Dissecting vancomycin-intermediate resistance in staphylococcus aureus using genome-wide association.

Area of Science:

• Microbiology
• Genomics
• Antimicrobial Resistance

Background:

• Vancomycin-intermediate Staphylococcus aureus (VISA) poses a significant clinical challenge.
• VISA is characterized by a minimal inhibitory concentration (MIC) of 4-8 µg/ml.
• VISA development involves genetic alterations in multiple loci, with over 16 candidate genes identified.

Purpose of the Study:

• To conduct a whole-genome comparative analysis of vancomycin-sensitive and VISA strains.
• To identify genetic variations associated with vancomycin resistance in S. aureus.
• To develop a predictive model for the VISA phenotype.

Main Methods:

• Whole-genome comparative analysis of 49 vancomycin-sensitive and 26 VISA S. aureus strains.
• Determination of vancomycin resistance using broth microdilution, Etest, and PAP-AUC.
• Genome-wide association studies (GWAS) to identify significant genetic associations.

Main Results:

• A highly significant association (P = 8.78 E-08) was found between a nonsynonymous mutation at codon 481 (H481) of the rpoB gene and increased vancomycin MIC.
• Rare mutations in candidate genes (walKR, vraSR, graSR, agrA) were identified using public genome databases.
• A preliminary predictive model (ECM+RMCG) achieved 81% accuracy and 73% sensitivity for VISA prediction.
• The level of vancomycin resistance positively correlated with the number of identified mutations.

Conclusions:

• GWAS is a powerful tool for identifying common genetic variants linked to antibiotic resistance in bacteria.
• Rare mutations in specific candidate genes, discoverable through large genomic datasets, are also associated with antibiotic resistance phenotypes.
• The findings contribute to a better understanding of VISA evolution and provide a basis for improved diagnostic and therapeutic strategies.