Laboratory Safety and Sample Collection Flashcards
“Treat all sample infectious”
Standard Precaution
“All sample can induce bloodborne pathogens”
Universal Precaution
Potential risks in parasitology laboratory
- Ingestion of eggs/ova
- Skin penetration of infective larva
- Infection of non-parasitic agents
True or false. Fixed stool using specimens are already free from pathogens.
False. They are still infectious.
When should blood specimens be collected?
Before treatment is initiated
Capacity of fecal sample container
0.5 pint or approx. 240 ml
Labile stage and feeding form of protozoans
Trophozoites
How many stools samples should be collected and how frequent?
3 specimens collected within 6-7 days (no more than 7 days)
How many stools samples should be collected for intestinal amebiasis and how frequent?
No more than 6 specimens collected within 10 days
How many weeks of deferment if the patient is taking antiprotozoan?
3-4 weeks
How many weeks of deferment if the patient is taking helminthic drugs?
5-6 weeks
Drugs that require 1 week deferment
o Antacids
o Anti-diarrheal
o Barium
o Bismuth
o Laxatives
Why does the intake of antibiotic affect the result of stool analysis?
They decrease the number of protozoan for several weeks
Amount of stool to be collected
Thumb-sized (solid)
5-6 tablespoons (watery)
Trophozoites are likely to die within _____ after passage
30 minutes to 1 hour
Acceptable temperature of refrigerator for stool samples
3-5C (most optimal = 4C)
An all-purpose fixative that can be an eye irritant
Formalin
Concentration of formalin recommended for protozoan cysts
5%
Concentration of formalin recommended for helminth eggs and larva
10%
When using formalin as a fixative, the stool must be fixed within how many minutes?
30 minutes
This fixative has Mercuric chloride in its stock solution, which is why it is often regarded as a dangerous fixative
Schaudinn’s solution
Best option for permanent staining
Mercuric chloride
A plastic resin which serves to adhere a stool sample onto a slide
Polyvinyl alcohol (PVA)
Main advantage: related to the preservation of protozoan cysts and trophozoites for permanent staining
Polyvinyl alcohol (PVA)
True or false. For modified PVA, copper is preffered over zinc
False
Function of iodine in Merthiolate-Iodine-Formalin (IMF)
Stain
Useful for the fixation of intestinal protozoans, helminth eggs, and larvae
Merthiolate-Iodine-Formalin (IMF)
Not suitable for permanent smears stained with trichrome
Merthiolate-Iodine-Formalin (IMF)
Interferes with other stains and fluorescence; may cause distortion of protozoa
Iodine in IMF
Has glacial acid that helps lyse the cells and albumin-glycerol which sticks the sample to the slide
Sodium acetate-acetic acid formalin (SAF)
What fixatives can be used for direct wet mount preparation?
Formalin, MIF, SAF
What fixatives can be used for concentration procedures?
Formalin, MIF, SAF
What fixatives can be used for permanent staining?
Schaudinn’s solution, PVA, Modified PVA, SAF
Predominant stage in watery sample
Trophozoites (processed within 30-60 mins)
Predominant stage in formed sample
Cyst (may be processed for up to 24 hours)
