MLSCI340 Parasitology Flashcards
Collection instructions for O&P specimen examination
- clean, dry container
- do not let urine contaminate stool sample (ie. urinate first before collection)
- collect from bloody/ slimy/ watery areas
Specimen interferences for O&P examination
- bismuth
- antibiotics
- anti-malarial drugs
- anti-diarrheal medicine
- antacids
- laxatives
Fixatives used in O&P examination
- SAF liquid (yellow top)
- buffered formalin (5% or 10%)
- PVA (polyvinyl alcohol)
- MIF
Explain collection/ handling of multiple specimens in O&P examination
If >1 specimens are requested, collect on alternate days WITHIN 10 DAYS
What kind of information is outlined on the Enteric pathogen history form that is relevant to O&P examinations ?
- immune status (compromised ? acquired immunodeficiency syndrome ?)
- travel history
- raw shellfish consumption
- immigaration
- employment
- close contact with Giardia lamblia/ Crypto cases
Significance, collection method, and common organisms detected in Duodenal Contents
- used to diagnose GI tract infections
- uses string test/ duodenal aspirates
= Giardia lamblia
Significance, collection method, and common organisms detected in Cellophane Tape Test/ Sticky Paddle
- used to diagnose pinworm eggs (Enterobius vermicularis)
- press tape along anal opening, then transfer to glass slide
- morning collection
Significance, collection method, and common organisms detected in Urine and Urethra
- detects urogenital infections
= Trichomonas vaginalis
Significance, collection method, and common organisms detected in Sputum
- detects pneumoniae, Loeffler’s Syndrome
= Strongyloides, Entamoeba histolytica
Describe macroscopic O&P examination
detects proglottids and worms in areas of blood and mucus
Describe microscopic O&P examination (3)
- fresh wet mounts = detects motile Entamoeba histolytica (directional motility)
- wetmount concentrates (sedimentaion vs floatation) = recovery of cysts, coccidian oocytes, spores, hemlinth eggs, larvae…
- stained slides = 100X; allows more detail for ID; modified acid-fast always required
T or F: even when iodine is used in wetmount concentrates, organisms may still be cultured
FALSE; when iodine is used in wetmount concentrates, ORGANISMS ARE DEAD
Sedimentation vs Flotation concentration techniques
Sedimentation:
- formalin-ethyl acetate
- parasites in sedimentation layer
- 4 layers
Floatation:
- zinc sulfate
- parasites in surface film layer
- 3 layers
Pros and cons of Sedimentation Wetmounts
Sedimentation (formalin-ethyl acetate):
PROS
- Under 100X; allows more detail for ID
- Stable (formalin)
- Cheap
- Easy to perform
CONS
- too much iodine obscures helminth eggs
Pros and cons of Floatation Wetmounts
Floatation (zinc sulfate):
PROS
- parasites acquired from cleaner material (surface film)
CONS
- heavy eggs will sink
- must be read <30 min
- more technical
Modified Acid-Fast stains in O&P
- modified ZN or Kinyoun stains = Cryptosporidium are bright pink
- required for ALL O&P examination
T or F: Modified Acid-Fast stains are required in all O&P examinations
TRUE; Modified Acid-Fast stains are required in all O&P examinations
Trichrome stains in O&P
- protozoa = BLUE/GREEN to PURPLE CYTOPLASM
- nuclei and inclusions (chromatoidal bars + RBCs) = BRIGHT PINK
- background debris = green
Iron-hematoxylin stains in O&P
- shades of grey
Modified Iron-hematoxylin stains in O&P
- a modified acid-fast component is added
- acid-fast organism = BRIGHT PINK
What are Charcot-Leyden Crystals ? Why are they reported with O&P examinations ?
- can indicate a systemic infection/ allergic response
- look like slender “toothpicks”
- formed from breakdown products of eosinophils
Describe Acanthamoeba sp. infection
- eye infections due to poor contact lens care, cutaneous infections or keratitis
- found in tap water
- chloride resistant (in pools)
Describe ID of Acanthamoeba sp.
- 7-day incubation: corneal scrapings OR contact lenses are inoculated into agar overlaid with E. coli = microscopic observation of trails in confluent E. coli
- confirmed using PCR
- calcofluor white for nonspecific fluorescence from corneal scrapings
Green-based parasitology stain
Trichrome
Full examination if a patient has this prior history
travel
Common non-pathogen containing 1-8 nuclei in cyst
Entamoeba coli
Causative agent of “itchy bum” (slang)
pinworm
Organism identified by sticky paddle or cellophane tape test
Enterobius vermicularis
Causative agent of cysticercosis
Taenia solium
Causative agent of beaver fever
Giardia lamblia
“fish tapeworm”; due to ingestion of poorly cooked freshwater fish
Diphyllobothrium latum
Found in sputum in cases of hyperinfestation; “threadworm”
Strongyloides sterocoralis
A possible corneal pathogen when you swim with contact lenses
Acanthamoeba sp.
Which protozoan stage is considered infective and non-infective
Cyst = INFECTIVE
Trophozoite = non-infective
Protozoan cyst contains 1-4 nuclei and the trophozoite may contain RBCs
Entamoeba histolytica
Preservative used in the Edmonton zone for O&P examination
SAF; sodium acetate-acetic acid-formalin
May cause bowel obstruction when worm burden is high; may require surgical intervention
Ascarcis lumbricoides
Detection occurs with modified acid-fast staining (Kinyoun)
Cryptosporidium sp.
Test used to directly detect Giardia lamblia from patient specimens without travel history
ELISA
“Whipworm;” soil-transmitted helminth
Trichuris trichiura
Classified as a flagellate BUT HAS NO FLAGELLA; associated with digestion of helminth eggs from E. vermicularis/ pinworm
Dientamoeba fragilis
