Module 2 Flashcards
Protozoa (trophozoite phase)
- actively motile, feeding stage
- motility is progressive and directional OR slow and random
- possess a single nucleus (except D. fragilis & G. lamblia)
microscopic features of trophozoite phase
- extension of pseudopodia (for movement)
- single nucleus with small central karyosome
- cytoplasm is finely granular
Protozoa (cyst stage)
- inactive stage, dormant stage
- can serve as stage of reproductive division
- may contain 1-8 nuclei
microscopic features of cyst phase
- enveloped with smooth outer membrane
- more than one nucleus
- reproductive replication as each nucleus forms an individual trophozoite upon excystation
- glycogen vacuole visible during early encystation
- can see chromatoidal bars
Classes of Protozoa
- Protozoa
- Flagellates
- Cilliates
- Coccidia
Protozoa class
- trophozoites are motile via extrusion of pseudopodia
- bacteria, debris or food vacuoles in cytoplasm
- multinucleated cysts produced during periods of adverse environmental conditions
Flagellates class
- movement via production of one or more flagella
- flagella energized by a nerve center (kinetoplast)
- body of trophozoite is rigid
- one or two nuclei may be present
- organelles contained in distinct, smooth membrane
Cilliates class
- locomotion via delicate cilia
- cilia present on entire cell membrane
- trophozoites and cysts of Baleantidium coli are large
- cytosome and macronucleus
Coccidia class
- small organisms
- replicate intracellularly within somatic cells
- use animals for extra-human sites of reproduction
Stages of protozoa life cycles
- freely motile, feeding trophozoites
- resting cysts
- asexual
Entamoeba histolytica (trophozoite phase)
- 15-20 microns
- single pseudopod = unidirectional motility
- cytoplasm is finely granular with ingested RBC’s
- single nucleus with small central karyosome
Entamoeba histolytica (cyst phase)
- 12-15 microns
- never posses more than four nuclei
- nuclei contain a small central karyosome
- bead-like, even distribution of chromatin
- chromatoidal bars with rounded ends
Entamoeba histolytica (clinical conditions)
Non-invasive luminal infection, locally invasive disease, fulminant colitis, extraintestinal amebiasis, and pleuropulmonary spread
Intestinal disease
- lower abdominal pain, mild to full-blown diarrhea, malaise, weight loss
- endemic to Mexico and Central America
Extra-intestinal disease
liver abscess, fever, right upper quadrant paint pain, point tenderness over the liver and pleurisy with pleural effusion
Stains for Entameoba histolytica
iron hematoxylin or trichrome stain
Tests for E. histolytica
EIA, Serum antibody detection or immunodiffusion
Entamoeba coli (trophozoite phase)
- 20-25 microns
- vacuolated cytoplasm with bacteria, yeasts and other debris
- single nucleus with large eccentric karyosome
Entamoeba coli (cyst phase)
- 15-25 microns
- spherical and commonly contain eight nuclei
- karyosomes are large, eccentric and the peripheral chromatin is coarse and irregular
- “junky” cytoplasm
- chromatoidal bars have pointed ends
Entamoeba coli (clinical significance)
non-pathogenic
Entamoeba hartmanni (trophozoite phase)
- similar to E. histolytica
- 5-10 microns
- motility is less directional
- erythrocytes are not ingested
Entamoeba hartmanni (cyst phase)
- 6-8 microns
- chromatoidal bars with round ends
Endolimax nana (trophozoite phase)
- 8-10 microns
- motility is sluggish and non-directional
- single nucleus with no chromatin ring
- large karyosome
Endolimax nana (cyst phase)
- 6-8 microns
- spherical, ovoid or elliptical
- four nuclei surrounded by an open halo without a chromatin ring (“ball in socket”)
E. nana (clinical significance)
non-pathogenic
Iodamoeba butschlii (trophozoite phase)
- 8-20 microns
- motility is sluggish and non-progressive
- single nucleus possesses a large karyosome surrounded by clear zone (“ball in socket”)
Iodamoeba butschlii (cyst phase)
- 5-20 microns
- single nucleus with large central karyosome
- intra-cytoplasmic vacuole that stains brown
Naegleria fowleri
- free-living amoeba
- causes primary amoebic meningoencephalitis, diffuse meningoencephalitis and purulent leptomeningitis
- infection via swimming in polluted fresh water
Ancanthamoeba
- free-living amoeba
- associated with granulomatous amoebic encephalitis with hematogenous spread from skin or pulmonary sites
- commonly associated keratitis
- may be found in the absence of an inflammatory infiltrate
- transmission in those with contact lenses or by swimming in polluted water
Amoebae
- Acanthamoeba species (free-living species)
- Blastocystis hominis
- Endolimax nana
- Entamoeba coli
- Entamoeba hartmanni
- Entamoeba histolytica
- Iodamoeba butschlii
- Naegleria fowleri (free-living species)
Amoebae (general features)
- trophozoite is motile via pseudopodia extension
- cyst is circular and enveloped in smooth membrane
- trophozoite has one nucleus, cyst has more than one
- trophozoite cytoplasm contains undigested material, cyst cytoplasm is smooth with a glycogen vacuole and/or chromatoidal bars
- transmission via fecal-oral route
- free-living amoeba are transmitted via contact with contaminated water/food
Entamoeba histolytica (complete life cycle)
Trophozoite in stool –> Immature cyst –> mature cyst –> trophozoite excystation –> trophozoite in bowel –> trophozoites in tissue
Blastocystis hominis
- intestinal parasite
- 5-50 microns
- blue-green staining body
- significant if > 5 per low power field
- associated with recurrent diarrhea
- irregular distribution of chromatin on outer membrane
Coccidia and Microsporidium
- Cryptosporidium parvum
- Cyclospora cayentaenensis
- Isospora belli
- Sarcocystis species
- Microsporidium: Enterocytozoon bieneusi, Encephalitozoon cuniculi, Encephalitozoon hellem and Nosema connori
Coccidia
- tissue parasite
- sexual (external intermediate host) and asexual stages
- sporogenesis and oocyst formation during sexual stage
- transmission via ingestion of contaminated food/water or ingestion of infected tissues
Coccidia external intermediate hosts
cat, calf or other animal
Cryptosporidium parvum
- small coccidian protozoa
- causes enterocolitis and diarrhea in animals
- watery diarrhea, cramping abdominal pain in immunosuppressed hosts (AIDS patients)
- diagnosis by observing oocysts (acid-fast staining, direct saline mounts and acid-fast stained fecal smears), DFA, IFA or EIA
- oocysts are very small
- sporocysts develop in brush border of intestinal epis
Cyclospora cayatenensis
- causes diarrheal syndrome (non-bloody), cramping abdominal pain
- transmission via ingestion of contaminated food/water
- one type of traveler’s diarrhea
- diagnosis via observing oocysts (acid-fast smears, saline mounts, safranin staining, autofluoresence)
- oocysts about 2x larger than Cryptosporidium
Isospora belli
- diarrhea, nausea, headache, steatorrhea, etc.
- sexual and asexual stages in human intestine
- no external animal host
- oocysts are spindle-shaped, acid-fast
- immature cysts contain no or one sporocyst
- mature cysts contain two sporocysts (infective)
- increasing number of cases in AIDS population
- diagnosis by detecting oocysts in stool
Sarcocystis species
- found in various animals and in muscle tissue
- infection via ingestion of undercooked beef or pork contaminated with sarcocysts
- intermediate host: humans
- enter circulation and travel to various tissues (especially cardiac and skeletal muscle)
Microsporidium
- asexual and sexual stages
- Enteocytozoon bieneusi, Encephalitozoon species, Nosema connori, Pleistophora species, Trachipleistophora species
- diagnosis via stained tissue sections (Weber stain), stool suspensions, IFA or duodenal aspirates
- spores have dark central cross band when stained
Enterocytozoon bieneusi
- infects enterocytes of small intestinal epis
- intestinal disease in AIDS patients
Encephalitozoon species
- infect epis and endothelial cells, fibroblasts, macrophages and other cells
- AIDS patients
- upper and lower respiratory tract infections, intestinal infections, upper and lower urinary tract infections, hepatic and gall bladder infections, CNS infections
- cuniculi and hellem: nervous system involvement, keratoconjunctivitis and chronic sinusitis
Nosema connori
rare isolate
Pleistophora species
associated myositis
Trachipleistophora species
multi-organ recovery in AIDS patients
