Saline Wet Mount Microscopy: Introduction, Principle, Test Requirements, Procedure, Result-Interpretation, Limitations, and Saline Wet Mount Microscopic Footages

Introduction of Saline Wet Mount Microscopy

Saline wet mount microscopy of the stool or feces or stool wet mount microscopy is the simplest and basic technique for the study of feces and is applicable in every medical laboratory even in a small setup. Saline wet mount microscopy uses for the following objectives-

1. To observe live trophozoites (e.g. Entamoeba histolytica/dispar, Girdia lablia, Trichomonas, etc.) and larvae of parasites (e.g. Strongyloides stercoralis) are motile except inactive forms.
2. To find out eggs or ova, cysts, and oocysts of different parasites (Helminths, protozoa, and coccidian parasites).
3. To determine the presence of leukocytes (WBCs) and erythrocytes in a fecal smear.
4. It also gives hints about the motility of bacteria (Shigella non-motile causing bacillary dysentery whereas Vibrio cholerae shows darting motility which is a causative agent of cholera).
5. It also remarks on the presence of fungal elements ( yeast cells, hyphae, or fungal spores).
6. It also visualizes the presence of non-parasitic structures like Charcot- Leyden crystal,  muscle fibers, fat globules, starch cells, vegetable fibers, hair, etc.
7. The growth of yeasts and bacteria on culture media may be differentiated by this simple technique.
8. The shape of bacteria, cocci, or bacilli can be differentiated from the colony of the culture plate by saline wet mount microscopy.

Principle of the Saline Wet Mount Microscopy

Saline wet mount preparation for stool/feces uses analyzing a stool specimen in coprology (study of feces). It utilizes a physiological saline solution (0.85% NaCl ) as an isotonic media to maintain the cellular structure of the various microbes as well as our cells that are found in stools and other stools too.

Requirements for Saline Wet Mount Microscopy

• Physiological saline (0.85% NaCl)
• Specimen: stool/feces
• Sterile bamboo sticks or a low cone on the end of a wooden applicator stick
• Clean and grease-free slides and
• Cove slips(22- by 22-mm)
• Microscope
• Gloves
• Waste bin

Saline wet mount of stool Preparation

1. First, wear the groves.
2. Take a clean and grease-free slide.
3. Add one drop of physiological saline and then add a stool equivalent to a match stick head (2 mg)  with the help of a stick.
4. Mix it properly and apply a coverslip over a uniform suspension without creating bubbles.
5. Note: If a fresh stool specimen is received and if blood and mucus are present, the specimen should be examined as a direct mount making sure to sample the bloody areas.
6. Examine the entire 22- by 22-mm coverslip systematically with the low power objective (10X ) and low light intensity.
7. If any suspicious objects encounter, examine them with the high dry objective (40X).

Result Interpretation of Feces Saline Wet Mount Microscopy

Presence of active trophozoite/s: Motile retractile bodies

Cyst, oocyst, egg, inactive trophozite/s, larvae: Retractile bodies and finally focus at high dry power field

Keynotes on Saline Wet Mount Microscopy

1. There is little difference between normal and physiological saline. Physiological saline is  0.85% NaCl whereas normal saline is 0.9% NaCl.
2. Gram’s iodine is not usable for staining parasitic organisms and for this D’Antoni’s iodine uses.
3. Oil immersion examination is also preferred in parasitology for the permanent stained smear of parasites.
4. Intestinal protozoa can not conform on the basis of a wet mount alone and thus permanent stained smears require to confirm the specific identification of suspected organisms.

Limitations of Saline Wet Mount Microscopy

1. Due to the lack of stain, it is difficult to get morphological details.
2. Inappropriate preparation of the smear may hide parasites.
3. Improper adjustment of the microscope in relation to the objective may create problems.

Saline Wet Mount Microscopic Footages

Entamoeba histolytica Cyst in Saline Wet Mount Microscopy

Cysts of Giardia lamblia in Saline Wet Mount Microscopic Image

Cyclospora cayetanensis Oocyst in Saline Wet Mount Microscopic Footage

An Infertile egg of Ascaris lumricoides or roundworm in saline wet mount Microscopy

A fertilized egg changing to the larva of Ascaris lumbricoides or roundworm in stored stool microscopy

A fertile egg of roundworm in human feces Microscopy

Tapeworm or Taenia solium or Taenia saginata egg in Saline Wet Mount Microscopy

Hookworm or Ancylostoma duodenale or Necator americanus egg in saline wet mount microscopic picture

Trichuris trichura or whipworm egg in a saline wet mount Microscopic Footage

Hymenolypsis nana or Vampirolepsis egg showing hooklets in feces microscopic image

Further Readings

1. Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji
2. Atlas of Medical Helminthology and protozoology -4th edn  -P.L.  Chiodini, A.H. Moody, D.W. Manser
3. Markell and Voge’s medical parasitology-9th edition.
4. Parasitology: 12th edition-K. D. Chatterjee
5. District laboratory practice in Tropical countries –Part-I-Monica Chesbrough
6. Isenberg clinical microbiology procedures Handbook-2nd edition. Vol. 2
7. http://www.med-chem.com/para-site.php