DIAGNOSTIC PARASITOLOGY (Stool examination)

Question 1

The container for stool examination should be:

Answer 1

• Clean (not necessarily sterile)
• Wide-mouthed
• With a tight-fitting lid

Question 2

Important considerations:

Intake of drugs (antidiarrheal, antacids, bismuth, barium, laxatives) leave crystalline residues, collection of stool should be:

Answer 2

Collect a week after intake

Question 3

Important considerations:

Antibiotic intake

Answer 3

Decreases recovery of protozoans

Question 4

Important consideration:

Amount of stool collected:

Answer 4

Formed: Thumb size
Watery: 5-6 tablespoons

Question 5

Important considerations:

Stool contaminated with toilet water, urine, and soil:

Answer 5

• Destroys protozoan trophozoites
• May contain free-living parasites

Question 6

Important consideration: Stool sample should be examined within:

Answer 6

Examined within 30 minutes to 1 hour

Question 7

Important consideration:
Storage of stool sample:

Answer 7

Refrigerator: (3-5C)
never freeze/keep in incubators

Question 8

Important consideration; If there is delay:

Answer 8

Use preservatives

Question 9

Stool:preservative ratio =

Answer 9

1:3

Question 10

Most frequently used; 5% for protozoan cysts; 10% for helminth eggs and larva, buffered with NaPhosphate

Answer 10

Formalin

Question 11

Contains mercuric chloride, used in preparation for staining:

Answer 11

Schaudinn’s solution

Question 12

Used in preservation of protozoan cysts and trophozoites for permanent staining; Normally incorporated into Schaudinn’s solution; has hgCl2; may use cupric sulfate instead of HgCl2 (toxic)

Answer 12

PVA (polyvinyl alcohol)

Question 13

No mercuric chloride, but stained smears are not as sharp as PVA or Schaudinn’s:

Answer 13

SAF (sodium acetate-acetic acid-formalin)

Question 14

Consistency of stool that may indicate presence of trophozites:

Answer 14

Watery to soft

Question 15

Consistency of stool that may indicate presence of cyst:

Answer 15

Formed to semi-formed

Question 16

Macrophages can be mistaken as:

Answer 16

Trophozoites

Question 17

Direct fecal smear (DFS) procedure:

Answer 17

2 mg of stool + 1 drop of NSS (and?or iodine for identification of amoeba)

Question 18

To better demonstrate nucleus in DFS, use:

Answer 18

Nair’s buffered methylene blue

Question 19

50-60 mg stool or size of 2 mongo beans is covered with cellophane soaked in glycerine and malachite green, then spread

This technique is called:

Answer 19

Kato Thick Smear (KTS)

Question 20

In KTS, glycerine is used as:

Answer 20

Clearing solution; clears fecal debris

Question 21

In KTS, malachite green is used to:

Answer 21

Create contrast to easily detect/identify; minimizes brightness of microscopic field: FOR HELMINTHS ONLY

Question 22

Sedimentation procedures:

Answer 22

1. Acid ether concentration technique
2. Formalin ether concentration technique

Question 23

Acid ether concentration technique components:

Answer 23

40% HCl: Dissolves albuminous material
Ether: Dissolves neutral fats, absorbs fecal debris

Question 24

Formalin ether concentration technique components:

Answer 24

10% Formalin: fixative
Ether: Dissolves neutral fats, adsorbs fecal debris

Question 25

Formalin ether concentration layers after centrifugation:

Answer 25

• Ether
• Debris
• Formalin
• Sediment

Mnemonic: “EDFS”

Question 26

In formalin ether concentration technique, for the recovery of helminth eggs (cestode eggs) and protozoan cysts (Giardia cysts), use ________ in place of ether:

Answer 26

ETHYL ACETATE

Question 27

Flotation procedures:

Answer 27

1. Zinc sulfate flotation
2. Sheather’s sugar flotation
3. Brine flotation

Question 28

Zinc sulfate flotation:
____% ZnSO4 with Specific gravity _______.

Answer 28

33% ZnSO4
S.G: 1.18 - 1.20

Note:
1.18 SG = FRESH SPECIMEN
1.20 SG = PRESERVED

Question 29

In Zinc sulfate flotation, if the SG is too high:

Answer 29

Distortion & shrinkage of ova and cyst

Question 30

Boiled sugar solution preserved with phenol; best for the recovery of coccidian cysts (intestinal)
Isospora
Cyclospora
Cryptosporidium

Answer 30

Sheather’s sugar flotation

Question 31

In Sheather’s sugar flotation, the SG of sucrose must be:

Answer 31

SG of sucrose: 1.25 - 1.27

Question 32

Flotation procedure that uses saturated salt solution; centrifugation not needed:

Answer 32

Brine flotation

Question 33

Disadvantages of Brine solution:

Answer 33

• Shrinks hookworms & Schisto eggs
• Operculated eggs do not float

Question 34

Stool culture methods:

Answer 34

1. Copro culture
2. Harada-mori/test tube culture method

Question 35

Egg counting procedures are used for:

Answer 35

For treatment and monitoring; reflects intensity of infections & disease severity

Question 36

Egg counting procedures:

Answer 36

1. Kato-Katz method/Cellophane covered thick smear (uses measured amount of stool)
2. Stoll egg count

Question 37

Stoll egg count diluent uses:

Answer 37

0.1N NaOH

Question 38

Stool displacement flask for stoll egg count is calibrated at:

Answer 38

Calibrated at 56 mL & 60 mL

Question 39

Stains used for stool specimen:

Answer 39

1. Acridine orange - for buffy coat malaria
2. Iron hematoxylin
3. Trichome
4. Chlorazol black E
5. Kinyoun’s acid-fast