Staphylococcus aureus biofilms: molecular mechanisms, resistance determinants, and emerging therapeutic strategies.

S. aureus is a significant opportunistic pathogen that causes a variety of community and healthcare-associated infections. Biofilm formation is one of its many virulence factors and contributes to persistent, recurrent, and device-associated infections through enhancing bacterial survival, immune system evasion, and resistance to antimicrobial agents. The development of biofilms is a complex, highly regulated process influenced by genetic regulators, environmental factors, and intercellular communication, leading to the formation of a structured microbial community with a protective extracellular matrix (ECM). These biofilms undergo large-scale physiological, transcriptomic, and proteomic changes, which help them survive harsh host conditions and reduce their susceptibility to immune responses and standard antibiotics. Biofilm-associated antimicrobial resistance is also facilitated by several complementary mechanisms, including limited penetration of antimicrobials, changes in bacterial physiology, persister cell formation, adaptive stress responses, and the presence of other clinically relevant microorganisms in polymicrobial biofilms. Recent evidence has also emphasized the importance of host-biofilm interactions in the establishment of chronic infections, including dysregulated inflammatory responses and immune evasion. Due to the intrinsic inefficacy of traditional antimicrobial drug treatment against mature biofilms, significant efforts have been made to develop novel anti-biofilm interventions, such as matrix-disrupting agents, quorum-sensing inhibitors, antimicrobial peptides, bacteriophages, nanotechnology-assisted delivery systems, CRISPR-Cas-based therapeutics, and rational combination therapy. This review aims to provide a comprehensive and up-to-date overview of the molecular biology of S. aureus biofilms, biofilm-associated antimicrobial resistance, interactions with the host, polymicrobial interactions, and emerging therapeutic strategies, and to highlight the ongoing challenges and future directions in the prevention and treatment of persistent biofilm-associated infections.