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

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

Answer: (C)

Carbohydrate fermentation patterns are used to distinguish Neisseria species in the lab. When an organism produces acid by fermenting a sugar, that sugar is being used as an energy source. Neisseria gonorrhoeae uniquely ferments glucose to acid but does not ferment maltose, lactose, or sucrose. This specific pattern helps separate it from other Neisseria species: meningitidis typically ferments both glucose and maltose, while other nonpathogenic Neisseria often ferment maltose and/or lactose in addition to glucose. So, an isolate that acidifies glucose medium but not media containing maltose, lactose, or sucrose points to Neisseria gonorrhoeae.