Gram Stain Workshop for the Laboratory Generalist Karen Stiles, SM(ASCP)CM State Training Coordinator Assistant Chemical Terrorism Coordinator Nebraska Public Health Laboratory 402-559-3590
[email protected] 1 GRAM STAIN OBJECTIVES: Upon completion, the participant will be able to: 1. Explain the principle of the Gram stain procedure, including what elements can affect staining results 2. Correlate the most common pathogens with positive Gram stains from blood cultures and direct specimen sterile body fluid smears 3. Perform and interpret Grams stains 2 Purpose of Gram Stain Classify bacteria based on form, size, cellular morphology, Gram reaction Assess quality of specimen Identify specific infectious agent from morphology and Gram reaction Correlation with culture growth Correlation with culture-independent methodologist Guide presumptive antibiotic therapy 3 Principle of Gram Stain Cell wall composition Gram positive – think peptidoglycan layer with teichoic acid Gram negative – high in lipid content Basic premise Crystal Violet – all cells take up primary stain Gram’s iodine – mordant to form complex Decolorizer – mixture of acetone and alcohol Dehydrate lipids in Gram negative cell walls, wash out complex Gram positive cells resistant, retain stain complex Safranin - counterstain 4 Gram negative cells take up counterstain Preparation of Samples Specimen Type Preparation CSF/sterile body fluids Cyto/Centrifuge Blood Culture Broth Drop to slide Tissue Touch prep Tissue homogenate Drop to slide Swabbed material Roll