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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]
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 ...
The results were difficult to interpret and not reliable, because of inaccurate results that were not standardised between laboratories. [ 25 ] Dilution has been used as a method to grow and identify bacteria since the 1870s, and as a method of testing the susceptibility of bacteria to antibiotics since 1929, also by Alexander Fleming. [ 25 ]
Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and Gram-negative bacteria have a thin layer of peptidoglycan. 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.
Before starting a test, one must confirm the cultured bacteria are Enterobacteriaceae, this is done by a quick oxidase test for cytochrome coxidase. Enterobacteriaceae are typically oxidase negative, meaning they either do not use oxygen as an electron acceptor in the electron transport chain , or they use a different cytochrome enzyme for ...
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.
Etest is a quantitative technique for determining the MIC of microoganisms. It is used for a range of Gram-negative and Gram-positive bacteria such as Pseudomonas, [2] [3] Staphylococcus, [4] and Enterococcus species, [5] as well as fastidious bacteria, such as Neisseria and Streptococcus pneumoniae. [1]
A Gram stain is performed to show Gram-positive cocci in chains. Then, the organism is cultured on blood agar. The rapid pyrrolidonyl arylamidase (PYR) test is commonly used, wherein a positive reaction confers a presumptive identification of group A beta-hemolytic streptococci if the appearance and clinical context is consistent.