醫(yī)學(xué)寄生蟲(chóng)學(xué)：溶組織內(nèi)阿米巴

1、Entamoeba histolytica溶組織內(nèi)阿米巴 Phylum: Sarcodina 肉足鞭毛門(mén)Class: Lobosea 葉足綱Order: Amoebida阿米巴目Family: Entamoebidae內(nèi)阿米巴科Brief conceptionThe only pathogenic intestinal amoeba of the Entamoeba species to infect humans. Disease: amebiasis or amebic dysentery.Approximately 10% of the world population is infec

2、ted with E. histolytica/dispar, but only a tenth of those people are infected with E. histolytica.in tropical countries or other areas with poor sanitary conditions, the prevalence may approach 50%. Over 50 million clinical cases and 100,000 deaths yearly result from amoebiasis, making it the third

3、most common cause of parasitic deaths in humans, after malaria and schistosomiasis. (histolytic = tissue destroying)Historical InformationClinical Asis. Lsch describes amoebae associated with bloody dysentery in stools of a patient, 1873. A dog became ill and showed ulceration in colon after rectal

4、injection of amoebae. The patient died from infection showed similar ulcers upon autopsy. However, it was confirmed after 30ys! Schaudinn, 1903, described the traphozoites and cysts of E. histolytica, died at age 35 of overwhelming amoebiasis, a tragic outcome of self-experimentation! MorphologyTrop

5、hozoite滋養(yǎng)體amorphous shape generally 15-30 m in diameter. ectoplasm appears gelled (gel)and clearendoplasm is liquid and filled with organellesOccasionally a glycogen vacuole is evident.often contain phagocytosed RBCs Nuclear (4-7 mm): a centrally placed karyosome核仁 and uniformly distributed peripher

6、al chromatin (chromatin granules染色質(zhì)粒)， and characteristic radial spokes.trichrome stain Ultrastucture of Entamoeba type nucleus . All species of Entamoeba display certain common characteristics with regard to their nuclear morphology . The nuclear membrane is lined with peripheral chromatin which ap

7、pears as electron dense masses, a circular nucleolus which is in the centre or eccentrically placed and the nucleoplasm which contains circular internuclear bodies . The function of these internuclear bodies is not known. NM= nuclear membrane; PC = peripheral chromatin; NI = nucleolus; INB = intranu

8、clear bodies; FV = food vacuole.20000.阿米巴吞入細(xì)菌trophozoite Trophozoites of Entamoeba histolytica with ingested erythrocytes (trichrome stain). The ingested erythrocytes appear as dark inclusions. Erythrophagocytosis is the only morphologic characteristic that can be used to differentiate E. histolytic

9、a from the nonpathogenic E. dispar. trichrome stain Entamoeba histolytica swallow erythrocytes(2.4 MB) Phase contrast photomicrograph of cultured Entamoeba histolytica trophozoites. Culture: From faecal samples - Robinsons medium, Jones medium Movement of E. histolytica The trophozoites move by exte

10、nding a finger-like pseudopodium (psd) and pulling the rest of the body forward (called ameboid movement).cystChromidial bodies and bars are semicrystalline arrays of riobosomesglycogen vacuole糖原泡 Round (10- 16 mm)Mature cysts have 4 nuclei: centrally located karyosomes, and fine, uniformly distribu

11、ted peripheral chromatin150 nm cyst wall is composed of chitin幾丁質(zhì)and has a smooth refractile appearance.Cyst (trichrome stain )Mature cysts have 4 nuclei. The cyst in left appears uninucleate while in right 4 nuclei are visible. The nuclei have characteristically centrally located karyosomes, and fi

12、ne, uniformly distributed peripheral chromatin. The cysts contain chromatoid bodies being particularly well demonstrated, with typically blunted ends. Entamoeba histolytica cysts usually measure 12 to 15 m.chromatoid body glycogen vacuole nucleiEntamoeba cysts (light microscopy iodine stained ) The

13、cysts are usually spherical and often have a halo. Mature cysts have 4 nuclei. The nuclei have characteristically centrally located karyosomes, and fine, uniformly distributed peripheral chromatin. Entamoeba histolytica cysts usually measure 12 to 15 m.Life cycleInfective stage: mature cyst (having

14、4 nuclei) Portal of Entry: Mouth Mode of Transmission Ingestion of mature cyst through contaminated food or waterTrophozoites live in large intestine (Colon and Cecum) ; liver, lung and other organs.Pathogenic stage: trophozoiteDiagnostic stage: cyst and trophozoiteLife cyclePathogenesisAttach to mu

15、cosal epithelial cells (MEC) Lyses MEC Ulcerate and invade mucosa (classic “Flask-shaped ulcer”) Cause dysentery（痢疾） Metastasize via blood and/or lymph Form abscesses in extraintestinal sitesPathogenesisA Attach to mucosal epithelial cells (MEC) B Lyses MECC Ulcerate and invade mucosa 260kDa Inhibit

16、able lectin （可抑制性凝集素）Amoeba pore（穿孔素）Cysteine proteinases（半胱氨酸蛋白酶）Pathogenesis Superficial ulceration of the large intestine by E. histolytica .H and E. 400 . Enlarged by 9.6.Ulcerate and invade mucosa (classic “Flask-shaped ulcer”)Pathogenesis Moderately severe ulceration of the large intestine by

17、E. histolytica. The muscularis mucosa is intact .H and E. 400 . Enlarged by 9.6.Severe ulceration of the large intestine by E. histolytica. A typical conical (flask-shaped) ulcer can be seen . the muscularis mucosa has been penetrated. H and E. 400. Enlarged by 9.6.PathogenesisThe pathologic sample

18、of colon of intestine amebiasisRight: lumenal side of the colon from fulminating amebiasis case showing several ulcers. Note raised edges (arrow). liver abscess pleuropulmonary amebiasis胸膜肺阿米巴病 brain and other organs cutaneous and genital diseases Extraintestinal amebiasisClinical Classification of

19、Amebiasis (World Health Organization)Asymptomatic infection is common”cyst passers” 90% cases (E. dispar?)Symptomatic infection 10% Intestinal Amebiasis 8-10% Acute dysentericChronic non-dysenteric Extra-intestinal Amebiasis 2% liver abscess pleuropulmonary amebiasis brain and other organs cutaneous

20、 and genital diseases 0.1% deathsEntamoeba histolytica killed by neutrophils (2.4 MB) Intestinal AmebiasisAcute Dysenteric Amebiasis Amebic Dysentery Symptoms: Bloody mucoid diarrhea: RBCs and few WBCs in stools Abdominal pain Weight loss Bloating, tenesmus (里急后重） Signs: Fever (33%) Diffuse abdomina

21、l tenderness Tender (enlarged) liver Stools positive for trophozoites / WBC Not cysts in loose stools fulminant colitis(暴發(fā)型，急腹癥) + perforation (peritonitis) Intestinal AmebiasisChronic non-dysenteric Amebiasis (“self-cured”) Symptoms: 37% symptomatic 5 years Intermittent diarrhea, stools sometimes c

22、ontain mucus but there is no visible blood, cramps絞痛, flatulence脹氣, nausea, and anorexia 厭食and/or weight loss ， 奇臭、“果醬、巧克力醬”樣大便E.histolytica trophozoites rarely in stools ameboma (amebic granuloma) 1.painful abdominal masses , obstructive symptoms or hemorrhages 2. Amebomas are infrequent and can be

23、 confused with carcinomas or tumors. Amebic Liver Abscess (ALA) Most common form of extraintestinal amebiasisSymptoms: dysentery, weight loss, abdominal pain, right upper quadrant painSigns: fever, hepatomegaly, leukotosisAmebic Liver Abscess (ALA)30-50% of patients with liver abscess show also pneu

24、monic involvementRupture is again a major thread, especially rupture into the pericardiumDraining abscesses is today only performed in extreme cases when rupture is fearedResponds well to chemotherapy Patient with amoebiasis liver absess, with perforation of abscess through abdominal skin. An Amoebi

25、c Liver Abscess Being AspiratedNote the reddish brown color of the pus (anchovy-sauce). This color is due to the breakdown of liver cells. Enlarged by 5.4Pathology of amebic abscess of liver. Tube of chocolate pus from abscess.Fast growing abscess filled with debris, amoebae are found only at border

26、sExtraintestinal amebiasisPulmonary amebiasis The next most common secondary lesion Metastaisis from a hepatic lesion or originate independently cough and chest painBrain amebiasis This is very rare. Symptoms are headache, vomiting, and seizures. 50% of patients with cerebral abscesses die. Other: T

27、his can include areas such as urinary tract problems, genital disease, perianal disease, and cutaneous lesions.DiagnosisStool examination : cysts and/or trophozoites Sigmoidoscopy (結(jié)腸鏡檢查）biopsy (reddish brown liquid trophozoites at abscess wall )Imaging : CT, MRI, ultrasound Serological tests (for c

28、hronic disease)DNA probe detection : histolytica/dispar DiagnosisTrophozoiteCystSpecimen/methodFeces/ direct smear with normal salineFeces/ direct smear with iodine stainDiseasesamoebic dysenterychronic intestinal amoebiasis or carriersDiagnostic featureRing and dot nucleus and chromatoid bodies Rem

29、arks1.container must clean2.examined soon after they have been passed.3.select bloody and mucous portion.4.keep specimen warm.5.drug using history.Ingested RBC; distinctive nucleus EpidemiologyWorldwide, with higher incidence of amebiasis in developing countries (2010). 480,000,000 people harbor Ent

30、amoeba 50,000,000 clinical cases 55,000-70,000 deaths per yearIn industrialized countries, risk groups include male homosexuals, travelers and recent immigrants, and institutionalized populations. Media: flies; black beetles (cockroaches) etc病 例 沈，女，6歲，因發(fā)燒、腹痛及膿血便7天而入院治療。發(fā)病前8天有跌入糞坑病史。體檢：T38，BP110/70m

31、mHg（14.7/9.33kpa）,精神萎靡,全腹有輕壓痛,臍中可觸及腸樣腫塊,可以移動(dòng).糞檢:RBC少量及巨噬細(xì)胞0-3/高倍鏡.病程記錄:入院后用青鏈霉素治療,次日大便呈果醬色,腹痛加重,而后出現(xiàn)全腹痛伴肌緊張,立即剖腹檢查,查見(jiàn)右下腹有一炎性腫快,盲腸壞疽有32的穿孔灶,闌尾已壞疽脫落,術(shù)后未用阿米巴藥物治療,因治療無(wú)效于術(shù)后46小時(shí)死亡.尸檢:腹腔右側(cè)有散在小膿腫20余處,結(jié)腸、空腸、回腸均可見(jiàn)潰瘍，以結(jié)腸為甚，且深；在粘摸下找到阿米巴原蟲(chóng)。討論該小孩是怎樣感染到阿米巴痢疾的？ 為什么糞便中找不到阿米巴滋養(yǎng)體？試分析有幾種可能性？ 典型的阿米巴痢疾患者有何癥狀？糞便有何特點(diǎn)？ 阿米巴痢

32、疾患者病變的原發(fā)部位多發(fā)生在何處？ 阿米巴痢疾患者腸壁潰瘍的病理變化呈何特征？ 為什么會(huì)引起腸穿孔？Treatment Metronidazole （甲硝銼） is the first choice Metronidazole (Flagyl) is the drug of choice for invasive amoebiasis (and should be combined with a lumen acting drug as it is not fully effective on luminal stages)Metronidazole甲硝咪唑is a prodrug which

33、 is activated by an enzyme involved in the microaerobic fermentation metabolism of E. histolyticParomomycin巴龍霉素-cystPrevention and controlDiagnosis and treatment of E.histolytica patients no animal reservoirs are known Cleaning of raw fruits and vegetables Avoiding the contamination of food or water

34、 with fecal material. Safe drinking water (boiling or filtration)Sexually Transmitted Disease (STD)( anal-oral sex with multiple partners) Health education( improving personal hygiene, sanitary disposal of feces, and hand washing )Protecting water supplies will lower endemicity and epidemics.Control

35、 of food vendors and food handlers Control of flies and cockroachesChemoprophylaxis is not recommended. Two species hypothesisThere are two morphologically indistinguishable species: E. histolytica E. dispar. (誤診?。?Only molecular data （PCR) or mAB identification We now know that most people are infected with the apathogenic E. disparEmile Brumpt 1877-1951Genetic evidence for two speciesisoenzyme同工酶Specific antibodies PCR!Numerous genes clear differences Repetitive DNA elements are differentconserved gene loci like actin is