Gram staining is done to detect the presence and identify the general type of bacteria or fungi in a sample taken from the infection localisation. In this way, further identification tests can be done. Any bacteria that is present, are categorized by colour and shape by the eye of a trained laboratory technician. If the special dye(purple) is absorbed by a bacteria or a group of bacterias, these are called the gram positive bacterias (eg:Staph infection) and if the stain (pink) is not absorbed by the bacteria or the group of bacterias these are called gram negative bacterias (eg:Escherichia Coli infection). Fungi is also recognisable by stain but viruses are not. The results of these tests are initial preliminary tests for identification of bacterial infection. In order to confirm the diagnosis, culture, antigen or antibody testing may be necessary. While waiting for spesific tests, the practician may start the antibiotic treatment with the result of gram negative or positive discrimination of the bacteria causing the infection.
Interpretation: A negative Gram stain is often reported as ‘No organism seen’, indicating that there is no bacterial infection or the amount of bacteria is inadequate for discrimination. Gram positive cocci – Staph Aureus, causes skin infections and toxic shock syndrome and Streptococcus pneumoniae may cause pneumonia. Gram negative cocci – Neisseria meningitidis causes meningitis while Neisseria gonorrhoeae causes sexually transmitted disease, gonorrhea. Gram positive bacilli – Bacillus anthracis (anthrax) can cause skin infections and pneumonia. Listeria monocytogenes can cause foodborne illnesses. Gram negative bacilli – Escherischia coli is a common cause of urinary tract infections.
Sample: Any sample arranged on a slide dried in air.
Working day: Everyday
Result Time: Same day 6:00 PM
