Potentiation of Antibacterial Activity of Ciprofloxacin by Essential Oil of Cymbopogon citratus against Fluoroquinolone-resistant Staphylococcus aureus and Escherichia coli

Background: Essential oil (EO) of Cymbopogon citratus has been demonstrated to have antibacterial activities against both Gram negative and Gram positive bacteria. The study was, therefore, conducted to evaluate the effects of combined use of C. citratus and ciprofloxacin against fluoroquinolone-resistant Staphylococcus aureus (FQRSA) and Escherichia coli (FQREC). Methods: The antibacterial activity of the essential oil was evaluated by agar dilution method while the combination studies were done using Checker-board agar dilution technique. Results: The mean MIC values of EO against the FQRSA and FQREC were 0.043 + 0.01 mg/ml and 0.049 mg/ml respectively. When ciprofloxacin was combined with EO of lemongrass, 53.9, 28.3, 17.8 and 0.0 % of the FQRSA isolates showed indifference, additive, synergistic and antagonistic effects respectively. Similarly, when ciprofloxacin was combined with EO of lemongrass at different ratios, 44, 35.5, 20.6 and 0.0 % of the FQREC isolates showed combined effects of additivity, synergism, indifference and antagonism respectively. Conclusions: The results revealed the invitro antibacterial potency of Cymbopogon citratus oil against fluoroquinolone resistant S. aureus and E. coli. More importantly, the study has proved that the combined use of ciprofloxacin and essential oil of lemongrass has increased the sensitivity of both FQRSA and FQREC bacteria.