A Gram stain is a laboratory test that checks for the bacteria at the site of infection. The gram staining process is done easily in the laboratory, and doctors usually use this stain to find out about common bacterial infections. We take the Gram stain test for bacterial infections and people suffering from the common cold. Gram stain test is usually one of the first tests that is done on a person's body fluid sample.
Gram staining is an important procedure in microbiology, and it is used to identify different strains of bacteria and treat them. Gram stain could be the preliminary test, but you need other tests to determine the exact type of infection in your body. The Gram stain procedure is fairly simple and quick, which is why a lot of microbiologists prefer it even today.
What is gram staining?
Gram staining is the staining procedure that differentiates between gram-positive and gram-negative bacteria. Gram-positive strains of bacteria stain violet, and gram-negative strains colour red. The staining process works on the cell wall and its constituents. The cell wall has peptidoglycan for some bacteria.
The staining process stains the cell wall and stains the wall violet when it has peptidoglycan. The Gram-negative bacteria stain red when the layers of peptidoglycan are thin and low. The low level of peptidoglycan does not retain the characteristic violet colour when it is washed with the decolouring agent. The gram stain process has been used for centuries, and it is still a relevant diagnostic test.
How does the process work?
There are usually three steps in the gram staining process. The first step is the treatment with a water-soluble dye, which is known as crystal violet. Another step is the decolorisation and the removal of crystal violet, followed by the staining of the wall with an alternate stain called Safranin.
The Safranin has an orange-red colour, and it stains the gram-negative bacteria red. Due to the difference in the thickness and composition of their walls, the gram-positive organisms retain the violet colour while the gram-negative bacteria decolourise and instead stain red.
- The bacterial cells are first stained with crystal violet dye, and then a Gram’s iodine solution is used to treat the cells. When the iodine solution is applied to the cells, the iodine and crystal violet form a complex together to stain the cell. The stain molecule is not soluble in water.
- After the crystal violet complex formation, the microbiologist uses a decoloriser such as ethyl alcohol or acetone to treat the cell. The decolourising agent is an alcohol-based compound that dehydrates and shrinks the peptidoglycan layer. The bacteria inside is already killed. The peptidoglycan layer and the cell wall tighten up, and this can lead to the large crystal violet molecule being retained inside. This happens for gram-positive bacteria. However, the same process does not happen for gram-negative bacteria.
Bacteria that are gram-negative react differently to the stain and decolouriser. The outer membrane of the Gram-negative bacteria gets degraded, and the thinner peptidoglycan layer is disrupted under the strong action of the decolourising agent or alcohol. The peptidoglycan layer is destroyed, so the cell is unable to retain the crystal violet colour, and the colour is lost. The gram-negative bacteria, thus, do not stain violet. These cells need another stain called safranin to stain the wall properly and visibly.
Therefore, safranin is the counterstain that is used in this case to stain the bacteria cells. The safranin molecule is smaller than the crystal violet complex, and it is water soluble. The thin and denatured cell wall of the bacteria retains the safranin because it is a smaller molecule and can be retained by the cell wall. The gram-negative organisms are coloured red by the safranin molecule. However, gram-positive cells do not show any change to red because they are already stained by a bigger molecule.
What is a gram stain test used for?
The gram staining process is a very common test that microbiologists use to test and find out the strain of bacteria. Examples of gram-positive bacteria are Staphylococcus species, Streptococcus species, and Listeria species. Examples of gram-negative bacteria are Moraxella and Escherichia coli.
The gram staining process is used to find the nature of the most basic bacterial infections. It is used to treat Urinary Tract Infections and diagnose bacterial pneumonia. A Gram stain is a process that helps you diagnose the condition, and it is used when you have common bacterial infections.
However, your doctor might not suggest a gram stain test for every problem because there are other kinds of tests to do. The sample of these tests also differ from one another. Usually, a blood or stool sample is taken to identify the type of infection you have.
Procedure
gram staining procedure. One is the collection of samples from the patient, the other is the processing of the sample, and the third is the examination of the sample. Gram stain test samples can be collected from the patient's cheek tissue by scraping. The scraping process is minimally invasive and can be useful. The sample could also be from a body fluid like blood or discharge. Any kind of infection, especially bacterial, is usually found in the body fluids. Our phlebotomist might also use a needle to conduct aspiration and draw fluid from the body to identify the pathogen.
Sometimes, the team might use swabbing of the throat or nostrils to collect the sample and then prepare the gram stain. The gram stain procedure is simple and usually does not affect the patient. However, sometimes, the patient could face minor discomfort and soreness from sample collection.
Conclusion
The Gram stain procedure is a simple and effective procedure for staining, and the stain is conducted by our leading microbiologists. At Agilus Diagnostics, we test for different strains of bacteria, fungi, and viruses very accurately. The Gram stain process is one of the basic processes in the extensive tests we conduct for you.
