The Emergence of Hypervirulent M1T1 Clone of Group A Streptococcus via Genetic Recombination and Host Selection

Streptococcus pyogenes (Group A Streptococcus, GAS) is a strictly human bacterial pathogen. Since the mid-1980s, GAS M1T1 clone has been the most prevalent and globally disseminated serotype and is the culprit causing invasive and severe streptococcal infections, urging a better understanding of the emergence of hypervirulent M1T1 clone from an evolutionary perspective. This review highlights the molecular and evolutionary events leading to pandemic M1T1 strains, and discusses the pressure driving the genetic acquisition of novel virulence genes and the selection of hypervirulent isolates in host. By understanding the evolutionary selection and pressures that select and shape the pandemic M1T1 clone, we could potentially develop new therapeutic strategies to tackle challenges when dealing with the globally disseminated M1T1 GAS clone.