Avaliação da atividade antibacteriana do óleo essencial, nanoemulsão e nanoemulgel de Eucalyptus staigeriana sobre cepas de Klebsiella pneumoniae

Abstract

Infections caused by multidrug-resistant microorganisms, such as Klebsiella pneumoniae, are a threat to public health due to their complex genetic mechanisms. In this context, essential oils of Eucalyptus staigeriana have promising antibacterial properties, however, their efficacy against Gram-negative strains is limited. Faced with this challenge, innovative drug delivery systems, such as nanoemulsions and nanoemulgels, can improve the stability and efficacy of these oils, which highlights the need for more research to confirm their potential. In this sense, the general objective of the study was to evaluate the antibacterial activities of the essential oil, nanoemulsion and nanoemulgel of Eucalyptus staigeriana against strains of Klebsiella pneumoniae, encompassing the obtention, development, and characterization of the nanostructured systems.For the essential oil, chromatographic analysis was performed and the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined by microdilution in plates, and the Minimum Adhesion Inhibitory Concentration (CIMA) by test tubes. The association of the essential oil with antibacterials was evaluated by diffusion in solid medium. For the emulsified systems, the value of the Hydrophilic-Lipophilic Equilibrium (EHL) was determined for the emulsification of the essential oil. The nanoemulsions were produced by ultrasonication, using essential oil, surfactants (Span® 80 + Tween® 80) and ultrapure water, and analyzed for organoleptic and physicochemical characteristics. Mean droplet size and polydispersion index (PDI) were determined using Zetasizer Ultra Red. The best formulation was selected and its stability evaluated from D1 to D90. The nanoemulgel was prepared by incorporating the nanoemulsion into a gel base with 1% carbopol, following the same evaluation criteria as nanoemulsions for characterization and stability. The antibacterial activity of the nanoemulsion was evaluated by MIC and CBM, while the nanoemulgel was tested by diffusion on well agar. The essential oil of Eucalyptus staigeriana showed strong antibacterial activity with MIC of 500μg/mL and MBC greater than 1000 mg/mL, demonstrating bacteriostatic effect. In addition to greater non-stick activity in a ratio of 1:2 compared to chlorhexidine digluconate. When combined with ciprofloxacin, a more pronounced synergistic effect was observed. The main components of the essential oil were: sylvan (40.81%), geraniol (13.45%), nerol (9.53%), terpinolene (5.75%) and methyl geranate (6.16%). The optimized nanoemulsion (15% oil, 10% surfactants and 75% water, EHL12) showed satisfactory physicochemical and organoleptic properties, with lower PDI (0.19) and mean droplet diameter ≤ 100 nm (94.29 nm), maintaining the antibacterial activity. Both the nanoemulsion and the nanoemulgel remained stable for up to 90 days, and the nanoemulgel also demonstrated antibacterial efficacy against the same strains. It is concluded that the essential oil of Eucalyptus staigeriana and the formulations of nanoemulsion and nanoemulgel, have effective antimicrobial action against Klebsiella pneumoniae, showing promise for the development of new pharmaceutical products.