Antibacterial interactions of pulegone and 1,8-cineole with monolaurin ornisin against Staphylococcus aureus .

The aim of this study was to investigate the antibacterial interactions of pulegone and 1,8-cineole with monolaurin ornisin against Staphylococcus aureus . The individual and combined antibacterial activities of the compounds were evaluated using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration index (FICi), and time-kill methods. Furthermore, the mechanism of the antibacterial action of the compounds was tested by measuring the release of cell constituents. The MIC values of pulegone, 1,8-cineole, nisin, and monolaurin were 5.85 µl/ml, 23.43 µl/ml, 6.25 µg/ml, and 0.031 mg/ml, respectively. A synergistic antibacterial activity (FICi = 0.5) was found between 1,8-cineole and nisin. The time-kill assay showed that the populations of S. aureus exposed to 1,8-cineole, nisin, and their combination were decreased by 5.9, 5.3, and 7.1 log CFU (colony-forming units)/mL, respectively. The combination of 1,8-cineole and nisin also induced the highest release of cell constituents. It was concluded that the combination of 1,8-cineole and nisin could be considered as a novel and promising combination which may reduce the required dose of each antibacterial compound.