Pathogenic Protozoa: Intestinal Parasites Flashcards
(144 cards)
1
Q
Protozoa are unicellular ____
A
Eukaryotes
2
Q
Do protozoa have cell walls? If not, what do they have?
A
NO! Cyst forms have a cyst wall
3
Q
Three types of protozoan locomotion appendages
A
- Cilia
- Flagella
- Pseudopodia
4
Q
These are temporary, foot-like projections filled w/ cytoplasm in amoeboids; mediate “crawling” over surfaces
A
Psuedopodia
5
Q
These are hairlike projections that typically cover the surface of ciliates; beat in waves that propels a cell
A
Cilia
6
Q
These are flexible, whip-like projections localized to specific areas on flagellates; movement propels a cell
A
Flagella
7
Q
Motile, feeding, and proliferative form of protozoa
A
Trophozoite (“troph”)
8
Q
Most protozoa produce a ____ form in response to adverse environmental stimuli
A
Cyst
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
10
Q
Process of forming a cyst
A
Encystation (enter)
11
Q
Process of leaving a cyst
A
Excystation (exit)
12
Q
For many pathogenic protozoa, what is the infectious form?
A
Cysts
13
Q
In fecal concentrates, ____ are damaged and unrecognizable, ____ remain intact and are observable
A
Trophs; cysts
14
Q
Three lab methods for detecting protozoa in stool specimens
A
- Ag detection assays
- Microscopic examination
- Molecular methods
15
Q
Which form of protozoa are found more in formed stool? Watery stool?
A
- Formed: cysts
- Watery: trophs
16
Q
Why should more than 1 fecal specimen be examined?
A
B/c of intermittent shedding of parasites in stool
17
Q
How should stool be collected for detecting protozoa?
A
Three specimens over the period of 10 days
18
Q
How long should you wait to preserve fecal specimens?
A
DON’T WAIT! Preserve immediately!
19
Q
Disadvantages of Ag detection assays
A
Only for a limited number of organisms
- Common ones → Giardia, Cryptosporidium, Entamoeba
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
21
Q
An important component of light microscopes used in parasitology labs
A
Ocular micrometer
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
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
24
Q
Dried smears are usually stained w/ what?
A
Trichrome stain
25
Stained smears should be first examined on low power and then use the ____ objective
100x oil immersion objective (1000x total magnification)
26
Three other methods besides trichrome to stain smears?
- Modified acid-fast stain (Cryptosporidium spp and coccida)
- Modified safranin stain (Cyclospora cayetanensis)
- Chromotrope R2/modified trichome (microsporidia)
27
Setback to molecular methods like the nucleic acid amplification test
Currently only available for detection of a limited number of intestinal protozoa
28
Enteric amoeba that lyses tissue
Entamoeba histolytica
29
Entamoeba histolytica
| - Intestinal and extra-intestinal diseases
- Amoebic dysentery
- Amoebic colitis
- Amoebic abscesses
30
Entamoeba histolytica
| - Geographic distribution
Worldwide but has a higher incidence of infection in developing countries
31
Entamoeba histolytica
| - What disease does it cause?
Amoebiasis
32
Entamoeba histolytica
| - Who are the hosts?
Humans are the only hosts
33
Entamoeba histolytica
| - Infectious form
Cysts
34
Entamoeba histolytica
| - How are cysts transmitted?
Fecal-oral route
35
Entamoeba histolytica
| - Common settings
?
36
Entamoeba histolytica
| - Test of choice?
EIA - high sensitivity and specificity
37
Entamoeba histolytica
| - Must be distinguished from ____ ____ and other protozoa and also must be distinguished from ____ ____!!!
- Nonpathogenic amoebae
| - Polymorphonuclear neutrophils
38
Entamoeba histolytica
| - Size of cysts
12-15µm
39
Entamoeba histolytica
| - Size of trophs
15-20µm
40
Entamoeba histolytica
| - Is morphologically indistinguishable from what two organisms?
- Entamoeba dispar
| - Entamoeba moshkovskii
41
How do you differentiate Entamoeba histolytica from Entamoeba hartmanni?
Exactly the same just much smaller
42
How do you differentiate Entamoeba histolytica trophs from Entamoeba coli trophs?
- 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
43
How do you differentiate Entamoeba histolytica cysts from Entamoeba coli cysts?
- 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
44
Only known pathogenic ciliate of humans
Balantidium coli
45
Balantidium coli
| - Geographic distribution
Worldwide
46
Balantidium coli
| - What disease does it cause?
Balantidiasis
47
Balantidium coli
| - What are the hosts?
- PIGS (infections are more common in areas where pigs are raised)
- Rodents
- Primates
48
Balantidium coli
| - Infectious form
Cyst
49
Balantidium coli
| - Symptoms
- Most cases are asymptomatic
- Persistent diarrhea, dysentery, and abdominal pain
- Weight loss
- Can be severe in debilitated hosts
50
Balantidium coli
| - What do we detect in the stool?
Trophs, not cysts
51
Balantidium coli
| - Appearance of trophs
- CILIATED
- Big cell (40-200µm)
- Bean-shaped macronucleus
- Cytosome at narrower end
52
What is one of the most common intestinal parasites in the world?
Giardia intestinalis
53
Giardia intestinalis
| - Other names
- G. lamblia
| - G. duodenalis
54
Giardia intestinalis
| - What disease does it cause?
Giardiasis
55
Giardia intestinalis
| - Geographic distribution
Worldwide but is more prevalent in warm climates and in children (day care)
56
Giardia intestinalis
| - How is it transmitted?
- Fecal-oral route
- Food
- Person-to-person
- Fomites (inanimate objects)
- Waterborne (most big outbreaks)
57
Giardia intestinalis
| - Who are the hosts?
Humans and animals
58
Giardia intestinalis
| - Common settings
- Children in daycares and their close contacts
| - Campers and backpackers (drinking contaminated water)
59
Giardia intestinalis
| - Infectious form
Cyst
60
Giardia intestinalis
| - Symptoms
- Diarrhea, bloating, nausea, vomiting
- Foul-smelling feces and flatulence (purple burps) due to waste products from G. intestinalis
- Weight loss
- Dehydration
61
Giardia intestinalis
| - Test of choice?
EIA - high sensitivity and specificity
62
Giardia intestinalis
| - How often are the parasites in the feces?
Varies from day to day (get 3 samples over a period of 10 days)
63
Giardia intestinalis
| - What motility should you look for in a fresh specimen?
"Falling leaf" motility
64
Giardia intestinalis
| - Troph appearance
- External flagella, pear shape
- Two nuclei (look like eyes) sucking disc, median bodies
- 12µm
65
Giardia intestinalis
| - Cyst appearance
- Small oval cyst
- 2-4 nuclei at one end
- Median bodies across middle, fibrils down the center
- 10µm
66
What is "fragile, enteric 'amoeba' w/ 2 nuclei" but is NOT an amoeba?
Dientamoeba fragilis
67
Dientamoeba fragilis
| - What disease does it cause?
Dientameobiasis
68
Dientamoeba fragilis
| - Geographic distribution
Worldwide
69
Dientamoeba fragilis
| - How is it transmitted?
Presumably fecal-oral route
70
Dientamoeba fragilis
| - Infectious form
Troph
71
Dientamoeba fragilis
| - Appearance of troph
- WITHOUT external flagella
- Irregular rounded shape
- 2 nuclei
- "Dirty" cytoplasm
- 4-12µm
72
Dientamoeba fragilis
| - Appearance of cyst
NO CYST FORM
73
Another name for pathogenic apicomplexa
Sporozoa
74
How do pathogenic apicomplex infect?
Invade and multiply w/in epithelial cells
75
Second most commonly diagnosed intestinal parasites in the U.S.?
Cryptosporidium spp
76
Cryptosporidium spp
| - Geographic distribution
Worldwide
77
Cryptosporidium spp
| - Habitat
- Waterborne → big outbreaks in Milwaukee, WI
78
Cryptosporidium spp
| - Host
Humans and many vertebrate animals
79
Cryptosporidium spp
| - How is it transmitted?
- Fecal-oral route
- Food
- Person-to-person
80
Cryptosporidium spp
| - Four common settings
- Municipal water supply-associated outbreaks (Milwaukee)
- Children in daycare
- People in contact w/ farm animals
- People w/ AIDS who have unrelenting, water diarrhea
81
Cryptosporidium spp
| - Infectious form
Oocyst
82
Cryptosporidium spp
| - Significant symptom
Profuse watery diarrhea (up to 10L/day)
83
Cryptosporidium spp
| - Test of choice
EIA - highest sensitivity and specificity
84
Cryptosporidium spp
| - What color do they stain in a modified-Kinyoun stain?
Red b/c they're ACID-FAST
85
Cryptosporidium spp
| - Oocyst appearance
- 4-6µm
| - 4 crescent-shaped sporozoite present w/ them
86
"Circular sporocytes"; a coccidian
Cyclospora cayetanensis
87
Cyclospora cayetanensis
| - Geographic distribution
- Most common in tropical and subtropical regions, exported to other regions of the planet
- No consistent seasonal pattern of occurrence in endemic areas
88
Cyclospora cayetanensis
| - What disease does it cause?
Cyclosporiasis
89
Cyclospora cayetanensis
| - Who are the hosts?
Humans
90
Cyclospora cayetanensis
| - How is it transmitted?
Fecal-oral route mainly through food and water, NOT DIRECT CONTACT
- Raspberries, basil, cilantro, other fresh produce
91
Cyclospora cayetanensis
| - Infectious form
Sporulated oocyst
92
Cyclospora cayetanensis
| - Highlights of the life cycle
- 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
Cyclospora cayetanensis
| - Symptoms
- 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
Cyclospora cayetanensis
| - Can be shed ____ so get more than one stool specimen
Intermittent
95
Cyclospora cayetanensis
| - Wet mounts are useless, but oocysts are ____ and ____ when excited w/ certain wavelengths of light
- Acid-fast
| - Autofluoresce
96
Cyclospora cayetanensis
| - Size of unsporulated oocysts
8-10µm → bigger than Cryptosporidium (4-6µm)
97
Cyclospora cayetanensis
| - Oocyst appearance
Small coccidian parasite, round, acid fast (can have ghost cells in af); stain red; no sports, wrinkled and crinkled
98
Cystoisospora belli
| - Causes what disease?
Cystoisosporiasis
99
Cystoisospora belli
| - Geographic distribution
Worldwide, especially in tropical and subtropical regions
100
Least common of the coccidia
Cystoisospora belli
101
Cystoisospora belli
| - Who is the host?
Immunocompromised patients, especially those w/ AIDS
102
Cystoisospora belli
| - How is it transmitted?
Fecal-oral route
103
Cystoisospora belli
| - Significant symptom
Eosinophilia
104
Cystoisospora belli
| - Infectious form
Mature oocyst
105
Cystoisospora belli
| - It will ____ when excited w/ UV light
Autofluoresce
106
Cystoisospora belli
| - Oocyst appearance
Large, ellipsoidal, contains 1 sporoblast (pig in a blanket)
107
Sarcocystis hominis and suihominis
| - Causes what disease?
Sarcocystosis
108
Sarcocystis hominis and suihominis
| - Geographic distribution
Worldwide; more common where livestock are raised
109
Sarcocystis hominis and suihominis
| - Who are the hosts?
Humans are a dead-end host
110
Sarcocystis hominis and suihominis
| - How is it transmitted?
By consumption of undercooked/contaminated meat
111
Sarcocystis hominis and suihominis
| - Infectious form
??Oocyst??
112
Sarcocystis hominis and suihominis
| - Symptoms
- Often asymptomatic but occassionally a mild fever, diarrhea, chills, and vomiting
113
Sarcocystis hominis and suihominis
| - Oocyst appearance
Paired (shrink-wrapped) ovals
114
Sarcocystis hominis and suihominis
| - Do these organisms autofluoresce?
YES
115
These are opportunistic, obligate, intracellular pathogens
Microsporidia
116
If microsporidia aren't protozoa, what are they?
Fungi
117
Two types of microsporidia that are common human gastrointestinal pathogens
- Enterocytozoon bieneus
| - Encephalitozoon intestinalis
118
Microsporidia
| - Geographic distribution
Worldwide
119
Microsporidia
| - Who are the hosts?
Severely immunocompromised AIDS patients
120
Microsporidia
| - How is it transmitted?
Consumption of contaminated food and water, contaminated fomites, and possibly airborne?
121
Microsporidia
| - Infectious form
Spore
122
Microsporidia
| - Symptoms
Diarrhea
123
Microsporidia
| - What stains should be used for the microscopic exam?
- Chromotrope 2R
| - Ryan's modified-trichrome stain
124
Microsporidia
- Gold test
- Test of choice?
- Gold test: transmission electron microscopy
| - Choice: immunofluorescence
125
Encephalitozoon spp
| - Appearance
Gram stain → resembles large GPRs
126
Blastocystis spp
| - Infectious form
Cyst (cyst released also)
127
Blastocystis spp
| - Role in disease
Debateable role (sometimes no symptoms, other times diarrhea etc.)
128
Chilomastix mesnili
| - Pathogenic or nonpathogenic?
Nonpathogenic protozoa
129
Chilomastix mesnili
| - Appearance of trophs
External flagella, lopsided shortened pear shape, one nucleus, cytosome looks like mouth (smiling fish)
130
Chilomastix mesnili
| - Appearance of cysts
Small lemon shape cyst, one nucleus, cytosine small, looks like a shephard's crook
131
Endolimax nana
| - Pathogenic or nonpathogenic?
Nonpathogenic
132
Endolimax nana
| - Appearance of troph
W/o peripheral nuclear chromatin, large irregular karyosome (nana with dilated pupil)
133
Endolimax nana
| - Appearance of cyst
four nuclei (nana has 4 eyes), short oval shape, small nuclei surrounded by clear space
134
Enteromonas hominis
| - Pathogenic or nonpathogenic?
Nonpathogenic
135
Enteromonas hominis
| - Appearance
?
136
Iodamoeba butschlii
| - Pathogenic or nonpathogenic?
Nonpathogenic
137
Iodamoeba butschlii:
- Cyst appearance
- Troph appearance
Cyst: large vacuole in the cyst
138
Pentatrichomonas hominis
| - Pathogenic or nonpathogenic?
Nonpathogenic
139
Pentatrichomonas hominis
| - Appearance of trophs
External flagella, lopsided pear shape, one nucleus, undulating membrane and axostyle (fish with spike)
140
Advantages of Ag detection methods
High sensitivity and specificity
141
Disadvantages of microscopic examination methods
- Objective analyses b/w techs
- Need baseline knowledge to ID
- Requires time to perform analyses
142
Advantages of microscopic examination methods
- Microscopes relatively inexpensive
- Can be purchase cordless
- Easy to train on how to use
- Don't "expire"
143
Advantages of molecular methods
- Detectable parasites can be ID'd by the same assay as bacteria
- High sensitivity and specificity
144
Disadvantages of molecular methods
- Detrct either dead or alive parasites
| - $$$
