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Updated: Oct 26, 2025
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
New Insights on Streptococcus dysgalactiae subsp. dysgalactiae Isolates
Cinthia Alves-Barroco1, João Caço1, Catarina Roma-Rodrigues1
1UCIBIO, Departamento de Ciências da Vida, NOVA School of Science and Technology/FCT NOVA, Universidade NOVA de Lisboa, Caparica, Portugal.
Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) in cattle harbors virulence genes from Streptococcus pyogenes phages, suggesting potential niche expansion. Bovine SDSD strains possess unique genetic traits, including a CRISPR/Cas IIA system, differentiating them from human strains and potentially necessitating a reevaluation of subspecies classification.
Area of Science:
- Microbiology
- Genomics
- Veterinary Medicine
Background:
- Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) is traditionally an animal pathogen, but recent human infections suggest a potential expansion of its host range.
- Previous studies indicated the presence of Streptococcus pyogenes phage virulence genes in bovine SDSD, but the mobile genetic elements were not fully identified.
Purpose of the Study:
- To characterize bovine SDSD isolates from 2011-2013 and compare them with earlier isolates (2002-2003) and related streptococcal genomes.
- To track temporal shifts in bovine SDSD genotypes and investigate the origins and maintenance of virulence genes.
- To assess the genetic relationship between bovine SDSD, human SDSD, and Streptococcus dysgalactiae subsp. equisimilis (SDSE).
Main Methods:
- Comparative genomic analysis of housekeeping genes and virulence genes.
- Identification and characterization of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas IIA systems in bovine SDSD.
- Analysis of prophage-encoded virulence genes, including superantigens (SAgs) and streptolysin S operon.
Main Results:
- Bovine SDSD isolates are genetically distinct from human SDSD and SDSE strains.
- All bovine SDSD isolates possess a CRISPR/Cas IIA system, indicating active adaptation.
- Bovine SDSD strains consistently carry specific virulence genes (speK, speC, speL, speM, spd1, sdn) from S. pyogenes phages, suggesting their long-term maintenance and exclusive association with this subspecies.
- Bovine SDSD isolates lack most of the streptolysin S operon, unlike SDSE and human SDSD strains.
Conclusions:
- Bovine SDSD strains maintain a distinct genetic profile and harbor specific virulence factors, potentially contributing to their pathogenicity.
- The findings suggest that horizontal gene transfer events may have occurred prior to the divergence of bovine SDSD and S. pyogenes.
- The genetic differences observed challenge the current subspecies classification, warranting further investigation into the relationship between 'dysgalactiae' and 'equisimilis'.
