Phenotypic Characterization and Serotypes Identification of CSF isolates in Acute Bacterial Meningitis

摘要

Background and Aim: Bacterial meningitis is a fatal disabling disease which needs prompt antibiotic management. As it causes a significant morbidity and mortality throughout the world, every developing country should have accurate information regarding the common etiological agents in bacterial meningitis cases. In the present study, we have serotyped the obtained agents in order to predict the usefulness of existing vaccines against bacterial meningitis. Materials and Methods: Two thousand nineteen cerebrospinal fluid (CSF) samples were obtained prospectively from suspected meningitis from January 2011 to July 2013 out of which 76 cases were approved by cytological, microbiological, molecular, and biochemical analysis as per the standard techniques. The isolated bacteria were serotyped to determine the predominant strain. Results: On the whole, 2019 CSF samples were collected, and bacterial etiology was isolated in 76 cases; S. pneumoniae in 31.5%, N. meningitides in 18.4%, and H. influenza in 10.5% of culture positive samples. Gram stained smears were positive in 63 samples. Among pneumococcal meningitis the most common serotype was 1, (29 %), followed by 19F, (25%), 18F, (8.3%), 6, (16.6%), 14, (12.5%), and 20 (8.3%). Out of the N. meningitidis positive CSF samples, 35.7%, 21.4%, and 35.7%, belonged to serogroups A, C, and W-135, respectively, and one non-groupable isolate were involved as S. pneumoniae meningitis. In the H. influenzae group only serotype b (87.5%), and untypable, 1, (7.5%) cases have been identified. Only 17, (0.8%) soluble antigens were detected from culture negative CSF samples. High protein and low sugar levels associated well with the features of ABM. The mean sugar and protein level in the CSF samples were 22.3 ± 9.8 mg/dl, 85.3 ± 51.29 mg/dl, respectively. Conclusions: The isolation rate of bacteria causing meningitis is 3.8%. Out of the total pneumococcal serotypes three of them were not included in the current vaccine in Ethiopia. Unusual findings and high a proportion of serogroup W-135 meningococci are observed in our study area The role of clinical presentations, routine CSF analysis in the rapid diagnosis of acute bacterial meningitis in cases of negative gram stained smears and a good knowledge of the bacterial epidemiology of meningitis can serve as a guide to start a rapid treatment as early as possible. Recommendation: the result of this study can be used to improve the existing vaccines to cover the detected serotypes and consequently reduce the incidence of bacterial meningitis.