Thermo Scientific Oxoid Remel Microdase Discs

Differentiate Staphylococcus from Micrococcus by detecting the oxidase enzyme with Thermo Scientific™ Remel™ Microdase Disk.

In 1956, Kovacs described the oxidase method that can be used to differentiate Gram-negative bacilli. Faller and Schleifer modified Kovacs' oxidase reagent by using a tetramethyl-p-phenylenediamine (TMPD) in dimethyl sulfoxide (DMSO). Tarrand and Groschel further tested modified Kovacs and confirmed it to be far superior to Kovacs' oxidase reagent.

All micrococci have cytochrome c whereas most staphylococci (with a few exceptions) lack this type of cytochrome. The oxidase reagent confirms the presence of cytochrome c4 by exhibiting colour change to blue or purple.

• Ready to use: Reagent-impregnated disk. No further preparation required.
• Easy to read: Visible colour change that confirms positive test
• Positive test: Blue or purple colour development within 2 minutes
• Negative test: No colour change (white to grey colour remains) within 2 minutes

Each Microdase Disk is impregnated with tetramethyl-p-phenylenediamine (TMPD) in dimethyl sulfoxide (DMSO). The DMSO provides solubility and stability against auto-oxidation and enhances the permeability of TMPD into the bacterial cell. In presence of atmospheric oxygen, the oxidase enzyme reacts with TMPD and cytochrome c in the organism to form the coloured compound indophenol.