Streptococcus pneumoniae meningitis remains a disease with a poor outcome for the patient. A region of the brain that has been neglected in the study of meningitis is the ependyma, which has been identified as a location of adult pluripotent cells. In this study we have used a rat model of meningitis to examine whether the ependymal layer is affected by S. pneumoniae. The effects included localized loss of cilia, a decrease of the overall ependymal ciliary beat frequency, and damage to the ependymal ultrastructure during meningitis. In conclusion, loss of ependymal cells and ciliary function exposes the underlying neuronal milieu to host and bacterial cytotoxins and this is likely to contribute to the neuropathology commonly observed in pneumococcal meningitis.Despite modern intensive care, antibiotic treatment, and the use of dexamethasone, the morbidity and mortality associated with Streptococcus pneumoniae meningitis remain high (15). Vaccines against this bacterium show no evidence of reducing the number of cases (17). The mechanisms by which S. pneumoniae causes neuronal damage (once it infects the cerebrospinal fluid [CSF]) are yet to be fully deciphered. To investigate the effect of S. pneumoniae and its virulence factors, we established an ex vivo method for the culture and differentiation of brain tissue into a monolayer of ciliated ependymal cells. Ependymal cells line the ventricular cavities and the cerebral aqueduct separating the CSF that is infected in meningitis and ventriculitis from neuronal tissue. Using this model, investigators have previously shown that both pneumolysin (4, 12) and pneumococcal hydrogen peroxide (H 2 O 2 ) (5) cause damage to ependymal cells. In addition, when clinically relevant concentrations of bacteria were added to brain slices prepared from the fourth ventricle there was a rapid inhibition of ependymal ciliary beat frequency (CBF) (5).The CBF of ependymal cilia may be measured directly and continually to assess the functioning and integrity of ependymal cells. The ependyma is thought to act as a filter relaying macromolecules to and from the CSF, and it also plays a role in controlling CSF volume (3). Recently, both ependymal (8) and subventricular zone (1) cells have been identified as adult neuronal stem cells, stressing the potential importance of the thin cellular layer that lines the ventricles and aqueducts of the brain.It was essential to determine whether our ex vivo findings (determined using the ciliated ependymal cells) were also observed during pneumococcal meningitis. We therefore established a modification of the rat meningitis model described by Pfister and colleagues (14). In this paper we show that during pneumococcal meningitis and as predicted from our ex vivo studies, ependymal CBF is inhibited and the integrity of the ependymal layer is compromised.Overview. A cannula was surgically implanted onto the atlanto-occipital membrane prior to perforation, according to the method of Huang and colleagues (6). The CSF was then infected with the desired bac...