Antibacterial Activity of A. ordosica Essential Oil

The antibacterial activity of the A. ordosica essential oil was evaluated using microorganism strains, including Staphylococcus aureus ATCC 6538 (Gram-positive bacteria), Escherichia coli ATCC 8739 (Gram-negative bacteria), and Salmonella abony NTCC 6017 (Gram-negative bacteria). The antibacterial assay was conducted by the broth microdilution method [37 (link)]. Colonies of the microbial strains were maintained on nutrient agar (Hopebio, Qingdao, China) at 37 °C in the incubator. Using a twofold dilution approach, emulsions were created with dimethyl sulfoxide (DMSO) for each essential oil sample to establish a concentration serial from 40 to 2.5 μL/mL in the final test. The MIC of each pathogen was determined using a test tube containing 3460 μL of nutrient broth (Hopebio, Qingdao, China). After adding the essential oil emulsion (500 μL) and broth, 40 μL of inoculum at a concentration of 3 × 10⁹ CFU/mL was added to each test tube. In the bacterial growth control group, neither essential oil nor detergent was applied to the test tubes. Each tube was visually checked for the existence of turbidity after 18 h of incubation at 37 °C. The MIC value is the concentration at which observable microorganism growth is inhibited relative to the control group. All tests were conducted in triplicate under aerobic conditions.