8 Difference Between Gram Staining And Acid-fast Staining

SHARE

What Is Gram Staining?

Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.  

The Gram Staining Steps Include:

  • Add several drops of crystal violet to the smear and allow it to sit for 1 minute. Rinse the slide with water.
  • Add several drops of iodine to the smear and allow it to sit for 1 minute. Rinse the slide with water.
  • Add drops of ethanol one at a time until the runoff is clear. Rinse the slide with water.
  • Add several drops of safranin to the smear and allow it to sit for a minute.
  • Air dry, blot dry and observe under microscope.
  • Gram-negative cells will be stained pink by the safranin. This dye has no effect on Gram-positive cells, which remain purple.

What You Need To Know About Gram Staining

  • Gram staining is a technique for the preliminary identification of bacteria in which a violet dye is applied, followed by a decolorizing agent and then a red dye.
  • Gram staining characterizes bacteria with different types of cell walls.
  • The primary stain used in Gram stain is crystal violet.
  • Iodine is used by the gram stain as a mordant.
  • Safranin is the main counterstain used in gram staining.
  • Gram-staining differentiates bacteria into gram-negative and gram-positive bacteria.
  • In Gram stain, Gram-positive bacteria appear in blue color whereas Gram-negative bacteria appear in red color.

What Is Acid-fast Staining?

Acid fast staining is a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium. Acid fast bacteria have a high content of mycolic acids in their cell walls. Acid fast bacteria will be red, while nonacid fast bacteria will stain blue/green with the counterstain with the kinyoun stain.

The acid-fast staining steps include:

  • Apply carbon fuchsin to a fixed slide for 1 minute followed by rinsing.
  • Apply the decolorizing agent, 3% hydrogen chloride is for 2 minutes and remove the primary stain and rinse.
  • Apply the counterstain, methylene blue for 2 minutes then rinse.
  • Allow to dry and observe slide with a light microscope.

What You Need To Know About Acid Fast Staining

  • Acid fast staining is a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium.
  • Acid-fast stain characterizes bacteria with myolic acid in the cell.
  • The primary stain used in acid-fast stain is carbofuchsin.
  • No mordant is used in the acid-fast stain.
  • Methylene blue is the main counterstain used in the acid-fast stain.
  •  Acid-fast staining differentiates gram-positive bacteria into acid-fast and non-acid-fast.
  • In acid-fast staining, acid-fast bacteria appear in red color while non-acid-fast bacteria appear in blue color.

Difference Between Gram Staining And Acid-fast Staining In Tabular Form

BASIS OF COMPARISON GRAM STAINING ACID-FAST STAINING
Description Gram staining is a technique for the preliminary identification of bacteria in which a violet dye is applied, followed by a decolorizing agent and then a red dye.   Acid fast staining is a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium.  
Function Gram staining characterizes bacteria with different types of cell walls.   Acid-fast stain characterizes bacteria with myolic acid in the cell.  
Primary Stain Used The primary stain used in Gram stain is crystal violet.   The primary stain used in acid-fast stain is carbofuchsin.  
Mordant Iodine is used by the gram stain as a mordant.   No mordant is used in the acid-fast stain.  
Counterstain Safranin is the main counterstain used in gram staining.   Methylene blue is the main counterstain used in the acid-fast stain.  
Purpose Gram-staining differentiates bacteria into gram-negative and gram-positive bacteria.   Acid-fast staining differentiates gram-positive bacteria into acid-fast and non-acid-fast.  
Result Interpretation In Gram stain, Gram-positive bacteria appear in blue color whereas Gram-negative bacteria appear in red color.   In acid-fast staining, acid-fast bacteria appear in red color while non-acid-fast bacteria appear in blue color.