Rapid oxidase method for testing oxidase-variable Aeromonas hydrophila strains

A rapid, same-day oxidase test procedure which obviates the problem of false-negative oxidase reactions of Aeromonas hydrophila removed from the surface of differential media such as MacConkey agar is described. This method allows oxidase testing to be performed within 3 h, rather than delaying the oxidase test for an additional 18 to 24 h. This procedure is applicable to any rapidly growing gram-negative rod.