O′Meara′s Reagent is used in the Voges-Proskauer (VP) test for the detection of acetoin production by bacterial strains. VP test is helpful in identifying members of the family Enterobacteriaceae based on their ability to produce acetylmethylcarbinol (AMC = acetonin) from glucose. Acetoin is an intermediate which is oxidized by oxygen under alkaline conditions (KOH) to 2,3-Butanediol. With creatinine (break down product from creatine) and the enhancement of α-naphtol a red color is formed (Meisenheimer complex)

The O′Meara reagent is a component of the Voges-Proskauer (VP) test, which is a commonly used laboratory technique in industrial microbiology to differentiate between bacterial strains based on their ability to produce acetylmethylcarbinol (AMC) from glucose. The VP test is often used as a tool to identify and authenticate bacterial strains in the food, beverage, and pharmaceutical industries.

To perform the VP test, a bacterial sample is inoculated into a nutrient broth and incubated. The O′Meara reagent, which contains a mixture of creatinine and potassium hydroxide (KOH), is then added to the culture. Acetoin produced in the medium by bacterial culture is oxidized under alkaline conditions in the presence of air to form diacetyl which reacts with creatine to give a pinkish-red compound.