Direct saline
mounts are examined using a microscope.
Physicians have a variety of tools at their disposal to aid them in diagnosing disease. Some are modern, multimillion dollar pieces of equipment. Others cost much less and have been in existence a long time. Direct examination of specimens using a microscope is an example of the latter. Direct saline mounts are a way of preparing a patient sample, usually stool, vaginal discharge or semen, for microscopic viewing.
Purpose
Saline mounts are a wet mount. Wet mounts are made by mixing a portion of the specimen with a liquid. Direct saline mounts are named as such because the liquid used to suspend the sample is a salt water solution called saline. This suspension is examined under a microscope to identify the presence of organisms not visible with the naked eye, particularly parasites. Parasites are organisms that require a host to complete all or part of their life cycle. Saline mounts are also useful for observing microorganism mobility. Movement assists in the detection and identification of disease-causing organisms.
Preparation
Direct saline mounts are prepared in one of two ways. The first method is performed by placing a drop of saline directly on a clean glass microscope slide, adding a small amount of specimen to it and mixing the two together. The second method involves mixing the saline and specimen together in a test tube or other container and adding a drop of the suspension to a slide. Both methods are completed by placing a small, thin piece of glass, called a coverslip, over the drop of diluted specimen. The slide should have enough liquid to allow a printed page to be seen through it. Viewing is difficult in preparations that are too thick.
Examination
The type of microorganisms found on a direct saline mount differ for each type of specimen used. Stools are examined for the presence of helminth (worm) eggs and larvae, as well as protozoa. Protozoa are single-celled parasites having two forms: a mobile form or trophozoite, and an inactive form, a cyst. Both forms are visible on a direct saline mount. In the United States, hookworms are the most common helminths and G. lamblia and E. hystolytica are the most prevalent protozoa. Vaginal discharges are viewed for detection of a protozoan called Trichomonas vaginalis, yeast and clue cells. Clue cells are indicative of a particular type of bacterial vaginal infection. Saline mounts of semen are useful in assessing sperm motility.
Advantages and Disadvantages
As with any technology, saline wet mounts have advantages and disadvantages. They are useful because they are rapid to perform and cost-effective compared to other methods used for diagnosing disease. They allow the health care professional to begin treating the patient sooner. A major disadvantage is that specimens need to be fresh in order to be of value. Consequently, specimens need to be delivered to the lab quickly. Saline mounts are not permanent, therefore they can not be stored and reviewed at a later time. Not all parasites are visible using this method. Sometimes staining techniques are required.
Additional Uses
Saline wet mounts are not limited to diagnosing human diseases. They are commonly used in veterinary medicine, as well. Parasites found in small animals include roundworms, tapeworms, whipworms and the protozoan G. lamblia . Cattle may be infected with hairworms, lung worms and liver flukes . Bloodworms, threadworms and roundworms are a few of the parasites that infect horses.
Tags: Direct saline mounts, Direct saline, diagnosing disease, direct saline, direct saline mount, saline mount, Saline mounts
