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Unformatted text preview: pneumococcal) can cause vascular thromboses or even superficial cerebritis, mimicking to some extent encephalitis.] 2. Pathogenesis Infection can occur in the CNS through four routes: hematogenous spread, contiguous spread (e.g. from paranasal sinuses, middle ear), direct inoculation (after surgery or accidental trauma) and, for a few agents, by retrograde spread up nerves (HSV, rabies). Most cases of bacterial meningitis begin with infection in the nasopharynx (which may be only minimally symptomatic). The infection spreads either by the hematogenous route or directly through the pharyngeal epithelium into the CNS. Encapsulated organisms (see slide) are prime offenders because, in the absence of specific antibody, their capsules protect them against phagocytic defenses....
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