Protozoans: Amoeba

• Protozoa


  Unicellular organisms and the lowest form of animal life
• Phylum Sarcomastigophora, subphylum Sarcodina

  Includes the pathogenic and nonpathogenic amebas
• Amoebas


  • Equipped with the ability to extend their cytoplasm in the form of pseudopods (false feet), which allows them move within their environment
• Morphologic forms in the amoeba


  • Trophozoites (the form that feeds, multiplies, and possesses pseudopods)
  • Cysts (non-feeding stage characterized by a thick protective cell wall)

  
• Trophozoites


  The form that feeds, multiplies, and possesses pseudopods
• Cysts


  Non-feeding stage characterized by a thick protective cell wall
• Entamoeba histolytica


  Common associated disease or condition names: Intestinal amebiasis, amebic colitis, amebic dysentery, extraintestinal amebiasis
• Entamoeba histolytica trophozoites


  • Size range: 8-65 um, with an average size of 12 to 25 um
  • Motility: Progressive, finger-like pseudopodia
  • Number of nuclei: One
  • Karyosome: Small and Central
  • Peripheral chromatin: Fine and evenly distributed
  • Cytoplasm: Finely granular
  • Cytoplasmic inclusion: Ingested Red Blood Cell

  
• Entamoeba histolytica cysts


  • Size range: 8-22 um, with an average range of 12 to 18 um
  • Shape: Spherical to round
  • Number of nuclei: One to four
  • Karyosome: Small and Central
  • Peripheral chromatin: Fine and evenly distributed
  • Cytoplasm: Finely granular
  • Cytoplasmic inclusion: Cromatoid bars, rounded ends in young cysts, Diffuse glycogen mass in young cysts

  
• Standard and alternative laboratory diagnosis methods for Entamoeba histolytica

  • ELISA (enzyme-linked immunosorbent assay)
  • IHA (indirect hemagglutination)
  • GDP (gel diffusion precipitin)
  • IIF (indirect immunofluorescence)
• Life cycle of Entamoeba histolytica


  Survival in a feces contaminated environment for up to 1 month is common

  
• Epidemiology of Entamoeba histolytica infection

  • Infection occurs in as many as 10% of the world's population and is considered a leading cause of parasitic deaths after only malaria

  
• Clinical Symptoms of Entamoeba histolytica

  • Asymptomatic
  • Symptomatic
• Treatments for Entamoeba histolytica

  • Paramomycin
  • Diloxanide furoate (Furamide)
  • Metronidazols (Flagyl)
• Prevention and Control of Entamoeba histolytica


  Improved sanitation will help to reduce the likelihood of transmission
• Trophozoite stage


  The active, feeding, multiplying stage of most protozoa
• Cyst stage


  A resting or dormant stage of a microorganism

  
• Entamoeba hartmanni trophozoite


  • Size range: 5-18 um
  • Motility: Non-progressive, finger-like pseudopods
  • Number of nuclei: One
  • Karyosome: Small and central
  • Peripheral chromatin: Fine and evenly distributed
  • Cytoplasm: Finely granular
  • Cytoplasmic inclusions: Ingested bacteria may be present

  
• Entamoeba hartmanni trophozoite


  Morphologically similar to Entamoeba histolytica trophozoite

  
• Entamoeba hartmanni trophozoite


  Differs from Entamoeba histolytica in that its cytoplasm contains bacteria and no RBCs

  
• Entamoeba hartmanni cyst


  • Size range: 5-12 um
  • Shape: Spherical
  • Number of nuclei: One to four
  • Karyosome: Small and central
  • Peripheral chromatin: Fine and evenly distributed
  • Cytoplasm: Finely granular
  • Cytoplasmic inclusions: Chromatoid bars, rounded ends in young cysts, Diffuse glycogen mass in young cysts

  
• Entamoeba hartmanni cyst


  Similar to Entamoeba histolytica cyst

  
• Entamoeba hartmanni cysts may have 2 or more distinct spherical nuclei

  
• Laboratory diagnosis is accomplished by examining the stool
• It is advisable to not base solely on the sizes of the amoeba as it may mislead results
• Transmission of Entamoeba hartmanni

  Ingestion of infected cysts present in contaminated food or water

  
• Entamoeba hartmanni infections


  Typically asymptomatic
• Entamoeba hartmanni


  Considered as nonpathogenic
• Prevention and control against Entamoeba hartmanni


  • Good sanitation and good hygiene practices
  • Protection of food and water from vectors like flies and cockroaches
• Endolimax nana


  The most common of the smaller intestinal amebae, usually encountered with about the same frequency as in Entamoeba coli, colonizes the colon

  
• Endolimax nana trophozoite


  • Small in size, 5-12 μm, structure of nucleus, moves slowly, feeds on bacteria and food debris

  
• Endolimax nana cyst


  • Typically measure 7-10 µm in size, forms as feces dehydrates, contains nuclei with large endosomes

  
• Endolimax nana infections are usually asymptomatic

  
• Endolimax nana is considered a nonpathogen
• Life cycle of Endolimax nana

  1. Intestine, organisms passed in feces

  2. Acquired via fecal-oral transmission of cysts

  
• Endolimax nana is found in areas with poor hygiene and substandard sanitary conditions
• Laboratory diagnosis of Endolimax nana is done by examination (concentration, permanent stained smear)

  
• Control of Endolimax nana involves improved hygiene and disposal of fecal waste
• Iodamoeba butschlii trophozoite


  • Size range: 8-12 um
  • Motility: Sluggish, usually progressive
  • Number of nuclei: One
  • Karyosome: Large, usually central refractive achromatic granules may or not may be present
  • Peripheral chromatin: Absent
  • Cytoplasm: Coarsely granular and vacuolated
  • Cytoplasmic inclusions: Bacteria, yeast cells, other debris

  
• Iodamoeba butschlii cyst


  • Size range: 5-22 um
  • Shape: Ovoid, ellisoid, triangular, other shapes
  • Number of nuclei: One
  • Karyosome: Large, eccentric achromatic granules on one side may be present
  • Peripheral chromatin: Absent
  • Cytoplasm: Coarsely granular and vacuolated
  • Cytoplasmic Inclusions: well defined glycogen mass granules may be present