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A Gram stain of mixed Staphylococcus aureus (S. aureus ATCC 25923, gram-positive cocci, in purple) and Escherichia coli (E. coli ATCC 11775, gram-negative bacilli, in red), the most common Gram stain reference bacteria. Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups ...
This results in the selective staining of only those cells that have a high density of cell wall material, such as acid-fast bacteria. [27] The Ziehl-Neelsen stain is a two step staining process. In the first step, the tissue is stained with a basic fuchsin solution, which stains all cells pink.
A simple staining method for bacteria that is usually successful, even when the positive staining methods fail, is to use a negative stain. This can be achieved by smearing the sample onto the slide and then applying nigrosin (a black synthetic dye) or India ink (an aqueous suspension of carbon particles).
Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through an optical microscope. This is because the thick layer of peptidoglycan in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test.
Kinyoun stain; For color blind people (or in backgrounds where detecting red bacteria is difficult), Victoria blue can be substituted for carbol fuchsin and picric acid can be used as the counter stain instead of methylene blue, and the rest of the Kinyoun technique can be used. [6] Various bacterial spore staining techniques using Kenyon e.g.
Clusters of bacteria (arrow) shown on Warthin–Starry stain. The Warthin–Starry stain ( WS ) is a silver nitrate -based staining method (a silver stain ) used in histology. It was first introduced in 1920 by American pathologists Aldred Scott Warthin (1866–1931) and Allen Chronister Starry (1890–1973), for the detection of spirochetes .
In pathology, the Grocott–Gömöri's methenamine silver stain, abbreviated GMS, is a popular staining method in histology. The stain was originally named after György Gömöri, the Hungarian physician who developed the stain. It is used widely as a screen for fungal organisms. It is particularly useful in staining carbohydrates.
The specimen, such as a wet bacterial culture spread on a glass slide, is mixed with the negative stain and allowed to dry. When viewed with the microscope the bacterial cells, and perhaps their spores, appear light against the dark surrounding background. An alternative method has been developed using an ordinary waterproof marking pen to ...