Epidemiology of Bacterial Meningitis in the Lombardy Region, Italy, from 2014 to 2024: An Observational, Retrospective Study

Bacterial meningitis remains a critical public health issue globally due to its high morbidity and mortality. Understanding regional epidemiological trends is essential to inform vaccination strategies and public health interventions. This observational, retrospective study analyzed cerebrospinal fluid (CSF) isolates collected from 731 confirmed cases of bacterial meningitis between 2014 and 2024 in Lombardy, Italy. Pathogen identification and serotyping of <i>Streptococcus pneumoniae</i> (SP), <i>Neisseria meningitidis</i> (NM), and <i>Haemophilus influenzae</i> (HI) were conducted using culture-based and molecular techniques. Trends were assessed across age groups and time using Kruskal-Wallis and chi-square tests. Results: SP was the predominant pathogen (78.4%), followed by NM (13.0%) and HI (8.6%). Significant temporal variation was observed for SP and NM, while HI trends remained stable. The impact of COVID-19-related restrictions was evident in a reduction in cases during 2020-2021. SP serotypes 3 and 8, HI non-typeable strains, and NM serogroup B were most frequent. No major shifts in serotype distribution were observed. Long-term surveillance data from Lombardy underscore the dominance of vaccine-targeted serotypes, ongoing circulation of resilient clones, and post-pandemic epidemiological shifts. These findings support continuous surveillance and inform vaccine strategy adjustments at the regional and national levels.