# Brain Abscesses Complicating Bacterial Meningitis—A Nationwide Cohort Study From the Netherlands

## TL;DR

This study examines how often brain abscesses occur in bacterial meningitis patients and identifies which bacteria are most associated with this complication.

## Contribution

The study provides the first nationwide assessment of brain abscesses in bacterial meningitis, including their prevalence, causative pathogens, and outcomes.

## Key findings

- Brain abscesses occurred in 1.9% of bacterial meningitis cases.
- Streptococcus anginosus group had the highest abscess prevalence among meningitis-causing bacteria.
- Patients with abscesses had a 71% chance of an unfavorable outcome despite treatment.

## Abstract

Brain abscesses rarely complicate bacterial meningitis while their clinical characteristics and outcomes have not been systematically assessed. We studied prevalence, pathogen distribution, clinical characteristics including treatment, and outcomes of brain abscess in bacterial meningitis patients.

In a prospective Dutch national cohort of community‐acquired bacterial meningitis (January 2006 to October 2023), we identified patients with a brain abscess diagnosed by the treating physician. Presence of abscesses was confirmed by re‐evaluation of the cranial imaging.

Of the 2918 episodes included, 56 were complicated by a brain abscess (prevalence 1.9%, 95% confidence interval [CI] 1.5–2.5). For
Streptococcus pneumoniae
the prevalence of abscesses among meningitis episodes was 1.1% (95% CI 0.7%–1.6%) while it was 3.6% (95% CI 2.6%–5.0%) for other bacteria. Prevalence was highest in meningitis caused by the
Streptococcus anginosus
group (11/21, 52.4%),
Klebsiella pneumoniae
(1/10, 10.0%),
Listeria monocytogenes
(8/175, 4.6%),
Escherichia coli
(1/22, 4.5%), and group A streptococcus (3/79, 3.8%). Prevalence increased between 2006–2014 and 2015–2023, with a ratio of 1.8 (95% CI 1.7–2.1). In meningitis patients with abscesses, 14‐day survival was 94% and 40 of 56 (71%) patients had an unfavourable outcome. In 9 of 56 (16%) patients the abscess was treated with a neurosurgical intervention (extra‐ventricular CSF drain or abscess aspiration). All received prolonged antibiotic treatment.

Most brain abscesses among meningitis patients were caused by pneumococci, but non‐pneumococcal streptococci had the highest risk for abscesses. Patients with abscesses had a high risk for an unfavourable outcome.

Prevalence, pathogen distribution, clinical characteristics, and outcomes of brain abscess in bacterial meningitis was assessed in this study.