DIRECT FECAL SMEAR (Saline and lodine Wet Mount Preparations) Flashcards
is commonly used as a quick screening test to check for the presence of any intestinal parasite in humans and even in animals.
Direct Fecal Smear (DFS)
DFS may be examined as a _______, or _____ and _____
wet mount, or can be dried and stained.
are useful for detecting motile organisms.
Wet mounts
Protozoa
are often detected via a direct fecal smear with_____ solution, and are best acquired from the surface of fresh feces, obtained via a fecal loop or thermometer, or from a swab of the rectum.
iodine
________ that is present on the surface of feces should also be examined microscopically since many protozoa will get trapped there.
Mucus
Fecal specimens
should be examined grossly for consistency (formed, soft, loose, or watery), and for presence of:
Mucus
Blood
larval or adult worms and
proglottids
are more likely to be found in watery or loose specimens
Protozoan trophozoites
predominate in formed or soft specimens
Cysts
may be found in any type of fecal specimen.
Helminths or their eggs
- may be more numerous in the last portion of stool and should be specifically sought in mucus
Protozoan trophozoites
allow detection and observation of motile protozoa trophozoites and helminth larvae.
Direct saline wet mounts of fresh feces
allow detection of parasites that do not concentrate well.
Concentration procedures increase the examiner’s ability to detect protozoa cysts and helminth eggs and larvae but are unsatisfactory for detecting protozoan trophozoites
Direct mounts of preserved specimens
are useful for detection and morphologic examination of protozoan trophozoites and cysts.
Permanent stains
The circumstances under which each procedure is performed varies depending on the type of specimen (4) submitted.
formed, soft, loose, or watery
may be concentrated by simple centrifugation rather than by floatation or formalin-ethyl acetate concentration.
Watery specimens
The direct wet mount may be omitted if the specimen is submitted in _____
preservatives
should be examined by a concentration procedure, although improved yield has been demonstrated when a permanent stain is added to the work-up
formed specimens
Advantagess of DFS
● Useful for detecting motile organisms.
● Protozoa are often detected via a direct fecal smear.
● Quick process
Disadvantages of DFS
● Small size of the sample limits its usefulness.
● You may get inaccurate results.
● If your examination finds no evidence of a parasite but the patient actually harbors the parasite, then the results are called a false negative result.
● False negative results are common with direct fecal smears.
MATERIALS for DFS
● Microscope slides
● Cover slips
● Sodium chloride solution
● Lugol’s lodine Solution
● Wooden applicator
● Fresh stool
● Gloves
Percent of NSS
.85%
Why do we need to mix the stool beforehand
For even distribution of suspected parasites
SLIDES
2 types of specimen prep
● Saline Specimen Prpn.
● lodine Specimen Prpn
Used to onserve for the motility of parasite
NSS
Trophozoites and cysts can be seen by using
NSS
Can only see cysts
Lugol’s iodine solution
Purpose of Lugol’s iodine
Used to visualize and enhance the morphology of internal structures
Trophozoites are toxic to
Iodine
Used to detect Ovas
Concentration Method
● A drop of warm____ or ____ is placed over a clean microscopic slide.
● About____ of stool sample should be taken and mixed with soln placed over the slide.
●_____ is placed avoiding air bubbles.
● Examined under Microscope.
Saline or Lugol’s lodine
2mg
Coverslip
● The fecal smear may be examined in its wet state by simply placing a cover slip over the drop of wet fecal material.
● This method is most useful looking for_____ which can be observed by their characteristic movement and appearance.
Wet Mount Technique
trophozoites
Wet Mount Technique
Procedure (3)
Collect sample from container
Add sample to slide
Place cover slip on sample
DFS
About______ of stool (amount forming a low cone at the tip of an applicator stick) is comminuted thoroughly with a drop of ______% sodium chloride solution (NSS) and then covered with a cover slip.
2 mg
0.85%
This is a routine method of stool examination primarily useful in the detection of motile protozoan trophozoites
DFS
DFS
In this preparation, the trophozoites appear very pale and transparent.
Trophozoites can be stained to demonstrate the nuclear morphology using__________ solution
Nair’s buffered methylene blue (BMB)
T or F
Protozoan cysts can also be seen in a DFS.
True
A weak iodine solution ______ or ______ can be used as a temporary stain to demonstrate nuclei
(Lugol’s solution or D’Antoni)
The cytoplasm will stain golden yellow, the nucleus will be pale and refractile, and the glycogen will be deep brown.
Helminth eggs and larvae can also be detected using this preparation.
Because the amount of stool used in DFS is very small, light infections may not be detected.
Iodine
a tool to measure cysts and ova, will be useful in specific species identification.
Micrometry
