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Micro I > GI Protozoans > Flashcards

GI Protozoans Flashcards

(51 cards)

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1
Q

How will infection with Giardia lamblia (aka G. intestinalis) present clinically?

A

Intermittent episodes of water diarrhea, NO BLOOD

May be asx or acute/ chronic diarrheal illness

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2
Q

G. lamblia is what type of disease?

A

Zoonotic

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3
Q

What populations are more greatly affected by G. lamblia?

A

Children, and problematic in IMC (no ability to build antibodies)

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4
Q

What is the most commonly identified intestinal parasite in the wold?

A

G. lamblia

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5
Q

What are the 2 morphological stages of G. lamblia?

A

Trophozoite and cyst

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6
Q

What is the most important structural element of G. lamblia?

A

Flagellate

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7
Q

Which morphological stage of G. lamblia is identified by the presence of 4 nuclei and contributes to protection of the organism?

A

Cyst

1 cyst produces 2 trophozoite, each trophozoite has 2 nuclei

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8
Q

Which morphological stage of G. lamblia is identified as teardrop shape with a bi-lobed ventral adhesive disc with 2 nuclei?

A

Trophozoite

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9
Q

The trophozoite form of G. lamblia feeds on mucus tissues and has what effect on tissues/ RBCs?

A

Does not invade tissue or destroy RBCs

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10
Q

How does G. lamblia become infectious?

A

Ingestion of the cyst from contaminated food/ water

highly contagious!

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11
Q

How does G. lamblia transition between the trophozoite and cyst stages? (5 steps)

A
  1. Ingest cyst (infectious)
  2. Excystation in stomach = trophozoite
  3. Trophozoite divides in small bowel
  4. Trophozoites in large bowel encyst
  5. Cysts passed into environment
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12
Q

Where is infection with G. lamblia most common?

A 
Western states (Rocky Mountains) 
(contributes ~2.5 mill deaths in combo w malnutrition/ co-infection)
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13
Q

G. lamblia is an infectious disease (including as an STI). How many cysts are considered to be an infectious dose?

A

10-25 cysts, >25 cysts = 100% infection rate

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14
Q

How can infection with G. lamblia contribute to malnutrition?

A

Vitamin B12 deficiency

organism feeds on it

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15
Q

What are the virulence factors of G. lamblia? (2)

A
  1. Ventral disc implants (“sucker”)

2. Malabsorption of intestinal tissue

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16
Q

What is the gold standard for diagnosis of G. lamblia?

A

Microscopic visualization of cysts/ trophozoites in stool samples
(O&P = egg and parasite examination)

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17
Q

What may be necessary for diagnosis of G. lamblia due to the shedding of cysts?

A

Multiple stool samples

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18
Q

Why can serological tests be problematic for the identification of G. lamblia?

A

Antibodies can be carried for > 2 years

if antibodies present, you will always test positive

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19
Q

What is the prognosis of infection with G. lamblia?

A

Most pts asx, self-limited but re-infections possible (if you did not build protective antibodies)

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20
Q

How is infection with G. lamblia controlled?

A

Purified water, avoid fecal contamination

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21
Q

What pathogen is responsible for a protozoan illness that can result in colitis and liver abscess?

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A

Entamoeba histolytica

many species but only one associated with human disease

22
Q

What is the importance of E. dispar in relation to E. histolytica?

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A

Does not cause disease but gets in the way of identifying E. histolytica (commensal)

23
Q

What organism has a non-flagellated trophozoite form with 1 nucleus and an infectious cyst form with 4 nuclei?

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A

E. histolytica

24
Q

What does E. histolytica feed off that leads to an important clinical symptom?

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A

RBCs (use as nutritional source) = bloody stool

25
How does the life cycle of E. histolytica continue after the ingestion of cysts?
Become trophozoites and colonize the colon | Trophozoites do not survive well in environment
26
Once the trophozoite form of E. histolytica colonizes the mucosa of the colon, it may encyst and be passed in feces or invade what?
Invade intestinal mucosal barrier and gain access to the blood stream = dissemination
27
What is important about the epidemiology of E. histolytica? (3)
1. Tropical areas 2. Passed via contaminated water/ food 3. Reportable disease
28
Disease via E. histolytica can be initiated by a small number of cysts and has diverse manifestations. What clinical presentations are the most common?
Acute amoebic colitis/ bloody stools | Dysentery to extraintestinal manifestations
29
Amoeba of E. histolytica hydrolyze the intestinal lining which results in what?
Results in ulcers, R upper quadrant pain | large scale ulceration
30
What are the virulence factors of E. histolytica? (4)
1. Lectin (adhesion) 2. Phospholipases (disrupt host membranes) 3. Amoebapore (host cell lysis) 4. Cysteine proteases ("chew away" other proteins)
31
How is infection with E. histolytica diagnosed?
Trophozoites/ cysts in stool sample Radiology for extraintestinal disease (also ELISA or PCR)
32
How is infection via E. histolytica controlled?
Purify water (cysts resistant to chlorine), avoid fecal contamination
33
Although infection with Cryptosporidosis can be caused by multiple species, which species have humans as the only host?
Cryptosporidium hominis | C. parvum bovine and human hosts
34
What population is more commonly affected by Cryptosporidium and how are healthy individuals affected?
Children, self limiting diarrheal illness in healthy individuals
35
What organism has the following 2 morphological forms: oocytes and sporozoites?
Cryptosporidium
36
Which stage of Cryptosporidium is infectious and how does it multiply?
Oocytes = infectious, does not multiply outside of the host
37
The life cycle of Cryptosporidium involves binding to the receptors on small intestine epithelial cells followed by what?
Ingested into parasitophorous vacuole
38
Once Cryptosporidium organisms are inside the epithelial cells, the parasite undergoes sexual and asexual reproduction to form what?
Thin walled oocytes (asexual) = reinfection | Thick walled oocytes (sexual) = shed into environment
39
Identification of what on morphology is important to identify Cryptosporidium?
Parasitophorous vacuole
40
What is important about the epidemiology of Cryptosporidium?
Contaminated water, recreational water, pools (cysts resistant to chlorine)
41
When are the oocytes of Cryptosporidium infectious?
Immediately after excretion
42
What is the cardinal symptom of infection with Cryptosporidium?
Watery diarrhea | also pt severely wasted, ~2 weeks, common if IMC
43
How is infection via Cryptosporidium identified?
Isolation of oocytes in stool sample (acid-fast oocytes are round)
44
What is the causative agent of infection with Cyclosporiasis?
Cyclospora cayetanensis
45
How is Cyclospora cayetanensis transmitted?
Contaminated water and imported foods (esp fresh fruits and vegetables from Latin America)
46
When is Cyclospora cayetanensis infectious?
Not immediately, oocytes shed in feces and then MUST first sporulate/ survive in the environment
47
What are the oocytes of Cyclospora cayetanensis resistant to?
Chlorine
48
What is the most identifiable clinical presentation of infection with Cyclospora cayetanensis?
Explosive, non-bloody, watery diarrhea
49
How is infection with Cyclospora cayetanensis identified on microscopy?
Large oocyte identified in stool sample, acid fast postiive, autofluorescent oocyte (much larger than Cryptosporidium)
50
What GI protozoan is characterized by the following: Disease via ingestion of cysts from contaminated food/ water (from animal feces) Large central vacuole surrounded by nuclei
Blastocystis hominis
51
What GI protozoan is characterized by the following: Zoonotic (pigs), fecal matter Can result in gut perforation (but no blood in stool) Trophozoite and cyst forms contain MACROnucleus Cilia evident on trophozoite
Balantidium coli

Micro I (9 decks)

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