Microdase Disks

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

In 1956, Kovacs¹ described the oxidase method that can be used to differentiate Gram-negative bacilli. Faller and Schleifer² modified Kovacs' oxidase reagent by using a tetramethyl-p-phenylenediamine (TMPD) in dimethyl sulfoxide (DMSO). Tarrand and Groschel³ 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 color change to blue or purple.

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

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Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.