Antimicrobial susceptibility and serotype replacement of Streptococcus pneumoniae in children before and after PCV13 introduction in Taiwan

[[[ Background: ]]] Since 2015, 13-valent pneumococcal conjugate vaccine (PCV13) was included in the national immunization program in Taiwan. Subsequently, the serotypes of the main circulating Streptococcus pneumoniae strains have changed. PCV administration is also associated with changes in the antimicrobial susceptibility of S. pneumoniae strains. Therefore, in this study, we analyzed the serotype distribution and antimicrobial susceptibility of S. pneumoniae in pediatric infections. [[[ Methods: ]]] Children with S. pneumoniae infections, including invasive pneumococcal disease (IPD) and non-IPD, were enrolled from January 2010 to December 2020. The samples were collected from Mackay Memorial Hospital, MacKay Children’s Hospital, and Hsinchu Mackay Hospital in Taiwan. We analyzed the epidemiology of sample collection site, infection diagnosis, and the serotype and antimicrobial susceptibility of S. pneumoniae strains. The study period was divided into time points before and after PCV13 administration. [[[ Results: ]]] In total, 322 isolates were collected during the study period. The incidence of IPD declined annually, from 29.7% before 2015 to 7.3% after 2015 (p < 0.001). The prevalence of serotype 19 A had increased gradually since 2010 but declined rapidly after 2013. Serotypes 15 A and 23 A were the most common serotypes after 2015. The non-susceptibility of the S. pneumoniae isolates to penicillin, cefotaxime, and ceftriaxone decreased. Based on meningitis breakpoints, the non-susceptibility to cefotaxime and ceftriaxone gradually decreased, but increased in 2020. [[[ Conclusion: ]]] PCV13 was considerably effective in reducing the incidence of IPD in children; however, the prevalence of serotypes 15 A and 23 A increased. The increase in antimicrobial non-susceptibility caused by non-vaccine serotypes must be continuously monitored.