Community-acquired bacterial meningitis in Southern Sweden 2013-2023: a population-based study of incidence, aetiology and diagnostic yield.

Purpose: Despite advances in medical care, bacterial meningitis still poses a considerable health issue from a global perspective. An ageing population and increasing development and use of vaccines are likely to affect the incidence and aetiology. The aim of this study was to describe the incidence and aetiology of community-acquired bacterial meningitis (CABM) in our setting, as well as the serotypes of Streptococcus pneumoniae and Neisseria meningitidis causing CABM, in relation to available vaccines.

Method: Patients of all ages with CABM in southern Sweden 2013-2023 were included. Patients were identified through records of cerebrospinal fluid tests from the Department of Clinical Microbiology, and through International Classification of Diseases 10 codes for bacterial meningitis. Age-standardised incidence rates were calculated based on the European Standard Population 2013.

Results: During the study period, 244 episodes of CABM in 238 individuals were identified. Definitive aetiology could be established in 93% of episodes. Mean incidence rate was 1.63 per 100,000 person-years, with a trend of declining incidence during the study period. Streptococcus pneumoniae was the most common pathogen, accounting for 46.7% of episodes. 63.6% of the episodes of pneumococcal meningitis were caused by serotypes included in current vaccines.

Conclusion: Pneumococcal meningitis is the primary driver of incidence and trends of all-cause community-acquired bacterial meningitis in southern Sweden. Further studies are warranted to investigate how vaccination could influence both disease incidence and shifts in serotype distribution, while also identifying optimal patient populations for targeted interventions.