Exploring new treatment strategies for Pseudomonas aeruginosa biofilm infections based on plant essential oils

Pseudomonas aeruginosa is an important cause of nosocomial and biofilm-associated infections which is often difficult to eradicate, due to its intrinsic resistance and capacity to undergo mutations and adaptations. This study aimed to assess the anti-biofilm activity of three essential oils (EOs) (Cinammon (Cinnamomum zeylanicum), Tea tree (TTO) (Melaleuca alternifolia) and Palmarosa (Cymbopogon martini), and the existence of synergistic effects of TTO and its major component (Terpinen-4-ol (T4ol)) combined with Ciprofloxacin (CIP), against 24-hour-old P. aeruginosa biofilms. Results showed that the treatment of pre-established P. aeruginosa biofilms with the three plant EOs, T4ol and CIP, individually, promoted a significant decrease of biofilm biomass and the number of biofilm entrapped cells, mainly for higher concentrations. Nevertheless, the antimicrobial synergisms combining TTO or T4ol with CIP revealed to be more successful, since significant disturbance of biofilms occurs for lower concentrations of the products. T4ol associated with CIP was the combination that revealed the most promising synergistic effects. Therefore, T4ol-CIP association may be a useful therapeutic option to treat P. aeruginosa biofilm infections.