The effect of fennel essential oil and trans-anethole on antibacterial activity of mupirocin against Staphylococcus aureus isolated from asymptomatic carriers

Introduction: Staphylococcus aureus constitutes the most pathogenic species within the staphylococcal genus. Humans remain the major reservoirs of this pathogen which colonizes mostly anterior nares of healthy individuals. Aim: To investigate the effect of fennel essential oil (FEO) and trans-anethole (tA) on antibacterial activity of mupirocin (MUP) against S. aureus strains isolated from asymptomatic carriers. Material and methods: The content of the FEO was analysed with use of the GC-MS method. The research done on 43 S. aureus isolates with different resistance patterns, obtained from nasal vestibule. Antibacterial activity of MUP in combination with FEO or tA was examined using the agar dilution method and E-test method. The data analysis was done with the Pearson's chi(2) test. Results: The chemical composition of FEO was consistent with the European Pharmacopoeia (EP) for the main constituent - tA (77.9%) according to the EP recommendations. Macrolide-lincosamide-streptogramin B resistance phenotype was prevalent among 39.5% of S. aureus isolates. FEO concentrations of 2.0% and 2.5% revealed antibacterial activity against 76.7% of isolates, whereas tA inhibited S. aureus growth at concentrations > 4.0%. The MIC values for MUP combined with FEO as well as for MUP combined with tA were < 0.064 mu g/ml for 79.1% and 86.0% of S. aureus isolates, respectively. Conclusions: Our experiment revealed FEO and tA influence on MUP effectiveness. The combination of MUP with FEO as well as MUP with tA are worth considering to implement in S. aureus eradication procedures. These findings will be useful in designing efficient antistaphylococcal agents which can limit the emergence of antibiotic resistance.