Page 284 - parasitology for medical and clinical laboratoryprofessionals

264 CHAPTER 12

PROCEDURE 12-2

(continued)

7. Centrifuge with holders that will accommodate the large centrifuge tubes
8. Fresh fecal specimen collected in a suitable container free of contaminants
including urine
9. Ethyl acetate
10. Cotton-tipped applicator sticks
11. Iodine stain
12. Standard microscope slides
13. 22-mm cover glasses

14. Parafilm or rubber caps sized to fit centrifuge tubes
Procedural Steps
1. Obtain a standard 1 3 3-in. microscope slide and place one drop of normal saline on
one end of the slide and a drop of iodine (1:5 dilution of Lugol’s iodine) on the other.
2. Add ½ to 1 teaspoon of fresh species to a container, such as a glass dish, and
use applicator sticks to mix the stool sample with 10 to 15 mL of 10% formalin.
3. Strain the mixture through two layers of dampened gauze squares into the
15-mL glass centrifuge tube. The use of larger thicknesses of gauze may trap
oocysts or microsporidia.

Clinical Precaution:
If the sample is extremely mucoid, the sample should not be strained but should
be centrifuged for 10 minutes at 1500 rpm and then placed on a slide with a drop of
iodine stain and a cover glass.

4. Centrifuge the suspension at 1500 rpm for 10 minutes and then carefully pour
off the supernatant into a container containing disinfectant. If the sample still
contains a large amount of fecal debris, resuspend the sample in 10 to 15 mL of
saline or formalin and recentrifuge. This procedure may be repeated in the pres-
ence of excess fecal debris.
5. Resuspend the rinsed sample (step 4) in 7 to 8 mL of formalin and 4- to 5-mL
ethyl acetate (this step is not necessary if only a small amount of fecal debris is
present following the previous step).
6. Cover the tube with Parafilm or a rubber cap and shake the mixture vigorously

for at least 30 seconds.
7. Remove the Parafilm or cap carefully to avoid splashing into the face or eyes.

8. Recentrifuge the suspension at 1500 rpm for 10 minutes.