IN-VITRO ANTIBIOFILM ACTIVITY AND GROWTH INHIBITORY EFFECTS OF Origanum onites ESSENTIAL OIL AND CARVACROL AGAINST Escherichia coli ATCC 25922 AND METHICILLIN-RESISTANT Staphylococcus aureus (MRSA) ATCC 43300

The treatment of infections caused by Escherichia coli and Methicillin-resistant Staphylococcus aureus (MRSA) has become difficult due to the increasing development of resistance to the antibiotics used. Nowadays, in the fight against these infections, the importance of natural and inexpensive plant essential oils and their bioactive molecules with known antibacterial activity has been increasing. This study aimed to investigate the antibacterial and antibiofilm effects of Origanum onites essential oil (OEO) and carvacrol, to which bacteria cannot develop resistance, as an alternative to antibiotics. The chemical content of OEO was analyzed by GC-MS system. Antibacterial activity was analyzed by disk diffusion, macro broth dilution, and antibacterial curve assays, and also antibiofilm activity was analyzed by the quantitative crystal violet method. Carvacrol was defined as the major component in the OEO composition. The results showed that OEO and carvacrol exhibited antibacterial activity against E. coli and MRSA with the minimum inhibition concentration (MIC) of 100 µg/mL and 50 µg/mL, respectively. The antibacterial curve assay results showed that OEO and carvacrol exhibited bactericidal activity against E. coli and MRSA. OEO and carvacrol inhibited the biofilm formation of E. coli and MRSA in the range of 15.5%-80.7% at MIC, 1/2MIC, and 1/4MIC concentrations.