Etiology of Acute Otitis Media and Characterization of Pneumococcal Isolates after Introduction of 13-Valent Pneumococcal Conjugate Vaccine in Japanese Children

BACKGROUND:Acute otitis media (AOM) is a leading cause of childhood morbidity and antibiotic prescriptions. We examined etiologic changes in AOM after introduction of 13-valent pneumococcal conjugate vaccine as routine immunization for Japanese children in 2014. Serotypes, resistance genotypes, antibiotic susceptibilities, and multilocus sequence typing of pneumococcal isolates were also characterized. METHODS:Otolaryngologists prospectively collected middle ear fluid from 582 children by tympanocentesis or sampling through a spontaneously ruptured tympanic membrane between June 2016 and January 2017. Causative pathogens were identified by bacterial culture and real-time PCR for bacteria. Serotypes, resistance genotypes, sequence types, and susceptibilities to14 antimicrobial agents were determined for pneumococcal isolates. RESULTS:At least 1 bacterial pathogen was identified in 473 of the samples (81.3%). Nontypable Haemophilus influenzae (54.8%) was detected most frequently, followed by Streptococcus pneumoniae (25.4%), Streptococcus pyogenes (2.9%), and others. Pneumococci of current vaccine serotypes have decreased dramatically from 82.1% in 2006 to 18.5% (P