Which organism is oxidase positive?

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Prepare for the NBME Microbiology Test. Study with flashcards and multiple-choice questions. Each query comes with hints and detailed explanations. Ace your exam!

Multiple Choice

Which organism is oxidase positive?

Explanation:
The test is about the presence of cytochrome c oxidase in the bacterial electron transport chain. Organisms that have this enzyme are oxidase positive, turning the reagent dark quickly; those without it are oxidase negative. Pseudomonas aeruginosa contains cytochrome c oxidase, so it yields a positive oxidase test. The other listed organisms—Salmonella typhi, Shigella dysenteriae, and Escherichia coli—are members of the Enterobacteriaceae family and typically lack cytochrome c oxidase, giving a negative result. Thus, the oxidase-positive organism is Pseudomonas aeruginosa.

The test is about the presence of cytochrome c oxidase in the bacterial electron transport chain. Organisms that have this enzyme are oxidase positive, turning the reagent dark quickly; those without it are oxidase negative. Pseudomonas aeruginosa contains cytochrome c oxidase, so it yields a positive oxidase test. The other listed organisms—Salmonella typhi, Shigella dysenteriae, and Escherichia coli—are members of the Enterobacteriaceae family and typically lack cytochrome c oxidase, giving a negative result. Thus, the oxidase-positive organism is Pseudomonas aeruginosa.

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