Reid V. Wilkening

Streptococcus pyogenes (Group A Streptococcus, GAS) is an enigmatic human-restricted pathobiont, capable of both colonization and infection

Streptococcus pyogenes is an obligate human pathobiont associated with many disease states. Here, we present a novel model of S. pyogenes infection using intact murine epithelium. From this model, we were able to perform RNA sequencing to evaluate the genetic changes undertaken by both the bacterium and host at 5- and 24-hours post infection. Analysis of these genomic data demonstrate that S. pyogenes undergoes significant genetic adaptation to successfully infect the murine epithelium, including changes to metabolism and activation of the Rgg2/Rgg3 quorum sensing (QS) system. Subsequent experiments demonstrate that an intact Rgg2/Rgg3 QS cascade is necessary to establish a stable superficial skin infection. Furthermore, activation of this pathway results in increased murine morbidity and increased bacterial burden on the skin. This phenotype is associated with gross changes to the murine skin, as well as histopathological evidence of inflammation. Taken together, these experiments offer a novel method to investigate S. pyogenes -epithelial interactions and demonstrate that a well-studied QS pathway is critical to a persistent infection. Importance: Streptococcus pyogenes remains a pathogen of global importance, with significant total disease burden worldwide. Much of this burden is due to skin infection or sequalae thereof, yet little is currently known about the initial interactions between the organism and host skin. Here we present a new mouse model of skin infection. From this model, we were able to study gene expression by both the bacteria and the host during early infection time points. Both genetic and phenotypic data derived from these results demonstrate that a well-conserved S. pyogenes communication network, the Rgg2/Rgg3 quorum sensing pathway, contributes to establishing and maintaining a durable skin infection. We propose that by better understanding the genetic pathways needed to colonize and adapt to new niches, new approaches to preventing and treating S. pyogenes may be possible.