Microbiology and clinical characteristics of brain abscess in adults from 3 tertiary hospitals in Singapore – a 11-year multicenter retrospective study

BACKGROUND: Brain abscess remains a serious infection with high morbidity and mortality despite advances in neuroimaging, molecular diagnostics and stereotactic neurosurgical techniques. Most large studies were based on European cohorts. Most Asian studies are single center, with smaller cohorts that consist almost entirely of patients with pyogenic brain abscess (PBA). Here, we present the results of our multi-center, retrospective study, representing the largest cohort of adults with brain abscess in Singapore. METHODS: Radiological reports of patients who underwent neuroimaging between 1 Nov 2013 and 31 Dec 2024 at three tertiary hospitals in Singapore were filtered for terms indicating brain abscess. Infectious diseases physicians reviewed the electronic medical records to identify patients who fulfilled pre-determined criteria for "definite" or "probable" diagnosis. RESULTS: Over the 11-year-old study period, there were 106 patients with brain abscess. The diagnosis of 54 and 52 patients were assessed to be "definite" and "probable", respectively. The median age (interquartile) of the patients was 59 years (49-67), 62.2% (66/106) were male, and 95.3% (101/106) were Singaporeans. 60.4% (64/106) were immunocompromised. PBA (n = 65) accounted for more than half of the cases, followed by tuberculosis (TB) (n = 20), toxoplasmosis (n = 9), Nocardia brain abscess (n = 7), invasive mold infection (n = 3) and cryptococcosis (n = 2), respectively. Most patients with PBA had only one organism identified from microbiological investigations (53/65, 81.5%), among which Klebsiella pneumoniae (n = 21), Streptococcus anginosus (n = 12) and Staphylococcus aureus (n = 8) were most commonly isolated. 28 out of 65 (43.1%) patients had oral cavity bacteria identified from microbiological investigations. Diabetes mellitus was the leading cause of immunosuppression in patients with PBA, while HIV infection was the leading cause in those with TB. In this cohort, 7.5% (8/106) and 14.2% (15/106) died within 30 and 90 days from date of presentation, respectively. On multivariate analysis, having undergone external ventricular drainage was the only clinical parameter found to be associated with increased mortality (OR 6.26, 95% CI: 1.44-27.1, P = 0.0014). CONCLUSIONS: This study has provided valuable insights into the microbiology and clinical characteristics of brain abscesses in adults in Singapore and highlighted challenges in distinguishing between different etiologies. Further study with a larger, multicenter cohort and prospective design may aid to address study limitations.