Effects of nanocapsulated and free forms of guaiacol available in Campsis radicans (L.) Seemann essential oil on antibiotic resistance genes expression of Pseudomonas aeruginosa, Escherichia coli, and Candida albicans

Pseudomonas aeruginosa, Escherichia coli, and Candida albicans are nosocomial pathogens that have made treatment difficult due to the antibiotic resistance. In the present study, the antimicrobial effect of Campsis radicans (L.) Seemann essential oil on Imipenem-resistant P. aeruginosa containing IMP gene, Cefixime-resistant E. coli containing TEM gene, and fluconazole-resistant C. albicans containing ERG gene was investigated. According to the results, all the strains were sensitive to the essential oil and the diameter of growth inhibition zone varied from 10 to 20 mm, with the highest sensitivity being observed in C. albicans. After identifying 32 compounds in the essential oil by GC/MS, guaiacol as its active ingredient was selected and nanocapsulated by two-phase emulsion method. The mean MIC was 268.7-537.5 and 67.18-268.75 µg.mL-1 in the free and encapsulated forms of the active ingredient, respectively which indicates that the encapsulated form is more effective than the free one. Study on the release of both forms within 72 hours showed that the release of encapsulated form was more targeted over a longer period of time which indicates its less toxicity. Then, the effectiveness of both active ingredient forms was evaluated on the antibiotic resistance genes and it was found that this reduction was more in P. aeruginosa and C. albicans than E. coli. In general, both free and encapsulated forms significantly reduced gene expression compared to the control gene 16s rRNA, which was more noticeable in the encapsulated form than the free one. Also, study on the synergistic effect of both forms showed that the combined use of each ingredient with its nanocapsules had a greater antimicrobial effect than the single use. The results of this study proved the antimicrobial effect of C. radicans essential oil and also showed that both forms of the active ingredient contained compounds to inhibit antibiotic resistance genes and therefore can be used as therapeutic supplements.