Emergence of type I restriction modification system-negative emm1 type Streptococcus pyogenes clinical isolates in...

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Streptococcus pyogenes emm1 type is a primary cause of streptococcal toxic shock syndrome (STSS).
• An increase in STSS cases in Japan has been recently reported.
• Analysis of clinical isolates post-2005 was conducted to understand evolving S. pyogenes strains.

Purpose of the Study:

• To investigate genetic changes in S. pyogenes emm1 type isolates in Japan.
• To identify novel genetic features associated with increased STSS incidence.
• To understand the potential impact of these genetic changes on bacterial adaptation and pathogenicity.

Main Methods:

• Analysis of S. pyogenes clinical isolates collected in Japan after 2005.
• PCR and Pulsed-Field Gel Electrophoresis (PFGE) for genetic characterization.
• Experimental electroporation to assess plasmid incorporation efficiency.

Main Results:

• A deletion in the Spy1908–1910 two-component regulatory system and type I restriction modification system was identified in some emm1 isolates.
• These deleted strains were exclusively found in isolates from 2010–2013, not earlier.
• 56.5% of emm1 isolates from 2010–2013 exhibited this deletion, including 71.4% of emm1 STSS isolates.
• Isolates with and without the deletion shared a similar genetic background.
• Strains with the deletion demonstrated significantly higher efficiency in incorporating exogenous plasmids.

Conclusions:

• Novel emm1 type S. pyogenes isolates with specific genetic deletions have emerged and are increasingly prevalent in Japan.
• The deletion facilitates enhanced exogenous plasmid uptake, suggesting a mechanism for adaptation and potential increased virulence.
• These findings highlight the dynamic nature of bacterial pathogens and their potential role in rising STSS rates.