Molecular and genetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) in a tertiary care hospital in Saudi Arabia.

Methicillin-resistant Staphylococcus aureus (MRSA) continues to pose significant challenges in healthcare settings due to its multi-drug resistance (MDR) and virulence. This retrospective study examines the molecular and resistance profiles of MRSA isolates from a tertiary care hospital in Saudi Arabia, providing valuable insights into regional epidemiology. A total of 190 MRSA strains were analysed to assess antimicrobial susceptibility, genetic diversity, and virulence factors. Antimicrobial susceptibility testing was conducted according to CLSI guidelines, while molecular characterization involved spa typing, SCCmec typing, and DNA microarray analysis to determine clonal complexes (CCs), resistance genes, and virulence determinants. The isolates showed extensive resistance to beta-lactam antibiotics, with 78% classified as MDR. Notably, resistance to fusidic acid and ciprofloxacin was detected in 70% and 55% of isolates, respectively. The most prevalent clonal complexes-CC5, CC6, and CC22-comprised over 60% of the isolates and exhibited diverse spa types. The Panton-Valentine leukocidin (PVL) gene, linked to heightened virulence, was identified in approximately 20% of isolates, particularly within CC5, CC30, and CC80. Enterotoxin genes (sea and seb) and immune evasion genes (sak, chp, and scn) were also commonly detected, reflecting the isolates' capacity to adapt and persist within the hospital environment. These findings underscore the high burden of MDR MRSA with considerable genetic diversity and virulence potential. The study highlights the urgent need for strengthened molecular surveillance and targeted infection control measures to limit MRSA transmission and effectively manage infection risks in healthcare facilities.