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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]
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is used by microbiologists to place bacteria into two main categories, Gram-positive (+) and Gram ...
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.
Koser’s agar, developed by Stewart A. Koser in 1923, is a clear, colorless agar that allows the observation of bacterial growth by turbidity. [6] With a colorless agar, misinterpreting negative results as positives is more common, which can be reduced by Simmons’ modification of adding bromothymol blue.
Proteus mirabilis appears as Gram-negative rods after Gram staining under bright-field microscopy with 1000 times magnification. Proteus mirabilis is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. P. mirabilis causes 90% of all Proteus infections in humans.
Observation of hemolysis is useful in the presumptive identification of bacteria, [1]: 165–6 especially streptococci, which are classified on the basis of their hemolytic reactions. [ 11 ] : 92 For example, Streptococcus pyogenes , which causes strep throat and scarlet fever , [ 12 ] displays beta-hemolysis, while Streptococcus pneumoniae ...
Microscopic observation of a Gram stained specimen of H. influenzae will show Gram-negative coccobacillus. The cultured organism can be further characterized using catalase and oxidase tests, both of which should be positive.
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 ...