Microbiology
- Protozoans are eukaryotic unicellular organisms that have organelles
- Many have a trophozoite form (active, motile), as well as a cyst form (vegetative)
- Stains:
- Iron hematoxilin, which stains nuclei on a black background
- Acid-fast stain, which highlights red Crypto/Cyclo/Iso
- Can combine both of the above
Classification
From largest to smallest family
- Amoebae
- Entamoeba histolytica/dispar (microscopically indistinguishable, but E. dispar is non-pathogenic)
- E. harmanni and E. coli (non-pathogenic)
- Endolimax nana
- Iodamoeba butchlii
- Flagellates
- Giardia lamblia
- Dientamoeba fragilis (no cystic form)
- Chilomastix mesnili
- Ciliates
- Balantidium coli
- Coccidia: small, may be seen as acid-fast
- Cryptosporidium
- Cyclospora
- Cystoisospora (previously Isospora)
- Sarcocystis hominis
- Microsporidia
Approach to Microscopy
- Some have classic appearance:
- Giardia trophs look like an owl
- Balantidium coli is huge
- Trichomonas and Chilomastix trophs have flagellae and are tear-drop shaped
- Isospora belli looks like an eye or halved egg
- Cyclospora is thick-walled and looks like a golf ball
- Cryptosporidium is the smallest (4-6 µm) and may have crescent-shaped sporozoites inside
- Sarcocystis is quite large (15 µm), non-acid-fast, and looks like 2 joined ovals
- In order to differentiate the larger Amoebae, need to consider the size, nucleus characteristics, and other features
- What kind of nucleus is it?
- Entamoeba: dark ing of peripheral chromatin, with a defined central nucleus and relatively clear perikarysomal space
- Non-entamoeba: more blob-like, less well defined
- Granulated: big dots, suggests Dientamoeba fragilis trophozoite
- How many nuclei?
- Trophs are mostly mono-nucleated, cysts may be poly-nucleated
- Dientamoeba has 2 nuclei in troph form
- What is the average size?
- Need a measurement microscope
- Other stuff
- Large vacuole suggests Iodamoeba butschlii
- Uneven chromatin suggests E. coli
- Chromatoidal bars suggests E. polecki, E. histolytica, or E. hartmanni
| Organism | Nucleus type | No. nuclei | Size | Other features |
|---|---|---|---|---|
| E. histolytica | Entamoeba type | 2-4 | > 10 µm | Chromatoidal bars |
| E. coli | Entamoeba type | 5-8+ | > 10 µm | |
| E. hartmanni | Entamoeba type | < 10 µm | Chromatoidal bars | |
| E. polecki | Entamoeba type but 1/3 cell width | > 10 µm | Chromatoidal bars, but may have glycogen mass | |
| Iodamoeba | Blob-like | 1 | Large vacuole | |
| Endolimax | Blob-like | 2-4 |
