溶组织内阿米巴 Entamoeba histolytica

互联网2013-09-06

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Introduction

1. The only pathogenic amoeba among all of the intestinal amoebae
2. Infecting perhaps 10% of the world's population.
3. Lead to invasive amoebiasis.
4. Taxonomy:

<center> <table> <tbody> <tr> <td>Kingdom</td> <td>Subkingdom</td> <td>Phylum</td> <td>Class</td> <td>Order</td> <td>Family</td> <td>Genus+Species</td> </tr> <tr> <td>Protista</td> <td>Protozoa</td> <td>sarcomastigophora</td> <td>Lobosea</td> <td>Amoebida</td> <td>Entamoebidae</td> <td>Entamoeba Histolytica</td> </tr> </tbody> </table> </center>

Morphology

Pay your attention to stages that have diagnostic value
Parasites stained with hematoxylin is described here.

1. cyst (non-motile)

(1) 10-20 mocrometers in size

(2) spherical in shape

(3) 1-2 nuclei (immature cyst); 4 nuclei (mature cyst-infective stage).

(4) inclusions:(become smaller and smaller as the cyst ages)
glycogen vacuole appears as a clear space; food reservoir
chromatoid body dark blue rods or dots; its function is not known

2. trophozoite (active form)

(1) Size : 10-40 micrometers in diameter, some are above 60 micrometers.

(2) Pseudopodium (ectopalsmic protrusion):
    A broad or finger-like in form
    B thrust out quickly
    C firstly, formed with ectoplasm, secondly, endoplasm flows slowly into it.
    D motility is progressive and directional.

(3) Endoplasm : red blood cells may be found in it.

(4) Nucleus (vesicular type)
      It is not visible in an unstained specimen; but its clear structure can be seen when stained with hematoxylin.
    A: membrane: distinct line
    B: chromatin granules: fine ane uniformally arranged in the inner surface of the nulear membrane.
    C: karyosome: small and centrally located.

Life Cycle

1 infective stage: mature cyst

2 access: mouth

3 ecological niches: large intestine; liver, lung and other organs.

4 pathogenic stage: trophozoite

5 diagnostic stage: cyst; trophozoites

Pathogenesis

一、Clinical classification

Asymptomatic infection (carrier)>90% cases

sympomatic cases<10%

A. Intestinal amoebiasis

a. dysentery

b. non-dysenteric colitis

c.appendicitis

d.amoeboma

B. Extra-intestinal amoebiasis

a. Hepatic

(1) acute non-suppurative

(2) liver abscess

b. Pulmonary

c. Brain

d. Skin

e. Other extra-intestinal amoebiasis

二、Pathogenic factors

1.toxicity of parasites pathogenic-nonpathogenic complex.

Entamoeba histolytica
Entamoeba dispar

2.symbiotic bacteria

3.defence barrier immunity

三、pathology

pinpoint lesion on mucous membrane

flask-shaped crateriform ulcers

Diagosis

<center> <table> <tbody> <tr> <td></td> <td> <p>trophozoite</p> </td> <td> <p>cyst</p> </td> </tr> <tr> <td>specimen</td> <td> <p>feces</p> </td> <td> <p>feces</p> </td> </tr> <tr> <td> <p>method</p> </td> <td>direct smear with normal saline</td> <td>direct smear with iodine stain</td> </tr> <tr> <td> <p>diseases</p> </td> <td>amoebic dysentery</td> <td>chronic intestinal amoebiasis or carriers</td> </tr> <tr> <td> <p>remarks</p> </td> <td> 1.container must clean <br /> 2.examined soon after they have been passed. <br /> 3.select bloody and mucous portion. </td> <td></td> </tr> </tbody> </table> </center>

Epidemiology

Distribution: tropical and subtropical areas.

Media: flies; black beetles etc.

Treatment and prevention

treatment:

diodoquin-carriers

metronidazole-dysentery

prevention

human feces should not be used as fetilizer

food and drinks must be protected from flies

personal hygiene: wash hands after defecation and before meals.