Fluoroquinolone-nonsusceptible Streptococcus pneumoniae isolates from a medical center in the pneumococcal conjugate vaccine era

FQ resistance initially emerged in either vaccine or nonvaccine serotypes. The majority of isolates were international clones or related variants, suggesting that resistance was disseminated through clonal spread. The wide use of pneumococcal conjugate vaccine since 2013 appears to have reduced the spread of FQ-nonsusceptible pneumococci.