Gram stain or also known as color Gram is the name given to a type of differential staining is used in the field of bacteriology to visualize the bacteria, especially in clinical samples. The name of this coloration is due to the Danish bacteriologist Christian Gram, who was responsible for developing the technique in 1884. Gram's main objective was to achieve a test that would allow him to differentiate various groups of bacteria in order to study them and develop a classification of them. Gran's experiments turned out to be very successful and he would quickly establish himself as one of the main techniques used for the study of bacteria, since it allowed them to be identified quickly and effectively in an infection and to select the antibiotic that is most appropriate to treat said infection.
The procedure to carry out a staining is as follows: the first thing is to take the sample of bacteria to be colored, then with a swab it must be spread on a slide and then it must be left to dry at room temperature or, failing that, use a lighter, taking special care not to burn the bacteria. After that, the sample should be fixed on the slide using methanol for approximately 1 minute.
Subsequently placed tint of violet gentian on the slide and let stand for 1 minute. Importantly, this dye has the ability to overcome any type of bacterial wall and that is why can dye both bacteria Gram positive and negative. After that, the sample should be rinsed with water and then Lugol added, so that said substance covers the entire sample and wait for one minute. Lugol is a compound that is largely made up of iodine, which in this case is responsible for fixing the gentian violet dye to the sample.
After the steps described above, the slide must be washed with a mixture of alcohol and acetone for a period of approximately 30 days, it is in this step, when the Gram stain really ends, this is because the mixture of alcohol and acetone is responsible for dissolving the complexes of lugol and gentian violet.
