U3 - Diagnostic Parasitology Flashcards
1
Q
common reagents
A
- carbon fuchsin
- formalin (5% and 10%)
- lugol’s iodine solution
- SAF (sodium acetate-acetic acid formalin)
2
Q
most common fixative
A
formalin
3
Q
T/F:
All stains favor formalin.
A
False;
not all
4
Q
2 types of stool analysis
A
macroscopic
microscopic
5
Q
gross examination of stool
A
macroscopic analysis
6
Q
analysis of stool under a microscope
A
microscopic analyses
7
Q
factors analyzed macroscopically
A
- consistency
- color
- presence of blood
- presence of mucus
- presence of adult worm
8
Q
type of stool examined macroscopically
A
fresh stool
9
Q
simplest and easiest technique to facilitate detection of intestinal parasites that infected subjects pass in their feces
A
direct fecal smear
10
Q
presence of intestinal protozoa (trophozoites or cysts)
or helminth eggs can be observed directly with what type of microscope?
A
light microscope
11
Q
Small amount of fresh feces is mixed with either __________ or ___________ ____________.
A
saline
lugol/ iodine solution
12
Q
purpose of saline
A
to detect the protozoa motility
13
Q
purpose of lugol/iodine solution
A
to reveal the parasite structure
14
Q
What does NSS stand for?
A
Normal Saline Solution
15
Q
concentration of NSS
A
0.85% NaCl
16
Q
type of stool used for direct wet preparation
A
fresh stool
17
Q
useful technique if parasite is in low count
A
concentration
18
Q
most ideal technique
A
permanent stain
19
Q
type of stool used for permanent stain
A
fresh or preserved
20
Q
T/F:
In permanent stain technique, stain must match the fixative.
A
True
21
Q
NSS observation
A
morphology and motility
22
Q
Lugol’s iodine observation
A
morphology
(cannot observe motility)
23
Q
Organism killed by lugol’s iodine
A
trophozoites
24
Q
organisms observed by saline
A
- motile trophozoites and larvae
- red blood cells
- Leukocytes
- Charcot–Leyden crystals
25
organisms observed by iodine solution
cysts of protozoa
26
When examining diarrheic or liquid feces containing mucus, which preparation should be applied to the mucous part of the stools?
both saline and iodine solutions
27
Explain the procedure of preparation.
1. left side: 1 drop of saline; right side: 1 drop of lugol's iodine
2. 2 mg of fecal specimen emulsified in saline drop
3. do the same with iodine drop
4. place a cover slip on each suspension
5. examine with a microscope
28
consideration in emulsifying stool in 2 solutions
separate applicator sticks must be used
29
chemical that kills any organisms present; thus, no motility is seen
iodine
30
specific procedure in placing coverslips
1. place on each suspension touching the edge of the drop (angled)
2. gently lower the coverslip onto the slide
31
purpose of angular method of coverslip upon placement
so no air bubbles are produced
32
recommended for monitoring large-scale treatment programs implemented for the control of soil-transmitted helminth infections
Kato-Katz Technique
33
Why is kato-katz technique the most recommended method for STH control?
1. simple format
2. ease of use in the field
34
What type of technique is kato-katz?
quantitative technique
(egg-counting)
35
purpose of kato-katz technique
quantifying eggs and establishing burden of intestinal infection
36
kato-katz technique
manner of reporting
eggs per gram stool (epg)
37
another purpose of kato-katz technique
to assess the efficacy of a treatment (if the number of eggs were reduced)
38
correlate the severity of the disease with the intensity of the infection
kato-katz technique
39
T/F:
kato-katz technique is applicable to all parasites
False;
not applicable to all;
some cases: no matter the amount, disease severity is the same
40
helminths that need soil to develop
soil-transmitted helminthes
41
causes of acquiring STH
poor sanitary and hygiene practices
42
unholy trinity according to WHO
1. Trichuris trichiuria
2. Ascaris lumbricoides
3. Hookworm (Necator americanus and Ancylostoma duodenale)
*** also Schistosoma spp.
43
materials for kato-katz technique
1. wooden applicator sticks
2. screen
3. template
4. spatula
5. microscope slides
6. hydrophilic cellophane
7. jar, forceps, toilet paper, tissue
8. newspaper
9. glycerol-malachite green
44
glycerol-malachite green solution is poured into ____________ _________ in a jar and left for at least ___ hours prior to use.
cellophane strips
24
45
clearing agent
glycerine/ glycerol
46
Kato-katz technique procedure
1. prepare materials
2. place sample on a newspaper
3. press nylon screen on top
4. scrape the sieved fecal material from screen
5. label glass slide
6. place template with hole on center of slide
7. fill hole in template with sired fecal material (avoid air bubbles and level feces off)
8. lift off template, place in a bucket of water with concentrated detergent and disinfectant for reuse
9. place cellophane (soaked in glycerol solution overnight) over fecal sample
10. invert microscope slide
11. press sample against cellophane strip on another slide or surface to spread feces in circle
12. pick up slide (avoid cellophane separation)
13. place it on bench with cellophane upwards
14. water evaporates while glycerol clears feces
15. when clarified, newspaper text must be read
47
Keep the slide for ___ hour(s) at ______ temperature to clear the fecal material prior to examination under the microscope.
1
room
48
Keeping the slide for an hour does not apply to __________.
hookworms
(eggs - thin shells)
49
Why must it not exceed 1 hour
might overclear and destroy organisms
50
done to speed up clearing and examination and allow action of the clearing agent
slide is placed in incubator
or kept in direct sunlight for several minutes
51
incubator temp
40 C
52
STH visibility/ recognizability duration
Ascaris lumbricoides: many months
Trichuris trichuria eggs: many months
Hookworm eggs: 30-60 minutes
Schistome eggs: several months (but examination within 24 hrs is preferred)
53
clear rapidly
hookworm eggs
54
In kato-katz technique, the smear should be examined _____________.
systematically
55
To give the number of eggs per gram of feces, what should the computation be?
egg count x factor (depending on template)
56
corresponding factors of used templates
50 mg template: x20
20 mg template: x50
41.7 mg template: x24
57
corresponding factor for 50 mg template
x20
58
corresponding factor for 20 mg template
x50
59
corresponding factor for 41.7 mg template
x24
60
template dimensions for amounts of stool
50 mg (x20): D=9mm; T=1mm
20 mg (x50): D=6.5mm; T=0.5mm
41.7 mg (x24): D=6mm; T=1.5mm
61
template dimensions for 50 mg stool
D=9mm; T=1mm
62
template dimensions for 20 mg stool
D=6.5mm; T=0.5mm
63
template dimensions for 41.7 mg stool
D=6mm; T=1.5mm
64
classification of intensity of infection for:
Ascaris lumbricoides
Trichuris trichuria
Hookworms
Schistosoma mansoni
Ascaris lumbricoides:
light: 1-4,999 epg
moderate: 5,000-49,000 epg
heavy: ≥50,000 epg
Trichuris trichuria:
light: 1-999 epg
moderate: 1,000-9,999 epg
heavy: ≥10,000 epg
Hookworms:
light: 1-1,999 epg
moderate: 2,000-3,999 epg
heavy: ≥4,000 epg
Schistosoma mansoni:
light: 1-99 epg
moderate: 100-299 epg
heavy: ≥400 epg
65
classification of intensity of infection for:
Ascaris lumbricoides
light: 1-4,999 epg
moderate: 5,000-49,000 epg
heavy: ≥50,000 epg
66
classification of intensity of infection for:
Trichuris trichuria
light: 1-999 epg
moderate: 1,000-9,999 epg
heavy: ≥10,000 epg
67
classification of intensity of infection for:
Hookworms
light: 1-1,999 epg
moderate: 2,000-3,999 epg
heavy: ≥4,000 epg
68
classification of intensity of infection for:
Schistosoma mansoni
light: 1-99 epg
moderate: 100-299 epg
heavy: ≥400 epg
69
2 types of blood film for malaria parasites
thick blood smear
thin blood smear
70
blood film used to determine if parasite is present
thick blood smear
71
blood film used to confirm the Plasmodium species present
thin blood smear
72
thick blood smear purpose
screening purposes
73
thin blood smear purpsoe
confirmatory purposes
74
3 examples of blood parasites and disease caused
1. plasmodium - malaria
2. ticks - babesia
3. hemoflagellates - trypanosomes
75
type of blood specimen collected for thick and thin smear
capillary
venous
76
more preferred blood specimen for thick and thin smear
capillary; directly observed without anticoagulant
77
Why is venous blood less preferred for malarial examination?
stored in EDTA - may alter parasite structure
78
gold standard
thick and thin blood smears
79
smear that is performed first
thick blood smear
80
stain preparation in thick blood smear for blood parasite
Giemsa stain
81
giemsa stain pH
7.2
82
blood smear diameter for thick smear
1-2 cm diameter
83
rationale behind proper preparation technique for blood smears
to prevent parasites from obscuring behind the red blood cells
84
stain preparation in thin blood smear for blood parasite
fixed with methanol
before Giemsa stain
85
Why should one start examining blood parasites with thick smear?
You might miss out on the parasite if you don't prioritize thick smear.
86
Compare thick and thin films:
RBCs
Thick: lysed RBCs
Thin: fixed RBCs, single layer
87
Compare thick and thin films:
volume
Thick: larger volume
Thin: smaller volume
88
Compare thick and thin films:
blood volume/ fields
Thick: 0.25 ul blood/ 100 fields
Thin: 0.005 ul blood/ 100 fields
89
Compare thick and thin films:
Thick:
Thin:
90
Compare thick and thin films:
elements
Thick: more concentrated
Thin: good species
91
Compare thick and thin films:
disadvantage
Thick: difficult species diagnosis
Thin: requires more time to read
92
Compare thick and thin films:
density
Thick: parasite density
Thin: low density infections can be missed
93
Compare thick and thin films:
result
Thick: positive or negative
Thin: parasite species
94
template for thick and thin blood smear
Sub. ID
Intls.
TimePt.
Date
Time
95
Explain blood smear procedure
1. use separate slides
2. thin film: hold spreader slide at 45-degree angle
3. thin film: wait until blood spreads along edge
4. thin film: push spreader slide forward
5. thick film: spread drop using slide corner
6. wait until both are dry; fix thin film with methanol
7. if same slide: fix only thin film
8. when both are dry, stain
96
T/F:
thick smear should not be too thick
True;
must be able to read newspaper text through it
97
methanol concentration for thin film fixation
100% (absolute) methanol
98
How long does it take the thick smears to dry?
1-2 hours
99
unstained blood smears must be protected from?
excessive heat
moisture
insects
100
where should unstained blood smears be stored?
covered box
101
how to quantify malaria parasites against RBCs
count the parasitized RBCs among 500-2,000 RBCs on the thin smear and express the results as %parasitemia
102
% parasitemia formula
% parasitemia = (parasitized RBCs/total RBCs) × 100
103
examination if parasitemia is:
high:
low:
high: [e.g., > 10%], examine 500 RBCs
low [e.g., <1%] ,examine 2,000 RBCs (or more)
104
T/F:
Asexual blood stage parasites and gametocytes must be counted separately.
True
105
T/F:
Only the former are clinically important and gametocytes of P. falciparum can persist after elimination of asexual stages by drug treatment.
True
106
purpose of cellophane swab
for diagnosis of:
1. Enterobiasis caused by a nematode, Enterobius vermicularis
2. Taeniasis caused by tapeworm, Taenia solium or Taenia saginata
107
other terms for cellophane swab
perianal swab
scotch tape swab
cellophane tape swab
108
pinworm/ social worm causing enterobiasis
Enterobius vermicularis
109
itching in perianal area
pruritus ani
110
When do nematodes (Enterobius vermicularis) usually lay eggs in the perianal region?
at night
when moisty
when humid
111
MOT for Enterobius vermicularis
fecal oral
inhalation
112
a tapeworm that has radial segmentations
Taenia saginata
113
shedding of gravid proglottids by the tapeworm
apolysis
114
segments or units of the tapeworm's body, often found in the perianal region or around the anus in cases of tapeworm infection
proglottids
115
also known as pinworm infection
Enterobiasis
116
Specimen of choice for the detection of Enterobius vermicularis (pinworm) eggs
cellophane swab
117
Explain how eggs are secreted by parasites in the perianal region
At night, when the body is at rest, gravid (pregnant) adult female worms exit the host, typically a child, through the rectum and lay numerous eggs in the perianal region.
118
cellophane swab:
time of collection
early in the morning
before the patient washes or defecates
119
Standard protocol for specimens collected daily for the number of negative tests that should be performed to rule out a pinworm infection is ______.
five
120
Each worm lays about how many eggs? and come infective in how many hours?
10,000-11,000 eggs
4-6 hours
121
T/F:
Laboratory technicians may need to explain the procedure to patients, their families, and/or other health care professionals.
True
122
When instructing others, why is it critical to emphasize the importance of exercising proper hygiene and preventive measures during specimen collection?
to avoid spreading infectious eggs into the environment.
123
Explain cellophane swab collection procedure
1. loop tape over end of wooden tongue depressor to expose adhesive surface
2. touch adhesive surface several times to perianal region
3. smooth tape on slide
4. apply drop of toluol or I2 in xylol
124
what solution is used in cellophane swab examination
toluol or I2 in xylol
125
Enterobius vermicularis:
worm type according to egg-laying capacity
oviparous
126
Enterobius vermicularis:
shape
D-shaped
127
Enterobius vermicularis:
size
50-60 x 20-30um
128
Enterobius vermicularis:
color
colorless
129
Enterobius vermicularis:
shell
thin
130
Enterobius vermicularis:
contents
single cell (immature egg) or
larva (mature egg)
131
other terms for adhesive tape test
transparent tape test
scotch test
132
method of choice to detect Enterobius vermicularis (pinworm) eggs and occasionally adult females
adhesive tape test
133
2 types of concentration techniques
sedimentation
flotation
134
procedures that allow for detection of parasitic elements
concentration (sedimentation and flotation)
135
Why should concentration procedures be carried out?
parasitic elements might be missed when examining only a direct wet smear
136
procedure that leads to recovery of all protozoan cysts and oocysts, helminth eggs and larvae present in stool specimen
Formalin-ethyl acetate sedimentation concentration
137
the easiest to perform
least subject to technical error allows broad recovery of parasitic elements
Formalin-ethyl acetate sedimentation concentration
138
Type of stool specimen for formalin-ethyl acetate sedimentation concentration
fresh or fixed
139
T/F:
Formalin-ethyl acetate sedimentation concentration preparation will often contain more debris than that obtained with the flotation and other procedures.
True
140
Formalin-ethyl acetate sedimentation concentration is not recommended for?
1. eggs of Fasciola spp.
2. larvae of Strongyloides stercoralis
141
sediment and surface examinations:
specific gravity
sediment:
solution = lower SG than parasite
surface:
solution - higher SG than parasite
142
In surface examination, why should the solution have a higher specific gravity than the parasite?
for the parasite to float
143
sedimentation mechanism
parasite will go to sediment
144
concentration technique:
easier to perform
applicable to all parasites
routinely performed
sedimentation
145
concentration technique:
clean procedure
floatation
146
Before: Formalin Ether Concentration Technique
Now: ?
FEACT: Formalin Ether-Ethyl Acetate Concentration Technique
147
dissolve lipid contents and other debris
ethyl acetate
148
Cite steps for sedimentatation
1. mix sample with fixative
2. strain suspension and centrifugate
3. remove supernatant and break sediment
4. add saline to sediment, seal tube
5. add ethyl acetate and shake vigorously
6. wait, remove stopper
7. centrifuge
8. contents will separate
9. detach plug of debris from tube wall, pour off the top 3 layers by invertion
10. mix sediment with remaining liquid
11. place a sediment drop on slide, cover with coverslip, place lugol-stained preparation
12. examine using microscope
149
4 layers in sedimentation
1. ethyl acetate
2. bulk debris
3. saline
4. sediment
150
allows separation of parasitic elements from the coarest organic debris
floatation technique
151
type of stool for floatation technique
fresh or fixed
152
most widely used floatation solutions
zinc sulfate solution
sodium chloride
153
eggs that are not efficiently concentrated with floatation technique
heavy eggs:
Fasciola eggs
infertile Ascaris eggs
154
In floatation technique, eggs and cysts tend to lose their typical shape after how long?
40-60 minutes
155
4 layers in floatation technique
1. meniscus
2. eggs/ (oo)cysts
3. floatant solution
4. sediment
156
Cite steps for floatation
1. add sample to formalin, mix, leave for at least 30 mins
2. filter suspension
3. centrifuge, discard supernatant
4. resuspend sediment in saline, repeat step 3
5. resuspend sediment in solution, centrifuge
6. remove tube from centrifuge, add drops of solution until meniscus forms
7. harvest upper part of meniscus by placing coverslip, pace it face down on a slide
8. examine using a microscope
157
In floatation technique, a few drops of this may be added to the slide to enhance morphological details of parasites (e.g. Giardia cysts)
Lugol's solution
158
10 miscellaneous concentration techniques
1. Harada-Mori Culture
2. Baermann Culture
3. Knott’s Concentration Technique
4. Sheather’s Flotation Technique
5. Brine Flotation Technique
6. McMaster Concentration Technique
7. Mini-FLOTAC Technique
8. Rapid Diagnostic Test for Malaria
9. Circumoval Precipitin Test (COPT)
10. Sabin-Feldman Dye Test
159
concentration technique:
- placing stool sample onto filter paper
- adding water
- examining water for filariform larvae detection
Harada-Mori Culture
160
concentration technique:
- sealing of funnel
- adding water
- stool wrapped up in cheesecloth
- Filariform larva will go out of cheesecloth
- examine water for larva presence
- uses more stool
Baermann Culture
161
concentration technique:
- blood concentration technique used for microfilaria
- add 20 mL of 2% formalin
- centrifuge at 500g for 10 minutes
sediment of conc. blood to slide (thick film)
Knott’s Concentration Technique
162
stain used in Knott's Concentration Technique
giemsa
163
concentration technique:
used for coccidians to recover oocyst
Sheather’s Flotation Technique
164
concentration technique:
involves mixing the sample with a salt solution to make the eggs and cysts float to the surface
Brine Flotation Technique
165
concentration technique:
involves diluting the fecal sample and then using a specialized counting chamber, which has two chambers and grid markings
McMaster Concentration Technique
166
concentration technique:
involves mixing the sample with a flotation solution and using a specialized chamber; parasite eggs or oocysts float to the top
Mini-FLOTAC Technique
167
concentration technique:
reacts through serological immunoassay
Rapid Diagnostic Test for Malaria
168
concentration technique:
confirmatory test used for Schistosoma
Circumoval Precipitin Test (COPT)
169
sample for COPT
serum
170
serum incubation period for COPT
24 hours
171
concentration technique:
for Toxoplasma gondii infection from cat stool
Sabin-Feldman Dye Test
172
vulnerable patients to Toxoplasms gondii infection
pregnant women
173
mechanism of Toxoplasma gondii infection
can cause placental barriers
can cause blindness
can cause cerebral defects in developing fetus
174
sample for Sabin-Feldman Dye Test
serum
175
dye used in Sabin-Feldman Dye Test
methylene blue dye
176
Sabin-Feldman Dye Test results
positive: dye did not bind to trophozoites
negative: dye bound to trophozoites
177
MOT of Toxoplasma gondii infection
ingestion of oocyst from cat feces
178
T/F:
Motility of trophozoites is best demonstrated using Lugol's iodine
False;
use NSS
179
T/F:
Improper placement of coverslip often leads to the formation of air bubbles in the fecal smear.
True
180
Identify: What reagent acts as a clearing agent in the Kato-Katz preparation?
Glycerine-glycerol
181
Identify: Currently, what is considered as the gold standard for the diagnosis of Malaria?
Thick and thin blood smears
182
Identify: What is the specimen of choice for the diagnosis of pinworm infections?
cellophane swab
