(c) Specimens preserved in PVA may be maintained for record or for
reference study material.
(d) When ordering polyvinyl alcohol powder, specify its use. All grades
of PVA are not satisfactory for preserving fecal specimens.
(e) If dehydration occurs, add more fixative.
c. Merthiolate-Iodine-Formaldehyde Fixative (MIF). This solution can be used
as a fixative, as a stain for wet preparations, and as a concentration procedure.
(1)
Stock reagents.
(a) Merthiolate-Formaldehyde (MF)--Solution A.
Distilled water .................................................... 250.0 ml
Formaldehyde (saturated) ................................. 25.0 ml
Tincture of merthiolate (Lilly 1:1,000) ................ 200.0 ml
Glycerin ............................................................. 5.0 ml
Store in a stoppered brown glass bottle.
(b) Lugol's Iodine Solution (I)--Solution B.
Iodine crystals (powdered) ................................ 5.0 gm
Potassium iodide ............................................... 10.0 gm
Distilled water .................................................... 100.0 ml
Dissolve the potassium iodide in water. Add the iodine crystals
slowly and shake until dissolved. Filter and store in a brown bottle.
This solution is stable only for three weeks.
(2) Working reagent. Add 18.0 milliliters of solution A to 1.2 milliliters of
solution B immediately prior to use. (For smaller or larger volumes, decrease or increase
both components proportionately). Mixing the two solutions too far in advance causes a
precipitate to form, thus reducing the staining properties.
(3)
Procedure.
(a) Stool specimens should be immediately submitted to the laboratory
or fixed at the collection site.
(b) With an applicator stick, thoroughly mix one part feces with 10 parts
MIF in a labeled 23 milliliter screwcap bottle. This should be performed immediately on
receipt of the specimen.
MD0841
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