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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 ...
Phage typing is a phenotypic method that uses bacteriophages ("phages" for short) for detecting and identifying single strains of bacteria. [1] Phages are viruses that infect bacteria and may lead to bacterial cell lysis. [2] The bacterial strain is assigned a type based on its lysis pattern. [3]
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 test differs from that used to detect catalase in other types of bacteria by using 30% hydrogen peroxide in a strong detergent solution (10% polysorbate 80). [1] Citrate. Sole carbon source [1] Egg medium. Growth on Löwenstein–Jensen medium (LJ medium) L-Glutamate. Sole carbon and nitrogen source [1] Growth rate
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 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 ...
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 ...
Colonial morphology serves as the first step in the identification of microbial species from clinical samples. [10] Based on the visual appearance of the colonies, microbiologists can narrow down the list of possible organisms, allowing them to select appropriate tests to provide a definitive diagnosis.