U1 - Lab Safety and Specimen Handling to Disposal Flashcards
Toxic substances are handled under?
a safety hood
parasites that will be thriving in the host
helminths
type of host during adult stage
definitive host
type of host during larval stage
intermediate host
type of host during the egg stage
parasite in diagnostic stage
types of helminth
- nematode
- trematode
- cestode
T/F:
When a specimen is “fixed”, it means that everything is already killed; hence, it is not infectious because it is already preserved.
True
best way to preserve the eggs and prevent development
warm/ heated 10% formalin
key in the laboratory
safety
difference between standard and universal precautions
standard: everything is infectious
universal: all samples are highly infectious
What should be practiced in the laboratory?
standard precautions
potential risks in the para lab
- ingestion of eggs/ ova
- skin penetration of infective larva
- infection of non-parasitic agents
T/F:
fixed stool specimens in formalin is no longer infectious
False;
may still be infectious
can still develop and are infectious even in preserved in formalin
Ascaris eggs
special factor in blood specimen collection
timing
T/F:
Blood should be collected before treatment is initiated.
True
Why is timing important?
to ensure that the parasite will not be missed
When these are suspected, blood smears should be examined without delay.
Malaria and Babesiosis
T/F:
Only one blood smear is needed.
False;
multiple blood smears might be needed
reason why multiple blood smears are needed
Parasitemia or the presence of parasites in the blood could actually fluctuate
exhibit periodicity and is seen in lymphatic fluids
Microfilariae
What type of blood samples are collected to detect parasitic infections?
venous and capillary
multiple specimens recommended for adequate yield of 1 parasite
fecal specimen
Criteria for fecal specimen container
- clean
- wide-mouthed
- made of waxed carboard or plastic
- has a tight-fitting lid
Why should the lid of the container be tight-fitting?
to ensure retention of moisture
to prevent accidental spillage
Fecal specimen should be submitted with these information
- patient’s name
- age
- sex
- date/time of collection
- requesting physician
- requested procedure
- presumptive diagnosis
- prior infections
- travel history
Specimen protocol:
___ specimens are collected every other day to consider the adequate or minimum necessary for the detection of ova and parasite with no more than ___ days
3
7
Specimen protocol:
___ specimens are collected every other day to consider the adequate or minimum necessary for the detection of intestinal amebiasis with no more than ___ days
> 6
10
information on the fecal specimen container
- patient’s name
- patient’s ID number
- date and time of collection
- requesting physician
3 types of stool consistency
watery
semi-formed
formed
amount of trophozoites from greatest to least in different types of stool consistency
- watery (greatest)
- semi-formed
- formed (least)
amount of cyst from greatest to least in different types of stool consistency
- formed (greatest)
- semi-formed
- watery (least)
time validity for examination of structures:
watery:
semi-formed:
formed:
watery: 30 minutes
semi-formed: 1 hour
formed: up to 24 hours
Stool is refrigerated at what temperature?
3-5 C
Important factors to consider
- intake of drugs/ medicinal substances
- intake of antibiotics
- amount of stool to be collected
- contamination with toilet water, urine or soil must be prevented
- age of stool sample is very important for diarrheic specimens
- delay in examination of specimens
- temporary storage of fecal samples
5 examples of drugs or medicinal substances
- antacids
- anti-diarrheals
- barium
- bismuth
- laxatives
deferral for intake of drugs or medicinal substances
1 week from last intake
effect of intake of drugs or medicinal substances
leaves crystallized residues
usually decreases the number of protozoans for several weeks
antibiotics
deferral for protozoan treatment/ anti-protozoan drugs
3-4 weeks after treatment
duration of deferral for anti-helminthic drugs
5-6 weeks after last intake
amount of fecal specimen for routine stool examination
formed: thumb-sized
watery: 5-6 tbsp.
effect of contamination with toilet water, urine, or soil
- can destroy protozoan trophozoites
- may contain free-living organisms that would complicate diagnosis of infections
Age of stool sample is very important for?
diarrheic specimens
Trophozoites are likely to die within _________ after passage
30 minutes to 1 hour
Why does stool require preservation?
to ensure that parasites are present in identifiable stage
effect of prolonged refrigeration
desiccation (drying)
effect of refrigeration
trophozoites: killed
helminth eggs: usually not damaged
protozoan cysts: usually not damaged
prohibitions of fecal storage
- never freeze
- never incubate
- never put in clean ref
Where should the fecal specimen be refrigerated?
dirty ref
3 examinations (gold standard for stool examination)
- direct stool examination (preserved sample)
- concentration methods (preserved sample)
- permanent smear (preserved sample)
T/F:
Motility of trophozoites can be observed in the preserved sample.
False
type of sample preserved by trophozoites
fresh sample
5 Stool Preservatives
- Formalin
- Schaudinn’s Solution
- Polyvinyl Alcohol (PVA)
- Merthiolate-Iodine Formalin (MIF)
- Sodium Acetate-Acetic Acid Formalin (SAF)
an all-purpose fixative
formalin
Formalin 5% and 10% concentration purposes
5% concentration: protozoan cysts
10% concentration: helminth eggs and larvae
Formalin may be buffered with _________ ____________ to preserve the morphological characteristics of the organisms
sodium phosphate
FECT stands for?
formalin-ether/ ethyl acetate concentration technique (FECT)
used to preserve fresh stool in preparation for staining the stool smears
Schaudinn’s solution
best preservative for the parasites
Schaudinn’s solution
What chemical does Schaudinn’s solution contain?
mercuric chloride
T/F:
Mercuric chloride is highly toxic to humans, and problems regarding its disposal may arise.
True
Stool: Fixative Ratio
1:3
Using formalin, stool must be fixed within how many minutes?
30 minutes
preservative designed for fresh stool specimens or samples from the intestinal mucosal surface for permanent staining
Schaudinn’s solution
a plastic resin which serves to adhere a stool sample onto a slide
polyvinyl alcohol (PVA)
PVA is normally incorporated into?
Schaudinn’s solution
T/F:
PVA is normally incorporated into Schaudinn’s solution, but actual fixation is done by the Schaudinn’s.
True
main advantage of using PVA
related to the preservation of protozoan cysts and trophozoites for permanent staining
stools preserved using this PVA can be concentrated using _____ and can be shipped to any laboratory for further examination.
FECT
Drawback of PVA
use of mercuric chloride
preservatives with mercuric chloride
Schaudinn’s solution
Polyvinyl alcohol (PVA)
As PVA is combined with Schaudinn’s solution, what are the bases?
Zinc sulfate
Copper sulfate
Mercuric chloride
In modified PVA copper or zinc, permanent smears can be made and stained with?
trichrome
T/F:
In modified PVA, copper is preferred over zinc.
False;
zinc over copper
T/F:
Modified PVA has mercuric chlorode.
False;
none
contains merthiolate (also called thimerosal) and iodine which act as staining components
Merthiolate-Iodine-Formalin (MIF)
merthiolate is also called?
thimerosal
staining components of Merthiolate-Iodine-Formalin (MIF)
merthiolate/ thimerosal
iodine
preservative component of MIF
formalin
useful for the fixation of intestinal protozoans, helminth eggs, and larvae
Merthiolate-Iodine-Formalin (MIF)
preservative that is useful for field surveys
Merthiolate-Iodine-Formalin (MIF)
preservative for all common types of stools and aspirates
Merthiolate-Iodine-Formalin (MIF)
can be a substitute for Schaudinn’s solution
MIF
T/F:
Using MIF, protozoans, eggs, and larva are identified without further staining in temporary wet mounts
True
preservative that has the advantage of not containing mercuric chloride
Sodium acetate-acetic acid formalin (SAF)
T/F:
Images of organisms fixed in SAF - not as sharp after staining compared with those fixed in PVA or Schaudinn’s solution
True
a liquid fixative with a long shelf-life
Sodium acetate-acetic acid formalin (SAF)
preservative that is used in concentration techniques, permanent staining, and fecal immunoassays
Sodium acetate-acetic acid formalin (SAF)
preservative where the sediment obtained is used for the preparation of permanent smears
Sodium acetate-acetic acid formalin (SAF)
Pros and cons of fresh stool
Pros:
1. stool fixatives are not required
2. trophozoite motility observation
3. low cost
4. good morphology of the organism
5. can be used for direct wet exam, concentration methods, permanent staining, immunoassays, special staining, etc.
Cons
1. excessive lag time between stool fixation or processing
2. trophozoites may disintegrate, yielding to a false-negative result
Pros and cons of preserved stool
Pros:
1. organism morphology is preserved when lag time between stool passage and fixation is short
2. delivery time is not critical
3. can be used for concentration methods, permanent staining, immunoassays, special staining, etc.
Cons:
1. expensive
2. disposal of specimens in mercuric chloride
Pros and cons of formalin
Pros:
1. useful for stool conc.
2. easy to prepare
3. long shelf life
4. formalized stools can be used with some immunoassay kits
Cons:
1. does not preserve trophozoites well
2. does not adequately preserve the morphology of the organism
3. morphologic details may fade through time
4. pose a potential health hazard for lab scientist
Pros and cons of Schaudinn’s solution
Pros:
1. good preservation of morphology of protozoan trophozoites and cysts
2. easy preparation of permanent stained smears
Cons:
1. less suitable for concentration procedures
2. contains mercuric chloride
3. inadequate preservation of morphology of helminth eggs and larvae, coccidia, and microsporidia
4. poor adhesion of liquid or mucoid specimens to slides
In Schaudinn’s solutions, are trophozoites destroyed?
killed but not destroyed
In Schaudinn’s solutions, is the trophozoite’s motility preserved?
motility: not preserved
morphology: preserved
Pros and cons of PVA
Pros:
1. good preservation of morphology of protozoan trophozoites and cysts
2. used widely for permanent stained smears
3. long shelf life at room temperature
Cons:
1. environmental and health hazard (mercuric chloride)
Pros and cons of MIF
Pros:
1. components both fix and stain organisms
2. easy to prepare
3. long shelf life
4. useful for field surveys
5. suitable for conc procedures
Cons:
1. not suitable for permanent smears stained with trichrome
2. inadequate preservation of morphology of protozoan trophozoites
3. iodine interferes with other stains and fluorescence
4. iodine may cause distortion of protozoa
Pros and cons of SAF
Pros:
1. suitable for both conc procedures and preparation of permanent stained smears
2. easy to prepare
3. long shelf life
4. suitable for acid-fast, safranin staining methods
5. compatible with fecal immunoassay kits
Cons:
1. requires adhesives
2. permanent stains not as good as with PVA or Schaudinn’s fixative
Fresh stool
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: yes
conc procedure: yes
permanent staining: yes
Formalin
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: yes
conc procedure: yes
permanent staining: no
Schaudinn’s solution
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: no
conc procedure: no
permanent staining: yes
PVA
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: no
conc procedure: no
permanent staining: yes
Modified PVA
direct wet mount: no
conc procedure: no
permanent staining: yes
MIF
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: yes
conc procedure: yes
permanent staining: no
SAF
direct wet mount:
conc procedure:
permanent staining:
direct wet mount: yes
conc procedure: yes
permanent staining: yes
After processing fresh stool sample, discard all consumables in a container with?
bleach solution
bleach solution ratio
1:10 or 10% sodium hypochlorite solution
What are the consumables that must be discarded in a container with bleach solution
applicator sticks
slides
Remaining unprocessed fresh samples may be preserved or discarded in a?
yellow waste container
T/F:
Stool must be tightly sealed inside the pilot container.
True
T/F:
Lugol’s iodine component should always be freshly prepared since it is unstable.
True
T/F:
Stool contaminated with toilet water must be rejected for analysis.
True
