Genomic Characterization of Hospital-acquired Methicillin-resistant Staphylococcus aureus (MRSA) based on Whole...

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-acquired infections and represents a major public health concern worldwide due to its association with severe clinical complications and limited therapeutic options. Conventional typing methods often lack sufficient discriminatory power for accurate characterization of circulating strains. Therefore, this study aimed to investigate the genomic characteristics and genetic diversity of hospital-associated MRSA isolates from Iraqi healthcare settings using whole-genome sequencing (WGS).

Three MRSA isolates representing different sequence types (ST239, ST6, and ST72) were subjected to genomic DNA extraction, library preparation, and sequencing using the DNBSEQ platform. Sequencing reads were processed through quality control, de novo genome assembly, and genome annotation pipelines. Antimicrobial resistance genes, virulence-associated determinants, and SCCmec structures were identified, and the relationship between phenotypic antimicrobial resistance and genotypic determinants was evaluated.

Genomic analysis demonstrated a strong correlation between phenotypic antimicrobial resistance profiles and detected resistance-associated genes. The mecA gene was associated with methicillin resistance, whereas blaZ contributed to penicillin resistance. Macrolide resistance was mainly linked to the ermC gene, while tetracycline resistance corresponded to the presence of tetM. Multilocus sequence typing (MLST) identified three distinct sequence types (ST239, ST6, and ST72), indicating genomic diversity among the analyzed isolates. Several virulence-associated factors, including γ-hemolysin and LukE-LukD, were commonly detected, whereas the ST72 isolate uniquely carried the enterotoxin egc cluster. In addition, multiple mobile genetic elements were identified, particularly in isolate ST6.

The findings highlight the genomic heterogeneity and diversity of antimicrobial resistance and virulence determinants among hospital-associated MRSA isolates. The integration of WGS with comparative genomic analysis provided valuable insights into the molecular epidemiology and phylogenomic relationships of the investigated strains.

Whole-genome sequencing revealed genomic diversity and multiple antimicrobial resistance determinants among hospital-associated MRSA isolates. These findings provide valuable genomic insights that may support molecular surveillance programs and contribute to improved infection control strategies in healthcare settings.