EXERCISE 5:

Question 1

is a routine part of parasitologic procedures that allows the detection of small numbers of parasites that may be missed by using only a direct fecal smear

Answer 1

stool concentration technique

Question 2

is indicated when the direct wet mount examination is negative despite the clinical symptoms indicating parasitic infection of a patient.

Answer 2

stool concentration technique

Question 3

Technically, the purpose of stool concentration is to

Answer 3

aggregate parasites
remove as much debris as possible

Question 4

Concentration techniques can be performed on

Answer 4

fresh or preserved stool specimens

Question 5

may be recovered by concentration

Answer 5

Helminth eggs and larvae, and protozoan cysts

Question 6

will not be seen as they are usually destroyed during the concentration procedure

Answer 6

protozoan trophozoites

Question 7

two types of stool concentration procedures:

Answer 7

(1) sedimentation
(2) flotation

Question 8

are designed to separate parasites from fecal debris by centrifugation and/or differences in specific gravity

Answer 8

(1) sedimentation
(2) flotation

Question 9

is accomplished by suspending the fecal specimen in water or aqueous solution of low specific gravity and allowing natural settling to occur, or accelerating the process by centrifugation, leaving the parasites at the bottom of the suspension

Answer 9

Sedimentation technique

Question 10

permits the separation of protozoan cysts and certain helminth eggs from excess debris through the use of a liquid with a high specific gravity

Answer 10

Flotation technique

Question 11

The parasites, by their buoyancy, are recovered in the (?), and the debris remains in the bottom of the tube.

Answer 11

surface film

Question 12

more efficient and easier to perform accurately

Answer 12

sedimentation technique

Question 13

is the most widely used sedimentation technique

Answer 13

Formalin – ether sedimentation procedure

Question 14

It is approved and recommended by the Department of Health for screening food handlers and Overseas Filipino Workers (OFW).

Answer 14

Formalin – ether sedimentation procedure

Question 15

As a sedimentation technique, its principle is based on

Answer 15

specific gravity

Question 16

is added to a formalin-fixed sample and the tube is then centrifuged

Answer 16

Ether

Question 17

are heavier than the solution and settle in the sediment of the tube

Answer 17

Parasites

Question 18

is usually lighter and rises to the upper layers of the test tube

Answer 18

fecal debris

Question 19

The tube is then decanted and the sediment is examined in a

Answer 19

wet preparation, unstained (i.e., with saline) and/or with iodine

Question 20

A (?) of fresh stool is mixed with Formalin (5-10%). Too much or too little specimen will result in an ineffective concentration.

Answer 20

half-teaspoon

Question 21

The stool-formalin mixture is allowed to stand a minimum of (?) before straining through a gauze for adequate fixation/preservation of parasites, if there’s any.

Answer 21

30 minutes

Question 22

When vigorously shaking the tube for (?) after the addition of ether, exert pressure on the stopper throughout and hold the tube so the stopper is directed away from your face.

Answer 22

10 seconds (up to 30 seconds)

Question 23

is used as an extractor of debris and fat from the feces and leaves the parasites at the bottom of the suspension.

Answer 23

Ether (ethyl ether)

Question 24

is widely recommended as a substitute for ether which is an explosive and flammable compound.

Answer 24

Ethyl acetate

Question 25

Ethyl acetate is used the same way in the procedure and is much safer, and more efficient for recovery of (?) and as well as eggs from (?) and (?)

Answer 25

Giardia lamblia cysts Taenia sp. Hymenolepis nana eggs

Question 26

Wait for (?) before the stopper is carefully removed to prevent explosive release of pent-up aerosol of ether/ethyl acetate after shaking.

Answer 26

15 to 30 seconds

Question 27

The current recommendation is centrifugation at (?) for a minimum of (?).

Answer 27

500 g

Question 28

Let the centrifuge reach the recommended speed before you begin to monitor centrifugation time. If the centrifugation time at the proper speed is reduced, some organisms (?) may not be recovered in the sediment.

Answer 28

coccidia and microsporidia

Question 29

Four layers should result:

Answer 29

a small amount of sediment (containing the parasites) in the bottom of the tube a layer of formalin, a plug of fecal debris on top of the formalin layer a layer of ether/ethyl acetate at the top

Question 30

After the plug of debris is rimmed with an applicator stick, properly decant the supernatant fluid by completely inverting the tube with a single movement and the fluid is allowed to drain for at least (?).

Answer 30

5 seconds

Question 31

(?) This is particularly important so as not to disturb the sediment. When working with plastic centrifuge tubes, while the tube is still upside down, the sides of the tube is swabbed with a (?) stick to remove excess ether/ethyl acetate.

Answer 31

Do NOT tap the tube. cotton-tipped applicator

Question 32

in the smear of the sediment prepared for examination, forms bubbles that obscure the material being examined.

Answer 32

Excess ethyl acetate

Question 33

After proper decanting, a drop or two of fluid remaining on the side of the tube may run down into the sediment. Mix this fluid with the (?) and transfer, using a Pasteur pipette, a small amount of material to a slide and add a coverslip.

Answer 33

sediment

Question 34

If the sediment is still somewhat solid, add a drop or two of (?) to the sediment, mix, and examine.

Answer 34

saline

Question 35

As in the direct wet smear, (?) can be added to enhance morphological detail.

Answer 35

iodine

Question 36

The formalin-ether or formalin-ethyl acetate technique has the following advantages:

Answer 36

1. Easy to perform, allows recovery of the broadest range of organisms - helminth eggs and larvae, and protozoan cysts, and is least subject to technical error. 2. Sediments can be stored for a long period of time. 3. Extracts and dissolves fats or mucoidal materials.

Question 37

Similar with other parasitologic methods, this technique also consists of limitations which are follows:

Answer 37

1. Use of ether which is an explosive and flammable compound. 2. The resulting preparation contains more debris. 3. Protozoan trophozoites are less likely to be seen.

Question 38

is also based on differences in specific gravity between the sample debris, which in this case is heavy and sinks to the bottom of the test tube, and potential parasites, which are lighter and float toward the top of the tube.

Answer 38

zinc sulfate flotation technique

Question 39

In this procedure, zinc sulfate, with a specific gravity of (?) to (?), is used as the concentrating solution.

Answer 39

1.18 (for fresh stool) 1.20 (formalin-fixed stool)

Question 40

is added to the stool specimen and centrifuged, the parasites float to the surface and can be skimmed from the top of the tube.

Answer 40

zinc sulfate

Question 41

A half-teaspoon of fresh stool is used to prepare an emulsion in distilled water (about 10 ml). Too much or too little specimen will result in an ineffective concentration.

Answer 41

distilled water (about 10 ml).

Question 42

However, the addition of fresh stool to distilled water will cause (?) present to rupture.

Answer 42

Blastocystis hominis

Question 43

Hence, (?) may substitute for water.

Answer 43

0.85% NaCl or 5-10% formalin

Question 44

Some prefer to use (?) for all the rinses throughout the procedure.

Answer 44

10% formalin

Question 45

Mix the stool and formalin thoroughly. Let the mixture stand a minimum of (?) for fixation

Answer 45

30 minutes

Question 46

A longer centrifugation time (?) for the wash steps are necessary for the possible recovery of coccidia or microsporidia.

Answer 46

(10 minutes at 500 g)

Question 47

The washing phase is carried until the supernatant fluid after the centrifugation is (?). Three washings and centrifugations are usually sufficient.

Answer 47

light tan or clear

Question 48

If fresh stool is used (or those fixed with non-formalin preservatives), the zinc sulfate should be prepared with a specific gravity of

Answer 48

1.180

Question 49

zinc sulfate with specific gravity of (?) is used for formalin-preserved stool.

Answer 49

1.200

Question 50

Prepare zinc sulfate ((?) aqueous solution).

Answer 50

33%

Question 51

Check the specific gravity of the zinc sulfate using a hydrometer (with a range that includes [?])

Answer 51

1.180 to 1.200

Question 52

Using the hydrometer (with the solution at room temperature):

Answer 52

•Mix the solution well. •Float the hydrometer in the solution, giving it a slight twist to see that it is completely free from the sides of the container. •Read the bottom meniscus. •Then, adjust to the desired specific gravity (1.180 or 1.200) by adding more zinc sulfate crystals to the solution if below the desired specific gravity ; OR diluting with distilled water the specific gravity is higher than desired.

Question 53

After addition of zinc sulfate, centrifuge for (?). Allow the centrifuge to come to a stop without interference or vibration.

Answer 53

1 minute at 500 g

Question 54

Remove the tubes from the centrifuge prior to sampling the (?). This is acceptable; however, there is more chance that the surface film will be disturbed prior to sampling.

Answer 54

surface film

Question 55

Two layers should result:

Answer 55

a small amount of sediment in the bottom of the tube and a layer of zinc sulfate

Question 56

Remove 1 or 2 drops of the (?) with a freshly flamed (and allowed to cool) wire loop and place them on a slide.

Answer 56

surface film

Question 57

Do not use the loop as a (?); simply touch the surface (bend the loop portion of the wire 90o so the loop is parallel with the surface of the fluid).

Answer 57

“dipper”

Question 58

Make sure the wire loop is not below the (?). A Pasteur pipette may be used instead of wire loop.

Answer 58

surface film

Question 59

Altenative procedure:

Answer 59

•Add a small amount of zinc sulfate to the tube so that the fluid forms a slightly convex meniscus. •A coverslip is then placed on top of the tube so that the undersurface touches the meniscus. •Leave undisturbed for 5 minutes. Carefully remove the coverslip, and place it on a slide for examination

Question 60

Remove the surface film for examination within (?) of the time the centrifuge comes to a stop.

Answer 60

5 minutes

Question 61

Parasites are subject to collapse and distortion when left in contact with (?) for a longer time.

Answer 61

high-specific-gravity zinc sulfate

Question 62

If zinc sulfate is the only concentration method used, examine both the (?) to ensure detection of all possible organisms.

Answer 62

surface film and the sediment

Question 63

The (?) is advantageous in that it yields a clear preparation than does the sedimentation technique.

Answer 63

zinc sulfate floatation technique

Question 64

Similar with the first concentration method, this technique also consists of limitations which are follows:

Answer 64

1. Protozoan cysts and thin-shelled helminth eggs are subject to collapse and distortion. 2. Some helminth eggs (operculated eggs, or unfertilized Ascaris eggs) do not concentrate well. 3. Cannot be used for fatty stool, or too hard stool.

Question 65

High specific gravity of the zinc sulfate causes the (?) to pop open; the eggs fill w/ fluid and sink to the bottom rather than float.

Answer 65

opercula

Question 66

Unfertilized eggs of (?) are very dense, thus they sink to the bottom of the solution.

Answer 66

Ascaris lumbricoides

Question 67

Primarily, a stool concentration technique is indicated when:

Answer 67

a. direct wet mount examination of stool samples are negative.

Question 68

2. Which of the following statements correctly describes a sedimentation technique?

Answer 68

A. Stool specimen is suspended in water or normal saline solution.

Question 69

3. This reagent is used as extractor of debris and fat from the stool to be examined after concentration.

Answer 69

C. Ether

Question 70

4. In the formalin-ether sedimentation concentration technique, appropriate fixation of parasites, if present, is achieved after addition of ether for:

Answer 70

A. 10 up to 30 seconds

Question 71

5. For purposes of safety, ether in the formalin-ether sedimentation concentration technique is widely substituted with:

Answer 71

B. ethyl acetate

Question 72

6. Centrifugation of set ups for formalin-ether sedimentation concentration technique should be carried out for 10 minutes at the speed of:

Answer 72

C. 500 g

Question 73

7. In the ZnSO4 flotation concentration technique, washing phase is carried out until:

Answer 73

B. the supernatant is clear

Question 74

8. The specific gravity of ZnSO4 to be used when formalin-preserved stools are to be subjected to flotation concentration technique is:

Answer 74

D. 1. 200

Question 75

9. Which instrument is used to measure specific gravity of solutions?

Answer 75

C. Hydrometer

Question 76

10. If specific gravity of the ZnSO4 is greater than desired, in order to come up with the desired specific gravity of ZnSO4, adjustment is made by addition of:

Answer 76

A. distilled water