Epidemiological characteristics in serotype 24 paediatric invasive pneumococcal disease according to an 11-year population-based study in Japan

Abstract

After the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), serotype replacement has occurred in Japan, and serotype 24 has become the most common serotype in pediatric invasive pneumococcal disease (IPD). To understand the characteristics of serotype 24-IPD in Japanese children in the post-PCV13 era, we conducted a retrospective study in children aged ≤15 years from 2010 to 2020 using a database of pediatric IPD surveillance in Chiba prefecture, Japan. We identified a total of 357 IPD cases and collected clinical information on 225 cases (24: 32 cases, non-24: 193 cases). Compared with the non-serotype 24-IPD, serotype 24-IPD was independently related to be <2 years of age (OR: 3.91, 95% CI: 1.47-10.44; p = 0.0064) and bacteremia (OR: 2.28, 95% CI: 1.01-5.13; p = 0.0475), as a result of the multivariate regression analysis. We also conducted a bacterial analysis, and the isolates of serotype 24-IPD had tendencies of PCG-susceptible (24: 100.0%, non-24: 61.3%; p < 0.0001) and macrolide-resistance (24: 100.0%, non-24: 87.3%; p = 0.0490). Their multilocus sequence typing was mostly ST2572 and the variants, which were unique to Japan. This tendency might have been a result of the progress made in the Japanese PCV13 immunization program.

Bacteriological and molecular characterization of temperature- and CO 2 -dependent Streptococcus pneumoniae serotype 24F ST162 isolated from Japanese children

“…This trend was also observed in the surveillance data between 2015 and 2017 ( 17 ); however, serotype 24F ST162 was not detected. In contrast, the most recent epidemiological analysis of pediatric IPD in a Japanese prefecture detected one ST162 strain of serotype 24F in the period 2010–2020 ( 8 ). The increase in the number of isolates of this clone in this study from 2017 to 2021 suggests an increase in the number of serotype 24F ST162 strains in Japan, especially in the last few years.…”

“…Serotype 24F is one of the most common serotypes associated with IPD following the introduction of PCV13 in Japan ( 3 , 4 ) and other countries ( 5 – 7 ). Serotype 24F has been detected in cases of bacteremia among children under 2 years of age at a significantly higher rate than that seen in older children in Japan ( 8 ).…”

Increase in prevalence of Streptococcus pneumoniae serogroup 24 in children upon introducing 13-valent pneumococcal conjugate vaccine in Japan

“…On the other hand, the incidence of IPDs caused by NVTs has increased [6, 16]. Among all the NVTs, serogroup 24 was one of the most prevalent serotypes in Japan [11]. Surprisingly, serogroup 24 is a major serogroup causing IPDs in children, but it has been rarely isolated from adults with IPDs in Japan [17, 18].…”

“…A survey of IPDs in children showed that the incidence of IPDs caused by serotype 24F increased considerably after the introduction of PCV13. In addition, we also found that the incidence of IPDs caused by serogroup 24 strains in children increased significantly after the introduction of PCV13 in Chiba Prefecture, Japan, while cases of IPD caused by serotype 24B strains have also increased since 2019 [ 11 ]. Therefore, a detailed analysis of serogroup 24 strains isolated from patients with IPD is required.…”

Factors affecting antimicrobial resistance in Streptococcus pneumoniae following vaccination introduction

“…It has increased in prevalence following the introduction of PCV13 and is a predominant cause of in IPD in several countries [50,51]. Serotype 24F was at the upper end of the invasiveness spectrum in a meta-analysis by Balsells et al [52], and has been associated with meningitis and bacteraemia in several studies [51,53]. Genomic characterisation of 24F isolates [54] has revealed it harbours many virulence genes which are conserved, including serine protease (htrA), hyaluronidase (hysA), streptococcal enolase (eno), choline binding proteins (cbpD, cbpG, lytA, lytB, lytC, pce/cbpE, pspA, pspC/cbpA), fibronectin and laminin-binding proteins (pavA, lmb), in addition to genes involved in iron and manganese uptake (piaA, piuA, psaA and cppA).…”