Staining Tips

The single most important step in the preparation of a well stained fecal smear is good fixation. If this has not been done, the protozoa may be distorted or shrunk, may not be stained, or may exhibit an overall pink or red color with poor internal morphology. 2. Slides should always be drained between solutions. Touch the end of the slide to a paper towel for two seconds to remove excess fluid before proceeding to the next step. You can also pull the slide from the fluid, allow the excess fluid to run back into the container, and then move the slide to the next reagent container. This will maintain the staining solution for a longer period. If you are using staining dishes and racks, lift the rack from the fluid, rest the rack against the dish to allow excess fluid to run back into the dish, and then move the rack to the next dish of reagent. 3. Incomplete removal of mercuric chloride (liquid Schaudinn’s fixative and liquid Schaudinn’s fixative with PVA) may cause smear to contain highly refractive crystals or granules, which may prevent detection or identification of any organisms present. The 70% ethanol-iodine solution removes the mercury from the slide; the subsequent alcohol rinses then removes the iodine (should be strong-tea color). Thus, when the slide is ready for trichrome staining, both the mercury and iodine have been removed. A few minutes (3-5 min) are usually sufficient to keep the slides in the iodine-alcohol; too long a time in this solution may also adversely affect the staining of the organisms. Lynne Garcia is currently th