In Vitro Trials of Dittrichia graveolens Essential Oil Combined with Antibiotics.

The chemical composition and antibacterial activity of Dittrichia graveolens (L.) Greuter essential oil were examined. Gas chromatography and gas chromatography/mass spectrometry were used to analyze the chemical composition of the essential oil. The antibacterial activity was investigated by the broth microdilution method against thirteen bacterial strains. The interactions of the essential oil and three standard antibiotics: chloramphenicol, tetracycline and streptomycin toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods: principal components analysis and hierarchical cluster analysis. Oxygenated monoterpenes were the most abundant compound class in the essential oil (40.6%), with bomyl acetate (21.7%) as the major compound. The essential oil exhibited slight antibacterial activity against the tested bacterial strains in vitro, but the combinations D. graveolens essential oil-chloramphenicol and D. graveolens-tetracycline exhibited mostly synergistic or additive interactions. These combinations reduced the minimum effective dose of the antibiotics and, consequently, minimized their adverse side effects. In contrast, the association of D. graveolens essential oil and streptomycin was characterized by strong antagonistic interactions against E. coli ATCC 25922, S. aureus ATCC 29213 and P. aeruginosa ATCC 27853. In the principal components analysis (PCA) and hierarchical cluster analysis (HCA), streptomycin against these bacterial strains stood out and formed a separate group.

In Vitro Evaluation of Nanoscale Hydroxyapatite-Based Bone Reconstructive Materials with Antimicrobial Properties.

In the field of oral implantology the loss of bone tissue prevents adequate patient care, and calls for the use of synthetic biomaterials with properties that resemble natural bone. Special attention is paid to the risk of infection after the implantation of these materials. Studies have suggested that some nanocontructs containing metal ions have antimicrobial properties. The aim of this study was to examine the antimicrobial and hemolytic activity of cobalt-substituted hydroxyapatite nanoparticles, compared to hydroxyapatite and hydroxyapatite/poly-lactide-co-glycolide. The antibacterial effects of these powders were tested against two pathogenic bacterial strains: Escherichia coi (ATCC 25922) and Staphylococcus aureus (ATCC 25923), using the disc diffusion method and the quantitative antimicrobial test in a liquid medium. The quantitative antimicrobial test showed that all of the tested biomaterials have some antibacterial properties. The effects of both tests were more prominent in case of S. aureus than in E coli. A higher percentage of cobalt in the crystal structure of cobalt-substituted hydroxyapatite nanoparticles led to an increased antimicrobial activity. All of the presented biomaterial samples were found to be non-hemolytic. Having in mind that the tested of cobalt-substituted hydroxyapatite (Ca/Co-HAp) material in given concentrations shows good hemocompatibility and antimicrobial effects, along with its previously studied biological properties, the conclusion can be reached that it is a potential candidate that could substitute calcium hydroxyapatite as the material of choice for use in bone tissue engineering and clinical practices in orthopedic, oral and maxillofacial surgery.

Chemoinformatics Approach to Antibacterial Studies of Essential Oils.

The chemical composition and antibacterial activity of Nepeta nuda (Lamiaceae) essential oil were examined, as well as the association between it and standard antibiotics: tetracycline and streptomycin. The antibacterial activities of 1,8-cineole, the main constituent of N. nuda oil, individually and in combination with standard antibiotics were also determined. The interactions of the essential oil and 1,8-cineole with antibiotics toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemoinformatics methods. Oxygenated monoterpenes were the most abundant compound class in the oil (57.8%), with 1,8-cineole (46.0%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antibiotics. The combinations N. nuda oil-antibiotic and 1,8-cineole-antibiotic produced a predominantly antagonistic interactions. Chemoinformatics survey confirms the antagonistic interactions as a consequence of membrane potential/proton motive force dissipation. These data indicate cytochrome c oxidase as a target for 1.8-cineole toxicity action mechanisms.

Antibacterial Investigation of Thyme Essential Oil and Its Main Constituents in Combination with Tetracycline.

The chemical composition and antibacterial activity of Thymus glabrescens Willd. (thyme) essential oil were examined, as well as its association with tetracycline. The antibacterial activities of geraniol and thymol, the main constituents of T. glabrescens oil, were also determined. Gas chromatography and gas chromatography/mass spectrometry were used to analyze the chemical composition of the oil. The antibacterial activities of the oil, geraniol, and thymol were investigated by the broth microdilution method. The interactions of the essential oil, geraniol, and thymol with tetracycline, toward five selected strains, were evaluated using the microdilution checkerboard assay. Oxygenated monoterpenes were the most abundant compound class in the oil (57.14%), with geraniol (22.33%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains. The combinations, essential oil-tetracycline and thymol-tetracycline, produced synergistic interaction to a greater extent compared with geraniol-tetracycline association. All synergistic combinations reduced the minimum effective dose of the antibiotic and, consequently, minimized its adverse side effects.

In vitro interactions of Peucedanum officinale essential oil with antibiotics.

The chemical composition and antibacterial activity of Peucedanum officinale L. (Apiaceae) essential oil were examined, as well as the association between it and antibiotics: tetracycline, streptomycin and chloramphenicol. The interactions of the essential oil with antibiotics were evaluated using the microdilution checkerboard assay. Monoterpene hydrocarbons, with α-phellandrene as the dominant constituent, were the most abundant compound class of the essential oil of P. officinale. The researched essential oil exhibited slight antibacterial activity against the tested bacterial strains in vitro. On the contrary, essential oil of P. officinale possesses a great synergistic potential with chloramphenicol and tetracycline. Their combinations reduced the minimum effective dose of the antibiotic and, consequently, minimised its adverse side effects. In addition, investigated interactions are especially successful against Gram-negative bacteria, the pharmacological treatment of which is very difficult nowadays.

An in vitro antibacterial study of savory essential oil and geraniol in combination with standard antimicrobials.

The chemical composition and antibacterial activity of Satureja kitaibelii Wierzb. ex Heuff. (savory) essential oil were examined, as well as the association between it and standard antimicrobials: tetracycline and chloramphenicol. The antibacterial activities of geraniol, the main constituent of S. kitaibelii oil, individually and in combination with standard antimicrobials were also determined. The interactions of the essential oil and geraniol with antimicrobials toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods. Oxygenated monoterpenes were the most abundant compound class in the oil (59.7%), with geraniol (50.4%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antimicrobials. The combinations savory oil-chloramphenicol, savory oil-tetracycline and geraniol-chloramphenicol produced predominantly synergistic interactions (FIC indices in the range 0.21-0.87) and substantial reductions in the MIC values of antimicrobials against Gram-negative bacteria, the pharmacological treatment of which is very difficult nowadays. In the PCA and HCA analyses these combinations form a separate group.

An in vitro synergistic interaction of combinations of Thymus glabrescens essential oil and its main constituents with chloramphenicol.

The chemical composition and antibacterial activity of Thymus glabrescens Willd. (Lamiaceae) essential oil were examined, as well as the association between it and chloramphenicol. The antibacterial activities of geraniol and thymol, the main constituents of T. glabrescens oil, individually and in combination with chloramphenicol, were also determined. The interactions of the essential oil, geraniol, and thymol with chloramphenicol toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods. Oxygenated monoterpenes were the most abundant compound class in the oil, with geraniol (22.33%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antibiotic and thymol. A combination of T. glabrescens oil and chloramphenicol produced a strong synergistic interaction (FIC indices in the range 0.21-0.87) and a substantial reduction of the MIC value of chloramphenicol, thus minimizing its adverse side effects. The combinations geraniol-chloramphenicol and thymol-chloramphenicol produced synergistic interaction to a greater extent, compared with essential oil-chloramphenicol association, which may indicate that the activity of the thyme oil could be attributed to the presence of significant concentrations of geraniol and thymol.