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Fresh bacterial preparations should be used. After colonies have grown on the medium, 2-3 drops of the reagent DMPD are added to the surface of each organism to be tested. A positive test (OX+) will result in a color change violet to purple, within 10–30 seconds. A negative test (OX-) will result in a light-pink or absence of coloration.
Counterstain, which is usually positively charged safranin or basic fuchsine, is applied last to give decolorized gram-negative bacteria a pink or red color. [3] [20] Both gram-positive bacteria and gram-negative bacteria pick up the counterstain. The counterstain, however, is unseen on gram-positive bacteria because of the darker crystal ...
During incubation, the bacteria interact with the substrates, leading to visible color changes if the reactions occur. Reading Results: After incubation, the results are interpreted by observing the color changes in each tube, which are indicative of positive or negative reactions. The pattern of reactions is compared to a reference database to ...
The process or results are called a WBC differential. This test is useful because many diseases alter the proportion of certain white blood cells. By analyzing these differences in combination with a clinical exam and other lab tests, medical professionals can diagnose disease. One commonly recognizable use of differential staining is the Gram ...
[7] [8] Microbiologic agents, such as bacteria and fungi, also appear more easily in Diff-Quik. [3] This is useful for the detection of for example Helicobacter pylori from gastric and pyloric specimens. [5] Due to its short staining time, Diff-Quik stain is often used for initial screening of cytopathology specimens.
Eosin methylene blue (EMB, also known as "Levine's formulation") is a selective and differential media used for the identification of Gram-negative bacteria, [1] specifically the Enterobacteriaceae. EMB inhibits the growth of most Gram-positive bacteria. EMB is often used to confirm the presence of coliforms in a sample.
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 ...
E. meningoseptica is positive by the catalase test, the oxidase test, and the indole test. It is negative by the urease test. In general, it is negative by the nitrate reductase test, although some strains are positive. [6] E. meningoseptica grows well on blood agar and chocolate agar. Colonies are very pale yellow and may not be easily evident ...