Thermo Scientific™ Urea-PDA Disk

Description

Demonstrate urease activity and phenylalanine deamination in Enterobacteriaceae with the reagent-impregnated Thermo Scientific™ Remel™ Urea-PDA Disk. Urease activity has been shown to differentiate Proteus and Providencia spp. from other organisms^1,2. In 1974, Ederer et al. incorporated urea and phenylalanine into one medium for use as a rapid test³. Golden et al. impregnated filter paper strips with urea and phenylalanine to differentiate members of the Enterobacteriaceae⁴.

Henriksen and Closs demonstrated that Proteus strains could be differentiated from other enteric Gram-negative bacilli by their action on phenylalanine^5,6. In 1950, Henriksen demonstrated that the rapid transformation of phenylalanine into phenylpyruvic acid nearly always coincides with strong urease activity and is practically limited to members of the Proteus group⁷.

• Easy to use - Rapid test
• Easy to interpret - Visible color change

The Urea-PDA disk contains urea and phenylalanine. Proteus produces the enzyme urease, which hydrolyzes urea to form ammonia. Ammonia that is produced causes the phenol red indicator to change from clear to dark pink or red. Proteus and Providencia spp. produce a type of amino acid oxidase enzyme, which causes oxidative deamination of phenylalanine yielding phenylpyruvic acid. When 10% ferric chloride is added to this, it chelates with phenylpyruvic acid to form a green color.