An example of an oxidase-positive, glucose nonfermenting organism is

An example of an oxidase-positive, glucose nonfermenting organism is

• A. Aeromonas hydrophila
• B. Escherichia coli
• C. Klebsiella pneumoniae
• D. Pseudomonas aeruginosa

Answer: (D)

The essential idea is to use both the oxidase reaction and the glucose fermentation pattern to distinguish Gram-negative rods. A positive oxidase test means the organism has cytochrome c oxidase, and a glucose nonfermenter does not convert glucose into acid or gas in fermentation tests. Pseudomonas aeruginosa fits this profile: it is oxidase-positive and does not ferment glucose, relying on oxidative metabolism instead. In contrast, organisms like Escherichia coli and Klebsiella pneumoniae are oxidase-negative and glucose fermenters, while Aeromonas hydrophila is oxidase-positive but can ferment glucose, so it’s not a glucose nonfermenter.

The essential idea is to use both the oxidase reaction and the glucose fermentation pattern to distinguish Gram-negative rods. A positive oxidase test means the organism has cytochrome c oxidase, and a glucose nonfermenter does not convert glucose into acid or gas in fermentation tests. Pseudomonas aeruginosa fits this profile: it is oxidase-positive and does not ferment glucose, relying on oxidative metabolism instead. In contrast, organisms like Escherichia coli and Klebsiella pneumoniae are oxidase-negative and glucose fermenters, while Aeromonas hydrophila is oxidase-positive but can ferment glucose, so it’s not a glucose nonfermenter.