Synergistic antibacterial and anti-biofilm effects of carvacrol and fluoxetine against Methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading clinical infectious agent owing to considerable drug resistance and formation of biofilms. In this in vitro study, we assessed the anti-biofilm and antibacterial activity of carvacrol -a monoterpenoid phenol- and fluoxetine -a selective serotonin reuptake inhibitor-. The minimum inhibitory and bactericidal concentrations (MIC and MBC, respectively) were determined using broth microdilution method. The synergistic effect was performed by checkerboard assay. MRSA isolates were resistant to conventional treatments such as tetracycline, trimethoprim-sulfamethoxazole, erythromycin, and clindamycin but sensitive to vancomycin and linezolid. They also had MIC and MBC levels of 256 µg/mL and 512 µg/mL against carvacrol, respectively. Moreover, these scores ranged respectively 128 µg/mL − 256 µg/mL against fluoxetine. Combining the two test agents clearly lowered the computed MICs and MBCs for carvacrol and fluoxetine. Furthermore, this combo resulted in notable downregulation of important adhesin genes and total suppression of biofilm development, therefore offering strong proof for a combined approach to reduce MRSA infections.