Chromogenic UTI Agar

Principle

• Chromogenic UTI agar is used for the presumptive identification of microorganisms causing urinary tract infections. The organisms mainly responsible for urinary tract infections are Escherichia coli, Staphylococcus saprophyticus, Klebsiella species, Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis, and other coliforms.
• Media is composed of peptone, chromogenic mixture, and agar. Peptone provides nitrogenous and long-chain amino acids. The chromogenic mixture contains chromogens and nutrients, the nutrients provide nitrogenous and carbonaceous compounds, vitamins, and essential nutrients including tryptophan.
• While the chromogenic substance used in this media are X-Glucoside, Red-β-Dgalactopyranoside, and isopropylthio-β-galactoside. X-Glucoside is a substrate for β-Glucosidase that, upon enzymatic action, gives an insoluble indigo-blue chromophore. Red-β-D-galactopyranoside is used for detection of beta-galactosidase.
• IPTG (isopropylthio-β-galactoside) is an inducer of β-galactosidase activity in bacteria and is suitable for use with X-gal or Red-gal to detect lac gene activity in E. coli or genetically modified microorganisms.
• The medium also contains tryptophan which acts as an indicator of tryptophan deaminase activity. Escherichia coli, produce ß-galactosidase enzyme activity, cleave red-β-D-galactopyranoside, and form pink color colonies.
• The enterococci cleave X-glucoside, by producing ß-glucosidase enzyme, and result in the formation of blue colonies. However, some members of the coliform group cleave both chromogens to form purple colonies.
• While Proteus, Morganella, and Providencia spp. are differentiated on the basis of tryptophan deaminase activity and generally form brown color colonies. Some Enterobacter cloacae lack ßglucosidase, resulting in pink colonies, similar to Escherichia coli, and further differentiated on the basis of indol production by using Kovac’s reagent. 

Use:

Recommended for presumptive identification of microorganisms causing urinary tract infections.