Bacterial meningitis in an urban area: etiologic study and prognostic factors.

OBJECTIVES: The study of clinical features, diagnostic methods and prognostic factors of bacterial meningitis, in an urban area. PATIENTS AND METHODS: All patients admitted between June 2001 and July 2004 in the emergency departments of a few hospitals, with the diagnosis of bacterial meningitis were included. CSF and blood cultures were performed in every case. Phenotypic characterization of strains of Streptococcus pneumoniae and Neisseria meningitidis identified by culture were performed. In order to detect the three most common agents it was done a PCR assay in culture negative CSF samples.
RESULTS: Bacterial meningitis was diagnosed in 201 patients. Etiologic definition was based on culture in 142 patients (70.6%), done by CSF PCR assay in 33 (16.4%) other patients and exclusively by latex agglutination test results in two cases. Thus, an etiologic diagnosis was established in 177 (88%) cases. Antigenic characterization showed a slight prevalence of N. meningitidis phenotype C:2b:P1; the S. pneumoniae serotype characterization showed that 43.8% of identified serotypes are not included in any of the available vaccines. Eighteen patients died (8.9%). The statistic analysis found that factors associated with an adverse outcome were age older than 50 years (OR 7.07; IC 95% 1.1-27.4), the presence of comorbidities (OR 3.3; IC 95% 1.1-9.6) and the occurrence of systemic complications (OR 5.8; IC 95% 2.1-16.0).
CONCLUSIONS: This epidemiologic pattern is similar to that found in other countries after the introduction of Haemophilus influenzae b conjugated vaccine. The association of culture and noncultural methods of diagnosis had a better performance in defining the etiology. Comparing to other series, in-patients mortality rate was lower (8.9%) than usually referred to, being considered unfavourable prognostic factors the age more than 50 years, the presence of comorbidities and of systemic complications.