A method of staining bacteria so that they can be identified [Described 1884. After Hans Christian Joachim Gram (1853-1938), Professor of Medicine in Copenhagen, Denmark. He discovered the stain by accident as a student in Berlin, Germany.]
Basic bacteriological staining method of wide application, by means of which all micro-organisms are classified as ‘Gram-positive’ or as ‘Gram-negative’ a reaction usually species-specific. The method consists of the application of a pararosaniline dye (crystal violet, methyl violet, gentian violet or Victoria blue) followed first by iodine solution, then by treatment with alcohol, acetone, or aniline oil, and finally by application of a counterstain such as neutral red, dilute carbol – fuchsin, safranine or (Sandiford’s counterstain) a mixture of malachite green and pyronine. The method is one which is applicable to smears and sections. Gram-positive bacteria retain the first dye despite the action of the solvent, appearing deep blue-black microscopically. Gram-negative organisms take up the counterstain, the violet dye having been extracted by the decolorising agent. Various modifications of the method (such as those of Kopeloff and Beerman, Jensen and Weigert) introduce variations of the 4 reagents and in the timing of the procedure.
A method for classifying bacteria into two groups on the basis of their cell wall composition, which causes them to stain either purple (positive) or pale red (negative).
Devised by Hans Christian Joachim Gram in 1884, this is a test that illuminates the composition/makeup of the physical structure of the cell wall of bacteria being tested. It is utilized to judge the effectiveness of a given chemical compound (e.g., an antibiotic) against bacteria types.
The test consists of a differential staining procedure, which allows most bacteria to be visually separated into two groups, known as Gram-Positive (G+) and Gram-Negative (G—). An antibiotic is defined in terms of the group of (pathogenic) bacteria that it is effective against, which is known as that antibiotic’s “spectrum of activity.” An antibiotic is said to have a spectrum of activity against gram-positive bacteria, gram-negative bacteria, or the bacteria of both groups. An antibiotic that is effective against both groups of bacteria is termed “broad spectrum” or “wide spectrum.”
A process of staining bacteria for identification.
Method of chemically staining bacteria that is used as a means of identifying and classifying them. A series of stains and solutions is applied to a bacterium; if it appears violet or blue, it is termed Gram-positive; if pink or red. Gram-negative. Also called Gram’s method.
A staining procedure used in the laboratory to distinguish between different types of microorganisms.
A widely used method for adding a color stain to normally colorless bacteria so they can be viewed and identified under a microscope. The bacteria are treated first with a dye called gentian violet and then with a solution of iodine, potassium, and water. Next, the bacteria are rinsed in alcohol, and a red dye is applied. The bacteria are then viewed under a microscope to see which color they have absorbed. If they are purple from the gentian violet, the bacteria are gram-positive. If they have absorbed the red dye, they are gram-negative. Gram-positive bacteria can usually be controlled with penicillin and similar antibiotics, while gram-negative bacteria resist these medications.
A diseased growth characterized by a mass of granulation tissue (tissue that develops in a wound during the healing process). Types of granuloma include granuloma annulare, granuloma inguinale, and pyogenic granuloma.
A method of staining bacterial cells, used as a primary means of identification. A film of bacteria spread onto a glass slide is dried and heat-fixed, stained with a violet dye, treated with decolorizer (e.g. alcohol), and then counterstained with red dye. Gram-negative bacteria lose the initial stain but take up the counterstain, so that they appear red microscopically. Gram-positive bacteria retain the initial stain, appearing violet microscopically. These staining differences are based on variations in the structure of the cell wall in the two groups.
A method of staining bacteria, which is important in their identification.
An employed technique for visualizing and categorizing bacteria is the staining procedure, which is commonly known as the Gram stain. This procedure facilitates the differentiation of bacteria into two distinct groups: the purple-stained organisms known as Gram-positive, and the red-stained organisms referred to as Gram-negative.
An iodine-based stain is employed to distinguish between different types of bacteria.
To differentiate between bacteria types, a bacterial specimen is first stained with gentian violet and Gram’s stain solution. Next, it undergoes treatment with a decolorizing agent like acetone, followed by counterstaining with a red dye. Bacteria that maintain the dark violet stain are classified as Gram-positive, while those that lose the violet stain during decolorization and appear pink after taking up the counterstain are classified as Gram-negative.
Gram-positive bacteria comprise species such as Streptococcus and Clostridium. On the other hand, Gram-negative bacteria encompass examples like Vibrio cholerae, the pathogen responsible for cholera, as well as various species of Salmonella.
A solution containing iodine and potassium iodide utilized for staining bacteria. Bacteria that retain the stain are termed “Gram-positive,” while those that don’t are “Gram-negative.” The technique is named after the Danish bacteriologist who developed it.