UNIT 3: FECAL CONCENTRATION TECHNIQUES

low;

negative;

Schistosoma and Taenia

Indications of Fecal Concentration

•          When the number of organisms in the stool specimen is ____

•          When the initial wet mount examination is _______

•          When the detection of _______________ is required

 

protozoan cysts;

worm eggs & larvae

Advantages of Fecal Concentration:

1.              Can recover all types of __________ and _________ (e.g., roundworms, schistosomes, tapeworms, and other flukes)

protozoan trophozoites

Disadvantages of Fecal Concentration:

1.              Not recommended for ________________ (destroyed in the procedure)

T

T or F

Thus, whenever possible, the stool should be concentrated.

1. Sedimentation

2. Flotation

2 General Types of Concentration Techniques

Sedimentation

2 General Types of Concentration Techniques

• In this technique eggs and cysts settle down at the bottom following centrifugation.

• It involves concentration of stool specimens by centrifugation. The protozoan cysts and helminths eggs are concentrated at the bottom of the test tube because they have greater density than the suspending medium.

specific gravity lower ;

sediment.

2 General Types of Concentration Techniques

• Sedimentation: Solutions of a _____________ than the parasitic organisms are used thus concentrating the eggs, cysts and other forms in the _______

Floatation

2 General Types of Concentration Techniques

• Uses solutions which have higher SG than the organisms to be floated so that the organisms rise to the top and the debris sinks to the bottom

Floatation

2 General Types of Concentration Techniques

• Produces a cleaner material than the sedimentation technique

eggs and cysts

2 General Types of Concentration Techniques

• Floatation: the walls of ___________ often collapse, thus hindering identification;

• some parasite eggs do not float

1. Acid Ether Concentration Technique

2. Formalin-Ether/Formalin-Ethyl Acetate Concentration Technique

3. Merthiolate-Iodine-Formaldehyde Concentration Technique

Types of Sedimentation

10mL of 10% formalin;

1 gram;

7mL mark;

3mL of ether, or ethyl acetate;

one minute;

supernatant;

Formalin-Ether Concentration Technique

•          Procedure

1.              Add ____________ to approximately _______ of feces and stir using an applicator stick, until it becomes a slightly cloudy suspension;

2.              Fit a gauze pad into a funnel and place the funnel on top of the centrifuge tube;

3.              Pass the fecal suspension through the pad into the centrifuge tube until the _______ is reached;

4.              Remove the pad and discard it with the lumpy residue;

5.              Add _________________________, and mix well for one minute;

6.              Transfer back to the centrifuge tube and centrifuge for __________;

7.              Loosen the fatty plug (i.e., debris) with an applicator stick, and pour away the ___________ by quickly inverting the tube.

8.             Replace the tube in its rack and allow the fluid on the sides of the tube to drain down to the sediment. Mix well and transfer a drop to a slide for examination under a cover glass;

9.             Use the 10x and 40x objectives to examine the whole area under the cover glass for ova, cysts, and larvae.

Name the parts in FECT

Formaldehyde-ether/ethyl acetate concentration

• Used for the routine recovery of protozoan cysts, helminth larvae and ova, including operculates and schistosoma eggs

• Hymenolepsis nana eggs

• Giardia lamblia & Iadomoeba butschilii cysts

Formaldehyde-ether/ethyl acetate concentration

• Disadvantages: Not for ___________________ and ____________________________

1. Brine flotation/saturated salt solution concentration

2. Sheather’s sugar centrifugal concentration

3. Zinc sulfate concentration

Types of Floatation

Brine flotation/saturated salt solution concentration

Types of Floatation

• Used for the recovery of ova other than operculates and Schistosoma

• Recommended for the screening of hookworms in a less suitable environment

• Inexpensive, easy-to-perform (rapid)

• Shrink = hookworm and strongyloides larvae, protozoan cysts, and Schistosoma eggs

• Float = Clonorchis, Opistorchis, and Heterophyid fluke eggs

Brine flotation/saturated salt solution concentration

• Shrink =

• Float =

• 500 g table sugar

• 320 ml distilled water

• phenol crystal melt in hot waterbath 6.5 g

Sheather’s sugar centrifugal concentration

• Composition of Sheather’s sugar solution:

• nematode eggs and protozoan cysts

Sheather’s sugar centrifugal concentration

• Advantage: Reveals most ________________________

• Fluke eggs and tapeworms

• nematode larvae

Sheather’s sugar centrifugal concentration

• Disadvantage: ___________________ are not demonstrated well;

• most _______________ are not demonstrated well

1 gram;

1 part;

2 parts;

1,500 RPM for 10 minutes;

10 minutes

Sheather’s sugar centrifugal concentration

Ø Soften _______ of feces with water;

Ø Strain the aqueous suspension through a gauze;

Ø Mix ________ aqueous suspension with _____ of Sheather’s sugar solution;

Ø Pour into a centrifuge tube, centrifuge at ____________

Ø Pour the supernatant into a meniscus and add a sufficient solution to bring the meniscus to the top

Ø Place a coverslip and wait for _________;

Ø Examine under a microscope

Types of Floatation

Ø A simple and efficient method for the recovery of ova, larvae, and protozoan cysts

Ø Recommended for the mass examination of roundworm eggs and protozoan cysts

Ascaris, Trichuris, Trematodes, and Pseudophyllid eggs;

fatty stools

Zinc sulfate concentration

• Disadvantage: not suitable for the recovery of _________________________

• not convenient when working with ______