Amoeba

• What does the term "Protozoa" refer to in clinical parasitology?

  Protozoa refers to unicellular organisms that perform all life functions.
• What are the main components of a protozoan cell?

  • Nucleus: usually single, may be double or multiple
  • Cytoplasm: divided into endoplasm (inner) and ectoplasm (outer)
  • Plasma membrane: controls secretions and excretions
  • Cytostome: cell mouth
  • Chromatoidal bodies: storage for glycogen and protein
• What is the function of contractile vacuoles in protozoa?

  Contractile vacuoles regulate osmotic pressure between the parasite and its environment.
• What are the structures for locomotion in protozoa?

  Pseudopodia, flagella, cilia, and undulating membranes.
• What is the role of ectoplasm in protozoa?

  Ectoplasm serves as an organ for motility and engulfment of food.
• How are protozoan parasites classified?

  • Subphylum Sarcodina: amoeba and free-living amoeba
  • Subphylum Mastigophora: flagellates, classified by location
  • Phylum Ciliophora: e.g., Balantidium coli
  • Phylum Apicomplexa: contains apical complex
  • Phylum Microspora: not medically important
• What is encystation in protozoans?

  Encystation is the process of forming a cyst or becoming enclosed in a capsule.
• What is excystation in protozoans?


  Excystation is the escape from a cyst, producing a trophozoite.
• What are the general rules for amebae?

  • All Entamoeba are commensal except for E. histolytica.
  • Pseudopodia are used for movement.
  • Encystation occurs except for E. gingivalis and Dientamoeba fragilis.
  • Inhabits the large intestine except for E. gingivalis.
  • Amebiasis refers to the presence of amoeba in any part of the body.
  • Asexually multiplies through binary fission.
• What is the infective stage of Entamoeba histolytica?

  The mature quadrinucleate cyst passed in feces.
• How is Entamoeba histolytica transmitted?

  Through the fecal-oral route via ingestion of contaminated food and/or water.
• What are the morphological forms of Entamoeba histolytica?

  • Trophozoite: motile and feeding stage
  • Precyst: contains glycogen vacuole and chromatid bars
  • Cyst: protective thick cell wall, capable of excystation
  • Metacyst: liberated quadrinucleate amoeba during excystation
• What are the differences between E. histolytica and E. coli in terms of trophozoite morphology?

  • Movement: E. histolytica is unidirectional, E. coli is sluggish
  • Shape of pseudopodia: E. histolytica has finger-like, E. coli has blunted
  • Nucleus: E. histolytica has a central karyosome, E. coli has an eccentric karyosome
  • Inclusions: E. histolytica has RBC, E. coli has bacteria and debris
  • Cytoplasm: E. histolytica is clean looking, E. coli is dirty looking
• What are the differences between E. histolytica and E. coli in terms of cyst morphology?

  • No. of nuclei: E. histolytica is quadrinucleate, E. coli has more than 4
  • Chromatoidal bar: E. histolytica has sausage-shaped, E. coli has broomstick-shaped
  • Nuclear membrane: E. histolytica has a thin membrane, E. coli has a thick membrane
  • Size: E. histolytica is smaller (10 to 15 µm), E. coli is bigger (10 to 35 µm)
• What are the symptoms of amoebic dysentery?

  • Gradual onset of abdominal pain
  • Diarrhea (with or without blood)
  • In children: bloody diarrhea, fever, and abdominal pain
• What are the pathogenic determinants of Entamoeba histolytica?

  • Galactose-inhibitable adherence lectin: receptor-mediated adherence
  • Amoeba ionophore: causes cell lysis and tissue invasion
  • Cystein proteinase: important tissue-invading factor
• What is the diagnostic stage for amoebiasis?

  • Identification of the cyst or trophozoite
  • Sample for ID: stool examined within 30 minutes from collection
• What are the laboratory diagnosis methods for Entamoeba histolytica?

  • Microscopic detection of cyst and trophozoite
  • Direct fecal smear
  • Concentration techniques (FECT, MIFC)
  • Culture methods
  • Serologic testing (ELISA, CIE, AGD, IHAT, IF-AT)
  • Molecular testing (PCR)
• What is the treatment for invasive amebiasis?

  • Metronidazole: drug of choice
  • Tinidazole and secnidazole: also effective
  • Diloxanide furoate: for asymptomatic cyst passers
  • Percutaneous drainage for liver abscess if needed
• What are the prevention and control measures for amoebiasis?

  • Proper hygiene
  • Sanitary disposal of human feces
  • Access to clean drinking water
  • Good food preparation practices
  • Avoid using "night soil"
  • Health education and promotion
• What is the role of the cytostome in protozoa?

  The cytostome acts as the cell mouth for ingestion.
• What is the function of chromatoidal bodies in protozoa?

  Chromatoidal bodies serve as storage for glycogen and protein.
• What is the primary difference between trophozoite and cyst stages of Entamoeba histolytica?

  Trophozoite is the motile feeding stage, while cyst is the non-motile protective stage.
• What is the most common extraintestinal form of amoebiasis?

  Amoebic liver abscess.
• What is the significance of Charcot-Leyden crystals in amoebic dysentery?

  They are products from the metabolism of eosinophils found microscopically in stool.
• How does the pathogenesis of amoebic dysentery differ from bacillary dysentery?

  Amoebic dysentery has a gradual onset and fewer pus cells, while bacillary dysentery has an acute onset with numerous pus cells.
• What is the role of the amoeba ionophore in pathogenesis?

  Amoeba ionophore causes cell lysis and tissue invasion.
• What is the purpose of serologic testing in diagnosing amoebiasis?

  Serologic testing helps identify antibodies against Entamoeba histolytica.
• What is the significance of the mode of transmission for Entamoeba histolytica?

  It highlights the importance of sanitation and hygiene in preventing infection.
• What is the role of proper hygiene in the prevention of amoebiasis?

  Proper hygiene reduces the risk of fecal-oral transmission of the parasite.
• What is the purpose of molecular testing such as PCR?

  To detect the presence of specific DNA sequences in a sample.
• What is the drug of choice for invasive amebiasis?

  Metronidazole
• What is the treatment for asymptomatic cyst passers?

  Diloxanide furoate
• When is percutaneous drainage of the liver abscess indicated?

  When patients do not respond to metronidazole and need prompt relief of severe pain.
• What are the key prevention and control measures for amebiasis?

  • Proper hygiene
  • Sanitary disposal of human feces
  • Access to clean drinking water
  • Good food preparation practices
  • Avoid using "night soil"
  • Examine food handlers for cyst carriage
  • Health education and promotion
• What is Entamoeba coli classified as?

  A harmless inhabitant of the colon.
• How do the cysts of Entamoeba coli differ from those of E. histolytica?

  Entamoeba coli cysts are larger and consist of 8 nuclei with diffuse karyosomes.
• What is the size range of Entamoeba coli cysts?

  10 to 35 microns.
• What is the motility of Entamoeba coli trophozoites like?

  Sluggish, not progressive and non-directional.
• What is the karyosome characteristic of Entamoeba coli?

  Large and located eccentrically, surrounded by a halo of non-staining material.