Detection of hospital-acquired methicillin-resistant Staphylococcus aureus strains harboring unusual genetic features in the Geneva area

Objectives The emergence or clonal dissemination of pathogenic bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), particularly those with enhanced virulence or infectivity, represents a major global concern. In our institution, we have implemented a continuous epidemiological surveillance strategy to detect and characterize all MRSA strains responsible for infection or identified during screening. Methods Our group has developed molecular assays based primarily on PCR and real-time PCR, enabling rapid characterization of S. aureus and MRSA strains, including the detection of unusual genomic features. Results Our long-term surveillance strategy, conducted over the past 22 years, has revealed the replacement of previously prevalent hospital clones by strains exhibiting diverse genomic profiles associated with specific clinical clonal complexes. We also observed a shift among community-acquired isolates, from highly diverse profiles to a predominance of USA300 strains. More recently, assays targeting the SCC mec element showed an increasing number of MRSA strains that could not be typed. Whole-genome sequencing identified isolates harboring novel SCC mec elements. Conclusions Sustained epidemiological surveillance is essential to monitor the ongoing evolution of MRSA genomic diversity and to detect emerging clones.