Eucalyptus camaldulensis essential oil inhibits biofilm formation and disrupts pre-formed biofilms in clinical isolates of Pseudomonas aeruginosa : an in vitro study

AIM: isolates. METHODOLOGY: EUEO was obtained by hydro-distillation and characterized by FT-IR and GC-MS. Antibacterial activity was assessed by agar well diffusion, MIC and MBC. Biofilm inhibition (oil added at the start of incubation) and disruption (oil added to 18-h pre-formed biofilms) were quantified. Membrane damage was inferred from the leakage of cytoplasmic content after 4, 8, and 12 h of exposure at 1×MIC. RESULTS: EUEO was rich in Eucalyptol, comprising 90%. 79.16% isolates formed strong biofilms with OD >0.240, 12.5% showed no biofilm formation (OD <0.120) and 8.3% had moderate biofilms (OD 0.120-0.240). MICs ranged from 3.125 to 25 µg/mL and MBCs from 25 to 50 µg/mL. At 1×MIC, EUEO reduced biofilm formation by 40-85.71% and reduced the biomass of pre-formed biofilms by 46-90%. Time-dependent increase in release of cytoplasmic content, post EUEO exposure was consistent with loss of membrane integrity. CONCLUSION: biofilms, although viability-based and in vivo studies are needed to confirm this.