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Gram stain of Candida albicans from a vaginal swab. The small oval chlamydospores are 2–4 μm in diameter. Gram staining is a bacteriological laboratory technique [8] used to differentiate bacterial species into two large groups (gram-positive and gram-negative) based on the physical properties of their cell walls.
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.
Gram-negative bacteria will stain a pink color due to the thin layer of peptidoglycan. If a bacteria stains purple, due to the thick layer of peptidoglycan, the bacteria is a gram-positive bacteria. [4] In clinical microbiology numerous other staining techniques for particular organisms are used (acid fast bacterial stain for mycobacteria).
Both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of teichoic acids in the cell wall. Some of ...
These acids resist staining by ordinary methods such as a Gram stain. [9] It can also be used to stain a few other bacteria, such as Nocardia. The reagents used for Ziehl–Neelsen staining are carbol fuchsin, acid alcohol, and methylene blue. Acid-fast bacilli are bright red after staining. [citation needed]
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.
Gram stain of cells from the vagina (the same magnification) with normal bacterial flora (top) and the bacteria that cause vaginosis (bottom). A variety of diagnosis techniques are currently available for identifying Gardnerella vaginalis such as the OSOM BV Blue assay, FemExam cards and nucleic acid amplification tests (NAATs), resulting in the determination of ongoing BV.
Eosin methylene blue (EMB, also known as "Levine's formulation") is a selective and differential media used for the identification of Gram-negative bacteria, [1] specifically the Enterobacteriaceae. EMB inhibits the growth of most Gram-positive bacteria. EMB is often used to confirm the presence of coliforms in a sample.