Culture Media for In Vitro
Merck provides culture media that are used for microbiological in vitro diagnostic tests, such as tests for the detection of antibacterial substances in urine. In vitro diagnostics (IVD) tests are medical devices or techniques for performing diagnoses in a controlled environment outside of living organisms.
Urotest® AB is a test system from Merck for the detection of antibacterial substances (inhibitors) in urine and thus for diagnosing urinary tract infections. The reaction zone of the Urotest® AB Strips contains spores of Bacillus subtilis ATCC 6051 as well as culture medium. The spores of this bacterium do not display any significant metabolic activity. However, the vegetative cells do. On germination of the spores, metabolism develops, i.e. enzyme reactions occur, unless antibacterial inhibitors prevent this from happening.
The test organism is provided with a glycoside as a substrate which its metabolism converts to sugar and the corresponding aglycone. In a subsequent reaction, two aglycone molecules combine to form a stable blue dye. This reaction sequence can be used to test whether or not urine samples are free from inhibitors by observing the color change.