New Medium Determines Source of Urinary Tract Infection

A new chromogenic medium is designed to simplify the identification of the main organisms responsible for urinary tract infections (UTI) by using color to differentiate among various bacteria.

The medium uses different colors for enterococci, Escherichia coli, coliforms, Staphylococcus aureus, and organisms with tryptophan deaminase activity (TDA), such as Proteus, Morganella, and Providencia spp. The background is clear, allowing easy match-up between sample and identification on multiple-sample plates. This reduces the need for subculturing and further lengthy identification procedures, even when more than one species is present in the sample.

The medium, called Clear Chromogenic UTI Medium, contains two specific chromogen substrates. One is cleaved by beta-glucosidase in enterococci, resulting in blue colonies, and the other is cleaved by beta-galactosidase in E coli, resulting in pink colonies. Since coliforms have the ability to cleave both chromogens, they produce purple colonies. In addition, tryptophan in the medium allows for the detection of TDA activity, causing such colonies to be brown, while Staphylococcus aureus colonies retain their typical appearance. The medium is the product of Oxoid (Basingstoke, UK).




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