Parasitology: Intestinal & Urogenital Protozoa Flashcards
(21 cards)
1
Q
What are organisms of the intestinal and urogenital protozoa?
A
- Amebae: Entamoeba
- Flagellates: Giardia and Trichomonas
- Ciliates: Balantidium
- Sporozoa: Cryptosporidium
2
Q
What is the basic trophocytic physiology and structure of Entamoeba histolytica?
A
- Found in faeces and crypts of the large intestine
- Motile in fresh stool
- 12-50 µm in size
- Round nucleus with a karyosome
- Evenly distributed chromatin granules around the nuclear membrane
- Ingested erythrocytes in cytoplasm
3
Q
What is the basic cystic physiology and structure of Entamoeba histolytica?
A
- Found in formed stool
- 10-20 µm in size
- 1-4 nuclei with a centrally located karyosome
- Round chromatoidal bars may be in cytoplasm
4
Q
Discuss the epidemiology of E. histolytica.
A
- Worldwide
- Highest tropical and sub-tropical areas
- Asymptomatic carriers and are reservoirs for the spread
- Trophozoites cannot survive in the external environment and also not in stomach
- Flies and cockroaches are vectors for spread of E. histolytica cysts
- Oral-anal sex practices
5
Q
Describe the life cycle of E. histolytica.
A
- Infx: Ingestion of cysts from faecally contaminated water, food, or hand
- Cysts: formed stool and Trophs: Watery stool
- Trophozoites cannot survive outside
- Low pH of stomach stimulates excystation
- Trophozoites migrate and multiply
- Cysts are protected by walls
- Trophs remain confined to intestinal lumen of asymptomatic carriers
- Invade intestinal mucosa and bloodstream
6
Q
What is the lab diagnosis of E. histolytica?
A
- Stool: Cysts
- Tissue: Trophozoites
- Multiple samples because microscopic exam of stool is extensive
- Liver MRI or serological testing
7
Q
What is the basic trophocytic physiology and structure of G. duodenalis?
A
- 9-12 µm long and 5-15 µm wide
- Flagella for movement
- 2 nuclei
- Central located karyosome
- 2 parabasal bodies
- Suckers for attachment
8
Q
What is the basic cystic physiology and structure of G. duodenalis?
A
- 8-12 µm long and 7-10 µm wide
- Mature cysts: 4 nuclei
- Immature cysts: 2 nuclei
- Central located cysts
- Parabasal bodies
9
Q
Describe the life cycle of G. duodenalis.
A
- Cysts and trophozoites passed in feces
- Cysts: resistant and responsible for transmission
- Cysts: hardy and survive in cold water
- Infx: Ingestion of contaminated food, water, fecal-oral route (hand or fomites)
- Excystation
- Trophozoites: longitudinal binary fission and remain in lumen of proximal small bowel
- Mucosa: ventral sucking disk
- Encystation: Colon
10
Q
What is the lab diagnosis of G. duodenalis?
A
- Onset of diarrhea and abdominal pain
- Examine stool for cysts or trophozoites
- Excretion in “showers”
- Negative again and giardiasis is suspected: duodenal aspiration
- Immunological tests for fecal antigen
11
Q
What is the basic trophocytic physiology and structure of T. vaginalis?
A
- Urogenital protozoa
- 4 anterior flagella and a short undulating membrane on one side
- 7-23 µm long and 6-8 µm wide
- Nucleus wider located
- Axostyle along center of parasite
12
Q
Discuss the epidemiology of T. vaginalis.
A
- Worldwide
- Sex
- Fomites (toilets, clothes)
- Infants: infected birth canal
13
Q
Describe the life cycle of T. vaginalis.
A
- T. vaginalis resides in the FLGT and male urethra and prostate
- Replicates by binary fission
- No cysts, only trophozoites
- Transmitted among humans
14
Q
What is the lab diagnosis of T. vaginalis?
A
- Examine vaginal/urethral discharge for trophozoites
- Stain: Giemsa, Papanicolaou stain or unstained
- Culture: Kupferberg’s STS and Diamond’s medium
- Monoclonal fluorescent Ab stain or nucleic acid probe
- Serology testing for epidemiological surveillance
15
Q
What is the basic trophocytic physiology and structure of N. coli?
A
- Covered with cilia
- 50-200 µm long and 40-70 µm wide
- Cytostome: funnel like mouth
- Large and small nucleus
- Food vacuoles
- 2 pulsating vacuoles seen in fresh preps
16
Q
What is the basic cystic physiology and structure of N. coli?
A
- 40-60 µm in size
- Surrounded by clear refractile wall
- A single nucleus in cytoplasm
17
Q
Describe the life cycle of N. coli.
A
- Cysts: Transmit balantidiasis
- Ingested with contaminated food/water
- Trophozoites colonize lumen of large intestine
- Replicate by binary fission and conjugation
- Encystation: large intestine
- Invade colon and multiply or return to lumen and disintegrate
- Mature cysts passed in feces
18
Q
What is the lab diagnosis of N. coli?
A
- Exam fecal sample for T&C
- Larger protozoans in comparison with others
- Easily detected in fresh, wet preparations
19
Q
Discuss the epidemiology of Cryptosporidium spp.
A
- Worldwide
- C. hominis and C. parvum common in humans
- Waterborne
- Zoonotic (A2H) and H2H by fecal-oral/oral-anal transmission
- Risk: Veterinarians, animal handlers, homosexual men, immunocompromised pt’s, municipal swimming pools, todlers at day-care centers
20
Q
Describe the life cycle of Cryptosporidium spp.
A
- Sporulated oocysts contain 4 sporozoites
- Infx: Contact w/ contaminated water
- Excystation: sporozoites are released and parasitize epithelial cells of the GIT or RT
- Asexual multiplication (schizogony) and sexual multiplication (gametogony) to produce microgamonts and macrogamonts
- Fertilization
- Thick walled and thin walled oocysts
- Oocysts are infective once excreted
21
Q
What is the lab diagnosis of Cryptosporidium spp.?
A
- Large nrs of unconcentrated stool samples collected for immunocompromised patients presenting with diarrhea
- Oocysts 5-7µm
- Concentrated sample must be modified with zinc sulphate centrifugal floatation technique or Sheater’s sugar floatation
- Acid Fast stains
- PCR’s
- Oocysts shed in stool fluctuate in concentration
