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Protozoans

• They are “single-celled” organisms which are generally classified according to their ‘organelles of locomotion’

• Unicellular, eukaryotic organisms

• “Animal-like” protists

• No cell wall

Additional info of protozoans

Organelles:

• Nucleus

• Nucleolus

• Mitochondria

• Locomotor Organelles

Two Regions of Cytoplasm:

• Ectoplasm (outer)

• Endoplasm (inner)

  Contains at least one and some several nuclei

  Some contain vacuoles

  With special organs for locomotion

Class Sarcodina

• Have protoplasmic processes, or pseudopodia, for locomotion

• Possess in their life cycle the:

• Trophozoite stage

• Precystic stage

• Cystic stage

• Metacystic stage

• With cystic stage exc. for Entamoeba gingivalis (mouth)

• Inhabit the large intestine exc. for Entamoeba gingivalis

• Commensals exc. for Entamoeba histolytica (non-pathogenic)

Cyst

• Non-motile

• Usually infective

• Found in formed feces

• Resistant to damage

• Usually smaller than trophozoite

• Best visualized using iodine

Trophozoite

• Motile

• Usually not infective

• Found in liquid feces

• Susceptible to damage; easily disintegrates

• Usually larger than cyst

• Best seen using permanent stains

• Entamoeba histolytica

  12-60 um

  central, indistinct “bull’s eye karyosome”

  Ingested RBCs

• Entamoeba coli

  15-50 um

  Eccentric, off-centered

  Bacteria, food vacuoles, & debri

• Endolimax nana

  6-12 um

  Irregular, “blot-like”

  Bacteria, food vacuoles, & debri

• Iodamoeba butschlii

  8-20 um

  Surrounded with achromatic granules

  Bacteria, food vacuoles, & debri

• Entamoeba gingivalis

  10-20 um

  Central and distinct

  Food vacuoles and WBCs

Entamoeba histolytica (Intestinal Amebiasis)

1. Acute/Symptomatic

   • Acute/Symptomatic

   • Blood diarrhea, abdominal pain

   • Patient passes out ‘trophozoites’ in feces

2. Chronic/Asymptomatic

   • Stool consistency is ‘normal’

   • Patient are carriers

   • Patient passess ‘cyst’ in feces

Entamoeba histolytica (Extraintestinal Amebiasis)

• Trophozoite is ‘tissue invading’ forms:

• Hepatic amebiasis

• Pulmonary amebiasis

• Cerebral amebiasis

Naegleria fowleri

• Cyst size: 7-15 um

• # of Nucleus: 1

  Trophozoite:

• Measures: 10-35 um

  2 Forms:

• Amoeboid Troph: Lobophodia

• Flagellated Troph: 2 Flagella

• Infective Stage: Amoeboid Trophozoite

• Diagnostic Stage: Trophozoite in CSF & Brain tissues; flagellated forms occasionally in CSF

  Cyst is ‘not seen’ in brain tissues

  Cyst has ‘double wall’

  Flagellated forms with 2 flagella and ‘rapidly motile’

Acanthamoeba spp.

• Cyst Size: 10-25 um

• # of Nucleus: 1

  Trophozoite:

• Measures: 15-45 um

• With “Spine-like” Projections: Acanthopodia

• Infective Stage: Cyst & Trophozoite

• Diagnostic Stage: Cyst & Trophozoites in tissues;

  Trophozoite has ‘spine-like’ process called “acanthophodia” (slowly motile”

Balamuthia mandrillaris

• Isolated from soil and dust or from autopsy specimens of infected humans and animals

• Infective Stage: Cyst & Trophozoite

• Can Enter Thru: Nasal Passages & Ulcerated & Broken Skin

  Cyst & Trophozoite in tissues

  Cyst is 10-25 um with ‘double cyst wall’

Dientomoeba fragilis

• Previously classified as an ‘amoeba’

• Trophozoite is 5-15 um

• With Hyaline “leaf-like” pseudopodia

• Karyosome is composed of a cluster of 4-8 granules

• Often referred to as “fragmented karyosome” or “tetrakaryosome”