Characteristics and prognostic factors in bacterial meningitis

Bacterial meningitis is a severe infectious disease of the central nervous system. Although vaccination has decreased incidence and improved prognosis, the disease still has a substantial morbidity and mortality. The overarching aim of this thesis was to describe clinical characteristics and prognostic factors of specific patient groups. We derived and validated a risk score to differentiate bacterial from viral meningitis, including readily available clinical and laboratory characteristics, in Dutch and American patients. This easy-to-use risk score was reliable in ruling out bacterial meningitis. Furthermore, we discovered that 2% of patients with bacterial meningitis have a normal cerebrospinal fluid leukocyte count upon admission, mainly those with severe pneumococcal meningitis and sepsis. In patients over 80 years, atypical pathogens are more common and mortality is high. However, 30% of patients survive with no or minimal neurological deficits. Moreover, patients with otitis and meningitis generally have a relatively favorable outcome. Ear surgery was performed in 55%, but its effect on outcome remains unclear. In meningococcal meningitis, a specific genetic subgroup (clonal complex 11) has previously caused an outbreak bearing serogroup C. We showed that a more recent outbreak bearing serogroup W (2016-2018) was associated with a high mortality, underlining the importance of monitoring outbreaks to guide vaccination strategies. We also studied Staphylococcus aureus meningitis in Denmark and the Netherlands, and showed that 89% had a concomitant infection outside the brain. Finally, we found that increased neurofilament light chain is an independent predictor of unfavorable outcome in bacterial meningitis.