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Category: Clinical Microbiology
Examination of Other Specimens from the Intestinal Tract and the Urogenital System, Page 1 of 2
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Symptoms that have been attributed to the pinworm infection, particularly in children, include nervousness, insomnia, nightmares, and even convulsions. In some cases, perianal granulomas may result. If the amount of material limits the examination to one procedure, the use of polyvinyl alcohol (PVA) fixative is highly recommended. Many physicians performing sigmoidoscopy procedures do not realize the importance of selecting the proper fixative for material to be examined for parasites. One of the organisms most strongly suspected when sigmoidoscopy is performed is Entamoeba histolytica, whose morphology is normally seen from the permanent stained smear; however, this identification assumes that RBCs are seen within the cytoplasm of the trophozoites. Duodenal drainage material can be submitted for examination as direct or concentration wet mounts or permanent stained smears, techniques that may reveal the parasites. Examination of urinary sediment is indicated in certain filarial infections. The occurrence of microfilariae in urine has been reported with increasing frequency in Onchocerca volvulus infections in Africa. The identification of Trichomonas vaginalis is usually based on the examination of a wet preparation of vaginal and urethral discharges and prostatic secretions or urine sediment. The efficiency of the polycarbonate membrane filtration technique for detecting Schistosoma haematobium eggs in urine is increased by using a pore size of 14 μm and the suction of a water jet pump.
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Collection of Enterobius vermicularis eggs by the cellulose tape method. (Illustration by Nobuko Kitamura.)
Diagram of a commercial kit (Evergreen Scientific) for use in sampling the perianal area for the presence of pin-worm (E. vermicularis) eggs. On the left is the vial containing the sampler, which has sticky tape around the end. Once this is applied to the perianal area and eggs are picked up on the tape, the label area is placed at one end of the slide. The sticky tape is rolled down the slide and attaches to the glass. This device is easy to use and provides an area sufficient for adequate sampling. A minimum of four to six consecutive negative tapes are required to rule out a pinworm infection; most laboratories are accepting four rather than requesting the full six.
(Top) Enterobius vermicularis (pinworm) eggs seen in a Scotch tape preparation; note the football-shaped eggs with one side a bit more flat than the other. In some preparations, eggs are seen that contain fully developed larvae; such eggs are infective. (Middle) Adult female pinworm found on a collection device. Note the large, round esophageal bulb. (Bottom) Adult female pinworm, enlarged anterior end. Note the cephalic expansions around the end of the head, as well as the large, round esophageal bulb.
Entamoeba histolytica trophozoites. (Left) Trophozoite in wet-mount preparation. (Right) Trophozoite in permanent stained smear. Note that the nuclear and cytoplasmic characteristics are more easily seen after staining (trichrome or iron hematoxylin).
Duodenal aspirate specimens. (Top) Giardia lamblia in mucus from a duodenal aspirate stained with trichrome stain. Note the teardrop trophozoites (from the front view) and the darker-staining trophozoites that resemble the curved part of a spoon (side view). Also notice the number of organisms contained within the mucus. (Middle) A Strongyloides stercoralis rhabditiform larva in a wet mount. The genital primordial packet of cells is visible about halfway down the larva on the right side. (Bottom) Cryptosporidium spp. oocysts in duodenal aspirate material stained with a modified acid-fast stain.
Entero-Test capsule for sampling duodenal contents. The device consists of a length of nylon yarn coiled inside a gelatin capsule. The yarn protrudes through one end of the capsule; this end of the line is taped to the side of the patient’s face. The capsule is then swallowed, the gelatin dissolves in the stomach, and the weighted string is carried by peristalsis into the duodenum. (Illustration by Nobuko Kitamura.)
(Upper) Trichomonas vaginalis trophozoite. (Illustration by Sharon Belkin.) (Lower) T. vaginalis trophozoites seen in a wet mount preparation.
Membrane filtration system. (Upper) Membrane holder, which can be attached to a syringe for filtration of various types of specimens, particularly urine. (Lower) Package of membranes; different sizes with various mesh sizes are available, depending on the clinical specimen and suspected organism size.
Schistosoma haematobium eggs from a urine filtration. Note the terminal spines on the eggs. Since the specimens were not preserved prior to filtration, determination of the viability of the eggs is possible. The viability information should be conveyed to the physician as a part of the report.