INTRODUCTION:
In the 1920’s Rebecca Lancefield developed the serological typing method, termed M-typing, which has defined the archetypical classification scheme of Streptococcus pyogenes. The first type strain characterized was termed ‘M1’ and is a remarkable clone, not simply because it dominates the clinical landscape in high-income settings today, but also for its historical persistence. Despite being one of the most characterized strains, there is still much to learn about the drivers of evolution of this lineage through time.
METHODS:
Accessing Lancefield’s original M1 S. pyogenes stocks and in collaboration with Rockefeller University, CDC and other international partners, we undertook a genomic investigation of over 400 M1 GAS isolated since 1918, encompassing the Great Lakes outbreaks of the 1970s, through to today’s newly emergent ‘M1UK’ clone.
RESULTS:
Four major ‘waves’ of M1 S. pyogenes clones are evident over 100 years of selection. We report the population evolutionary markers of M1 based on the SNPs, indels, inversions, and convergent evolution both in the context of population selection and in evolutionary phylodynamics.
CONCLUSION:
Since its inception over 100 years ago, Lancefield’s M-serotyping (emm typing) remains the primary epidemiological marker for defining S. pyogenes epidemiology. The Lancefield collection of isolates enables a key baseline to identify genetic events that shapes clinical landscape today. The ongoing application of ‘omic’ technologies is key to defining the genetic signatures that influence S. pyogenes biology across an ever-changing global landscape.