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Antibiotic resistance tests: Bacteria are streaked on dishes with white disks, each impregnated with a different antibiotic. Clear rings, such as those on the left, show that bacteria have not grown—indicating that these bacteria are not resistant. The bacteria on the right are fully resistant to all but two of the seven antibiotics tested. [33]
The catalase test tests whether a microbe produces the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide. Smearing a colony sample onto a glass slide and adding a solution of hydrogen peroxide (3% H 2 O 2) will indicate whether the enzyme is present or not. Bubbling is a positive test while nothing happening is a negative ...
Voges–Proskauer / ˈ f oʊ ɡ ə s ˈ p r ɒ s k aʊ. ər / or VP is a test used to detect acetoin in a bacterial broth culture. The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth, which is a glucose-phosphate broth that has been inoculated with bacteria. A cherry red color indicates a positive ...
Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50–90% of cell envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer (10% of cell envelope), so do not retain the purple stain and are counter-stained pink by safranin. There are four basic steps of the ...
The rate by which arylsulfatase enzyme breaks down phenolphthalein disulfate into phenolphthalein (which forms a red color in the presence of sodium bicarbonate) and other salts is used to differentiate certain strains of Mycobacteria. 3 day arylsulfatase test is used to identify potentially pathogenic rapid growers such as M. fortuitum and M ...
The analytical profile index, or API, is a classification system for bacteria based on biochemical tests. The system was developed to accelerate the speed of identifying clinically relevant bacteria. It can only be used to identify known species from an index. [1] The data obtained are phenotypic traits.
The disk diffusion test (also known as the agar diffusion test, Kirby–Bauer test, disc-diffusion antibiotic susceptibility test, disc-diffusion antibiotic sensitivity test and KB test) is a culture-based microbiology assay used in diagnostic and drug discovery laboratories. In diagnostic labs, the assay is used to determine the susceptibility ...
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]