Gram2018-09-25T15:06:37+00:00

Gram

Principle

Gram staining is commonly used in histology to classify bacteria. The process enables to separate most of the bacteria in two groups according to the proportion of membrane peptidoglycans:
–          Gram + bacteria which are rich in peptidoglycans and poor in lipids
–          Gram – bacteria, rich in lipids and poor in peptidoglycans

The first step in the process is effected with crystal violet staining which has an affinity to form an iodine-crystal violet complex from the iodine mordant. Then, an alcoholic solution will weaken and permeabilize the membranes containing most of lipids, in order to clean iodin-Crystal violet complex from Gram – bacteria. It is the step of discoloration. Finally, Gram + bacteria will stained in violet while Gram – bacteria will take the dye of the counterstaining.

Applications

Gram staining is commonly used in microbiology to differentiate Gram + and Gram – bacteria. It is an important step in the classification and differentiation of microorganism populations. Gram staining can be used in biopsies to detect infections in the organism, this method is quicker than a classical culture. It is possible to detect:
–          Staphylococci and streptococci (Gram + bacteria) in violet
–          E-Coli (Gram – bacteria) in pink or red according to the counterstaining (Fuchsine or Safranin)

Concerned organs/tissues

Gram staining can be used in all kinds of tissues and organs.