Gram Stain Kit - 1 set (4 x 100 ml Reagent Solutions)

Staining kit made of 4 ready-to-use solutions.

Gram-positive microorganisms appear purple, Gram-negative microorganisms pink to red.

Principle:
The different staining of Gram-positive and Gram-negative bacteria is closely correlated with the different structure of the cell walls of these bacterial groups. Staining with crystal violet and subsequent mordanting with Lugol's solution creates a dye-iodine complex in the cell, which in Gram-positive bacteria is retained in the cell under the action of the decolorizer (alcohol, acetone) due to reduced cell wall permeability. Therefore, Gram-positive microorganisms retain the violet stain. In Gram-negative bacteria, the dye-iodine complex diffuses out through the cell wall under the action of the decolorizer. During subsequent counterstaining with safranin, Gram-negative germs absorb this dye and now appear pink to red.

Preparation of smears - the alpha and omega for successful and clear staining:
-apply a thin layer of the sample (ideal concentration approx. 10Exp4 - 10 Exp5 cells / ml) to a microscope slide with a sterile loop or a swab kit;
-after air-drying, heat-fix by repeatedly passing the slide through a flame (caution: excessive heating of the slide leads to destruction of the cell (wall) structures);
-too low cell concentrations easily lead to false negative assessments;
-insufficient fixation (see above) can lead to the cells / bacteria being washed away by the staining reagents themselves.

We also teach Gram staining technique in our AUROSAN hands-on courses: see www.aurosan.de

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