Protozoan Biology: Morphology, Life Cycle, and Diagnosis

Protozoan

Unicellular organisms that can infect humans.

Amoebas

Protozoa characterized by pseudopodia for movement.

Trophozoite

Feeding, growing stage of protozoa; fragile.

Cyst

Non-feeding stage; allows survival outside host.

Excystation

Conversion from cyst to trophozoite in intestine.

Encystation

Conversion from trophozoite to cyst in adverse conditions.

Macrocnucleus

Vegetative nucleus in protozoan morphology.

Micronucleus

Reproductive nucleus in protozoan morphology.

Karyosome

Nucleolus used to distinguish Entamoeba species.

Endoplasm

Site of metabolism and organelles in protozoa.

Ectoplasm

Region where locomotion organelles arise.

Saline Wet Preparation

Method to observe motility of amoebic trophozoite.

Iodine Wet Preparation

Enhances visibility of internal structures in protozoa.

Permanent Smears

Used to confirm identification of parasites.

Ciliates

Protozoa that move using hair-like cilia.

Sporozoa

Intestinal and tissue-dwelling protozoan parasites.

Blastocystis hominis

Sole member of class Blastocystea.

Pneumocystis jiroveci

Formerly Pneumocystis carinii; a unique protozoan.

Entamoeba histolytica

Causes intestinal amoebiasis; identified in 1903.

Amoebic Dysentery

Severe intestinal infection caused by E. histolytica.

Entamoeba dispar

Morphologically similar to E. histolytica; non-pathogenic.

Entamoeba coli

Commensal amoeba; not typically pathogenic.

Entamoeba hartmanni

Smaller form of E. histolytica; non-pathogenic.

Endolimax nana

Non-pathogenic amoeba; small size.

Iodamoeba bütschlii

Non-pathogenic amoeba with distinctive morphology.

Entamoeba polecki

Amoeba found in pigs and humans.

Intestinal Amoebiasis

Infection caused by pathogenic amoebae in intestines.

Amoebic Colitis

Inflammation of colon due to amoebic infection.

Amoebic Dysentery

Severe diarrhea with blood and mucus from amoebae.

Extraintestinal Amoebiasis

Amoebic infection outside the intestines, like liver.

E. histolytica

Pathogenic amoeba causing intestinal and extraintestinal disease.

E. dispar

Non-pathogenic amoeba, often misidentified as E. histolytica.

Trophozoite

Active, vegetative stage of amoeba, motile and feeding.

Precyst

Unripe cyst formed from undigested food and cells.

Cyst

Mature infectious stage with four nuclei.

Metacyst

Stage following cyst, leading to metacystic trophozoite.

Metacystic Trophozoite

Stage after metacyst, ready to invade host.

Pseudopodium

Extension of amoeba for locomotion and feeding.

Binary Fission

Asexual reproduction method in amoebae.

Encystation

Process of forming cysts in intestinal lumen.

Glycogen Vacuoles

Inclusions in amoeba, storage for energy.

Chromatoidal Bars

Sausage-shaped bodies in cysts, indicate maturity.

Active Progression

Movement direction of trophozoites during locomotion.

Asymptomatic Cyst Passers

Individuals carrying cysts without showing symptoms.

Amebic Liver Abscess (ALA)

Common extraintestinal complication, causing liver abscess.

Virulence Factors

Molecules aiding pathogen adherence and tissue damage.

Gal/Gal Nac Lectin

Adhesion factor for E. histolytica to host cells.

Amebapores

Pore-forming proteins damaging host cell membranes.

Cysteine Proteinases

Enzymes causing tissue damage in host during infection.

Flask-Shaped Ulcers

Characteristic ulcers formed by trophozoite invasion.

Common Ulcer Sites

Cecum, ascending colon, and sigmoid are affected.

Entamoeba histolytica

Pathogenic amoeba causing intestinal and liver infections.

Trophozoite

Active form of Entamoeba histolytica in tissues.

Portal vein

Vein transporting blood from intestines to liver.

Periportal inflammation

Inflammation around the portal vein in the liver.

Anchovy sauce-like aspirate

Necrotic debris in liver abscess, odorless.

Amoebic ulcer

Ulcer caused by Entamoeba histolytica in intestines.

Incubation period

Time before symptoms appear, varies from days to months.

Chronic intestinal amoebiasis

Long-term infection with intermittent diarrhea and discomfort.

Acute amoebic dysentery

Severe form resembling bacillary dysentery.

Differential diagnosis

Distinguishing between bacillary and amebic dysentery.

Microscopy

Examination method for identifying pathogens in stool.

Charcot-Leyden crystals

Crystals indicating eosinophilic response, found in stool.

Gold standard diagnosis

Microscopic examination of stool specimens.

Concentration methods

Techniques enhancing detection sensitivity of amoebic cysts.

Stool culture

Culturing stool to identify pathogens, more sensitive than microscopy.

PCR

Molecular method for species identification of amoeba.

Serology

Antibody detection methods for diagnosing amoebic infections.

Metronidazole

First-line treatment for amoebic colitis, 800 mg thrice daily.

Tinidazole

Alternative treatment for amoebic infections, effective like metronidazole.

Luminal amoebicide

Drug to clear intestinal parasites after invasive treatment.

Prevention of amoebiasis

Improved hygiene and clean water access to reduce infection.

Commensal amoeba

Non-pathogenic amoeba that can be mistaken for E. histolytica.

Cysts

Infective form of amoeba, resistant to environmental conditions.

Epidemic potential

Amebic dysentery is seldom epidemic compared to bacillary dysentery.

Fecal Contamination

Contamination of food or water by feces.

Non-Pathogenic Amoebae

Amoebae that do not cause disease.

Entamoeba dispar

Non-invasive, non-pathogenic amoeba similar to E. histolytica.

Entamoeba hartmanni

Smaller strain of E. histolytica, non-pathogenic.

Entamoeba coli

Harmless inhabitant of the human colon.

Entamoeba polecki

Non-pathogenic amoeba found in pigs and humans.

Entamoeba gingivalis

Found in the human mouth, lacks cyst stage.

Endolimax nana

Small, non-pathogenic amoeba in the intestines.

Iodamoeba beutschlii

Non-pathogenic amoeba with large karyosome.

Entamoeba genus

Amoebae with spherical nucleus and chromatin granules.

Endolimax genus

Amoebae with vesicular nucleus and irregular karyosome.

Iodamoeba genus

Amoebae with chromatin-rich karyosome and globules.

Trophozoite

Active feeding stage of amoebae.

Precyst

Stage before cyst formation in amoebae.

Cyst

Dormant stage of amoebae, resistant to environment.

Metacystic

Stage following cyst, before returning to trophozoite.

E. histolytica

Pathogenic amoeba causing dysentery.

Cyst differentiation

Cysts of E. histolytica and E. dispar indistinguishable.

Trophozoite size

E. hartmanni trophozoites are 4-12µm.

Cyst size

E. hartmanni cysts measure 5-10µm.

Sluggish movement

Characteristic movement of E. coli trophozoites.

Differential Diagnosis

Comparison of E. histolytica and E. coli characteristics.

Cytoplasmic Inclusions

Bacteria and debris found in E. coli trophozoites.

Entamoeba polecki

Parasite of pigs and monkeys; rare in humans.

Cyst

Uninucleated structure in Entamoeba polecki.