The B-galactosidase test is used to identify which species of Neisseria?

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The B-galactosidase test is designed to identify Neisseria lactamica due to its ability to ferment lactose and produce the enzyme β-galactosidase. This characteristic distinguishes it from other species within the Neisseria genus. Neisseria lactamica will typically yield a positive result in this test because it can utilize lactose as a carbon source, leading to the production of acid and/or gas, which indicates fermentation.

In contrast, other species such as Neisseria meningitidis and Neisseria gonorrhoeae do not express this enzyme and therefore do not ferment lactose, resulting in a negative result on the B-galactosidase test. Neisseria flavescens may also fail to produce a positive test result for β-galactosidase activity. Thus, the unique enzymatic activity of Neisseria lactamica in the context of lactose fermentation is pivotal for its identification through this specific test.