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Parasitology Laboratory > Lab safety and Specimen Collection, Handling and Disposal > Flashcards

Lab safety and Specimen Collection, Handling and Disposal Flashcards

1
Q

the key in the laboratory

A

Safety

practice preventive measures to prevent any infections

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2
Q
  • Potential Risks
A

Ingestion of eggs / ova
skin penetration of infective larva
infection of non-parasitic agent

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3
Q

Mode of transmission of parasites

A

ingestion of eggs

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4
Q

most infective stage of parasite

A

eggs/ova

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5
Q

Examples of larvae that can penetrate skin

A

Filariform larvae / Hookworm

Cercaria / Schistozomes

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6
Q

TRUE OR FALSE

Fixed stool specimens may still be infectious

A

TRUE

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7
Q

Examples of parasites that are infectious even when preserved with formalin

A

Ascaris Lumbricoides / Giant intestinal round worm

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8
Q

Most common fixative / presevative

A

Formalin

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9
Q

Fecal specimen is best collected in

A

Clean, wide-mouthed containers made of waxed cardboard or plastic with a tight-fitting lid

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10
Q

Reason for the collection container of fecal specimen

A

to ensure retention of moisture and to prevent accidental spillage

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11
Q

Drugs that can interfere with the detection and diagnosis of parasitic infection

A
  • Antacids
    • Anti-diarrheals
    • barium
    • bismuth
    • Laxatives
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12
Q

Antacids, Anti-diarrheals, barium, bismuth and Laxatives can cause

A

FALSE NEGATIVE result

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13
Q

If a person has ingested laxative drugs, he should collect stool samples:

A

7 days / a week after last intake

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14
Q

Intake of antibiotics can cause

A

FALSE NEGATIVE

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15
Q

What happens when a person take antibiotics

A

decreases the number of protozoans (unicellular) for several weeks

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16
Q

Most challenging parasite to identify

A

Protozoan parasite (Unicellular)

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17
Q

Amount of stool to be collected in routing stool examination

A

Formed stool : thumb size

Water stool : about 5-6 tablespoons

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18
Q

Contamination of these 3 should be avoided

A

Toilet water, urine, soil

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19
Q

What happens when specimen is contaminated with toilet water, urine and soil

A

Can destroy protozoan trophozoites as they may contain free-living organisms that can complicate diagnosis

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20
Q

Age of stool sample if very important for

A

diarrhetic specimens

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21
Q

Protozoan trophozoites are commonly seen in

A

watery sample

22
Q

watery sample containing protozoan trophozoites must be processed

A

30 mins to 1 hour after passage

23
Q

Protozoan cysts are commonly seen in

A

formed sample

24
Q

Formed sample with protozoan cyst must be processed

A

within 24 hrs

25
Q

If examination of specimens will be delayed it must be

A

preserved to ensure that parasites are present in the identifiable stage

26
Q

Preserving the specimen is done to

A

prevent degradation of parasites

27
Q

Temporary storage of fecal sample is

A

in refrigerator

28
Q

prolonged refrigeration can cause

A

Desiccation

29
Q

In refrigeration these parasites are usually not damaged

A

Helminth eggs and protozoan cyst

30
Q

In temporary storage what must never be done

A

never freeze stool samples

Never keep them in incubators

31
Q
  • all purpose fixative / preservative to prevent degradation
A

Formalin

32
Q
  • cheapest and most common fixative
A

Formalin

33
Q
  • May be buffered with sodium phosphate to preserve the morphological characteristics of organisms
A

Formalin

34
Q

Preserved stool can be concentrated using

A

formal-ether/ ethyl acetate concentration technique (FECT)

35
Q

In FECT samples should be

A

formalinized

36
Q

Advantage and disadvantage of Formalin

A

Cheapest

Not used for permanent staining

37
Q

5% conc formalin

A

protozoan cyst

38
Q

10% conc formalin

A

helminth eggs and larvae

39
Q
  • Used to preserve FRESH STOOL in preparation for staining the STOOL SMEARS
A

Schaudinn’s solution

40
Q

Schaudinn’s solution contains highly toxic substance

A

Mercuric chloride

41
Q

Advantage and disadvantage of Schaudinn’s

A

Recommended for permanent staining

Very toxic because of mercuric chloride

42
Q
  • Partner of Schaudinn’s solution
A

Polyvinyl alcohol (PVA)

43
Q
  • A plastic resin that serves to adhere a stool sample onto a slide
A

Polyvinyl alcohol (PVA)

44
Q

TRUE OR FALSE

Stools preserve in PVA can be concentrated using FECT

A

True

45
Q

Advantage and disadvantage of PVA

A

related to preservation of protozoan cysts and trophozoites for permanent staining

use of mercuric chloride

46
Q

Merthiolate-iodine-formalin (MIF) / Thiomersal

A
  • Stool preservative useful for the fixation of intestinal protozoans, helminth eggs and larvae
47
Q

In MIF what preserves and what stains

A

Preserves / FIxates : Formalin

Stains : Iodine

48
Q

Used as substitute for permanent staining

A

Sodium acetate-acetic acid formalin (SAF)

49
Q

Images fixed in SAF are

A

not as sharp as those fixed in PVA and Schaudinns

50
Q

Liquid Fixative with long shelf life

A

Sodium acetate-acetic acid formalin (SAF)

51
Q

Container with stool preservative for protozoan trophozoites

A

Modified Cupric Sulfate - PVA

Parasitology Laboratory (12 decks)

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