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Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae in paediatric patients in Japan

Satoshi Nakano1, Takao Fujisawa2, Shota Koide1

  • 1Antimicrobial Resistance Research Center, National Institute of Infectious Diseases, Japan Institute for Health Security, Tokyo, Japan.

Journal of Medical Microbiology
|December 12, 2025
PubMed

Insights

Resistant pneumococcal strains, particularly non-vaccine serotypes 15A and 35B, are prevalent in Japanese children. Current vaccines offer limited protection, highlighting the need for enhanced surveillance and new vaccine strategies.

Area of Science:

  • Microbiology
  • Epidemiology
  • Genomics

Background:

  • Streptococcus pneumoniae causes invasive diseases in children globally.
  • Pneumococcal conjugate vaccines (PCVs) reduce disease burden, but non-vaccine serotypes and antimicrobial resistance remain challenges.
  • Recent epidemiology of pediatric invasive pneumococcal disease (IPD) in Japan post-COVID-19 and pre-PCV15/20 introduction is not well-characterized.

Purpose of the Study:

  • To investigate recent pneumococcal serotype distribution in Japan (2020-2023).
  • To analyze antimicrobial susceptibility patterns of pediatric pneumococcal isolates.
  • To determine the genetic characteristics of these isolates.

Main Methods:

  • Nationwide prospective surveillance study from March 2020 to April 2023.
  • Collected 151 pneumococcal isolates from children under 15 years (126 IPD, 25 non-IPD).
  • Performed serotyping, antimicrobial susceptibility testing, and whole-genome sequencing.

Main Results:

  • Most common IPD serotypes were 15B/C (23.0%), 15A (11.1%), and 24B (10.3%).
  • Vaccine coverage for PCV13, PCV15, and PCV20 was 0.8%, 13.5%, and 42.1% respectively.
  • High resistance rates observed for penicillin (31.8%) and erythromycin (88.7%); serotypes 15A and 35B showed high resistance to beta-lactams including meropenem.

Conclusions:

  • Prevalent non-vaccine and multidrug-resistant pneumococcal clones (e.g., 15A-CC63, 35B-CC558) identified in Japanese children.
  • PCV20 covers less than half of the identified IPD isolates.
  • Emphasizes the need for ongoing genomic surveillance, antimicrobial stewardship, and development of vaccines targeting additional serotypes like 15A and 35B.

Keywords:
JapanStreptococcus pneumoniaeinvasive pneumococcal diseasespaediatricpneumococcal conjugate vaccineswhole-genome sequencing

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