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Medical Microbiology > Intestinal And Urogenital Protozoa > Flashcards

Intestinal And Urogenital Protozoa Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
0
Q

What organs are targeted by intestinal and urogenital Protozoa?

A

Oropharynx.
Small intestine.
Colon.
Urogenital tract.

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1
Q

Give some examples of intestinal and urogenital Protozoa.

A

Amoebae
Entamoeba histolytica : intestinal amoebiasis.

Flagellates
Giardia lamblia : diarrhoea
Trichomonas vaginalis : vaginitis, urethritis, prostatitis

Ciliates
Balantidium coli : ulcerative amoebiasis

Apicomplexa
Isospora belli : chronic diarrhoea

Microsporidia
Microsporidia : hepatitis

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2
Q

What is the mode of transmission for amoebae and flagellates?

A

Oral-fecal route and Veneral route.

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3
Q

List some prevention methods.

A

Improved sanitation, chlorination, iodination, filtration of water supplies.

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4
Q

Amoebae are classified as?

A

Primitive unicellular microorganisms.

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5
Q

Give a brief description of their life cycle.

A

Simple life cycle consisting of the ‘feeding stage’ (trophozoite), a favourable environment where they are activity motile (pseudopod) and the ‘infective stage’ (cyst), an unfavourable environment where they are quiescent (inactive).

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6
Q

Most are commensal (take benefit without harming the host) organisms. True or False?

A

True.

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7
Q

Give one example of a pathogenic amoebae.

A

Entamoeba histolytica.

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8
Q

Give two examples of a commensal entamoebae.

A

E. coli and E. dispar.

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9
Q

What is the epidemiology of Entamoeba histolytica?

A

Highest incidence in tropical and subtropical countries as well colder regions such as Alaska, Canada and Eastern Europe.

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10
Q

What is their life cycle?

A

Mature cysts are ingested and then passed in faeces along with trophozoites.

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11
Q

What organ is affected?

A

The intestine.

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12
Q

What do the symptoms depend on?

A

1) the location of the parasite.

2) the extent of invasion of tissues affected.

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13
Q

What is the asymptomatic carrier state?

A

Cysts are passed through stool with no clinical symptoms (low virulence strain). Amoeba may reproduce but no symptoms are visible.

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14
Q

What is symptomatic intestinal amoebiasis?

A

Localised tissue destruction in large intestine.
Amoebic colitis: intestinal infection associated with all or some of the following symptoms; abdominal pain, cramping, diarrhoea, and chronic weight less.
Secondary bacterial infection: may develop after the formation of flask-shaped amoebic ulcers in the colon, cecum and appendix.
Amoebic dysentery: blood and mucus in the stool. Causes weight loss.

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15
Q

What is symptomatic extra-intestinal amoebiasis?

A

Trophozoites that migrate into the bloodstream 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.
E. histolytica may also migrate to other organs (lung, spleen, skin and brain).

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16
Q

Liver abscess is more common amongst women. True or False?

A

False. 10 times more common in men.

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17
Q

What are the mechanisms of pathogenesis for E. histolytica?

A

Outcome is influenced by genetics (host and parasite) and environmental factors (malnutrition).
Tissue destruction: the parasite kill and ingest host cells in a contact-dependent manner (activation of apoptosis).
Mechanism of tissue destruction: amoebapores, 50 cysteine proteases, inflammatory host immune response.

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18
Q

What are the methods used for diagnosis for intestinal diseases?

A

Stool examination for cysts and trophozoites.
Sigmoidoscopy (colon examination) to reveal ulcers.
Aspirates for trophozoite detection.

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19
Q

Diagnosis can be difficult. True or False?

A

True. This is because other parasites can look very similar to E. histolytica when seen under a microscope. Antigen detection kits can help distinguish from E. dispar.

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20
Q

What are the methods of diagnosis for extra-intestinal diseases?

A

‘Serology’ which is useful but antibodies could be the memory of a past infection.
Non-invasive Imaging (detection of hepatic abscesses) using ultrasounds, X-ray and magnetic resonance imaging (MRI).

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21
Q

Name two drugs used for treatment.

A

Metronidazole and iodoquinol.

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22
Q

Give a few examples of preventative measures.

A

Education to sexual partners, travellers as well as adequate sanitation and filtration of water supplies.

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23
Q

Where can Giardia lamblia be found?

A

Worldwide distribution found in streams, lakes, contaminated water, food and vegetables, unusual sexual practices spread the infection.

24
Q

What is the site of colonisation?

A

Upper region of the small intestine.

25
Q

It is non-invasive. True or False?

A

True.

26
Q

What is the mode of transmission?

A

Oral-fecal route.

27
Q

Describe their life cycle.

A
  1. Excretion of cysts by host 1.
  2. Ingestion of cysts by host 2.
  3. Excystation in the duodenum involving flagellar activity, breaking of the cyst wall, release of trophozoite and attachment to intestinal epithelium.
  4. Asexual replication of trophozoites.
    2 nuclei becomes 4.
  5. Encystation involving the trophozoite rounding up, detachment from the intestinal epithelium and secretion of the cyst wall.
28
Q

G. lamblia is asymptomatic in 30% of infected carriers. True or False?

A

False. 50% asymptomatic.

29
Q

What is the onset of the disease?

A

1-4 weeks.

30
Q

What are the symptoms?

A

Nausea, foul smelling watery diarrhoea, abdominal cramps, foul sulfuric belching.

31
Q

What is the mechanism of pathogenesis?

A

Irritation of intestinal epithelium.
Inflammation.
Lactase deficiency.

32
Q

What are the methods for diagnosis?

A

Stool examination for cysts and trophozoites.
Biopsy of small intestine.
Duodenal aspiration.
Immunological tests including ELISA and indirect immunofluorescent staining.

33
Q

Name a drug used for treatment.

A

Metronidazole effectively clears the parasite.

34
Q

List some preventative measures.

A

Avoidance of contaminated water and food. Boiled water is appropriate. Proper sanitation, food handling and personal hygiene is also required.

35
Q

Describe the structure of Trichomonas vaginalis.

A

Four flagella and short undulating membrane.

36
Q

It exists only as a trophozoite in urethras and vaginas of women and prostate glands in men. True or False?

A

True.

37
Q

What is the mode of transmission?

A

Veneral route (sexual intercourse) but can also be passed on through mothers infected birth canal.

38
Q

List some symptoms.

A

Itching, burning, painful urination as well as watery vaginal discharge.

39
Q

Men are asymptomatic carriers serving as a reservoir for infections in women. True or False?

A

True. However, men occasionally experience urethritis, prostatitis, and other UT problems.

40
Q

What are the methods for diagnosis?

A

Microscopic examination of vaginal and urethral discharge for trophozoites.
PCR probes and serological tests.
Monoclonal fluorescent staining.

41
Q

Name a drug used for treatment.

A

Metronidazole. Highly effective but both partners should be treated to avoid reinfection.

42
Q

What are some of the preventative measures?

A

Personal hygiene, using condoms and avoidance of shared toilet articles and clothing.

43
Q

Describe the structure of Balantidium coli.

A

Trophozoite is covered with hair-like cilia and has a characteristic funnel like cytosome (used to ingest cells), a large and small nucleus involved in reproduction, food vacuoles, and two contractile vacuoles.

44
Q

What is the epidemiology?

A

Worldwide distribution. Swine and monkeys are most important reservoirs. Parasite can be passed on through contaminated food.

45
Q

What is the mode of transmission?

A

Faecal-oral route.

46
Q

What are the clinical syndromes?

A

Asymptomatic.

Symptomatic: abdominal pain, nausea, anorexia, watery stools with blood and pus.

47
Q

Name two drugs used for treatment.

A

Tetracycline and metronidazole.

48
Q

Give a brief description of their life cycle.

A

Life cycle involves ingestion of infectious cysts, excystation and invasion of trophozoites into the mucosal lining of large intestine, cecum and terminal ileum.

49
Q

Why are amoebae found in environments that have a low oxygen pressure?

A

Because the Protozoa are killed by ambient oxygen concentrations.

50
Q

Name two vectors for the transmission of E. histolytica.

A

Flies and cockroaches.

51
Q

E. histolytica is actually two distinct species. Name the non-pathogenic species.

A

Most asymptomatic individuals are infected with the non-invasive E. dispar.

52
Q

Why is using microscopic examination of stool for detection of E. histolytica insensitive?

A

Because the Protozoa are not usually distributed homogeneously in the specimen and the parasites are not concentrated in the stool.

53
Q

Diseases produced by flagellates (G. lamblia and T. vaginalis) are primarily the result of mechanical irritation and inflammation. True or False?

A

True.

54
Q

The cyst stage for G. lamblia is resistant to chlorine concentrations. True or False? And how should this be overcome?

A

True. Adequate water treatment should include chemicals with filtration.

55
Q

Recovery from G. lamblia generally occurs after 10-14 days, although a more chronic disease with multiple relapses may develop. This poses a problem for some patients, why?

A

Because they are immunoglobulin A deficient. (IgA includes antibodies found in external bodily secretions such as the salvia, tears and sweat.)

56
Q

Why should a physician never accept the results of a single negative stool specimen?

A

Because G. lamblia can be detected in stool on a given day and none detected the next day.

57
Q

How is disease produced by B. coli similar to amebiasis?

A

Because the organisms elaborate proteolytic and cytotoxic substances that mediate tissue invasion and intestinal ulceration.

Medical Microbiology (8 decks)

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