In Vitro Evaluation of the Antibacterial Activity and Interactive Effects of Sweet Basil and Hemp Oils Against Pseudomonas aeruginosa

Background The increasing prevalence of antimicrobial resistance in Pseudomonas aeruginosa has intensified the search for alternative and complementary antibacterial agents. Plant-derived oils and extracts have attracted considerable interest because of their diverse bioactive constituents and potential antimicrobial properties. However, the antibacterial activity of different plant oils may vary considerably, and their combined effects require experimental evaluation. Objective The present study aimed to evaluate the in vitro antibacterial activity of sweet basil oil and hemp oil, individually and in combination, against Pseudomonas aeruginosa and to compare their activity with a conventional antibacterial agent. Methods An experimental laboratory-based in vitro study was performed using a P. aeruginosa isolate obtained from a research laboratory in Dehradun, Uttarakhand, India. The isolate was revived and confirmed by Gram staining and standard biochemical tests. Antibacterial activity was evaluated using the agar well diffusion method on Mueller–Hinton agar. Sweet basil oil, hemp oil, their combination, and streptomycin were evaluated, with DMSO used as a negative control. Each treatment was tested in triplicate. Minimum inhibitory concentration (MIC) was further assessed using a broth microdilution assay with resazurin as a growth indicator. Results The agar well diffusion assay demonstrated differential antibacterial activity among the tested agents. Hemp oil produced no measurable zone of inhibition (0 mm), whereas sweet basil oil produced a mean inhibition zone of 14 mm. Streptomycin showed the highest antibacterial activity, producing a mean inhibition zone of 33 mm, while DMSO produced no inhibition zone. MIC assessment showed growth inhibition by sweet basil oil at higher concentrations, whereas hemp oil showed limited antibacterial activity. The combination of sweet basil oil and hemp oil did not demonstrate a marked enhancement of antibacterial activity compared with sweet basil oil alone. Conclusion Under the experimental conditions of this study, sweet basil oil demonstrated greater antibacterial activity against P. aeruginosa than hemp oil, whereas streptomycin remained substantially more active than the tested plant-derived agents. The combination of sweet basil and hemp oils did not produce an apparent enhancement in antibacterial activity. These findings support further investigation of sweet basil-derived antibacterial compounds, including studies involving standardized formulations, broader concentration ranges, additional bacterial strains, and mechanistic evaluation.