Which Neisseria species produces acid from glucose but not from maltose, lactose, or sucrose?

• A. Neisseria gonorrhoeae
• B. Neisseria lactamica
• C. Neisseria meningitidis
• D. Neisseria sicca

Answer: (A)

Carbohydrate fermentation patterns are used to distinguish Neisseria species. When a Neisseria isolate ferments glucose, it produces acid, visible as a color change in the testing medium. If it does not ferment maltose, lactose, or sucrose, there’s no acid production from those sugars, indicating those metabolic pathways are absent or inactive for the organism.

This specific pattern—acid from glucose only and no acid from the other sugars—is characteristic of Neisseria gonorrhoeae. Other Neisseria species typically ferment additional sugars (for example, maltose) and would show acid production with those sugars as well, so they wouldn’t match this glucose-only profile.

In practice, recognizing this pattern helps differentiate gonorrhoeae from other Neisseria that utilize a broader range of carbohydrates.