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

Staining kit with 4 ready-to-use solutions.

Gram-positive microorganisms appear violet, gram-negative microorganisms appear pink to red.

Principle:
The differential 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. In gram-positive bacteria, this complex is retained in the cell under the action of the decolorizing agent (alcohol, acetone) due to reduced cell wall permeability. Therefore, gram-positive microorganisms retain the violet color. In gram-negative bacteria, the dye-iodine complex diffuses out through the cell wall under the action of the decolorizing agent. During the 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;
-after air-drying, heat-fix by repeatedly passing the slide through a flame (caution: excessive heating of the slide leads to the 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 the Gram staining technique in our AUROSAN hands-on courses: see www.aurosan.de