Spread of virulent group A Streptococcus type emm59 from Montana to Wyoming, USA

Area of Science:

• Microbiology
• Genomics
• Epidemiology

Background:

• Group A Streptococcus (GAS) is a significant human pathogen.
• Hypervirulent strains of GAS can cause severe invasive disease.
• The emm59 GAS type has emerged globally and is associated with increased virulence.

Purpose of the Study:

• To characterize a novel outbreak of severe invasive GAS infections in Wyoming.
• To determine the genetic relatedness of the causative strain to previously identified emm59 clones.
• To investigate the epidemiological links and geographic origin of the Wyoming strain.

Main Methods:

• Whole-genome sequencing of clinical isolates from Wyoming.
• Phylogenetic analysis of genome data to infer evolutionary relationships.
• Comparison with publicly available emm59 GAS genome sequences.

Main Results:

• Full-genome sequencing identified a hypervirulent clone of GAS emm59 responsible for severe invasive infections in Wyoming.
• Phylogenetic analysis indicated the Wyoming strain is closely related to emm59 strains previously identified in Canada and the United States.
• Evidence suggests the strain was introduced into Wyoming from Montana.

Conclusions:

• A hypervirulent emm59 GAS clone has expanded its geographic range into rural northeastern Wyoming.
• The findings highlight the importance of genomic surveillance for tracking the emergence and spread of virulent bacterial clones.
• Public health interventions may be needed to control the spread of this hypervirulent strain.