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BB2716 Medical Microbiology > Parasitology - Intestinal and Urogenital Protozoa > Flashcards

Parasitology - Intestinal and Urogenital Protozoa Flashcards

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1
Q

What are the three types of helminths?

A
  1. Nematodes (roundworms)
  2. Trematodes (flukes)
  3. Cestodes (tapeworms).

Helminths never take caution

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2
Q

What are the different modes/routes of transmission of protozoa? [6]

A
  1. Oral-faecal route (ingestion)
  2. Contaminated water (Giardia infections)
  3. Contact with infected cats (Toxoplasmosis)
  4. Venereal route (sexual intercourse, Trichomonas vaginalis)
  5. Insect bite (Malaria, Trypanosomiasis, Leishmaniasis)
  6. Direct skin penetration (wound infection)
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3
Q

What are the four types of pathogenic protozoa?

A
  1. Sporozoa
  2. Amoebae
  3. Flagellates
  4. Ciliates
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4
Q

What are the types of intestinal and urogenital protozoa? [5]

A
  1. Amoeba
  2. Flagellates
  3. Ciliates
  4. Apicomplexa
  5. Microsporidia
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5
Q

Give an example of an intestinal and urogenital amoeba.

A

Entamoeba histolytica

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6
Q

Give an example of an intestinal and urogenital flagellate.

A

Giardia lamblia (duodenalis)

Trichomonas vaginalis

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7
Q

Give an example of an intestinal and urogenital ciliate.

A

Balantidium coli

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8
Q

Give an example of an intestinal and urogenital apicomplexa.

A

Isospora belli

  • Cryptosporidium* species
  • Cyclospora* species
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9
Q

What are the three major intestinal and urogenital protozoa?

A
  1. Giardia lamblia
  2. Entamoeba histolytica
  3. Trichomonas vaginalis
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10
Q

What organs are targeted by intestinal and urogenital protozoa?

A
  • Oropharynx
  • duodenum
  • small bowel
  • colon
  • urogenital tract
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11
Q

How are intestinal and urogenital protozoa prevented?

A
  • Improved sanitation
  • Chlorination, iodisation and filtration of water
  • Improved public health knowledge and awareness
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12
Q

Outline the main characteristics of amoebae. [3]

A
  • Primitive unicellular microorganisms
  • simple lifecycle (feeding stage and infective stage)
  • most are commensal organisms (benefit from host without harm).
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13
Q

Name some commensal amoebae.

A
  • E.coli
  • E.hartmanni
  • E.dispar (indistinguishable from E.histolytica)
  • E.gingivalis
  • Endolimax nana
  • Iodamoeba butschlii
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14
Q

List some pathogenic amoebae.

A
  • Entamoeba histolytica
  • Entamoeba polecki
  • Naegleria fowleri (opportunistic)
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15
Q

Outline the epidemiology and transmission of Entamoeba histolytica.

A

Epidemiology:

  • worldwide distribution, high incidence in tropical and subtropical regions (poor sanitation), cold regions (Alaska, Canada, Eastern Europe)
  • 35-50 million cases of symptomatic disease, 100,000 deaths annually.

Transmission:

  • pass trophoziotes and cysts in stool
  • flies and cockroaches spread cysts
  • anal-oral sexual practices.
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16
Q

Outline the lifecycle of Entamoeba histolytica.

A
  1. Cysts and trophoziotes passed in faeces
  2. Mature cysts ingested
  3. Excystation
  4. Trophoziotes multiply
  5. Some form cysts and exit host
17
Q

What are the clinical syndromes presented by Entamoeba histolytica?

A

Varies depending on the location in the host, extent of the tissue invasion.

  1. Asymptomatic carrier
  2. Symptomatic intestinal amoebiasis
    • amoebic colitis
    • amoebic dysentery
  3. Symptomatic extra-intestinal amoebiasis
    • liver infection + abscesses
18
Q

How do you diagnose intestinal disease due to Entamoeba histolytica?

A
  • cysts and/or trophoziotes in faeces or tissues
    • stool examination + microscopy
  • sigmoidoscopy
    • aspirates or biopsies + microscopy

Diagnosis can be difficult as other parasites can look identical, such as E.dispar, a commensal protozoa. Antigen tests needed to distinguish the two.

19
Q

What are the differences between trophozoites and cysts?

A

Trophozoites:

  • The feeding stage of the protozoa
  • Is actively motile (pseudopode)
  • Replicates by binary fission
  • Exists in favourable environments

Cysts:

  • Quiescent and resistant
  • Infective stage
  • Develops mutliple trophozoites in mature multinucleated cysts
  • Exists in unfavourable conditions
20
Q

Outline amoebic colitis.

A

Amoebic colitis is an infection of the intestine which is a form of symptomatic intestinal amoebiasis. It has the following symptoms:

  • Abdominal pain, cramping
  • Diarrhoea, flatulence
  • Chronic weight loss and anorexia
  • Chronic fatigue

Secondary bacterial infection may develop after the formation of flask-shaped amoebic ulcers in the colon, cecum, appendix or rectosigmoid area of the intestine (mucosa).

21
Q

Outline amoebic dysentery.

A

Amoebic dysentery is an infection of the intestine which is a form of symptomatic intestinal amoebiasis. It occurs gradually and has the following symptoms over several weeks:

  • Abdominal pain and tenderness
  • Tenesmus (painful and sudden bowel evacuation)
  • Diarrhoea
  • Weight loss
22
Q

Outline symptomatic extra-intestinal amoebiasis.

A

Trophozoites migrate into the blood stream and are filtered by the liver where they take residence. This may result in right lobe liver abscess, associated with pain over the liver and fever.

Trophozoite extension through the diaphragm may cause pneumonitis -> Liver infection associated with cough.

Symptoms include: Weakness, weight loss, sweating, nausea, vomiting, constipation.

E. histolytica may also migrate to other organs (lung, spleen, skin, brain).

23
Q

How do you diagnose extra-intestinal disease?

A
  • Serology, useful but cannot distinguish from current and past infections
  • Non-invasive imaging (hepatic abscess)
    • Ultrasound
    • CT
    • MRI
24
Q

How do you treat and prevent Entamoeba histolytica?

A
  • Metronidazole followed by iodoquinol for acute fulminating amoebiasis
  • Adequate sanitation
  • Education to sexual partners
  • Education to travellers
  • Chlorination and filtration of water supplies
25
Q

Outline the epidemiology and characteristics of Giardia lamblia.

A

Giardia lambia is distributed worldwide and can be found in streams, lakes, contaminated food and water, and spread through unusual sexual practices.

  • The cysts are resistant to chlorination.
  • 200 million cases per year
  • colonises upper small intestine and duodenum (duodenalis)
  • non-invasive, 50% asymptomatic.

Transmitted through the oral-faecal route, trophozoites divide by binary fission.

26
Q

Describe the lifecycle of Giardia lambia.

A

Typical oral-faecal transmission cycle

  1. Excretion of cysts by host 1
  2. Ingestion of cysts by host 2
  3. Excystation in the duodenum (low pH)
    • Flagellar activity
    • Breakage of the cyst wall (proteases)
    • Release of the trophozoite
    • Attachment to intestinal epithelium (adhesive disk)
    • Twisting motion (4 pairs of flagella)
  4. Asexual replication of trophozoites
    • (2 nuclei) => (4 nuclei)
    • Cytokenesis => 2 binucleated trophozoites
  5. Encystation
    • The trophozoite rounds up
    • Detachment from the intestinal epithelium
    • Secretion of the cyst wall
27
Q

List the symptoms and pathogenesis of Giardia lambia.

A

Symptoms:

  • ranges from mild diarrhoea to severe malabsorption syndrome.
  • chronic syndromes: weight loss, failure to thrive.
  • 1-4 weeks: nausea, loss of apetite, foul-smelling watery diarrhoea, blood and mucous rare, abdominal cramps, flatulence, foul sulphuric belching.
  • Patient can spontaneously recover, except if there is an IgA deficieny.

Pathogenesis:

  • irritation of intestinal epithelium
  • inflammation
  • lactase deficiency.
28
Q

Outline how you would diagnose a Giardia lambia infection.

A
  • Examine cysts and trophozoites in stool after diarrhoea.
  • Examine stool specimen for three days
    • In negative, but highly suspected cases a duodenal aspiration/small intestine biopsy is needed.
  • Immunological tests for faecal antigen
    • Immunoelectrophoreis
    • ELISA
    • Chromatographic and Indirect immunofluorescent staining (88-98% sensitive)
29
Q

How do you treat, control, and prevent Giardia lamblia infections?

A
  • Treat with metronidazole
  • Avoid contaminated water, food, and faeces
  • Boiled water/iodine treatment (chlorine not effective)
  • Pubic health awareness.
30
Q

Outline the main characteristics and epidemiology of Trichomonas vaginalis.

A
  • Four flagella and undulating (short, smooth, wave-like motion) membrane.
  • Exists only as a trophozoite in urethras, the vaginas of women, and the prostate of men.

Epidemiology:

  • Worldwide distribution
  • Transmitted through sexual intercourse, infants infected through mother’s infected birth canal.
  • Prevalence in developed countries: 5-20% women, 2-10% men.
31
Q

Outline the symptoms of Trichomonas vaginalis infection.

A
  • Most infected women are asymptomatic or have scant (not enough) watery vaginal discharge.
  • Vaginitis: itching, burning, painful urination.
  • Men are asymptomatic carriers.
  • Men occasionally experience urethritis, prostatitis.
32
Q

How would you diagnose a Trichomonas vaginalis infection?

A
  • Microscopic examination of vaginal or urethral discharge for trophozoites.
  • Monoclonal fluorescent staining.
  • PCR probes and serological tests available.
33
Q

How would you treat, prevent, and control Trichomonas vaginalis?

A
  • Treat using metronidazole (both partners, resistance must be reported)
  • Good personal hygiene
  • Safe sexual practices (condoms)
34
Q

Describe the morphology and epidemiology of Balantidium coli?

A

Morphology: trophozoite covered in hair-like cilia, has a funnel-like cytosome.

Epidemiology: worldwide distribution, swine and monkey reservoirs, infection via the faecal-oral route, outbreaks associated with contaminated food.

35
Q

What are the clinical symptoms and treatment for Balantidium coli?

A

Symptoms: abdominal pain and tenderness, nausea, anorexia, watery stools with blood and pus, ulceration of intestinal mucosa.

Treatment: tetracycline, metronidazole alternative.

36
Q

Desribe the lifecycle of Balantidium coli.

A
37
Q

What are the main similarities and differences between Giardia lamblia, Entamoeba histolytica, and Trichomonas vaginalis?

A
  • G.lamblia and T.vaginalis are flagellates, whereas E.histolytica is an amoeba.
  • They all have a worldwide distribution.
  • G.lamblia and E.histolytica exists as trophozoites and cysts, whereas T.vaginalis only exists only as a trophozoite.
  • G.lamblia and E.histolytica are transmitted through the faecal-oral route, whereas T.vaginalis is transmitted through sexual intercourse.
  • All can be treated with metronidazole.

BB2716 Medical Microbiology (20 decks)

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