Gram Staining - Uses

Uses

Gram staining is a bacteriological laboratory technique used to differentiate bacterial species into two large groups (Gram-positive and Gram-negative) based on the physical properties of their cell walls. Gram staining is not used to classify archaea, formerly archaeabacteria, since these microorganisms yield widely varying responses that do not follow their phylogenetic groups.

The Gram stain is not an infallible tool for diagnosis, identification, or phylogeny, and it is of extremely limited use in environmental microbiology. It has been largely superseded by molecular techniques even in the medical microbiology lab. Some organisms are Gram-variable (that means, they may stain either negative or positive); some organisms are not susceptible to either stain used by the Gram technique. In a modern environmental or molecular microbiology lab, most identification is done using genetic sequences and other molecular techniques, which are far more specific and informative than differential staining.

Gram-staining has proven to be as effective a diagnostic tool as PCR, particularly with regards to gonorrhoea diagnosis in Kuwait.The similarity of the results of both Gram stain and PCR for diagnosis of gonorrhea was 99.4% in Kuwait.