OBJECTIVE: To describe the frequency of etiologic agents of bacterial meningitis (BM) among children aged 2-59 months in a sample of patients in Salvador, Northeast Brazil, with emphasis on the frequency of BM of unknown etiology (BMUE), just before, during and after the implementation of routine immunization of infants with Haemophilus influenzae type b (Hib) vaccination. METHOD: Demographic, clinical and cerebrospinal fluid (CSF) information was collected from the chart of every patient, aged 2-59 months, whose CSF exam was performed at the CSF Lab - José Silveira Foundation, between January 1989 and December 2001. Every CSF exam was completely performed according to standard methods. The etiologic diagnosis was based on either culture and/or latex-agglutination test. When the agent was only seen on Gram stained smear, the diagnosis was descriptive. BMUE was defined as: glucose < 40mg / dl, protein > 100 mg / dl, white blood cell count > 20 cells / mm³, percentage of neutrophils > 80%. RESULTS: Of 1519 patients, 894 (58.9%) had normal exams and BM was diagnosed in 95 (6.2%). Etiologic agents were: Hib (44.2%), meningococcus (13.7%), Gram-negative bacilli (11.6%), Mycobacterium tuberculosis (6.3%), pneumococcus (4.2%), other agents (4.2%); BMUE was diagnosed in 15.8% of cases with BM. By analysing the frequency of BMUE and Hib among all exams performed yearly, the peaks were recorded in 1989 (5.3%) and 1990 (16.9%), respectively, decreasing to 0.7% and 0% in 2001. CONCLUSION: It is possible that the implementation of the conjugate Hib vaccine during the 1990's has been decreasing not only the occurrence of Hib meningitis but also of BMUE.
meningitis; childhood; Haemophilus influenzae type b; immunization; cerebrospinal fluid; bacterial meningitis of unknown etiology
