PNEUMOCOCCAL MENINGITIS IN ADULTS: ANALYSIS OF SEROTYPE DISTRIBUTION AND ANTIMICROBIAL RESISTANCE

Streptococcus pneumoniae can cause a wide range of diseases. Among them, meningitis is associated with the highest mortality rates. This study analysed trends in pneumococcal meningitis from 1990 to 2022. A laboratory-based retrospective study including all adult (≥18 years) with pneumococcal meningitis. Pneumococci were serotyped (Quellung or sequenced) and tested for antimicrobial susceptibility (microdilution, EUCAST). For analysis, three periods were defined regarding on the subsequent introduction of pneumococcal conjugate vaccines (PCV) in the paediatric schedule: Pre-PCV7 (1990-2000), Pre-PCV13 (2001-2011) and Post-PCV13 (2012-2022). There were 199 pneumococcal meningitis over the study period (51, 81 and 67, in each respective period). Cerebrospinal fluid (CSF) leak (35.3%) was the main focus in the Pre-PCV7 period, whereas acute otitis media (AOM) was it in the subsequent periods (45.7% and 53.7%, respectively). The overall mortality rates were 27.5%, 11.1% and 13.4%, respectively. Based on the meningitis focus, serotypes 16F, 23F, and 24F were the most frequent among patients with a CSF fistula; serotypes 3, 19A, and 19F in AOM; and serotypes 8, 10A, and 22F in the haematogenous focus (Figure1). After PCVs introduction, the proportion of meningitis cases caused by PCV13 or PCV20 serotypes decreased progressively from 56.9% and 72.5% to 25.4% and 49.3%, respectively (Figure2). Over the study period, rates of penicillin- (PEN) and cefotaxime-susceptibility (CTX) increased from 60.8% and 74.5% to 74.6% and 94.0%, respectively. Serotypes 9V, 14 and 19A were associated with non-susceptibility over the whole period (Figure3). Additionally, the antibiotic-resistant serotype 6C has garnered interest in recent years. The PCVs introduction for children changed the epidemiology of pneumococcal meningitis in adults. Despite the overall decrease in PCV13 serotypes, serotype 3 persisted across all periods associated with AOM focus. Besides the resilience of serotype 19A, susceptibility to penicillin and cefotaxime increased over the study period. These findings underscore the need for continued surveillance of serotype distribution and antimicrobial resistance trends.