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Distribution of emm genotypes among group A streptococcus isolates from patients with severe invasive streptococcal

T Ikebe1, K Hirasawa, R Suzuki

  • 1Department of Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan.

Epidemiology and Infection
|February 10, 2007
PubMed

Insights

Group A Streptococcus (GAS) emm genotype 1 remained dominant but decreased in prevalence. Emerging emm types altered vaccine coverage for invasive streptococcal infections.

Area of Science:

  • Microbiology
  • Epidemiology
  • Infectious Diseases

Background:

  • Group A Streptococcus (GAS) is a significant human pathogen.
  • emm genotypes are key determinants of GAS epidemiology and vaccine efficacy.
  • Monitoring emm genotype prevalence is crucial for public health.

Purpose of the Study:

  • To analyze trends in emm genotypes of GAS isolates from severe invasive infections between 2001-2005.
  • To compare current emm genotype prevalence with the preceding 5-year period.
  • To assess the impact of changing emm genotypes on the coverage of a 26-valent GAS vaccine.

Main Methods:

  • Retrospective analysis of GAS isolates from patients with severe invasive infections.
  • emm genotyping of isolates.
  • Comparison of genotype frequencies between two 5-year periods (1996-2000 and 2001-2005).

Main Results:

  • emm1 remained the dominant genotype during 2001-2005.
  • The frequency of emm1 decreased compared to the 1996-2000 period.
  • An increase in the diversity of emm genotypes was observed.
  • The projected coverage of a 26-valent GAS vaccine decreased from 93.5% (1996-2000) to 81.8% (2001-2005).

Conclusions:

  • While emm1 remains prevalent, shifts in emm genotype distribution are occurring in invasive GAS strains.
  • These changes have led to a reduced effectiveness of the current 26-valent GAS vaccine.
  • Continued surveillance of emm genotypes is essential for adapting prevention and treatment strategies.

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