Abstract

Treatment failure and persistent infection are two serious problems that result from Staphylococcus aureus having decreased vancomycin susceptibility. The present study investigates the effects of Rosmarinus officinalis L. leaves extract on the growth and quorum sensing (QS) of heterogeneous vancomycin-intermediate S. aureus hVISA isolates. Real-time RT-polymerase chain reaction (PCR) is used to determine the transcriptional changes of the accessory gene regulator (agr) in the (hVISA) strain after and before being treated with the R. officinalis leaves extract. The antibacterial activity of the EOs was determined through the use of a microtitre plate test (MtP); with a minimum inhibitory concentration (MIC) of 0.7 mg/ml against hVISA, a rosemary leaves extract has a high level of inhibitory activity. However, the extraction of essential oils is done in a soxhlet apparatus by using ethanol 96. Gas chromatography and mass spectrometry (GC/MS) and revealed the most common chemicals containing verbenone, 36.20, and 1,8-cineol (Eucalyptol), 12.14. Finally, after treatment with sub-MIC concentration, hld gene levels significantly decreased in hVISA strains (a mean of 0.4-fold) in comparison to the control strains (1.0-fold) in late-exponential phases, regardless of whether the agr mutation is present. The down regulation of the hld gene may be a significant genetic event in the hVISA strain. © 2022 University of Kerbala.