Antimicrobial susceptibility of <i>Streptococcus pneumoniae</i>: a 12-year analysis at the department of otolaryngology and head and neck surgery, Tohoku University Hospital

<p>Introduction: In recent years, concerns have been raised regarding the decreasing susceptibility of Streptococcus pneumoniae to antibiotics and the issue of serotype replacement due to the introduction of pneumococcal vaccines. In this study, we examined the current status of antimicrobial susceptibility of S. pneumoniae detected in our department over the past 12 years.</p><p>Methods: We conducted a retrospective analysis of the antimicrobial susceptibility of S. pneumoniae and the clinical characteristics of patients based on culture tests performed in the Department of Otolaryngology and Head and Neck Surgery at Tohoku University Hospital between February 2010 and September 2022.</p><p>Results: During the study period, a total of 89 strains of S. pneumoniae were detected in our department (25 pediatric isolates and 64 adult isolates). The prevalence of penicillin-resistant S. pneumoniae (PRSP) was similar for pediatric and adult isolates (8.0% and 9.4%, respectively). Although susceptibility to penicillin G (PCG) was relatively good among pediatric isolates from 2014 to 2017, the proportion of PRSP and penicillin-intermediate-resistant S. pneumoniae notably increased from 2018 to 2022. Conversely, among adult isolates, the proportion of PRSP increased during the same period, but penicillin-susceptible S. pneumoniae remained the majority. Additionally, the proportion of isolates with reduced susceptibility to meropenem (MEPM) showed an increasing trend from 2018 to 2022 for pediatric and adult isolates.</p><p>Discussion: In our pediatric isolates of S. pneumoniae, a recent decline has been observed in susceptibility to PCG and an increase in the proportion of isolates with reduced susceptibility to MEPM. Continuous monitoring of the antimicrobial susceptibility of S. pneumoniae is considered necessary.</p>