

Amoebiasis is an infection with the intestinal
protozoa Entamoeba histolytica.



About 90% of infections are asymptom...


Entamoeba histolytica


Trophozoites
•
•

•

•

10 - 60 μm in D
Cytoplasm – # outer clear ectoplasm
# inner granular e...


Entamoeba histolytica
 Precyst
Intermediate form
• Oval with blunt pseudopodia
• No food vacuoles
•

 Cysts
•
•
•

•
...
World


worldwide in distribution



3rd most common parasitic death



India, China, Africa, South America



2-60% p...


Source of infection is a case or carrier
-1∙5 X 107 cysts per day



Reservoir is only human – several years



Resis...


All age groups affected



No gender or racial differences



Institutional, community living, MSM



Severe if chil...


Low socio-economic status



Poor sanitation, sewage contamination



Night soil for agriculture



Seasonal variati...


1- 4 weeks



1- 4 weeks



Faeco -oral route
•

contaminated water and food

•

direct hand to mouth



Agency of f...


Most

common

type

of

amoebic

infection

is

asymptomatic cyst passage


Intestinal amoebiasis – abdominal cramps w...


90% without symptoms



does not damage lumen



flask shaped ulcers superficial or deep



abd pain (tenesmus)



...


Pseudotumoral lesion



Necrosis, edema and inflammatory thickening of mucosa
and submucosa of intestinal wall



1% ...
Macroscopy

Character

Amoebic dysentry

Bacillary dysentry

Number

6-8 motions per day

> 10 motions per day

Amount

Co...
Microscopy
Character

Amoebic dysentry

Bacillary dysentry

In clumps

Discrete or in Rouleaux

Pus cells

Few

Numerous

...


Most common extra-intestinal presentation



The parasite reaches liver via portal system



Occurs within 5 mths of ...


Rupture is the most dreaded complication



It may spread to pleura, lungs, peritoneum, pericardium or open
outside th...


Adhesion



Surface adhesins




Gal/GalNAc Lectin

Lipophosphoglycan like molecules

Invasion



Neuraminidase

...


E. dispar



E. moshkovskii



E. coli



E. hartmanii



E.gingivalis



E. dispar is morphologically

indistingu...
E. histolytica

E.coli

20-30 μm

20-50 μm

Active, unidirectional,
“purposeful motility”

Sluggish, nonpurposeful

Ectopl...


Endolimax nana



Iodamoeba buetschlii



Commensals of the human gut



Can be easily differentiated microscopicall...
Samples :

Stool ( 3 consecutive samples)
Biopsy material from the ulcers (colonoscopy or
sigmoidoscopy)
Aspirate from liv...


Both saline and iodine wet mounts are prepared



Any motile trophozoite is better seen in saline mount



Iodine mou...


Antibody



Antigen detection

detection



ELISA



ELISA



Coagglutination



IHA



IFA

 Copro-antigen dete...


Xenic media


Locke-egg media ( NIH media – Locke’s
modification of Boeck and Drbohlav media)





Axenic media


...


Locke’s solution ( per litre)
*

8 gm NaCl

0.2 gm CaCl2

*

0.01gm MgCl2

2 gm NaH2PO4

*

0.4 gm NaHCO3

0.3 gm KH2PO...


Polymerase Chain Reaction



DNA probes



18 S rRNA gene sequencing for speciation



A zymodeme comprises those En...
Luminal amoebicide
Diloxanide furoate
 Paromomycin
 Diiodohydroxiquin


Liver, gut wall and other tissues
Emetine
 Deh...
Amoebiasis lecture
Amoebiasis lecture
Amoebiasis lecture
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Amoebiasis lecture

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Amoebiasis lecture

  1. 1.  Amoebiasis is an infection with the intestinal protozoa Entamoeba histolytica.  About 90% of infections are asymptomatic  Remaining 10% produce a spectrum of clinical syndromes  Ranging from - asymptomatic to dysentery to abscesses of liver or other organs
  2. 2.  Entamoeba histolytica  Trophozoites • • • • 10 - 60 μm in D Cytoplasm – # outer clear ectoplasm # inner granular endoplasm # food vacuoles with RBCs, leukocytes & tissue debris Motile by pseudopodial extensions Nucleus with central karyosome, surrounded by delicate membrane lined with chromatin granules
  3. 3.  Entamoeba histolytica  Precyst Intermediate form • Oval with blunt pseudopodia • No food vacuoles •  Cysts • • • • • Spherical, 10 - 15 μm in D Uninucleate, later bi- or quadri- nucleate Thick chitinous wall Glycogen mass – not in quadrinucleate Chromidial or Chromatoid bars
  4. 4. World  worldwide in distribution  3rd most common parasitic death  India, China, Africa, South America  2-60% prevalence  100,000 deaths/yr  500 million infections  50 million cases India  15% prevalence (3.6-47.4%)  variation according to sanitation
  5. 5.  Source of infection is a case or carrier -1∙5 X 107 cysts per day  Reservoir is only human – several years  Resistant to chlorine in normal conc.  Readily killed by freezing or heating(55 C)
  6. 6.  All age groups affected  No gender or racial differences  Institutional, community living, MSM  Severe if children, old, pregnant, PEM  Develops antibodies in tissue invasion
  7. 7.  Low socio-economic status  Poor sanitation, sewage contamination  Night soil for agriculture  Seasonal variation
  8. 8.  1- 4 weeks  1- 4 weeks  Faeco -oral route • contaminated water and food • direct hand to mouth  Agency of flies, cockroaches, rats, etc.  Sexual contact via oro -rectal route
  9. 9.  Most common type of amoebic infection is asymptomatic cyst passage  Intestinal amoebiasis – abdominal cramps with mild diarrhoea to colitis and dysentry  Extra-intestinal amoebiasis – Amoebic liver abcess, rarely lungs, skin, genitalia and CNS are affected  Amoeboma – inflammatory and edematous reaction around trophozoites
  10. 10.  90% without symptoms  does not damage lumen  flask shaped ulcers superficial or deep  abd pain (tenesmus)  diarrhoea, dysentery, fever  peri-anal ulcers  <0.5%  severely ill with high fever  intestinal bleeding, perforation  paralytic ileus  CFR-40%  Uncommonly, a chronic form of amoebic colitis can be confused with inflammatory bowel disease
  11. 11.  Pseudotumoral lesion  Necrosis, edema and inflammatory thickening of mucosa and submucosa of intestinal wall  1% of cases  palpable mass with trophozoites  Always coexists with ulceration  Single, rarely multiple in different parts of colon, on skin at site of ALA aspiration
  12. 12. Macroscopy Character Amoebic dysentry Bacillary dysentry Number 6-8 motions per day > 10 motions per day Amount Copious Small Odour Offensive Odourless Colour Dark red Bright red Acidic Alkaline Non-adherent Adherent Reaction Consistency
  13. 13. Microscopy Character Amoebic dysentry Bacillary dysentry In clumps Discrete or in Rouleaux Pus cells Few Numerous Macrophages Few Numerous, many have RBCs and may mimic EH Eosinophils Present Scarce Charcot-Leyden crystals Present Absent Pyknotic bodies Present Absent Ghost cells Absent Present Parasites Trophozoites of EH Absent Bacteria Many motile bacteria Few or Absent RBCs
  14. 14.  Most common extra-intestinal presentation  The parasite reaches liver via portal system  Occurs within 5 mths of dysentery in 95% of cases  But concomitant active diarrhea is seen in less than a third of cases  Pain and point tenderness over right hypochondrium and fever  Jaundice rare, pleural effusion is common  Older pt. from endemic areas usually have chronic disease  Right lobe is commonly affected, abscess of left lobe is more dangerous due to its proximity to heart –> rupture –> pericardial effusion  Necrotic cavitary lesion filled with cellular debris and parasite trophozoites – Anchovy sauce pus
  15. 15.  Rupture is the most dreaded complication  It may spread to pleura, lungs, peritoneum, pericardium or open outside through the anterior abdominal wall  Serous pleural effusion or contiguous spread from ALA  Rupture from ALA into pleural space  Hepato-bronchial fistula with necrotic material in sputum may mimic blood – trophozoites can be present  CNS involvement – rare – hematogenous spread  Genital ulcer can occur – by contiguous spread or hematogenous route
  16. 16.  Adhesion   Surface adhesins   Gal/GalNAc Lectin Lipophosphoglycan like molecules Invasion   Neuraminidase  Phospholipase A1, A2, and L1  Metallocollagenase   ATPase Cysteine protease Lysis  Amoebopore – insertion of protein ion channels – cytolytic and bactericidal
  17. 17.  E. dispar  E. moshkovskii  E. coli  E. hartmanii  E.gingivalis  E. dispar is morphologically indistinguishable from E. histolytica and so is E. moshkovskii  etc. Most asymptomatic cases of amoebic infestation are believed to be one of these two species  The other species are also nonpathogenic but can be microscopically differentiated
  18. 18. E. histolytica E.coli 20-30 μm 20-50 μm Active, unidirectional, “purposeful motility” Sluggish, nonpurposeful Ectoplasm & endoplasm Not defined Cytoplasmic Inclusions RBC, leukocytes, tissue debris, no bacteria Bacteria and cell debris but no RBCs Nucleus Central karyosome, delicate membrane, fine chromatin grains Eccentric nucleus, coarse granules line a tough membrane Precyst Oval, 10-20 μm, blunt pseudopodium 20 μm, resembles E. histolytica precyst Spherical, 10-15 μm Spherical, 15-20 μm 1-4 1-8 Rounded Filamentous Trophozoite Size Motility Cytoplasm Cyst Size No. of nuclei Chromidial bars
  19. 19.  Endolimax nana  Iodamoeba buetschlii  Commensals of the human gut  Can be easily differentiated microscopically
  20. 20. Samples : Stool ( 3 consecutive samples) Biopsy material from the ulcers (colonoscopy or sigmoidoscopy) Aspirate from liver abcess Serum Pleural fluid Pericardial fluid Sputum
  21. 21.  Both saline and iodine wet mounts are prepared  Any motile trophozoite is better seen in saline mount  Iodine mount stains the internal structures and is used to identify cysts  Permanent stains can also be used to stain smears
  22. 22.  Antibody  Antigen detection detection  ELISA  ELISA  Coagglutination  IHA  IFA  Copro-antigen detection by ELISA is another recent and very useful method
  23. 23.  Xenic media  Locke-egg media ( NIH media – Locke’s modification of Boeck and Drbohlav media)   Axenic media   Robinson’s media Diamond media – TYI-S-33, YI-S, LYI-S-2 Monoxenic media
  24. 24.  Locke’s solution ( per litre) * 8 gm NaCl 0.2 gm CaCl2 * 0.01gm MgCl2 2 gm NaH2PO4 * 0.4 gm NaHCO3 0.3 gm KH2PO4  Break surface-sterilised eggs in a sterile container, blend and filter  To 45 ml of egg soln. add 12∙5 ml of Locke’s soln.  5-10 ml of this soln. is dispensed per tube and is solidified by inspissation  Tubes are kept at an angle during solidification to form a slant  The media is then overlayed with 6-10 ml of Locke’s soln. and stored  Before inoculation, 0∙2 ml (1mg) of a stock soln. of rice starch (5mg/ml) is added to each tube
  25. 25.  Polymerase Chain Reaction  DNA probes  18 S rRNA gene sequencing for speciation  A zymodeme comprises those Entamoeba strains that share the same electrophoretic pattern and mobility for certain enzymes like – malic enzyme, phosphoglucomutase, hexokinase, glucose phosphate isomerase, aldolase etc  24 different zymodemes – 21 of human strains  Currently however only 3 zymodemes are attributed to EH one only for E. dispar
  26. 26. Luminal amoebicide Diloxanide furoate  Paromomycin  Diiodohydroxiquin  Liver, gut wall and other tissues Emetine  Dehydroemetine  Hepatic amoebicide  Chloroquine Both tissue and intestinal amoebicide (Nitroimidazoles) Metronidazole [500-800 mg TDS X 5 (5-10) days]  Tinidazole [ 2 gm OD X 1-3 days]  Ornidazole [ 2 gm OD X 1-3 days] 
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