Streptococcus castoreus, an uncommon group A Streptococcus in beavers

Area of Science:

• Veterinary Microbiology
• Zoonotic Diseases
• Microbial Pathogenesis

Background:

• Streptococcus castoreus is a beta-hemolytic group A Streptococcus with a known affinity for beavers.
• This bacterium is part of the normal mucosal microbiota but can cause disease.

Purpose of the Study:

• To investigate the pathogenic potential of Streptococcus castoreus in beavers.
• To characterize genetic diversity and population structure of S. castoreus isolates.
• To include S. castoreus from North American beavers (Castor canadensis) for the first time.

Main Methods:

• Phenotypic analyses including biochemistry, antimicrobial resistance, MALDI-TOF MS, and FTIR spectroscopy.
• Classic molecular analyses using 16S rRNA and sodA genes.
• Genomic fingerprinting techniques such as pulsed-field gel electrophoresis (PFGE), BOX-, (GTG)5-, and RAPD-PCR.

Main Results:

• Isolates were phenotypically and genetically similar based on classic methods, showing no distinct patterns related to host species or origin.
• PFGE differentiated isolates into numerous pulsotypes, but these did not represent true epidemiological lineages.
• Genomic fingerprinting revealed subclusters correlated with host species, geographic origin, or year, indicating potential host-specific adaptations.
• Co-colonization of individual beavers with multiple S. castoreus isolates was confirmed.

Conclusions:

• Streptococcus castoreus functions as an opportunistic pathogen in beavers, associated with purulent lesions.
• While classic typing methods show little diversity, genomic fingerprinting highlights genetic subclusters and potential host-specific variations.
• This study expands the understanding of S. castoreus in both Eurasian and North American beaver populations.