[Failure of the treatment with penicillin in a case of Neisseria meningitidis meningitis].

Most Neisseria meningitidis are susceptible to penicillin with a minimal inhibitory concentration (MIC) < or = 0.6 mg/L and mortality related to meningococcal meningitis has been low. In recent years, however, N. meningitidis moderately susceptible to penicillin (MIC 0.12-1 mg/L) has been isolated in South Africa, England, USA, and mainly Spain. We report a case of a 16-year old male patient, who was admitted with a diagnosis of meningitis. Because group C N. meningitidis was isolated from cerebrospinal fluid, the patient received 300,000 Ul/Kg penicillin G. Seventy-two hours later, a new lumbar puncture was performed, and N. meningitidis was again isolated from culture. Beta-lactamase activity of the isolate was negative and MIC measurement showed that it was moderately susceptible to penicillin, probably due to modification of a penicillin binding protein. Penicillin G was then discontinued, and the patient was given 50 mg/Kg ceftriaxone. A third lumbar puncture performed on the eighth day after admission showed a negative bacteriological culture. The patient was discharged without neurological sequelae after 14 days of treatment. This case report shows that small changes in N. meningitidis sensitivity may be of clinical relevance.