Staphylococcus aureus strains sustain their high-virulent phenotype during native endocarditis

Area of Science:

• Infectious Diseases
• Microbiology
• Cardiovascular Research

Background:

• Staphylococcus aureus endocarditis is a severe infection causing significant valve and cardiac tissue damage.
• Understanding bacterial adaptation and virulence factors is crucial for treating this life-threatening condition.

Purpose of the Study:

• To analyze the virulence characteristics of S. aureus endocarditis isolates.
• To assess the potential adaptation of S. aureus to the host environment during endocarditis.

Main Methods:

• Paired S. aureus isolates from valve tissue and blood cultures of 10 endocarditis patients were analyzed.
• Molecular and phenotypic analyses, including whole-genome sequencing and in vitro assays, were performed.
• Quantitative analysis of wild-type and small colony variants (SCVs) from different infection sites was conducted.

Main Results:

• High genetic identity was observed between paired blood and valve isolates.
• Genes encoding adhesins and toxins were prevalent, with no significant differences in invasion, cytotoxicity, or biofilm formation between blood and valve isolates.
• Isolates from native heart tissue predominantly showed wild-type phenotypes, while SCVs were more frequent in soft tissue infections and osteomyelitis.

Conclusions:

• S. aureus largely maintains a highly virulent phenotype in native valve endocarditis, contributing to tissue destruction.
• Exposure to the intravascular environment may limit phenotypic adaptation, sustaining bacterial virulence.