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Updated: Dec 7, 2025
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Molecular epidemiological characterization in mucoid-type Streptococcus pneumoniae isolates obtained from invasive
Kimiko Ubukata1, Takeaki Wajima2, Misako Takata1
1Department of Infectious Diseases, Keio University School of Medicine, Tokyo, Japan.
Introduction:
Streptococcus pneumoniae with a mucoid-type capsule is associated with invasive pneumococcal diseases (IPDs). Despite the introduction of pneumococcal vaccines, IPDs caused by mucoid-type isolates are still prevalent. The present study aimed to characterize mucoid-type S. pneumoniae isolated from IPD patients throughout Japan in 2017 (post-vaccination era).
Methods:
A total of 225 mucoid-type isolates were collected. The serotype, antimicrobial susceptibility, and multilocus sequence type of these isolates were determined.
Results:
The prevalence of IPDs caused by mucoid-type isolates was high in adults, especially in the elderly (≥65 years of age), and prognosis in these patients was significantly poor. Of the mucoid-type isolates, the predominant serotype was serotype 3 (84.4%), and the remaining were serotypes 37 (15.1%) and 8 (0.4%). Antimicrobial susceptibility showed that most mucoid isolates exhibited the penicillin-intermediate resistant S. pneumoniae genotype (gPISP). However, the serotype 3 isolate exhibited the penicillin-resistant S. pneumoniae genotype (gPRSP). This gPRSP isolate was classified into ST166, which is related to serotypes 9 V and 11 strains. Sequence analysis of the capsule-coding regions and its flanking regions indicated that recombination occurred upstream and downstream of the capsule-coding region, suggesting that gPRSP (serotype 9 V/ST166) obtaining the type-3 capsule gene cluster resulted in the emergence of gPRSP (serotype 3/ST166).
Conclusions:
Our findings indicated that IPDs caused by mucoid-type S. pneumoniae are still a serious concern and mucoid-type S. pneumoniae with novel phenotype could emerge via capsular switching in response to environmental changes such as introduction of vaccines and improper use of antimicrobial agents.
Insights
Mucoid-type Streptococcus pneumoniae causes invasive pneumococcal disease (IPD), particularly in the elderly. Novel resistant strains may emerge through capsular switching, posing an ongoing public health threat.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Mucoid-type Streptococcus pneumoniae is linked to invasive pneumococcal diseases (IPDs).
- Despite vaccination, IPDs caused by mucoid strains remain prevalent.
- Characterizing these strains is crucial for understanding disease dynamics.
Purpose of the Study:
- To characterize mucoid-type Streptococcus pneumoniae isolates from IPD patients in Japan (2017).
- To investigate serotype, antimicrobial susceptibility, and genetic relatedness.
- To understand the emergence of novel resistant phenotypes.
Main Methods:
- Collected 225 mucoid-type S. pneumoniae isolates.
- Determined serotype, antimicrobial susceptibility, and multilocus sequence type (MLST).
- Performed sequence analysis of capsule-coding regions and flanking areas.
Main Results:
- IPDs were prevalent in adults, especially the elderly (≥65 years), with poor prognosis.
- Serotype 3 was predominant (84.4%), followed by serotypes 37 and 8.
- Most isolates were penicillin-intermediate resistant (gPISP); serotype 3/ST166 was penicillin-resistant (gPRSP) due to capsular switching.
Conclusions:
- Mucoid-type S. pneumoniae remains a significant cause of IPDs.
- Novel phenotypes can emerge via capsular switching in response to vaccines and antimicrobial use.
- Continuous surveillance and characterization are essential.
