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Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. [1] The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884. [2]
A counterstain is a stain with colour contrasting to the principal stain, making the stained structure easily visible using a microscope. Examples include the malachite green counterstain to the fuchsine stain in the Gimenez staining technique and the eosin counterstain to haematoxylin in the H&E stain . [ 1 ]
A Ziehl–Neelsen stain is an acid-fast stain used to stain species of Mycobacterium tuberculosis that do not stain with the standard laboratory staining procedures such as Gram staining. This stain is performed through the use of both red coloured carbol fuchsin that stains the bacteria and a counter stain such as methylene blue.
Safranin (Safranin O or basic red 2) is a biological stain used in histology and cytology. Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endospore staining. It can also be used for the detection of cartilage, [2] mucin and mast cell granules.
One commonly recognizable use of differential staining is the Gram stain. Gram staining uses two dyes: Crystal violet and Fuchsin or Safranin (the counterstain) to differentiate between Gram-positive bacteria (large Peptidoglycan layer on outer surface of cell) and Gram-negative bacteria. Acid-fast stains are also differential stains.
Fungal yeast forms are inconsistently stained with Acid-fast stain which is considered a narrow spectrum stain for fungi. [21] In a study on acid-fastness of fungi, [ 22 ] 60% of blastomyces and 47% of histoplasma showed positive cytoplasmic staining of the yeast-like cells, and Cryptococcus or candida did not stain, and very rare staining was ...
The stain proved popular and in 1884 was used by Hans Christian Gram to stain bacteria. He credited Paul Ehrlich for the aniline-gentian violet mixture. [ 32 ] Grübler's gentian violet was probably very similar, if not identical, to Lauth's methyl violet, which had been used as a stain by Victor André Cornil in 1875.
Aggregatibacter actinomycetemcomitans is a Gram-negative coccobacillus prevalent in subgingival plaques. Acinetobacter strains may grow on solid media as coccobacilli. Bordetella pertussis is a Gram-negative coccobacillus responsible for causing whooping cough. Yersinia pestis, the bacterium that causes plague, is also coccobacillus. [26]