How do oxidase tests assist in differentiating Vibrio species from many Enterobacteriaceae?

How do oxidase tests assist in differentiating Vibrio species from many Enterobacteriaceae?

• A. Enterobacteriaceae are oxidase-positive; Vibrio are oxidase-negative
• B. Vibrio are oxidase-positive; most Enterobacteriaceae are oxidase-negative
• C. Oxidase tests are not useful
• D. Both groups are oxidase-positive

Answer: (B)

The oxidase test looks for the presence of cytochrome c oxidase, the enzyme that transfers electrons to oxygen in the bacterial electron transport chain. If the organism has this enzyme, the reagent (a redox dye) is rapidly oxidized and produces a color change within seconds. Vibrio species typically have cytochrome c oxidase and yield a positive oxidase test, turning color, while most Enterobacteriaceae lack this enzyme and remain colorless (negative). This difference provides a quick way to distinguish vibrios from many Enterobacteriaceae in routine ID work, helping you separate oxidase-positive vibrios from oxidase-negative Enterobacteriaceae.

The oxidase test looks for the presence of cytochrome c oxidase, the enzyme that transfers electrons to oxygen in the bacterial electron transport chain. If the organism has this enzyme, the reagent (a redox dye) is rapidly oxidized and produces a color change within seconds. Vibrio species typically have cytochrome c oxidase and yield a positive oxidase test, turning color, while most Enterobacteriaceae lack this enzyme and remain colorless (negative). This difference provides a quick way to distinguish vibrios from many Enterobacteriaceae in routine ID work, helping you separate oxidase-positive vibrios from oxidase-negative Enterobacteriaceae.