Nitric oxide concentrations and cerebrospinal fluid parameters in an experimental animal model of Streptococcus pneumoniae meningitis

Streptococcus pneumoniae is a common cause of meningitis. Nitric oxide (NO) has been implicated in causing cerebral edema. Modulating NO production in cerebrospinal fluid (CSF) may have a role in the treatment of bacterial meningitis. Experimental S. pneumoniae meningitis was induced in a rabbit model to determine CSF parameters and NO concentrations. An electrochemical probe in the CSF throughout the 7-hour experiment monitored NO concentrations. The animals had S. pneumoniae (10 ⁵) injected intracisternally and incubated for 1 hour. Cerebrospinal fluid 200-300 μl was obtained by intracisternal puncture at zero, 2, 4, and 7 hours after drug administration to measure glucose, protein, and lactic acid by standard chemical methods. White blood cell count was measured by hemocytometry. Three groups of five animals were used - control (C), ceftriaxone (CTX), and ceftriaxone plus dexamethasone (CTX+D). Ceftriaxone concentrations in CSF were obtained by microdialysis and analyzed by high-performance liquid chromatography. Mean (± SEM) CSF white blood cell count was significantly higher at 2 hours in the C group than in the other two groups (C 7307 ± 1302, CTX 605 ± 345, CTX+D 730 ± 43/mm ³, p0.05), whereas they did not rise significantly until 7 hours in the CTX group (CTX 18.7 ± 0.7, C 8.9 ± 0.4 μM, p=0.055; CTX+D 8.1 ± 2.2 μM, p