The molecular basis of Staphylococcus aureus resistance to linezolid and the role of silver nanoparticles in attenuating linezolid resistance

BackgroundSeveral linezolid resistance mechanisms have been reported in human pathogen methicillin-resistant Staphylococcus aureus (MRSA). This study investigated the molecular basis of methicillin resistance in S. aureus with increased linezolid minimum inhibitory concentrations (MICs).Methods and resultsThe antimicrobial efficacy of silver nanoparticles (AgNPs) derived from S. aureus and rosemary leaves (Rosmarinus officinalis) was evaluated against linezolid-resistant S. aureus strains. 81% of the isolates were MRSA, and 20% were linezolid resistant. Twelve isolates were linezolid-resistant S. aureus (LRSA) via the agar dilution. Molecular confirmation of linezolid-resistant S. aureus was performed by detecting the nuc gene and sequencing the 16 S rRNA gene. Molecular analysis of the resistant isolates revealed that mutations in domain V of the 23 S rRNA, rplC and rplV genes were detected in all the isolates, whereas the cfr gene was not assigned. DNA sequencing revealed that the major mutation in our isolates was a G to A mutation at different positions despite the presence of the T2500A mutation.ConclusionsAgNPs synthesized from rosemary leaves and S. aureus had a significant antimicrobial effect on LRSA isolates. In addition, the LRSA isolates became sensitive to linezolid after mixing linezolid with the synthesized AgNPs.