Antibiotic-resistant S. aureus infections can be life-threatening. Linezolid is known to hinder S. aureus biofilm formation, but the underlying molecular mechanism remains unclear. Molecular docking revealed that linezolid can bind to icaA, and this was confirmed by thermal drift assays. Linezolid demonstrated a dose-dependent inhibition of icaA enzyme activity. Mutating Trp267, a key residue identified through molecular docking, significantly decreased linezolid binding and inhibitory effects on mutant icaA activity. However, the mutant icaA Trp267Ala showed only slight activity reduction compared to icaA. Linezolid had minimal impact on icaB's thermal stability and activity. The 50S ribosomal L3ΔSer145 mutant S. aureus exhibited similar growth and biofilm formation to the wild-type strain. Linezolid effectively suppressed the growth and biofilm formation of wildtype S. aureus. Although linezolid lost its ability to inhibit the growth of the mutant strain, it still effectively hindered its biofilm formation. Linezolid exhibited weaker attenuation of sepsis-induced lung injury caused by 50S ribosomal L3ΔSer145 mutant S. aureus compared to wild-type S. aureus. These findings indicate that linezolid hampers S. aureus biofilm formation by directly inhibiting icaA activity, independently of its impact on bacterial growth.
Keywords: S. aureus; antibiotic resistance; biofilm formation; linezolid; sepsis-induced lung injury.