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Molecular epidemiology and serogroup 6 capsular gene evolution of pneumococcal carriage in a Japanese birth cohort

Taketo Otsuka1, Bin Chang2, Akihito Wada2

  • 1Department of Pediatrics, Sado General Hospital 161 Chigusa, Sado, Niigata, 952-1209, Japan.

Journal of Medical Microbiology
|September 13, 2013
PubMed

Insights

Antibiotic resistance in Streptococcus pneumoniae is driven by a few dominant clones, not diverse ones. These prevalent clones adapt well to community settings, posing a global health challenge.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Antibiotic resistance in Streptococcus pneumoniae is a significant global health concern.
  • The clonal diversity associated with antibiotic resistance in S. pneumoniae remains unclear.

Purpose of the Study:

  • To investigate whether antibiotic resistance in S. pneumoniae is linked to a few prevalent clones or many diverse clones.
  • To analyze the genetic basis of antibiotic resistance and capsular gene evolution in S. pneumoniae.

Main Methods:

  • Monitoring of 349 healthy children with nasopharyngeal cultures over 5 time points (4–36 months).
  • Characterization of 497 S. pneumoniae isolates using capsular serotyping, multilocus sequence typing (MLST), and antibiotic resistance genotyping (ermB, mefA/E, pbp mutations).

Main Results:

  • 25 serotypes and 66 sequence types (STs) were identified, including 24 new STs.
  • Most resistant clones (86.4%) possessed a single resistant or susceptible genotype.
  • Penicillin-non-susceptible isolates (84.1%) were predominantly linked to six specific clones (e.g., ST90, ST236).
  • Analysis of serogroup 6 revealed recombination events in the capsule locus, suggesting vaccine escape mechanisms.

Conclusions:

  • Drug-resistant S. pneumoniae is primarily associated with a limited number of highly prevalent clones adapted to the community.
  • Capsular gene recombination in serogroup 6 indicates ongoing evolution and potential for vaccine escape.

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