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Liz's Parasitology Course > Pathogenic Protozoa: Intestinal Parasites > Flashcards

Pathogenic Protozoa: Intestinal Parasites Flashcards

1
Q

Protozoa are unicellular ____

A

Eukaryotes

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2
Q

Do protozoa have cell walls? If not, what do they have?

A

NO! Cyst forms have a cyst wall

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3
Q

Three types of protozoan locomotion appendages

A
  • Cilia
  • Flagella
  • Pseudopodia
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4
Q

These are temporary, foot-like projections filled w/ cytoplasm in amoeboids; mediate “crawling” over surfaces

A

Psuedopodia

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5
Q

These are hairlike projections that typically cover the surface of ciliates; beat in waves that propels a cell

A

Cilia

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6
Q

These are flexible, whip-like projections localized to specific areas on flagellates; movement propels a cell

A

Flagella

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7
Q

Motile, feeding, and proliferative form of protozoa

A

Trophozoite (“troph”)

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8
Q

Most protozoa produce a ____ form in response to adverse environmental stimuli

A

Cyst

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9
Q

What is the purpose of the cyst form?

A

Cyst encases the troph w/in a thick shell to protect from harsh conditions

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10
Q

Process of forming a cyst

A

Encystation (enter)

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11
Q

Process of leaving a cyst

A

Excystation (exit)

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12
Q

For many pathogenic protozoa, what is the infectious form?

A

Cysts

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13
Q

In fecal concentrates, ____ are damaged and unrecognizable, ____ remain intact and are observable

A

Trophs; cysts

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14
Q

Three lab methods for detecting protozoa in stool specimens

A
  • Ag detection assays
  • Microscopic examination
  • Molecular methods
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15
Q

Which form of protozoa are found more in formed stool? Watery stool?

A
  • Formed: cysts

- Watery: trophs

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16
Q

Why should more than 1 fecal specimen be examined?

A

B/c of intermittent shedding of parasites in stool

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17
Q

How should stool be collected for detecting protozoa?

A

Three specimens over the period of 10 days

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18
Q

How long should you wait to preserve fecal specimens?

A

DON’T WAIT! Preserve immediately!

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19
Q

Disadvantages of Ag detection assays

A

Only for a limited number of organisms

- Common ones → Giardia, Cryptosporidium, Entamoeba

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20
Q

For microscopic examination of wet mounts of preserved feces, what are usually destroyed and what remains intact?

A

Trophs are destroyed, cysts remain

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21
Q

An important component of light microscopes used in parasitology labs

A

Ocular micrometer

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22
Q

When making wet mounts, you should make two different types of mounts on the same slide…what are they?

A

Saline and iodine mounts

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23
Q

Smears of preserved, concentrated stool are made on a slide. Many modern fixatives permit specimen adherence to the slide. How do you make this slide?

A

Use an applicator stick (up and down motion) to make thick and thin areas

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24
Q

Dried smears are usually stained w/ what?

A

Trichrome stain

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25
Q

Stained smears should be first examined on low power and then use the ____ objective

A

100x oil immersion objective (1000x total magnification)

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26
Q

Three other methods besides trichrome to stain smears?

A
  • Modified acid-fast stain (Cryptosporidium spp and coccida)
  • Modified safranin stain (Cyclospora cayetanensis)
  • Chromotrope R2/modified trichome (microsporidia)
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27
Q

Setback to molecular methods like the nucleic acid amplification test

A

Currently only available for detection of a limited number of intestinal protozoa

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28
Q

Enteric amoeba that lyses tissue

A

Entamoeba histolytica

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29
Q

Entamoeba histolytica

- Intestinal and extra-intestinal diseases

A
  • Amoebic dysentery
  • Amoebic colitis
  • Amoebic abscesses
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30
Q

Entamoeba histolytica

- Geographic distribution

A

Worldwide but has a higher incidence of infection in developing countries

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31
Q

Entamoeba histolytica

- What disease does it cause?

A

Amoebiasis

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32
Q

Entamoeba histolytica

- Who are the hosts?

A

Humans are the only hosts

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33
Q

Entamoeba histolytica

- Infectious form

A

Cysts

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34
Q

Entamoeba histolytica

- How are cysts transmitted?

A

Fecal-oral route

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35
Q

Entamoeba histolytica

- Common settings

A

?

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36
Q

Entamoeba histolytica

- Test of choice?

A

EIA - high sensitivity and specificity

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37
Q

Entamoeba histolytica

- Must be distinguished from ____ ____ and other protozoa and also must be distinguished from ____ ____!!!

A
  • Nonpathogenic amoebae

- Polymorphonuclear neutrophils

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38
Q

Entamoeba histolytica

- Size of cysts

A

12-15µm

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39
Q

Entamoeba histolytica

- Size of trophs

A

15-20µm

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40
Q

Entamoeba histolytica

- Is morphologically indistinguishable from what two organisms?

A
  • Entamoeba dispar

- Entamoeba moshkovskii

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41
Q

How do you differentiate Entamoeba histolytica from Entamoeba hartmanni?

A

Exactly the same just much smaller

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42
Q

How do you differentiate Entamoeba histolytica trophs from Entamoeba coli trophs?

A
  • E. histolytica: Karyosome in the center, is compact, peripheral chromatin is smoothly and evenly arranged “clean” cytoplasm
  • E. coli: karyosome is off-center (messy looking), spread out, peripheral chromatin is clumpy and unevenly arranged in “dirty” cytoplasm
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43
Q

How do you differentiate Entamoeba histolytica cysts from Entamoeba coli cysts?

A
  • E. histolytica: Nuclei usually paired on each side in 2 different focal planes, chromatic bodies with rounded ends
  • E. coli: Nuclei scattered randomly throughout cyst in many different focal planes, chromatoid bodies with splintered ends
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44
Q

Only known pathogenic ciliate of humans

A

Balantidium coli

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45
Q

Balantidium coli

- Geographic distribution

A

Worldwide

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46
Q

Balantidium coli

- What disease does it cause?

A

Balantidiasis

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47
Q

Balantidium coli

- What are the hosts?

A
  • PIGS (infections are more common in areas where pigs are raised)
  • Rodents
  • Primates
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48
Q

Balantidium coli

- Infectious form

A

Cyst

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49
Q

Balantidium coli

- Symptoms

A
  • Most cases are asymptomatic
  • Persistent diarrhea, dysentery, and abdominal pain
  • Weight loss
  • Can be severe in debilitated hosts
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50
Q

Balantidium coli

- What do we detect in the stool?

A

Trophs, not cysts

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51
Q

Balantidium coli

- Appearance of trophs

A
  • CILIATED
  • Big cell (40-200µm)
  • Bean-shaped macronucleus
  • Cytosome at narrower end
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52
Q

What is one of the most common intestinal parasites in the world?

A

Giardia intestinalis

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53
Q

Giardia intestinalis

- Other names

A
  • G. lamblia

- G. duodenalis

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54
Q

Giardia intestinalis

- What disease does it cause?

A

Giardiasis

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55
Q

Giardia intestinalis

- Geographic distribution

A

Worldwide but is more prevalent in warm climates and in children (day care)

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56
Q

Giardia intestinalis

- How is it transmitted?

A
  • Fecal-oral route
  • Food
  • Person-to-person
  • Fomites (inanimate objects)
  • Waterborne (most big outbreaks)
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57
Q

Giardia intestinalis

- Who are the hosts?

A

Humans and animals

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58
Q

Giardia intestinalis

- Common settings

A
  • Children in daycares and their close contacts

- Campers and backpackers (drinking contaminated water)

59
Q

Giardia intestinalis

- Infectious form

A

Cyst

60
Q

Giardia intestinalis

- Symptoms

A
  • Diarrhea, bloating, nausea, vomiting
  • Foul-smelling feces and flatulence (purple burps) due to waste products from G. intestinalis
  • Weight loss
  • Dehydration
61
Q

Giardia intestinalis

- Test of choice?

A

EIA - high sensitivity and specificity

62
Q

Giardia intestinalis

- How often are the parasites in the feces?

A

Varies from day to day (get 3 samples over a period of 10 days)

63
Q

Giardia intestinalis

- What motility should you look for in a fresh specimen?

A

“Falling leaf” motility

64
Q

Giardia intestinalis

- Troph appearance

A
  • External flagella, pear shape
  • Two nuclei (look like eyes) sucking disc, median bodies
  • 12µm
65
Q

Giardia intestinalis

- Cyst appearance

A
  • Small oval cyst
  • 2-4 nuclei at one end
  • Median bodies across middle, fibrils down the center
  • 10µm
66
Q

What is “fragile, enteric ‘amoeba’ w/ 2 nuclei” but is NOT an amoeba?

A

Dientamoeba fragilis

67
Q

Dientamoeba fragilis

- What disease does it cause?

A

Dientameobiasis

68
Q

Dientamoeba fragilis

- Geographic distribution

A

Worldwide

69
Q

Dientamoeba fragilis

- How is it transmitted?

A

Presumably fecal-oral route

70
Q

Dientamoeba fragilis

- Infectious form

A

Troph

71
Q

Dientamoeba fragilis

- Appearance of troph

A
  • WITHOUT external flagella
  • Irregular rounded shape
  • 2 nuclei
  • “Dirty” cytoplasm
  • 4-12µm
72
Q

Dientamoeba fragilis

- Appearance of cyst

A

NO CYST FORM

73
Q

Another name for pathogenic apicomplexa

A

Sporozoa

74
Q

How do pathogenic apicomplex infect?

A

Invade and multiply w/in epithelial cells

75
Q

Second most commonly diagnosed intestinal parasites in the U.S.?

A

Cryptosporidium spp

76
Q

Cryptosporidium spp

- Geographic distribution

A

Worldwide

77
Q

Cryptosporidium spp

- Habitat

A
  • Waterborne → big outbreaks in Milwaukee, WI
78
Q

Cryptosporidium spp

- Host

A

Humans and many vertebrate animals

79
Q

Cryptosporidium spp

- How is it transmitted?

A
  • Fecal-oral route
  • Food
  • Person-to-person
80
Q

Cryptosporidium spp

- Four common settings

A
  • Municipal water supply-associated outbreaks (Milwaukee)
  • Children in daycare
  • People in contact w/ farm animals
  • People w/ AIDS who have unrelenting, water diarrhea
81
Q

Cryptosporidium spp

- Infectious form

A

Oocyst

82
Q

Cryptosporidium spp

- Significant symptom

A

Profuse watery diarrhea (up to 10L/day)

83
Q

Cryptosporidium spp

- Test of choice

A

EIA - highest sensitivity and specificity

84
Q

Cryptosporidium spp

- What color do they stain in a modified-Kinyoun stain?

A

Red b/c they’re ACID-FAST

85
Q

Cryptosporidium spp

- Oocyst appearance

A
  • 4-6µm

- 4 crescent-shaped sporozoite present w/ them

86
Q

“Circular sporocytes”; a coccidian

A

Cyclospora cayetanensis

87
Q

Cyclospora cayetanensis

- Geographic distribution

A
  • Most common in tropical and subtropical regions, exported to other regions of the planet
  • No consistent seasonal pattern of occurrence in endemic areas
88
Q

Cyclospora cayetanensis

- What disease does it cause?

A

Cyclosporiasis

89
Q

Cyclospora cayetanensis

- Who are the hosts?

A

Humans

90
Q

Cyclospora cayetanensis

- How is it transmitted?

A

Fecal-oral route mainly through food and water, NOT DIRECT CONTACT
- Raspberries, basil, cilantro, other fresh produce

91
Q

Cyclospora cayetanensis

- Infectious form

A

Sporulated oocyst

92
Q

Cyclospora cayetanensis

- Highlights of the life cycle

A
  • People ingest sporulated (mature) oocysts
  • Unsporulated oocysts (in fresh feces) are not infectious
  • Oocysts must mature in the environment for several days to weeks before they’re infectious
93
Q

Cyclospora cayetanensis

- Symptoms

A
  • Water diarrhea can be severe
  • Weight loss, abdominal pain, nausea, vomiting, etc.
  • Untreated infections can last a while (10-12 weeks)
  • Dehydration, which is sometimes severe
  • Relapse is not uncommon if initially untreated
94
Q

Cyclospora cayetanensis

- Can be shed ____ so get more than one stool specimen

A

Intermittent

95
Q

Cyclospora cayetanensis

- Wet mounts are useless, but oocysts are ____ and ____ when excited w/ certain wavelengths of light

A
  • Acid-fast

- Autofluoresce

96
Q

Cyclospora cayetanensis

- Size of unsporulated oocysts

A

8-10µm → bigger than Cryptosporidium (4-6µm)

97
Q

Cyclospora cayetanensis

- Oocyst appearance

A

Small coccidian parasite, round, acid fast (can have ghost cells in af); stain red; no sports, wrinkled and crinkled

98
Q

Cystoisospora belli

- Causes what disease?

A

Cystoisosporiasis

99
Q

Cystoisospora belli

- Geographic distribution

A

Worldwide, especially in tropical and subtropical regions

100
Q

Least common of the coccidia

A

Cystoisospora belli

101
Q

Cystoisospora belli

- Who is the host?

A

Immunocompromised patients, especially those w/ AIDS

102
Q

Cystoisospora belli

- How is it transmitted?

A

Fecal-oral route

103
Q

Cystoisospora belli

- Significant symptom

A

Eosinophilia

104
Q

Cystoisospora belli

- Infectious form

A

Mature oocyst

105
Q

Cystoisospora belli

- It will ____ when excited w/ UV light

A

Autofluoresce

106
Q

Cystoisospora belli

- Oocyst appearance

A

Large, ellipsoidal, contains 1 sporoblast (pig in a blanket)

107
Q

Sarcocystis hominis and suihominis

- Causes what disease?

A

Sarcocystosis

108
Q

Sarcocystis hominis and suihominis

- Geographic distribution

A

Worldwide; more common where livestock are raised

109
Q

Sarcocystis hominis and suihominis

- Who are the hosts?

A

Humans are a dead-end host

110
Q

Sarcocystis hominis and suihominis

- How is it transmitted?

A

By consumption of undercooked/contaminated meat

111
Q

Sarcocystis hominis and suihominis

- Infectious form

A

??Oocyst??

112
Q

Sarcocystis hominis and suihominis

- Symptoms

A
  • Often asymptomatic but occassionally a mild fever, diarrhea, chills, and vomiting
113
Q

Sarcocystis hominis and suihominis

- Oocyst appearance

A

Paired (shrink-wrapped) ovals

114
Q

Sarcocystis hominis and suihominis

- Do these organisms autofluoresce?

A

YES

115
Q

These are opportunistic, obligate, intracellular pathogens

A

Microsporidia

116
Q

If microsporidia aren’t protozoa, what are they?

A

Fungi

117
Q

Two types of microsporidia that are common human gastrointestinal pathogens

A
  • Enterocytozoon bieneus

- Encephalitozoon intestinalis

118
Q

Microsporidia

- Geographic distribution

A

Worldwide

119
Q

Microsporidia

- Who are the hosts?

A

Severely immunocompromised AIDS patients

120
Q

Microsporidia

- How is it transmitted?

A

Consumption of contaminated food and water, contaminated fomites, and possibly airborne?

121
Q

Microsporidia

- Infectious form

A

Spore

122
Q

Microsporidia

- Symptoms

A

Diarrhea

123
Q

Microsporidia

- What stains should be used for the microscopic exam?

A
  • Chromotrope 2R

- Ryan’s modified-trichrome stain

124
Q

Microsporidia

  • Gold test
  • Test of choice?
A
  • Gold test: transmission electron microscopy

- Choice: immunofluorescence

125
Q

Encephalitozoon spp

- Appearance

A

Gram stain → resembles large GPRs

126
Q

Blastocystis spp

- Infectious form

A

Cyst (cyst released also)

127
Q

Blastocystis spp

- Role in disease

A

Debateable role (sometimes no symptoms, other times diarrhea etc.)

128
Q

Chilomastix mesnili

- Pathogenic or nonpathogenic?

A

Nonpathogenic protozoa

129
Q

Chilomastix mesnili

- Appearance of trophs

A

External flagella, lopsided shortened pear shape, one nucleus, cytosome looks like mouth (smiling fish)

130
Q

Chilomastix mesnili

- Appearance of cysts

A

Small lemon shape cyst, one nucleus, cytosine small, looks like a shephard’s crook

131
Q

Endolimax nana

- Pathogenic or nonpathogenic?

A

Nonpathogenic

132
Q

Endolimax nana

- Appearance of troph

A

W/o peripheral nuclear chromatin, large irregular karyosome (nana with dilated pupil)

133
Q

Endolimax nana

- Appearance of cyst

A

four nuclei (nana has 4 eyes), short oval shape, small nuclei surrounded by clear space

134
Q

Enteromonas hominis

- Pathogenic or nonpathogenic?

A

Nonpathogenic

135
Q

Enteromonas hominis

- Appearance

A

?

136
Q

Iodamoeba butschlii

- Pathogenic or nonpathogenic?

A

Nonpathogenic

137
Q

Iodamoeba butschlii:

  • Cyst appearance
  • Troph appearance
A

Cyst: large vacuole in the cyst

138
Q

Pentatrichomonas hominis

- Pathogenic or nonpathogenic?

A

Nonpathogenic

139
Q

Pentatrichomonas hominis

- Appearance of trophs

A

External flagella, lopsided pear shape, one nucleus, undulating membrane and axostyle (fish with spike)

140
Q

Advantages of Ag detection methods

A

High sensitivity and specificity

141
Q

Disadvantages of microscopic examination methods

A
  • Objective analyses b/w techs
  • Need baseline knowledge to ID
  • Requires time to perform analyses
142
Q

Advantages of microscopic examination methods

A
  • Microscopes relatively inexpensive
  • Can be purchase cordless
  • Easy to train on how to use
  • Don’t “expire”
143
Q

Advantages of molecular methods

A
  • Detectable parasites can be ID’d by the same assay as bacteria
  • High sensitivity and specificity
144
Q

Disadvantages of molecular methods

A
  • Detrct either dead or alive parasites

- $$$

Liz's Parasitology Course (8 decks)

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