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The TSI slant is a test tube that contains agar, a pH-sensitive dye , 1% lactose, 1% sucrose, 0.1% glucose, [2] and sodium thiosulfate and ferrous sulfate or ferrous ammonium sulfate. All of these ingredients are mixed together, heated to sterility, and allowed to solidify in the test tube at a slanted angle.
Other enterobacteria such as E. coli will ferment the lactose present in the medium to an extent that will prevent pH reversion by decarboxylation and acidify the medium, turning it yellow. Salmonella species: red colonies, some with black centers. The agar itself will turn red due to the presence of Salmonella type colonies. Shigella species ...
OF-glucose deeps contain glucose as a carbohydrate, peptones, bromothymol blue indicator for Hugh-Leifson's OF medium or phenol red for King's OF medium, and 0.5% agar. To perform the OF-glucose test, two tubes of OF-glucose medium are inoculated with the test organism.
Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color. The media inhibits growth of gram-positive organisms with crystal violet and bile salts, allowing for the selection and isolation of gram-negative bacteria. The media detects lactose fermentation by enteric bacteria with the pH indicator neutral red. [2]
The pH indicator Methyl Red is added to one tube and a red color appears at pH's lower than 4.2, indicating a positive test (mixed acid fermentation is used). The solution remaining yellow (pH = 6.2 or above) indicates a negative test, meaning the butanediol fermentation is used. The VP test uses alpha-naphthol and potassium hydroxide to test ...
Raoultella planticola on MacConkey agar, showing a positive result (the microorganism has the ability to degrade lactose, which is detected by the pH indicator neutral red). The technique of the streaking is done by using 13 streaks.
Cystine tryptic agar (CTA), also known as cystine trypticase agar, [1] [2] is a growth medium used for the identification of microorganisms. [3]It can be used to determine if organisms can ferment various carbohydrates, including maltose, lactose, and sucrose.
Phenol red was used by Leonard Rowntree and John Geraghty in the phenolsulfonphthalein test to estimate the overall blood flow through the kidney in 1911. [9] It was the first test of kidney function and was used for almost a century but is now obsolete. The test is based on the fact that phenol red is excreted almost entirely in the urine.