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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.
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).
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.
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 ...
Although L-forms can develop from Gram-positive as well as from Gram-negative bacteria, in a Gram stain test, the L-forms always colour Gram-negative, due to the lack of a cell wall. The cell wall is important for cell division, which, in most bacteria, occurs by binary fission.
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.
The Nugent Score is a Gram stain scoring system for vaginal swabs to diagnose bacterial vaginosis (BV).The Nugent score is calculated by assessing for the presence of large Gram-positive rods (Lactobacillus morphotypes; decrease in Lactobacillus scored as 0 to 4), small Gram-variable rods (Gardnerella vaginalis morphotypes; scored as 0 to 4), and curved Gram-variable rods (Mobiluncus spp ...
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.