Which staining method distinguishes between Gram-positive and Gram-negative bacteria?

Which staining method distinguishes between Gram-positive and Gram-negative bacteria?

• A. Tissue pathology
• B. Gram stain
• C. Edema
• D. Punch biopsy

Answer: (B)

Distinguishing bacteria by their cell wall structure is what the Gram stain does. The process uses crystal violet and iodine to fix dye to the cells; Gram-positive organisms have thick peptidoglycan that traps the dye and stay purple, while Gram-negative organisms have a thinner peptidoglycan layer plus an outer membrane that allows decolorization and then takes up a pink counterstain. This staining pattern is clinically useful because it helps guide antibiotic choices and provides quick information about the organism’s properties. Other terms describe tissue evaluation, fluid buildup, or a skin sampling procedure, not a staining method.

Distinguishing bacteria by their cell wall structure is what the Gram stain does. The process uses crystal violet and iodine to fix dye to the cells; Gram-positive organisms have thick peptidoglycan that traps the dye and stay purple, while Gram-negative organisms have a thinner peptidoglycan layer plus an outer membrane that allows decolorization and then takes up a pink counterstain. This staining pattern is clinically useful because it helps guide antibiotic choices and provides quick information about the organism’s properties. Other terms describe tissue evaluation, fluid buildup, or a skin sampling procedure, not a staining method.