Gene Expression Analysis of Biofilm Formation and Antimicrobial Resistance in Clinical Methicillin-Resistant Staphylococcus Aureus

Overview

Staphylococcus aureus are Gram-positive cocci that asymptomatically colonize the skin and mucosal surfaces of approximately 20-30% of healthy individuals . Although they commonly exist as a harmless commensal organisms, S. aureus are one of the most clinically significant opportunistic pathogens, causing a wide range of community and healthcare-associated infections. These infections vary from superficial skin and soft tissue infections to severe invasive diseases, including bacteremia, infective endocarditis, pneumonia, osteomyelitis, and device-associated infections .

The global emergence and dissemination of methicillin-resistant Staphylococcus aureus (MRSA) have further complicated the treatment of these infections because of its resistance to β-lactam antibiotics and many other antimicrobial agents, leading to increased morbidity, mortality, prolonged hospitalization, and substantial healthcare costs worldwide. The pathogenicity of Staphylococcus aureus is largely attributed to its diverse virulence factors, which facilitate bacterial adhesion, tissue invasion, immune evasion, and persistence within the host. These virulence determinants include microbial surface components recognizing adhesive matrix molecule, extracellular enzymes, cytotoxins, superantigens, and immune evasion proteins, all of which contribute to successful colonization and disease progression . Among these virulence factors, biofilm formation is considered one of the most important determinants of S. aureus pathogenicity. Biofilms are highly organized bacterial communities embedded within a self-produced extracellular polymeric matrix (EPS). This matrix enhances bacterial adherence to both biotic and abiotic surfaces while protecting the bacteria from host immune defenses and antimicrobial agents . Consequently, biofilm-associated infections are often characterized by persistent infection, failure in treatment , and increased antimicrobial resistance, Therefore, disrupting biofilm formation has become a key target for developing novel therapeutic strategies. Probiotics have attracted increasing attention as promising addition to conventional antimicrobial therapy because of their ability to inhibit pathogenic microorganisms, interfere with biofilm formation, and modulate bacterial virulence . Many of these beneficial effects are mediated by probiotic-derived cell-free supernatants (CFS), which contain a variety of bioactive compounds, including organic acids, bacteriocins, hydrogen peroxide, biosurfactants, and other antimicrobial metabolites. Several studies have demonstrated that probiotic-derived CFS can inhibit Staphylococcus aureus biofilm formation and suppress the expression of virulence-associated genes, thereby reducing bacterial pathogenicity . Surgical site infections (SSIs) represent a major healthcare burden in Egyptian hospitals, with reported prevalence rates ranging from 9% to 26% among postoperative patients .