Biosynth Launches RUG™, an Advanced Substrate for Fast and Sensitive E. coli Detection

Escherichia coli is the most important indicator organism for fecal contamination of drinking water, food and beverages. It can be reliably detected with growth media that contain substrates for beta-glucuronidase, an enzyme that occurs almost exclusively in E. coli. Today 4-Methylumbelliferyl beta-D-glucuronide (MUG) is recommended in international guidelines as a fluorogenic substrate for E. coli detection. In standard assays bacteria culture media are supplemented with MUG and incubated at 37°C. In the presence of E. coli a blue fluorescence can be detected under UV light after 24 hours. The detection limit of such assays is typically 10 CFU/ml.

Biosynth recently launched RUG™, a new substrate for beta-glucuronidase that is based on Resorufin - one of the most intensely fluorescent materials known today. RUG™ (Resorufin-beta-D-glucuronic acid methyl ester) is a highly sensitive chromogenic and fluorogenic indicator for E. coli. After removal of the methyl ester group by unspecific hydrolysis, the product is cleaved by beta-glucuronidase in liquid media and yields an intense pink color. Red fluorescence is obtained upon excitation at 560-570 nm. RUG™ is 5 to 10 times more sensitive than MUG and fluorescence develops in liquid culture media in less than half the time - after only 10 hours. These findings suggest the usage of RUG™ in place of MUG for the development of fast fluorescence E. coli assays.

As RUG™ generates a strong pink coloration that can be detected by the naked eye it further opens possibilities for the use of RUG™ in situations where fluorescence detection is not possible. Field studies are currently being carried out under the auspices of the WHO using RUG™ to test drinking water in hot climates. As RUG™ is chemically stable, prepared dry media containing RUG™ may be stored at ambient temperature for several months.