Comparative Genomics Identifies Novel Genetic Changes Associated with Oxacillin, Vancomycin and Daptomycin...

Area of Science:

• Microbiology
• Genetics
• Infectious Diseases

Background:

• Vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) infections pose significant treatment challenges due to vancomycin failure.
• The molecular basis of the hVISA/VISA phenotype is complex and not fully elucidated.
• Previous work characterized clinical and in vitro vancomycin-selected S. aureus strains.

Purpose of the Study:

• To perform whole genome sequencing of isogenic hVISA/VISA strains.
• To identify genetic alterations associated with vancomycin resistance.
• To investigate changes in strains selected in vivo and in vitro.

Main Methods:

• Whole genome sequencing of four isogenic S. aureus strains (two clinical, two in vitro selected).
• Analysis of single nucleotide polymorphisms (SNPs), insertions/deletions (INDELs), and IS256 insertions.
• Comparison of genetic changes with known resistance mechanisms.

Main Results:

• No SNPs were found in the VraSR, WalKR, or GraXRS regulatory operons.
• Genetic variations, including SNPs, INDELs, and IS256 insertions, were identified in vancomycin-selected strains.
• Alterations occurred in genes downstream of regulatory operons, affecting cell wall metabolism, staphylococcal growth, and biofilm formation.

Conclusions:

• Genetic changes outside of major regulatory pathways contribute to vancomycin resistance in S. aureus.
• Identified genetic alterations offer new insights into mechanisms of antibiotic resistance.
• These findings may reveal novel targets for combating resistant S. aureus infections.