Streptococcus pneumoniae is a significant bacterial pathogen responsible for invasive and non-invasive infections. One of its most concerning traits is capsular switching, which can lead to multidrug resistance (MDR) and contribute to the development of hard-to-treat infections. This systematic review examined the sequence types of Streptococcus pneumoniae associated with multidrug resistance and/or capsular switching, focusing on their genetic relatedness. A systematic review was conducted following PRISMA guidelines and registered in PROSPERO. A comprehensive literature search was performed across PubMed, Scopus, and Web of Science. Studies published between 1991 and 2024 were screened based on predefined inclusion criteria. Eligible studies documented sequence types associated with MDR and/or capsular switching. Through a review of 133 studies across 152 countries, we identified dominant MDR sequence types: ST177, ST63, ST199, ST156, ST242, and ST338, and their genetic relationships with other MDR lineages. Notably, we compiled 390 documented capsular switching events spanning 184 distinct sequence types, providing a broad global synthesis of capsular switching in S. pneumoniae . We observed common trends of switching from vaccine to non-vaccine serotypes, alongside within-serogroup switching and within-vaccine group switching, predominantly in the post-vaccination era. Findings underscore a rapidly evolving genetic landscape of S. pneumoniae , in which MDR lineages diversify through capsular switching and serotype replacement. Despite (Pneumococcal Conjugate Vaccine) PCV introduction, vaccine-type MDR clones persist, raising concerns for serotypes such as 3, 6A/B, 19F, 14, and 23F. In addition, the global distribution and MDR profiles of ST320 and ST271 support their consideration as potential new (Pneumococcal Molecular Epidemiology Network) PMEN clone candidates, reinforcing the need for sustained genomic surveillance in the post-PCV era. • Analysis of 133 studies across 152 countries identified 451 multidrug-resistant (MDR) sequence types and 390 capsular-switching events, demonstrating the extensive global diversity of S. pneumoniae . • ST177, ST63, ST199, ST156, ST242, and ST338 emerged as globally dominant MDR lineages. • Capsular switching frequently moves strains from vaccine-covered to non-vaccine serotypes—especially in the post-PCV era—fueling serotype replacement and complicating disease control. • ST320 (serotype 19A) and ST271 (serotype 19F) show wide global distribution and strong MDR phenotypes, supporting their consideration as emerging PMEN-like clones. • Persistent MDR clones—including serotypes 3, 6 A/B, 19F, 14, and 23F—highlight the need for sustained genomic surveillance and robust antibiotic stewardship. • Many emerging MDR variants were identified as single-, double-, or triple-locus variants of well-established PMEN clones—including ST63, ST236, and ST81.
Akwetey et al. (Fri,) studied this question.