Prominent Binding of Human and Equine Fibrinogen to Streptococcus equi subsp. zooepidemicus Is Mediated by Specific SzM Types and Is a Distinct Phenotype of Zoonotic Isolates

Research output: Contribution to journalArticle


Streptococcus equi subsp. zooepidemicus is an important pathogen in horses that causes severe diseases such as pneumonia and abortion. Furthermore, it is a zoonotic agent, and contact with horses is a known risk factor. In this study, we investigated the working hypothesis that the zoonotic potential varies among S. equi subsp. zooepidemicus strains in association with differences in M-like protein-mediated binding of host plasma proteins. We demonstrate via in-frame deletion mutagenesis of two different S. equi subsp. zooepidemicus strains that the M-like protein SzM is crucial for the binding of fibrinogen to the bacterial surface and for survival in equine and human blood. S. equi subsp. zooepidemicus isolates of equine and human origins were compared with regard to SzM sequences and binding of equine and human fibrinogens. The N-terminal 216 amino acids of the mature SzM were found to exhibit a high degree of diversity, but the majority of human isolates grouped in three distinct SzM clusters. Plasma protein absorption assays and flow cytometry analysis revealed that pronounced binding of human fibrinogen is a common phenotype of human S. equi subsp. zooepidemicus isolates but much less so in equine S. equi subsp. zooepidemicus isolates. Furthermore, binding of human fibrinogen is associated with specific SzM types. These results suggest that SzM-mediated binding of human fibrinogen is an important virulence mechanism of zoonotic S. equi subsp. zooepidemicus isolates.


  • René Bergmann
  • Maria Christin Jentsch
  • Albrecht Uhlig
  • Uwe Müller
  • Mark van der Linden
  • Magnus Rasmussen
  • Andrew Waller
  • Maren von Köckritz-Blickwede
  • Christoph Georg Baums
External organisations
  • Leipzig University
  • Universitätsklinikum der RWTH Aachen
  • University of Veterinary Medicine Hannover
  • Animal Health Trust
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Pathobiology
  • Microbiology in the medical area


  • fibrinogen binding, M-like proteins, survival in blood, szm deletion mutant, whole-blood bactericidal assay, zoonosis
Original languageEnglish
Article numbere00559-19
JournalInfection and Immunity
Issue number1
Early online date2019 Dec 17
Publication statusPublished - 2020 Jan
Publication categoryResearch