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Epidemiological characteristics in serotype 24 paediatric invasive pneumococcal disease according to an 11-year

Kenichi Takeshita1,2, Noriko Takeuchi2, Misako Ohkusu2

  • 1Department of Pediatrics, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba-shi, Chiba, Japan.

Epidemiology and Infection
|March 21, 2022
PubMed

Insights

In Japan, serotype 24 is now the leading cause of invasive pneumococcal disease (IPD) in children after the 13-valent pneumococcal conjugate vaccine (PCV13) introduction. Serotype 24 IPD is more common in children under two and associated with bacteremia.

Area of Science:

  • Pediatric Infectious Diseases
  • Vaccinology
  • Bacteriology

Background:

  • The 13-valent pneumococcal conjugate vaccine (PCV13) has altered the landscape of invasive pneumococcal disease (IPD) globally.
  • In Japan, a notable shift has occurred, with serotype 24 emerging as the predominant cause of pediatric IPD post-PCV13 introduction.

Purpose of the Study:

  • To investigate the clinical and microbiological characteristics of serotype 24 IPD in Japanese children during the post-PCV13 vaccination era.
  • To identify risk factors and unique features associated with serotype 24 IPD.

Main Methods:

  • A retrospective study was conducted using a pediatric IPD surveillance database in Chiba prefecture, Japan, from 2010 to 2020.
  • Clinical data from 225 IPD cases (32 serotype 24, 193 non-serotype 24) were analyzed.
  • Multivariate regression analysis and bacterial characterization, including antibiotic susceptibility and multilocus sequence typing (MLST), were performed.

Main Results:

  • Serotype 24 IPD cases were significantly associated with younger age (<2 years) and bacteremia compared to non-serotype 24 IPD.
  • All serotype 24 isolates were penicillin-susceptible but exhibited 100% macrolide resistance, contrasting with non-serotype 24 isolates.
  • MLST revealed a predominance of ST2572 and its variants, strains unique to Japan.

Conclusions:

  • Serotype 24 represents a significant challenge in pediatric IPD in Japan, particularly in young children.
  • The unique characteristics of serotype 24 isolates, including macrolide resistance and specific MLST profiles, highlight the impact of the PCV13 immunization program.
  • Continued surveillance and targeted interventions are crucial to address the evolving epidemiology of IPD.

Keywords:
13-valent pneumococcal conjugate vaccineInvasive pneumococcal diseaseserotype 24serotype replacement

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