Neisseria lactamica meningitis following skull trauma.

A woman developed meningitis due to Neisseria lactamica in association with a cribriform plate fracture. Cerebrospinal fluid antigen tests for Neisseria meningitidis were negative. The patient recovered with intravenous penicillin therapy. N. lactamica can be rapidly distinguished from N. meningitidis by the hydrolysis of ONPG (o-nitrophenyl-beta-D-galactopyranoside). In contrast to N. meningitidis and Neisseria gonorrhoeae, N. lactamica lacks virulence properties. As 100% of N. lactamica strains are susceptible to penicillin and all three previously described patients with N. lactamica meningitis have recovered with penicillin treatment, the reason for distinguishing the organisms in this context is primarily to prevent unnecessary anxiety and prophylaxis among contacts.