How can Kingella denitrificans be differentiated from Neisseria gonorrhoeae?

• A. Able to grow on Thayer-Martin agar
• B. Able to reduce nitrate
• C. Oxidase positive
• D. Glucose positive

Answer: (B)

Nitrate reduction capability is the key trait used to separate Kingella denitrificans from Neisseria gonorrhoeae. Kingella denitrificans has nitrate reductase and can reduce nitrate in the medium, sometimes leading to denitrification with gas production. Neisseria gonorrhoeae does not reliably reduce nitrate in standard testing, so a positive nitrate reduction result points toward Kingella denitrificans rather than Neisseria gonorrhoeae. The oxidase test is not helpful here because both organisms are oxidase positive, and carbohydrate utilization patterns or growth on selective media can be variable and overlap. So, the ability to reduce nitrate is the clearest differentiator.