Evolution of the serotypes causing invasive pneumococcal disease along 2008-2022 in a Level 2 Public Hospital of the Madrid Region, in relation to their inclusion in different conjugate vaccines

The use of conjugate vaccines against Streptococcus pneumoniae originates changes in the invasive pneumococcal disease (IPD). The aim of this study was to in vestigate the evolution of S. pneumoniae serotypes isolated in the Hospital Universitario de Getafe between 2008 and 2022. 313 of S. pneumoniae strains were studied. Serotyping was carried out by latex agglutination (Pneumotest-latex) and the Quellung reaction. In addition, the minimal inhibitory concentration (MIC) was determined against penicillin, erythromycin and levofloxacin by the concentration gradient method (E-test) according the EUCAST breakpoints. The most frequent serotypes throughout the study period were 8, 3, 19A, 1, 11A and 22F corresponding to 46.6% of the isolates. Along 2008-2012 the serotypes 3, 1, 19A, 7F, 6C and 11A represented altogether 53.6% of the isolates. Between 2013 and 2017 the serotypes 3, 8, 12F, 19A, 22F and 19F grouped 51% of the isolates. During 2018-2022 the serotypes 8, 3, 11A, 15A, 4 and 6C included the 55.5% of the cases. In total 5 strains (1.6%) were penicillin resistant, 64 (20.4%) erythromycin resistant and 11 (3.5%) levofloxacin resistant. The MIC50 and MIC90 levels maintained stables along the time. The conjugate vaccines use with different serotype coverage conditioned a decrease of the vaccine-included and an increase of non-covered. Despite these changes, the global antimicrobial susceptibility patterns to erythromycin and levofloxacin maintained relatively stables. The resistance a penicillin was low, not finding this type of resistant strains in the last study period.