Why do gram stains work

Apply a smear of bacteria on to a slide. Air dry and then heat fix by passing it through a flame a few times. Make sure you air dry the bacteria before heat fixing. Let stand for one minute. Bacteria will stain purple. Wash briefly with water and shake off excess. Add about 5 drops of iodine solution to the culture. Let stand for 30 seconds, wash briefly with water and shake off excess. Tilt slide and decolorize with solvent acetone-alcohol solution until purple color stops running.

Be careful not to over-decolorize. Wash immediately within 5 seconds with water and shake off excess. Add about 5 drops of Safranine O. Let stand for one minute, wash briefly with water and shake off excess. Staphylococcus Mostly harmless sphere-shaped, skin bacteria ; Streptococcus rod shaped bacteria: Rheumatic fever, Scarlet fever. How does your stain look? You can test your reagents against a known negative sample and a known positive sample. The oral bacteria present will show positive and negative in a good stain.

This test differentiate the bacteria into Gram Positive and Gram Negative Bacteria, which helps in the classification and differentiations of microorganisms. When the bacteria is stained with primary stain Crystal Violet and fixed by the mordant, some of the bacteria are able to retain the primary stain and some are decolorized by alcohol.

The cell walls of gram positive bacteria have a thick layer of protein-sugar complexes called peptidoglycan and lipid content is low.

Decolorizing the cell causes this thick cell wall to dehydrate and shrink, which closes the pores in the cell wall and prevents the stain from exiting the cell. So the ethanol cannot remove the Crystal Violet-Iodine complex that is bound to the thick layer of peptidoglycan of gram positive bacteria and appears blue or purple in colour.

In case of gram negative bacteria, cell wall also takes up the CV-Iodine complex but due to the thin layer of peptidoglycan and thick outer layer which is formed of lipids, CV-Iodine complex gets washed off. When they are exposed to alcohol, decolorizer dissolves the lipids in the cell walls, which allows the crystal violet-iodine complex to leach out of the cells.

Then when again stained with safranin, they take the stain and appears red in color. Gram Negative Bacteria: Escherichia coli E. A mordant fixes or binds cells intensifying stains in cell or tissue to allow for visual clarity under a microscope. I would say yes. The role of iodine is that it act as grams mordant and increases the interaction between bacterial cell wall and the dye crystal violet so that the dye is more tightly bound on the cell and is more stained.

Hi Very much appreciated Would be great if u also add some points about the modifications and variations and also gram variable bacteria and some general info about why gram staining is needed and where it is not indicated!!

But you may need more tests to find out which specific fungal infection you have. Learn more about laboratory tests, reference ranges, and understanding results. If you are diagnosed with a bacterial infection, you will probably be prescribed antibiotics. It's important to take your medicine as prescribed, even if your symptoms are mild.

This can prevent your infection from getting worse and causing serious complications. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Gram Stain. What is a Gram stain? The two categories cause different types of infections: Gram-positive infections include methicillin-resistant Staphylococcus aureus MRSA , strep infections , and toxic shock. Gram-negative infections include salmonella , pneumonia , urinary tract infections , and gonorrhea.

Other names: Gram's stain. What is it used for? Why do I need a Gram stain? What happens during a Gram stain? Wound sample: A provider will use a special swab to collect a sample from the site of your wound. Blood test: A provider will take a sample of blood from a vein in your arm. Urine test: You will provide a sterile sample of urine in a cup, as instructed by your health care provider. Throat culture: Your health care provider will insert a special swab into your mouth to take a sample from the back of the throat and tonsils.

Your health care provider will ask you to cough up sputum into a special cup, or a special swab may be used to take a sample from your nose.

Will I need to do anything to prepare for the test? You don't need any special preparations for a Gram stain. Are there any risks to the test?

There is no risk to having a swab, sputum, or urine test. What do the results mean?