Abstract
Streptococcus pneumoniae causes invasive pneumococcal disease (IPD) in adults. The introduction of pneumococcal conjugate vaccines (PCVs) has reduced vaccine serotypes but has also led to the rise of non-vaccine serotypes. The aim of this study was to analyse pneumococcal lineages and their association with recent changes in IPD among adults in Spain. Data from adult IPD cases (≥18 years) were collected from six Spanish hospitals in 2019-2021. Strains were serotyped, tested for antibiotic susceptibility and subjected to whole genome sequencing (WGS). Findings were compared with data from previous periods (2008-2016). A total of 655 IPD episodes were examined. Pneumonia was the main focus (515/655), and 366 episodes occurred in adults over 64 years. Although IPD incidence decreased during COVID-19 pandemic, the burden of disease caused by PCV13 serotypes was significant. Notably, serotype 3 persisted (GPSC12-ST180 and GPSC83-ST260), and a new serotype 4 lineage emerged (GPSC162-ST13022). Among non-PCV13 serotypes, serotype 8 expanded (GPSC3-ST53) and a new serotype 12 F lineage emerged (GPSC55-ST8060). Most serotypes presented a dominant Global Pneumococcal Sequencing Cluster (GPSC) like GPSC16-ST67 of 9 N or GPSC19-ST433 of 22 F. Nevertheless, some GPSCs were associated with several serotypes, the most numerous were GPSC3 (serotypes 8, 11 A, and 33 F) and GPSC6 (serotypes 11 A and 14). The overall penicillin non-susceptibility rate was 17.0 %, 14.6 % resistance for meningitis and 1.6 % for pneumonia (15.1 % susceptible at increased exposure [SIE]). Serotypes 11 A and 14 (GPSC6-ST156/6521) and 19 A (GPSC1-ST320) had penicillin MICs above 1 mg/L. Acquired resistance genes associated with macrolide and/or tetracycline resistance were present in 19.4 % of isolates, particularly among serotypes 6 C (GPSC47-ST386/4310) and 19 A (GPSC1-ST320). The burden of PCV13 serotypes in adult IPD remains significant, and serotype 3 is the primary contributor. However, the rise of stable lineages associated with non-PCV13 serotypes, particularly 8, 9 N, and 22 F highlights a shifting epidemiology. The persistence of multidrug-resistant lineages, such as GPSC6-ST156 and GPSC1-ST320, emphasizes the need for continued surveillance. Vaccination of high-risk adults with current and broader coverage PCVs would help to control the burden of pneumonia and IPD among adults.
Published Version
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