DETERMINATION OF ANTIBACTERIAL AND ANTIBIOFILM ACTIVITY OF TERPINEN 4-OL AGAINST SOME STANDARD BACTERIAL STRAINS

Objective: Antimicrobial resistance in bacteria is becoming increasingly common and poses a serious challenge, particularly in treatment of infections where biofilm formation is involved. Biofilms enable bacteria to survive under harsh conditions and increase their resistance to antibiotics, thereby reducing the success of standard treatments. Terpinen-4-ol, the main compound of Melaleuca alternifolia (tea tree) essential oil, has shown notable antimicrobial effects. This study focuses on evaluating the antimicrobial effectiveness of terpinen-4-ol against selected standard bacterial strains and also determinating the antibiofilm activity at subMIC concentrations. Material and Method: In this study, Enterococcus faecalis WHO3 (vanA), Pseudomonas aeruginosa PAO1, Staphylococcus aureus ATCC 43300 (MRSA), Staphylococcus epidermidis ATCC 35984, and Streptococcus mutans ATCC 12575 were used to be tested. Minimum inhibitory concentrations (MICs) were determined by broth microdilution method according to EUCAST standards. Biofilm formation and inhibition assays were tested by the modified crystal violet method. The antibiofilm activity of terpinen-4-ol was evaluated at a sub-inhibitory concentration corresponding to MIC/2, and the extent of inhibition was quantified as the percentage reduction relative to untreated control biofilm formation. Result and Discussion: The MIC values of terpinen-4-ol against the tested bacteria ranged from 0.0625% to 0.5% (v/v). Even at subMIC levels, terpinen-4-ol significantly reduced biofilm formation. Inhibition rates were 79.95% for P. aeruginosa PAO1, 77.79% for S. epidermidis ATCC 35984, and 73.23% for S. mutans ATCC 12575. These results suggest that terpinen-4-ol is effective not only in inhibiting bacterial growth but also in reducing biofilm formation, highlighting its potential as a promising candidate for alternative or complementary treatment strategies, especially against biofilm-associated and resistant infections.