Background and Aim: Pseudomonas aeruginosa is a multidrug resistant pathogen and an important cause of nosocomial infections. Quorum - sensing (QS) is a process which regulates production of many virulence factors including pigment production and biofilm f ormation essential for establishment of chronic infections. We evaluated the inhibitory activity of some native plant extracts on biofilm formation and pigment production by P. aeruginosa PAO1.
Methods: Thirty native Iranian plants were screened for anti - QS activity against P. aeruginosa PAO1. Methanolic extracts were prepared by maceration, dried and were then dissolved in DMSO. Inhibition of biofilm formation was evaluated by the microbroth dilution method and the inhibitory effect on pyocyanin production was measured by spectrophotometry using different concentrations of the extract. The active extracts were further fractionated by HPLC and all fractions were tested for antibiofilm activity. The active fractions were also tested for inhibition of pyocyanin production. Finally, the components of the active fractions were identified by LC - DAD - MS.
Results: : Pistacia atlantica leaves extract had the highest anti - biofilm activity at 2 mg/ml (92% inhibition) and 1 mg/ml (79% inhibition). Pyocyanin production was inhibited 100% at 2 mg/ml and 83% at 1 mg/ml. Four active HPLC fractions had minimum biofilm inhibitory concentrations (MBIC) of 0.30 mg/ml and inhibited pyocyanin production at < 0.30 mg/ml. Initial identification of the active fraction components showed that all four belonged to the flavonoid family.
Conclusion: The anti - QS ability of Pistacia atlantica extract suggests its potential for treatment of chronic infections caused by Pseudomonas aeruginosa.