Predominant Pneumococcal Serotypes in Isolates Producing Invasive Disease in a Spanish Region: Study of Their Relationship with Clinical Factors, Antimicrobial Resistance and Vaccination Coverage

Pneumococcus is a significant pathogen due to its high morbidity and mortality rates, especially among vulnerable populations. This study investigates the epidemiology of Streptococcus pneumoniae serotypes causing invasive pneumococcal disease in the Region of Comunidad Valenciana, analyzing data from 1587 isolates collected between 2014 and 2023. Serotyping and antimicrobial sensitivity were assessed, and whole genome sequencing was conducted on 104 isolates to examine clonal relationships. The study found that serotype 8 was the most common (17.5%), followed by serotype 3 (14.7%). There were significant variations in serotype distribution over the years, with serotype 8 increasing notably from 2019 onwards, while serotype 19A has decreased. Age was a significant factor, with serotype 8 being more prevalent in individuals older than 10 years. The overall patient recovery rate was 72%, with the higher mortality observed in serotypes 3 and 15A. Vaccination rates were higher among children under five, and the study highlighted the necessity for continuous monitoring of vaccine efficacy. Antimicrobial resistance was most significant for erythromycin (20%) and clindamycin (16%), with serotypes 19A and 6C showing the highest resistance rates. Whole genome sequencing revealed that ST53 and ST180 were the predominant sequence types for serotypes 8 and 3, respectively, reflecting global trend. The study underscores the importance of ongoing surveillance to adapt vaccination strategies and antimicrobial treatments, given the dynamic nature of pneumococcal epidemiology and resistance patterns. The findings also emphasize the need for targeted interventions to manage high-risk serotypes and improve patient outcomes.