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Pathogenic Amoebae Pathogenic Amoebae Human Pathogen II Assoc. Prof. Dr. Anchalee Wannasan 1 Objectives • be able to identify and describe the pathogenic amoebae in terms of morphology, life cycle, pathology, symptoms, transmission and diagnosis Entamoeba histolytica • Disease: amoebiasis • Distribution: worldwide - second leading cause of death after malaria - developing countries: poor sanitation areas - developed countries : immigrants or travelers from endemic areas • Transmission: - fecal-oral route - venereal transmission (homosexuals) • 2 stages in the life cycle Cyst (dormant form) Trophozoite (active form) • Infective satge: mature cyst with 4 nuclei www.medical-labs.net karyosome Chromatoid body Peripheral chromatin www.medical-labs.net 5 Cyst ~10-20 µm • round or oval shape • thin and tough cyst wall • contains 1, 2 or 4 nuclei • centric karyosome • peripheral chromatin • chromatoid bar with rounded ends (Cigar-like) 7 Trophozoite ~15-60 µm • irregular shape • a round nucleus • small, centric karyosome • peripheral chromatin scattered evenly throughout the inner nuclear membrane • fine granular endoplasm (food vacuoles + RBC) 10 Rapid movement by finger-like pseudopodia 12 Pathology and symptoms • Amoebiasis is a disease caused by E. histolytica. • Forms of amoebiasis 1) Intestinal amoebiasis - 90% is asymptomatic cyst passers (E. dispar ?) - 10% is symptomatic (Invasive amoebiasis) 2) Extraintestinal amoebiasis 1. Intestinal amoebiasis (Invasive amoebiasis) ❑ incubation period is variable, (mostly 1-4 w) ❑ characterized by 4 markers: o amoebic dysentery (mucus and bloody diarrhea) o trophozoites with ingested RBC (feces, rectum biopsy) o amoebic colitis (endoscopy) o positive serological test for specific Ab ❑ Other clinical manifestations o increasing diarrhea progressing to mucous-bloody o lower abdominal pain, tenesmus o weight loss, fever o similar to other colonic diseases o WBC are rarely seen in stools o progressive involvement - Fulminant necrotitizing colitis, toxic megacolon - Acute rectocolitis - Amoebic appendititis - Amoeboma (immune response to trophozoites) 15 Ameboma https://www.wjgnet.com/1007-9327/full/v22/i36/8234.htm • Granulation tissue and fibrotic thickening caused by host immune response to trophozoites, Fig A, B) 16 Amebic colitis http://intranet.tdmu.edu.ua/data/kafedra/internal/med_biologia/classes_stud/en/med/prophylactic%20medicine/ptn/medical%20biology/1%20course/theme%2008.htm • Severe dysentery with multiple ulcers in the large bowel, and a bloody diarrhea 17 Intestinal amebic ulcers https://cmr.asm.org/content/13/2/318/figures-only https://link.springer.com/chapter/10.1007/978-4-431-55200-0_23 1) Nodular lesion (0.1- to 0.5-cm in diameter) o rounded and small ulcer with slightly elevated rims o necrotic center - appears dimpled or hemorrhagic - filled with yellowish mucous 18 2) Irregular lesion (1- 5 cm in length) o shallow but broad with elevated rims o filled with fibrin and yellow exudates https://www.researchsquare.com/article/rs-29990/v1 Irregular cecum 19 lesions Flask-shape amoebic ulcer 4.bp.blogspot.com 20 Pathogenesis • glandular hyperplasia • stromal edema • atrophy of villi & epithelium • infiltration of neutrophils • deep into submucosa • 2nd bacterial infection 21 (flask-shape amoebic ulcer) 2. Extraintestinal amoebiasis • Hematogenously spread to liver and other organs (lung, pericardium, brain, skin, and genitourinary tract, etc.) • Liver is the most common involvement site • 3–9 % of all intestinal amebiasis cases develop to amoebic liver abscess (ALA) Amoebic liver abcess (ALA) ▪capillary obstruction in portal system (necrosis) ▪ pin head-like lesion, then enlarged and became abscess acute - right upper quadrant abdominal pain - fever - liver tenderness and hepatomegaly chronic - weight loss, vague abdominal symptoms Rupture of abscesses into the abdomen or chest may lead to death. Amoebic liver Amoebic https://www.sciencephoto.com/media/250192/view/liver-abscess https://en.wikipedia.org/wiki/Amoebic_liver_abscess abcess d_Pathogenesis/figures?lo=1 https://www.researchgate.net/publication/221929027_Amoebiasis_in_the_Tropics_Epidemiology_an Diagnosis Intestinal amebiasis • Microscopic examination (stool or rectal smear) - dysenteric stool : trophozoites - nondysenteric stool : cysts - differential diagnosis from E. dispar using isozyme analysis, serological methods, PCR • Biopsy from colonoscopy / sigmoidoscopy 25 • Extraintestinal amebiasis • stool exam may not be helpful • aspirates from abscess may not find amoebae • biopsy from liver abscess rims (recommended) • imaging procedure (ultrasound/ CT / MRI) • serological methods (ELISA) - discriminate ALA from pyogenic liver abscess - negative in Entamoeba dispar infected patient • PCR 26 http://medicinembbs.blogspot.com/2013/01/amoebic-liver-abscess.html Charateristics of pus from ALA: anchovy paste-liked color without smell Treatment drugs of choice : Metronidazole - effective to both intestinal and tissue amoebiasis Nitroimidazole derivatives such as secnidazole, nimorazole and tinidazole ALA - Percutaneous drainage or surgical aspiration E. dispar infection does not require the treatment 28 Pathogenic free-living amebae Naegleria fowleri o Primary amoebic meningoencephalitis (PAM) Acanthamoeba spp. o Granulomatous amoebic encephalitis (GAE) o Acanthamoebic keratitis (AK) Balamuthia mandrillaris o GAE Sappinia pedata o GAE 29 Common features (pathogenic FLA) • facultative free-living parasites • generally found in the environment • mortality rate approach 100% • no specific therapeutic agents 30 Naegleria fowleri • known as the brain-eating amoeba • Distribution : worldwide (water and soil resources) • Disease : primary amebic meningoencephalitis most cases were immunocompetent host • Most clinical isolates are thermophilic (> 45°C). • 3 stages in LC: cyst , trophozoite and flagellate (Amoeboflagellate) 31 Morphology Cyst ~ 8-20 µm https://www.si.mahidol.ac.th/th/department/parasitology/articledetail.asp?ac_id=7&pageno=1 • round with double cyst walls • big karyosome surrounded by halo • never found cyst stage in host tissue Trophozoite Flagellate ~ 10-35 µm ~ 10-16 µm reversible (Lobopodia) (flagellum) • Enflagellation test: In distilled water or nutrients depriving condition, trophozoite transforms into flagellate (2 flagella) 33 Life cycle 34 Risk activities: • Diving or swimming in fresh water resources • Performing ‘neti’ (nasal rinse) https://www.insider.com/neti-pot-tap-water-is-it-dangerous-brain-eating-amoeba-2018-12 • a ritual cleansing that includes nasal passages 36 Clinical manifestation Incubation period: 3-7 days acute common cold-like symptoms: fever, rhinitis, stiff neck, sore throat and severe headache similar to that of acute bacterial and viral meningitis Rapidly progression with high fever, vomiting, seizure, edema of lung and brain, respiratory failure, coma Death within 10 days 37 Diagnosis immunocompetent host (mainly children & young adult) history of water exposure (exp. swimming) CSF sedimentation : found only trophozoite o culture on non-nutrient agar with gram (-ve) bacteria o enflagellation test, PCR • brain tissues: found only trophozoite o staining o IFA, Immunohistochemistry o PCR Treatment no specific therapeutic agents Combination of available drugs which can cross blood- brain barrier Miltefosine or combination anti-microbial therapy: amphotericin B, Azithromycin, rifampin, and azole drugs Intensive supportive care is required Only a few from hundred cases survive 39 Prevention Chlorine in swimming pool 1-2 ppm Avoid swimming in fresh natural resources Wear the nose clip during swimming Blow the nose using sterile reagent 40 Acanthamoeba • Free-living protozoan (facultative) parasites - worldwide distribution : soil, air, dust, fresh and sea water, Jacucci tubs, dental irrigation unit, contact lens, etc. - usually concentrate at the bottom of the lake • Pathogenic to man (thermophilic) • Exp. A. castellani, A. culbersoni, A. diviornensis, A. hatchetti, A. healyi, A. polyphaga, A. rhysodes, etc. 41 Morphology A) Cyst ~ 5-25 µm - uninucleated - thick-wall polygonal , stellate, oval or spherical endocyst with ostioles - wrinkle ectocyst ~ 10-45 µm B) Trophozoite - uninucleated - irregular shape - acanthopodia (thorn-liked) www2.le.ac.uk www.med-chem.com ww.labor-spiez.ch Trophozoite, 10-45 µm Cyst, 5-25 µm 43 Disease 1. Granulomatous Amoebic Encephalitis (GAE) - common in immunocompromised hosts - primary infection at the skin ulcer or lung, then spread hematogenously to brain - no evidence of infection via olfactory nerves 2. Acanthamoeba keratitis (AK) - mostly in healthy persons (contact lens wearers) 3. Cutaneous infection - subacute granulomatous dermatitis - immunocompromised hosts 45 1. Granulomatous Amoebic Encephalitis (GAE) Symptoms ▪ subacute (IP 8-30 days) with no specific symptoms ▪ resemble viral, bacterial or tuberculosis meningitis ▪ mental status changes (86%), seizures (66%) hemiparesis (53%), fever (53%), stiff neck headache (53%), meningismus (40%), etc. 46 GAE DOI: 10.5005/jp-journals-10028-1080 P. Singh, R. Kochhar, R.K. Vashishta, N. Khandelwal, S. Prabhakar, S. Mohindra and P. Singhi American Journal of Neuroradiology June 2006, 27 (6) 1217-1221; •The terms “ granulomatous” indicates hemorrhagic necrotizing lesions or brain abscess (detected by neuroimaging scans) with severe meningeal irritation and encephalitis. (NA Khan - Am J Infect Dis: 79-83, 2005) GAE http://www.med-chem.com/para-site.php?url=org/acantham GAE: spread hematogenously, possible
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