Gram Staining (P) Flashcards
What is gram staining method?
1) It is the most important procedure in microbiology
2) It is still the cornerstone of bacterial identification and taxonomic division
Who developed gram staining (and what is his / her nationality)?
Hans Christian Gram (a Danish physician)
When is gram staining developed?
1884
What type of staining procedure is gram staining?
It is a differential staining procedure
What is the principle of differential staining procedure?
It separates most bacteria into two groups on the basis of cell wall composition
What are the characteristics of gram (+) bacteria?
1) It has a thick layer of peptidoglycan
2) It stains purple
What are the characteristics of gram (-) bacteria?
1) It has a thin layer of peptidoglycan and high lipid content
2) It stains red or pink
What is the purpose of crystal violet?
It stains both gram (-) and (+) bacteria
What is the purpose of Gram’s iodine?
It fixes the stain in gram (+) bacteria
What is the purpose of ethanol or acetone?
It washes the stains from gram (-) bacteria
What is safranin?
It is a counterstain
What is the purpose of safranin?
It will re-stain gram (-) bacteria while not interfering with the previous stain in gram (+) bacteria
How to report gram smears?
1) Numbers of bacteria present (whether many, moderate, few, or scanty)
2) Gram reaction of the bacteria {whether Gram (+) or gram (-)}
3) Morphology of the bacteria (whether cocci, diplococci, streptococci, rods, or coccobacilli; also whether the organisms are intracellular)
4) Presence and number of pus cells
5) Presence of yeast cells and epithelial cells
How to do QC for gram staining?
Always check new batches of stains and reagents for correct staining reactions using a smear containing known Gram (+) and Gram (-) organisms
What is (example?) gram (+) control?
Staphylococcus aureus ATCC 25923
