What does CGB mean in UNCLASSIFIED

CGB is a chromogenic substrate used in the Canavanine-Glycine-Bromothymol (CGB) test, a biochemical test used to differentiate between Gram-negative and Gram-positive bacteria.

The CGB test is based on the ability of certain enzymes to hydrolyze the substrate CGB. Gram-negative bacteria typically possess β-glucuronidase, an enzyme that can break down CGB into canavanine, glycine, and bromothymol blue. When this happens, a blue color is produced, indicating a positive test result. Gram-positive bacteria generally do not produce β-glucuronidase and thus give a negative test result.

The CGB test is a valuable diagnostic tool for differentiating between Gram-negative and Gram-positive bacteria. This distinction is essential for guiding appropriate antibiotic treatment and preventing antibiotic resistance.

The CGB test is typically performed on bacterial cultures grown on a nutrient agar plate. A drop of the CGB substrate is added to the culture, and the plate is incubated. After a specified incubation period, the reaction is observed for color changes. A blue color indicates a positive test result, while no color change indicates a negative result.

While the CGB test is generally reliable, there are some limitations. It is important to note that some Gram-positive bacteria may produce β-glucuronidase and give a false-positive result. Additionally, the test may not be reliable for certain Gram-negative bacteria that do not possess β-glucuronidase.

The CGB test offers several advantages. It is a simple and inexpensive test that can be easily performed in a laboratory setting. It provides rapid results, typically within a few hours. Additionally, the test is highly specific for β-glucuronidase, making it a valuable tool for differentiating between Gram-negative and Gram-positive bacteria.