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Microbiology COPY > Exam #5: Parasitic Infections of the GI Tract > Flashcards

Exam #5: Parasitic Infections of the GI Tract Flashcards

1
Q

What parasitic infection of the GI tract is most commonly diagnosed in the US?

A

Giardia lamblia (duodenalis)

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2
Q

What are the four classes of protozoa? How are they classified?

A 
Ameba= pseudopodia
Flagellates= flagella 
Sporozoans= gliding ("tank tread") 
Cilites= cilia
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3
Q

How do most protozoa reproduce?

A

Asexually by binary fission

Important because you only need to be infected by one parasite & then there is exponential growth; also, v. low infectious dose

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4
Q

What is the cyst form of a protozoa?

A

An environmentally protected form of a parasite

  • Resistant to UV light
  • Resistant to drying out
  • Allows for passage through the acidic pH of the stomach
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5
Q

What is Amebiasis? What causes it? What is the typical presentation of Amebiasis?

A

Amebiasis is the disease caused by amebae infection. The organism that causes amebiasis is Entamoeba histolytica.

Typical presentation is diarrhea/ dysentery.

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6
Q

What are the two forms of Entamoeba histolytica?

A

Trophozoic= unstable in environment & can be killed by acid pH of stoamch

Cyst= stable/ resistant (this is the form that is transmissible & found in the environment)

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7
Q

Describe the lifecycle of Entamoeba histolytica.

A
  • Infected individual excretes cyst & trophozoic forms of Entamoeba histolytica
  • Cyst is transmitted from infected individual to environment, and then to new host
  • In host it “excysts”
  • Invades the wall of the colon and multiples

Can cause intestinal disease or extraintestinal disease (liver abscess)

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8
Q

Which form of Entamoeba histolytica is more infectious in terms of symptoms?

A

Asymptomatic infection= mainly cyst

vs.

Symptomatic infection= trophozite that is readily destroyed in the environment.

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9
Q

What are the symptoms of Entamoeba histolytica infection?

A

Dysentery (bloody & mucousy diarrhea)

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10
Q

What is the difference between Entamoeba histolytica dysentery & bacterial?

A

Fever–no fever in Entamoeba histolytica

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11
Q

What type of lesion does Entamoeba histolytica cause in the intestinal wall?

A

“Flask-shaped” lesion

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12
Q

What symptoms can be caused by spread of Entamoeba histolytica to the bloodstream?

A

Fever
Liver abscess (abdominal pain)
Leukocytosis/ sepsis

The amoeba basically perforates the bowel & intestinal bacteria are transmitted through the blood to other areas on the body

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13
Q

How is Entamoeba histolytica diagnosed?

A
  • Stool examination (ova & parasite ordered)
  • Antigen detection
  • Biopsy or Serology for extra-intestinal
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14
Q

How is Entamoeba histolytica infection prevented? How is it treated?

A

Sanitation & hygiene prevent disease

Treatment is Metronidazole (Flagyl)

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15
Q

What is the morphological features that distinguishes Entamoeba histolytica?

A

4 nuclei

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16
Q

What is Giardiasis? What organism causes it?

A

Giardiasis is one of the most common diseases caused by intestinal protozoa, and specifically, it is caused by a flagellated protozoa, Giardia lamblia. Characteristics of Giardia lamblia include:

  • Flagellated
  • 2x nuclei
  • Sucker that makes it stick to the intestinal epithelium

Most common parasitic infection in the US

17
Q

Describe the lifecycle of Giardia lamblia.

A
  • Ingestion of cyst
  • Excyst
  • Multiplies by binary fission
  • Trophozites are NOT invasive, but can absorb nutrients from the bowel

Does NOT invade–>just get diarrhea

18
Q

When is Giardia lamblia commonly seen?

A

The cyst form of Giardia Lamblia is relatively resistant to standard water treatment procedures; thus, US outbreak are commonly associated with contaminated water.

Also, infection is more common in the young (<10)

*Note that peak transmission is in the summer months, & infection is most commonly acquired by drinking untreated surface water while hiking or camping

19
Q

What are the symptoms of Giardia lamblia?

A

Acute disease leading to sudden:

  • Abdominal cramping
  • Malabsorption that leads to:
  • Greasy
  • Foul-smelling
  • Floating stool

*NO blood & NO fever
Note that chronic disease can lead to malnutrition

20
Q

How do the symptomatic & asymptomatic invidiauls compare with Giardia lamblia infection?

A

Symptomatic= more trophozites

Asymptomatic= cyst

21
Q

How is Giardia lamblia diagnosed?

A

Observing cysts in stool
Observing trophozites in diarrhea
Fecal antigen detection (commercial assay)

22
Q

What is the only ciliated parasite that infects humans? What does it cause?

A

Balantidium coli is the only ciliated parasite to infect humans, and infection causes Balantidiasis.

23
Q

Describe the lifecycle of Balantidium coli.

A

Basically the same as the others.

  • Cyst form is ingested
  • Excystation occurs in small intestine
  • Trophozites can colonize the large intestine, or invade the walls of the colon
24
Q

What are the symptoms caused by Balantidium coli infection? What is it similar to? How do you tell the difference?

A
  • Can lead to dysentery diarrhea
  • Presentation is identical to Entamoeba hystilica i.e. amebic dysentery; however, as the primary host is pigs, Balatidiasis is more commonly associated with those that work with pigs
25
Q

What is Cryptosporidiosis? What causes it?

A

Cryptosporidosis is the disease caused by sporozoan infection, specifically, Cryptosporidium parvum.

26
Q

Describe the lifecycle of Cryptosporidium parvum.

A

Sexual & asexual reproduction

  • Unlike the others
  • Ingest oocyst (cyst produced by sexual reproduction) that excysts in the small intestine, releasing sprozoites
  • Sporozites penetrate and infect intestinal epithelial cells, where they differentiate into trophozoites
27
Q

How does Cryptosporidium parvum stain?

A

Modified acid fast staining protocol detects fresh oocysts in stool samples

*note that it was the development of this staining protocol that led to the realization that this was much more prevalent than originally thought

28
Q

What is a reservoir of Cryptosporidium parvum?

A

Cows/ livestock

*This is the only parasite so far that has a true reservoir so far

29
Q

What is the connection between Cryptosproidium and AIDS?

A

15-20% of AIDS patients with diarrhea have Cryptosporidium positive stool. Because of the prevalence of the disease, prophylaxis has become routine.

30
Q

What are the symptoms of Cryptosporidium parvum infection?

A

Profuse watery diarrhea
Cramping
Fatigue
Weight loss

NO blood

*Note that generally this is self-limiting, but in the severely immunosuppressed it can lead to severe dehydration & death

31
Q

What is Isospora belli? What does it cause?

A

Sporozoan/ cocyst based disease that is increasingly diagnosed in immunosuppressed individuals i.e. the second most common cause of chronic diarrhea in AIDS patients (to Cryptosporidium)

32
Q

What are the symptoms of Isospora belli in AIDS patients?

A 
Watery diarrhea
Malabsorption 
Weight loss 
Electolyte imbalance 
Death
33
Q

What is Cyclospora? What is it associated with?

A

Cyclospora cayetanesis is the causative agent of Cyclosporiasis, another sporozoan caused GI disease. Infection has been associated with contaminated water & contaminated raspberries imported from Guatemala.

34
Q

What are the symptoms of Cyclospora?

A

Profuse watery diarrhea
Cramping
Fatigue
Weight loss

*Generally more severe & of longer duration in AIDS patients

35
Q

How is Cyclospora diagnosed?

A
  • Pink staining oocysts that look like Cyrptosporidium (with modified acid fast stain
  • However, Cyclospora oocysts FLOURESCENT under UV light

*Note that cryptosporidium parva does NOT flouresce under UV light

36
Q

What is microsporidiosis? What is it caused by?

A

Microsporidosis is an intestinal disease caused by Microsporidia.

37
Q

What does microsporidia cause?

A
  • Debilitating diarrhea
  • Extra-intestinal i.e. disseminated disease e.g. to the kidney, lung, and eye.
  • Note that keratoconjuncitivits–eye infection–is an early indicator of dissemination in immunosuppressed patients

Microbiology COPY (49 decks)

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