Strep by Strep: Houston Methodist Researchers Unravel Genetics Powering Emerging Infectious Threat

A fast-rising strep bacterium has become increasingly notorious for causing serious infections in humans, including complications that can lead to muscle damage and patient death. New Houston Methodist researchopens in new tab/window appearing in The American Journal of Pathologyopens in new tab/window, published by Elsevier, sheds light on how Streptococcus dysgalactiae subspecies equisimilis (SDSE) causes disease and may provide important insights to aid in vaccine development.

To better understand how SDSE causes disease compared to its better-known close relative, Strep A, Houston Methodist scientists, led by James Musser, MD, PhD, chair of the Department of Pathology and Genomic Medicine and director of the Center for Infectious Diseases at Houston Methodist, used a genomic screening method known as transposon-directed insertion-site sequencing (TraDIS) to test gene function in SDSE. The study examined two closely related SDSE strains, which helped detect subtle strain‑specific differences that influence infection behavior.

“We identified several genes that were essential for bacterial survival in both laboratory and infection conditions,” Dr. Musser said. “The study also identified various genes in each strain that influenced the bacteria’s ability to grow and persist during muscle infection.”

Unexpectedly, several genes traditionally associated with Strep A infection were found to reduce the survival and growth in SDSE when active, suggesting fundamental differences in how the two closely related bacteria cause disease.

“By defining which genes are truly required for growth and survival of the bacteria during infection, this work provides a foundation for understanding how SDSE causes severe disease and provides important information that may help in creating a SDSE vaccine,” Dr. Musser explained.

The researchers said as SDSE continues to be a threat, the findings provide a critical resource for future studies aimed at developing novel strategies to prevent and treat invasive SDSE infections.

Notes for editors

The article is “Gene Contribution of Streptococcus dysgalactiae Subspecies equisimilis, an Emerging Pathogen, to Experimental Primate Necrotizing Myositis,” by S.M. Nayeemul Bari, Jesus M. Eraso, Randall J. Olsen, Luchang Zhu, and James M. Musser (https://doi.org/10.1016/j.ajpath.2026.04.009opens in new tab/window). It appears online in The American Journal of Pathology, ahead of volume 196, issue 8 (August 2026), published by Elsevier.

The article is openly available for 90 days at https://ajp.amjpathol.org/article/S0002-9440(26)00131-8/fulltextopens in new tab/window.

Full text of the article is also available to credentialed journalists upon request. Contact Eileen Leahy at +1 732 406 1313 or [email protected]opens in new tab/window to request a PDF of the article or more information. To reach the study’s authors, contact Nathaniel Godwin, Senior Editor, Research Media Relations, Houston Methodist, at +1 681 285 8818 or [email protected]opens in new tab/window.

The study was supported by the Fondren Foundation.

About The American Journal of Pathology

The American Journal of Pathologyopens in new tab/window, official journal of the American Society for Investigative Pathologyopens in new tab/window, published by Elsevier, seeks high-quality original research reports, reviews, and commentaries related to the molecular and cellular basis of disease. The editors will consider basic, translational, and clinical investigations that directly address mechanisms of pathogenesis or provide a foundation for future mechanistic inquiries. Examples of such foundational investigations include data mining, identification of biomarkers, molecular pathology, and discovery research. High priority is given to studies of human disease and relevant experimental models using molecular, cellular, and organismal approaches. ajp.amjpathol.orgopens in new tab/window

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