Isolation from a Healthy Carrier and Characterization of a Neisseria meningitidis Strain That Is Deficient in γ-Glutamyl Aminopeptidase Activity

γ-Glutamyl aminopeptidase (GGT) activity is used as a specific marker for the identification of Neisseria meningitidis. We isolated from a healthy carrier and characterized an N. meningitidis isolate which lacked the activity due to the insertional mutation of the ggt gene, suggesting that naturally occurring N. meningitidis isolates do not always possess GGT activity.