disease progresses rapidly and usually causes death within 1 to 12 days.
PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM)
Motile trophozoites are demonstrated in wet mounts of fresh sample of CSF or brain tissue specimen.
Naegleria fowleri
The amebae can also be stained with a variety of stains, such as Giemsa-Wright or a modified trichrome stain, for identification.
Naegleria fowleri
can be grown on non-nutrient agar plates coated with bacteria.
Naegleria fowleri
Escherichia coli can be used to overlay the non-nutrient agar plate and a drop of CSF sediment added to it.
Naegleria fowleri
Plates are then incubated at 37°C and checked daily for clearing of the agar in thin tracks, which indicate that the trophozoites have fed on the bacteria.
Naegleria fowleri
The plate is microscopically inspected and cysts are identified by their morphology.
Naegleria fowleri
Confirmation of Naegleria presence can be done by a so-called (?), where the organism is exposed to a hypotonic environment (distilled water).
FLAGELLATION TEST
in contrast to other amoebae, differentiates within two hours into the flagellar state
Naegleria fowleri
Pathogenicity can be further confirmed by exposure to high temperature (42°C)
Naegleria fowleri
is able to grow at this temperature
Naegleria fowleri
non-pathogenic; not able to grow at this temperature
Naegleria gruberi
A specific antibody to N. fowleri can be used in conjunction with another antibody that deposits a chemical (?) or glows under specific types of light (?) to directly stain the amebic antigens in tissue.
immunohistochemistry [IHC]
indirect immunofluorescence [IIF]
Specific molecular tools can amplify DNA from the amebae in CSF or tissue to specifically identify if the amebae are present.
Polymerase Chain Reaction (PCR) of Naegleria fowleri
Geographical distribution of Naegleria fowleri
Cosmopolitan
Naegleria fowleribameba can be found in:
- Bodies of warm freshwater, like lakes and river
- Geothermal (naturally hot) water, like hot springs, and drinking water sources (from water going up the nose)
- Warm water discharge from industrial plants
- Also in the soil
Humans become infected when water containing the agent enters the nose, usually while swimming.
N. fowleri
Some factors that might increase risk of Naegleria infection include:
Freshwater swimming
Heat waves
Age
Most people who become ill have been swimming in a freshwater lake or in swimming pools that are poorly maintained, minimally-chlorinated, and/or un-chlorinated.
Freshwater swimming.
Causing water temperatures to rise which is favorable for the growth and survival of N. fowleri.
Heat waves
Children and young adults are the most likely age groups to be affected, possibly because they’re likely to stay in the water longer and are more active in the water.
Age
Infection has also happened when people use contaminated drinking water to cleanse their nasal passages during religious practices, use a neti pot or other device to rinse their sinuses through the nose, or get the contaminated water up their nose during recreational play.
Naegleria fowleri
15-45 um
Acanthamoeba Trophozoites
Spine-like pseudopodia (acanthapodia) – sluggish polydirectional motility
Acanthamoeba Trophozoites
A single nucleus with a large, dense central nucleolus surrounded by a nuclear clear zone
Acanthamoeba Trophozoites
Finely granular cytoplasm, as a rule, contractile vacuoles are usually visible in the cytoplasm
Acanthamoeba Trophozoites
10-25 um
Acanthamoeba Cysts
Double-walled cysts are generally polygonal, spherical, or star-shaped
- smooth inner wall of the cyst
- wrinkled outer wall at a number of points, forming
Acanthamoeba Cysts
Nucleus containing a large dense central nucleolus surrounded by a clear nuclear halo
Acanthamoeba Cysts
have been found in fresh, brackish, and sea water and in the soil.
Acanthamoeba
has only two stages, cysts and trophozoites , in its life cycle
Acanthamoeba
The trophozoites replicate by mitosis (nuclear membrane does not remain intact)
The trophozoites are the infective forms Entry can occur through the eye , the nasal passages to the lower respiratory tract , or ulcerated or broken skin
Acanthamoeba
When they enters the eye it can cause severe keratitis in otherwise healthy individuals, particularly contact lens users
Acanthamoeba
When it enters the respiratory system or through the skin, it can invade the central nervous system by hematogenous dissemination causing granulomatous amebic encephalitis (GAE) or disseminated disease , or skin lesions `in individuals with compromised immune systems.
Acanthamoeba
Its cysts and trophozoites are found in tissue.
Acanthamoeba
is a rare disease that can affect anyone, but is most common in individuals who wear contact lenses.
Acanthamoeba keratitis
Symptoms include corneal ulcerations, progressive corneal infiltration and clouding, iritis, scleritis, severe pain, loss of vision.
Acanthamoeba keratitis
Disseminated infection typically shows up as inflammation of the lungs or sinuses, and/or skin infections but has the potential to spread to the brain.
Granulomatous Amebic Encephalitis (GAE)
Skin infections caused by Acanthamoeba can appear as reddish nodules, skin ulcers, or abscesses in the skin.
Granulomatous Amebic Encephalitis (GAE)
Disseminated infection can occur both with and without
Granulomatous Amebic Encephalitis (GAE)
Granulomatous Amebic Encephalitis (GAE) Symptoms of GAE include:
- Mental status changes
- Loss of coordination
- Fever
- Muscular weakness or partial paralysis affecting one side of the body
- Double vision
- Sensitivity to light
- Other neurologic problems
The infection is usually diagnosed by an eye specialist based on symptoms, growth of the amoeba from a scraping of the eye, and/or seeing the amoeba by a process called confocal microscopy.
Acanthamoeba keratitis
are more difficult to diagnose and are often at advanced stages when they are diagnosed
Granulomatous Amebic Encephalitis (GAE) and disseminated infection
Tests useful in the diagnosis of GAE include
brain scans, biopsies, or spinal taps for detection of trophozoites and/or cysts
In disseminated disease, (?) can be useful in diagnosis.
biopsy of the involved sites (e.g. , skin, sinuses)
For people who wear contact lenses, certain practices can increase the risk of getting Acanthamoeba keratitis:
-Storing and handling lenses improperly -Disinfecting lenses improperly (such as using tap water or topping off solutions when cleaning the lenses or lens case) -Swimming, using a hot tub, or showering while wearing lenses
-Coming into contact with contaminated water
-Having a history of trauma to the cornea
are very rare forms of Acanthamoeba infection and primarily affect people with compromised immune systems
Granulomatous Amebic Encephalitis (GAE) and disseminated infection
While unusual, disseminated infection can also affect
healthy children and adults
Conditions that may increase a patient’s risk for GAE and disseminated infection include:
-AIDS
-Organ/Tissue transplant
-Steroids or excessive use of antibiotics
-Diabetes Mellitus
-Cancer
-Disorders in which white blood cells in the lymphatic tissue are overproduced or abnormal
-Disorders in which blood cells or blood clotting mechanisms do not function properly or are abnormal
-Liver cirrhosis
-Lupus
has been placed within an informal group, the stramenopiles
Blastocystis hominis
are defined, based on molecular phylogenies, as a heterogeneous evolutionary assemblage of unicellular and multicellular protists including brown algae, diatoms, chrysophytes, water molds, slime nets, etc
Stramenopiles
Cavalier-Smith (1998) considers stramenopiles to be identical to infrakingdom (?) under the kingdom (?).
Heterokonta
Chromista
according to Cavalier-Smith, B. hominis is a
heterokontid chromista
It was originally described as yeasts, fungi, or ameboid, flagellated, or sporozoan protozoa.
B. hominis
-Varies greatly in size, with diameters ranging between 2µm and 200µm
Blastocystis hominis Vacuolar (or central body) form
-Has a large central vacuole surrounded by a thin band of peripheral cytoplasm which contains other organelles
Blastocystis hominis Vacuolar (or central body) form
-Gives rise to multi-vacuolar (multiple fission) forms
Blastocystis hominis Vacuolar (or central body) form
Somewhat morphologically similar to the vacuolar forms except that distinct granules are observed in the central vacuole and / or cytoplasm
Blastocystis hominis Granular form
-Amoeba-like
Blastocystis hominis
-Exhibit active extension and retraction of pseudopodia
Blastocystis hominis Amoeboid form
-Mostly oval or circular, or polymorphic
Blastocystis hominis Cyst
-Varies in size from 6-40 µm
Blastocystis hominis Cyst form
-Thick-walled cysts are believed to be responsible for external transmission; thin-walled cysts might cause reinfection within the host’s intestinal tract
Blastocystis hominis Cyst form
is not yet understood, including the infectious stage and whether (and which of the) various morphologic forms of this polymorphic organism that have been identified in stool or culture constitute distinct biologic stages of the parasite in the intestinal tract of hosts
Blastocystis
The cyst form is postulated to be an infectious stage, but not confirmed.
Blastocystis
The predominant form found in human stool specimens is referred to as the vacuolar (or central body) form.
Blastocystis
Replication appears to occur via binary fission.
Blastocystis
Other morphologic forms (e.g., ameboid and granular forms) also have been noted in stool samples and/or culture; their biological role and eventual developmental fate require further investigation.
Blastocystis
may be with or without symptoms
Blastocystosis
Symptoms include watery or loose stools, diarrhea, abdominal pain, anal itching, weight loss, constipation, and excess gas.
Blastocystosis
Detection of B. hominis in
stool
Geographical distribution of B. hominis
Cosmopolitan
B. hominis Prevalence:
(?) in developed countries; upto (?) in developing countries
5-10%
50%
Possibly by the fecal-oral route through ingestion of contaminated water or food.
B. hominis
harbor Blastocystis species similar to those found in humans.
Farm animals, birds, rodents, reptiles, amphibians, fish, and cockroaches
