Antibacterial and Antibiofilm Potency of Ziziphora clinopodioides Essential Oil: An In Vitro Study

Objective: The present study examined the antibacterial and antibiofilm efficacy of Ziziphora clinopodioides (Z. clinopodioides) essential oil (EO) against the primary biofilm colonizers, such as Streptococcus sanguinis (S. sanguinis), Streptococcus mitis (S. mitis), and Streptococcus oralis (S. oralis). Methods: The hydrodistillation process was used for the essential oil extraction, and its components were analyzed using gas chromatography-mass spectrometry (GC-MS). Antibacterial effect against ATCC strains of S. sanguinis, S. mitis, and S. oralis was assessed using agar well diffusion. Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were investigated using the broth macrodilution method. Qualitative tube methods were used to evaluate the antibiofilm efficacy of the Z. clinopodioides EO. 0.12% Chlorhexidine (CHX) served as a positive control. Results: GC–MS recognized 24 elements with menthol (29.85%), (R)-carvone (10.53%), and eucalyptol (9.88%) as main constituents. Z. clinopodioides EO demonstrated dose-dependent inhibition zones among species and mixtures; generally, inhibition zones were smaller than CHX. The MICs for S. mitis and S. oralis were 2.34 μL/mL, while for S. sanguinis and the three-species mixture were 6.25 μL/mL; The MBCs were 4.68 and 12.5 μL/mL, respectively. The essential oil exhibited weak (S. sanguinis) to moderate (S. mitis, S. oralis, and the mixed culture) antibiofilm activity. Conclusions: Z. clinopodioides EO demonstrated antibacterial and antibiofilm effectiveness against primary biofilm colonizers; however, its effectiveness was lower than that of chlorhexidine.