Special Stain Protocol- Grocott's Methanamine Silver

862 Words4 Pages
GROCOTT’S METHANAMINE SILVER- GMS Purpose: When used appropriately, Grocott’s Methenamine Silver Stain demonstrates the presence of defined fungi and infectious agents such as Aspergillus sp., Pneumocystis carinii and Cryptococcus neoformans. This method is intended for use with specimen sections that have been fixed in formalin and embedded into paraffin. Principle: Grocott’s Methenamine Silver Stain uses aldehyde groups that react with silver nitrate. This reaction changes the cationic silver into metallic silver, which makes the fungi visible. The reaction begins with the oxidation of the polysaccharide rich fungal cell wall, by use of Chromic Acid. Oxidation of the polysaccharides forms and releases aldehyde groups, which now cover the cell wall. When Methanamine Silver solution is added, the aldehyde groups work together to reduce the silver ions to metallic silver. Gold Chloride is then added as a contrast to the silver, to produce contrast and clarity, making the fungi more crisp and easily viewed. Specimen: The specimen is to be fixed in 10% Neutral Buffered Formalin, and paraffin sections should be cut at four to five microns and placed on Plus (+) slides. The tissue is dried for 20-30 minutes in an oven at 68°C. Deparaffinization and rehydration should be carried out immediately before staining. Positive controls are to be processed at the same time as the unknown test slide. Equipment and Supplies: The equipment and supplies needed are acid cleaned glassware, coplin jars, and an incubator oven. Safety Requirements: Lab coats and gloves, and all personal protection equipment should be worn at all times. Pants and proper footwear should be worn to avoid contact with substances corrosive to the skin. Long hair should also be pulled back to avoid contact with chemicals. Reagents: 2% Chromic Acid * Chromium trioxide 10.0 gm *

More about Special Stain Protocol- Grocott's Methanamine Silver

Open Document