Exercise No. 6b Flashcards
Entamoeba histolytica Trophozoite Size
10-60 µm (ave: 15-20 µm)
Entamoeba histolytica Trophozoite Motility and Pseudopodia
Progressive, rapid, unidirectional motility; with hyaline, fingerlike pseudopodia formed rapidly
Entamoeba histolytica Trophozoite Nucleus Number
1
Entamoeba histolytica Trophozoite Peripheral chromatin
Fine granules, uniform in size and usually evenly distributed; may have beaded appearance
Entamoeba histolytica Trophozoite Karyosome
Small, compact, centrally located
Entamoeba histolytica 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.
Entamoeba histolytica 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
Entamoeba histolytica Trophozoite Inclusions
RBCs are diagnostic; few ingested bacteria or debris in vacuoles
Entamoeba histolytica Cyst Size
10-20 µm (12-15 µm)
Entamoeba histolytica Cyst Shape
Usually spherical
Entamoeba histolytica Cyst Nucleus Number
1-4; mature cyst contains 4 nuclei
Entamoeba histolytica Cyst Peripheral chromatin
Similar to that seen in trophozoite
Entamoeba histolytica Cyst Karyosome
Similar to that seen in trophozoite
Entamoeba histolytica Cyst Cytoplasm Chromatoidal bodiesMay be present; usually elongate with blunt, rounded, smooth ends (cigarshaped); may be round or oval.
Entamoeba histolytica 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
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.
Formed stool specimens are more likely to contain cysts.
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)
Formed stool specimens are more likely to contain cysts.
Direct fecal smear (DFS)
Few, Numerous
Bacteria
Scanty, well-preserved; Numerous, degenerated
Pus cells
Often in rouleaux; Unaltered, scattered
RBC
NOT a feature; May be numerous (may have RBC)
Macrophage
May be present; Absent
Charcot-Leyden crystals
Present; Absent
Trophozoite
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
Red, sometimes with a tinge of purple
TRICHROME
Green, provides nice contrast with the protozoa
TRICHROME
Blue-gray; Blue-gray
IRON HEMATOXYLIN
Darker than cytoplasm, bluegray to black
IRON HEMATOXYLIN
Lighter shade of blue-gray
IRON HEMATOXYLIN
Scraping obtained is often contributory.
Examination of sigmoidoscopy specimen
Examination method includes a direct wet mount and permanent staining.
Examination of sigmoidoscopy specimen
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 sigmoidoscopy specimen
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 sigmoidoscopy specimen
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 sigmoidoscopy specimen
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 sigmoidoscopy specimen
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.
Antibody detection
An(?) for stool is now commercially available.
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.
Radiologic examination
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 of Commensal Amoebae
(?) attached to the nuclear membrane by fibrils radiating to the periphery; no peripheral chromatin.
Large irregular karyosome of Commensal Amoebae
(?) surrounded by refractile achromatic granules called periendosomes; no peripheral chromatin.
Large circular karyosome of Commensal Amoebae
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
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
