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Updated: Jun 11, 2025
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Bacteriological characteristics and changes of Streptococcus pneumoniae serotype 35B after vaccine implementation in
Haruko Miyazaki1, Bin Chang2, Michinaga Ogawa2
1Department of Microbiology, Tokyo Medical University, Tokyo, Japan.
Abstract:
Streptococcus pneumoniae serotype 35B, a non-vaccine type, is a major contributor to the increase in pneumococcal infection post-vaccination. We aimed to understand the mechanism of its spread by characterizing 35B. The serotype, type 1 pilus (T1P) positivity, and antimicrobial susceptibility of 319 isolates in 2018-2022 were analysed and compared with those of isolates in 2014-2017 to find the changes. 35B accounted for 40 (12.5%) isolates. T1P positivity was notably higher in 35B (87.5%) than in the other serotypes. To confirm the role of T1P, an adhesion factor, we compared adherence to A549 cells between T1P-positive 35B isolates and their T1P-deficient mutants, showing contribution of T1P to adherence. Penicillin-non-susceptible rate of 35B was 87.5%, and meropenem-resistant 35B rate was 35.0%, which increased from 14.5% of 2014-2017 (p = 0.009). Multilocus sequence typing was performed in 35B strains. Prevalence of clonal complex 558, harbouring T1P and exhibiting multidrug non-susceptibility, suggested the advantages of 35B in attachment and survival in the host. The emergence of ST156 isolates, T1P-positive and non-susceptible to β-lactams, has raised concern about expansion in Japan. The increase of serotype 35B in pneumococcal diseases might have occurred due to its predominant colonizing ability after the elimination of the vaccine-serotypes.
Insights
Streptococcus pneumoniae serotype 35B, a non-vaccine type, is increasing due to its enhanced ability to attach, facilitated by type 1 pilus (T1P). This serotype also shows concerning antimicrobial resistance, particularly to meropenem.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- *Streptococcus pneumoniae* serotype 35B is a non-vaccine type contributing to increased pneumococcal infections post-vaccination.
- Understanding the spread mechanisms of serotype 35B is crucial for public health interventions.
Purpose of the Study:
- To characterize *Streptococcus pneumoniae* serotype 35B isolates to understand their increasing prevalence.
- To investigate the role of type 1 pilus (T1P) in the adherence and spread of serotype 35B.
- To assess antimicrobial susceptibility patterns and genetic relatedness of serotype 35B strains.
Main Methods:
- Analysis of 319 *Streptococcus pneumoniae* isolates from 2018-2022, comparing serotype, T1P positivity, and antimicrobial susceptibility with 2014-2017 data.
- In vitro adherence assays comparing T1P-positive 35B isolates with T1P-deficient mutants using A549 cells.
- Multilocus sequence typing (MLST) of serotype 35B strains.
Main Results:
- Serotype 35B accounted for 12.5% of isolates, with significantly higher T1P positivity (87.5%) compared to other serotypes.
- T1P was confirmed to contribute to the adherence of 35B to A549 cells.
- High rates of penicillin non-susceptibility (87.5%) and a concerning increase in meropenem resistance (35.0%) were observed in 35B.
- MLST identified clonal complex 558, associated with T1P and multidrug resistance, suggesting advantages in host attachment and survival.
- Emergence of T1P-positive, beta-lactam non-susceptible ST156 isolates raises concerns for expansion in Japan.
Conclusions:
- Type 1 pilus (T1P) enhances the colonization and adherence of *Streptococcus pneumoniae* serotype 35B, contributing to its increased prevalence.
- The rising antimicrobial resistance, particularly to meropenem, in serotype 35B is a significant public health concern.
- Specific clonal complexes, like CC558 and ST156, possess advantageous traits for spread and survival, necessitating enhanced surveillance.
