The in vitro antibiofilm activity of Rosmarinus officinalis L. essential oil against multiple antibiotic resistant Pseudomonas sp. and Staphylococcus sp.

Rosmarinus officinalis (rosemary) is widely used as a flavouring agent for food and well known medicinally for its chemical composition. The aim of this study was to investigate the antibiofilm activity of the essential oil from Rosmarinus officinalis against biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Pseudomonas fluorescens, Bacillus cereus and Bacillus subtilis. Essential oil was obtained from the aerial parts of the plant by using a Clevenger apparatus for 4 h. The antibacterial activity of the obtained essential oil from Rosmarinus officinalis was determined using disc diffusion technique, minimum inhibitory concentrations (MICs) and minimum bacterial concentration (MBC). Staphylococcus sp. and Pseudomonas sp. were evaluated as the resistant microorganisms in the antibacterial assays. The antibiofilm effect of MBC, MIC, MIC/2, MIC/4, MIC/8 and MIC/16 concentrations of Rosmarinus officinalis essential oil was assessed by the microplate biofilm assay. The essential oil exhibited significant antibacterial activity against all tested bacteria. In contrast to the antibacterial activity, MBC and subinhibitory concentrations of essential oil showed limited antibiofilm activity. MBC concentrations of essential oil attenuated the biofilm formation at 60.76% and 74.7% for Staphylococcus aureus MU 47 and Pseudomonas aeruginosa MU 187, respectively. Direct observation by scanning electron microscope (SEM) analysis further revealed an exact reduction for the bacterial biofilm formation in response to the effective concentration. This study has demonstrated that the Rosmarinus officinalis essential oil may be considered as a potent agent for the prevention of biofilm-related applications that are increasingly problematic in the food processing environments and medical industries.