Evaluation of natural oils as antibacterial and antioxidant agents against multidrug-resistant bacterial isolates

Background: This study evaluated the antibacterial and antioxidant activities of natural oils (garlic, thyme, tea, anise, clove, fennel, oregano, and carvacrol) against six multidrug-resistant bacterial isolates from clinical sources. Methods: Isolates CI5, DN4, DO2, DO3, CI7, and CI8 were identified as Acinetobacter baumannii complex (CI5), Klebsiella pneumoniae subsp. pneumoniae (DN4, DO2), Pseudomonas aeruginosa (DO3), and Staphylococcus aureus (CI7, CI8) using biochemical tests and Vitek2 system. Results: Antibiotic susceptibility testing via disc diffusion showed 100% resistance in CI5, DN4, and DO3 to all tested agents, while CI7 and CI8 exhibited 38% and 25% resistance, respectively. ​ Natural oils demonstrated notable antibacterial effects, with thyme, oregano, and carvacrol producing inhibition zones against resistant isolates, including those fully resistant to antibiotics. Antioxidant assays revealed strong radical-scavenging activity in garlic, clove, and anise oils, comparable to ascorbic acid, while others showed moderate to weak dose-dependent effects. ​Conclusion: These results highlight natural oils as promising alternatives to combat antibacterial resistance and oxidative stress. ​