Genomic adaptations of methicillin-resistant Staphylococcus aureus in healthcare environments

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) exemplifies genomic adaptation to selective pressures in high-stress environments, such as healthcare facilities. This study investigates the genomic divergence and adaptive mechanisms of MRSA strains isolated over three years (2021–2023) in a leading healthcare facility in southern India. A total of 36,127 patient samples were analyzed, yielding 1825 Staphylococcus aureus isolates, of which 364 (19.94 %) were identified as MRSA through phenotypic testing for oxacillin and cefoxitin resistance.

Molecular characterization using polymerase chain reaction confirmed the presence of mecA in 98 % of MRSA isolates and icaA and icaD in 87 %, indicating their critical role in methicillin resistance and biofilm formation. MRSA prevalence increased significantly over the study period, peaking at 27.08 % in 2023. Exudate samples accounted for 77.47 % of MRSA isolates, highlighting the role of biofilm-mediated persistence in wound infections. The Surgery department reported the highest burden, with 29.9 % of MRSA infections.

Antibiotic resistance was highest for cefoxitin (99.05 %), penicillin (96.27 %), and levofloxacin (87.47 %), while vancomycin and linezolid remained effective, with sensitivity rates of 99.33 %. These findings illustrate MRSA's genomic adaptations, showcasing its evolutionary resilience under anthropogenic pressures. By integrating molecular insights, this study provides critical insights into resistance evolution, biofilm-mediated persistence, and species diversification in high-stress ecosystems. Such findings highlight the importance of linking ecological genomics to strategies for mitigating antimicrobial resistance, addressing an urgent global health challenge.