Gram method


Gram method
Gram stain an empirical staining procedure in which microorganisms are stained with crystal violet, treated with 1:15 dilution of strong iodine solution, decolorized with ethanol or ethanol-acetone, and counterstained with a contrasting dye, usually safranin O. Those microorganisms that retain the crystal violet stain are said to be gram-positive, and those that lose the crystal violet stain by decolorization but stain with the counterstain are said to be gram-negative. Gram-positive organisms that lose the stain easily, so that samples appear to be a mixture of gram-positive and gram-negative organisms, are said to be gram-variable.

Gram stain demonstrating gram-positive diplococci in sputum smear.


Medical dictionary. 2011.

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  • Gram method — noun a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram s solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the… …   Useful english dictionary

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  • Gram method stain solution — (gram) [Hans Christian Joachim Gram, Danish physician, 1853–1938] see Stains and Staining Methods, under stain, and see gram negative and gram positive …   Medical dictionary

  • Gram-negative — bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram s method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (called peptidoglycan).… …   Medical dictionary

  • Gram-positive — bacteria retain the color of the crystal violet stain in the Gram stain. This is characteristic of bacteria that have a cell wall composed of a thick layer of a particular substance (called peptidologlycan). The Gram positive bacteria include… …   Medical dictionary

  • Gram's method — n. Biol. a method of differentiating bacteria by staining with a dye, then attempting to remove the dye with a solvent, for purposes of identification. Phrases and idioms: Gram positive (or negative) (of bacteria) that do (or do not) retain the… …   Useful english dictionary

  • Gram stain — noun a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram s solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the… …   Useful english dictionary

  • Gram's stain — noun a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram s solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the… …   Useful english dictionary

  • Gram's procedure — noun a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram s solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the… …   Useful english dictionary

  • Gram staining — (or Gram s method) is an empirical method of differentiating bacterial species into two large groups (Gram positive and Gram negative) based on the chemical and physical properties of their cell walls.cite book | last = Bergey | first = David H.… …   Wikipedia