Increased rates of severe human infections caused by Streptococcus subspecies

Closely related to group A streptococcus (also commonly known as Streptococcus pyogenes), which has been very well studied, little is known about SDSE.

The findings of this study are described in a paper titled "Integrative genomic, virulence, and transcriptomic analysis of emergent Streptococcus dysgalactiae subspecies equisimilis (SDSE) emm type stG62647 isolates causing human infections," appearing Oct. 17 in the journal mBio, which is published by the American Society for Microbiology in association with the American Academy of Microbiology. James M. Musser, M.D., Ph.D., chair of the Department of Pathology and Genomic Medicine at Houston Methodist, is the corresponding author on the paper.

"Given its great emerging importance to human health, our limited understanding of SDSE molecular pathogenesis is remarkable," said Jesus M. Eraso, Ph.D., an assistant research professor of pathology & genomic medicine with Houston Methodist and lead author on the study.

To close this knowledge gap, the Houston Methodist team used a sophisticated integrative approach to study 120 human isolates of a particular SDSE subtype, called stG62647. They analyzed the subtype's genome, where the information of its DNA is stored, its transcriptome, which provides a snapshot of the complete gene expression profile at the time the SDSE cells were collected, and its virulence, which refers to the degree of damage it causes to its host. The stG62647 SDSE strains are important to study because they have been reported to cause unusually severe infections, and understanding the relationships and interplay between these three entities gave the researchers a richer understanding of how it causes disease.

The data from this integrative analysis provided much new data about this important emerging human bacterial pathogen and are useful in vaccine research. It also raised many new questions and generated new hypotheses to be studied in this ongoing line of investigation.

Musser and Eraso's collaborators on this study were Randall J. Olsen, S. Wesley Long and Ryan Gadd with the Center for Infectious Diseases in the Houston Methodist Research Institute, and Sarrah Boukthir, Ahmad Faili and Samer Kayal from Université Rennes in France.

These studies were funded, in part, by the Fondren Foundation.