Which member of the Enterobacteriaceae is oxidase positive?

Which member of the Enterobacteriaceae is oxidase positive?

• A. Cronobacter
• B. Ewingella
• C. Plesiomonas
• D. Vibrio

Answer: (C)

Oxidase testing reveals whether an organism has cytochrome c oxidase, an enzyme used in the electron transport chain. Most Enterobacteriaceae are oxidase negative, which helps distinguish them from oxidase-positive groups. Plesiomonas shigelloides is oxidase positive, meaning it retains cytochrome c oxidase and will produce a positive oxidase reaction. Cronobacter and Ewingella are typically oxidase negative, so they fit the common Enterobacteriaceae pattern. Vibrio, while oxidase positive, is not part of Enterobacteriaceae, so it isn’t the correct genus in this context. Therefore, the oxidase-positive member within these options is Plesiomonas shigelloides.

Oxidase testing reveals whether an organism has cytochrome c oxidase, an enzyme used in the electron transport chain. Most Enterobacteriaceae are oxidase negative, which helps distinguish them from oxidase-positive groups.

Plesiomonas shigelloides is oxidase positive, meaning it retains cytochrome c oxidase and will produce a positive oxidase reaction. Cronobacter and Ewingella are typically oxidase negative, so they fit the common Enterobacteriaceae pattern. Vibrio, while oxidase positive, is not part of Enterobacteriaceae, so it isn’t the correct genus in this context. Therefore, the oxidase-positive member within these options is Plesiomonas shigelloides.