Prevention of polymicrobial biofilms composed of Pseudomonas aeruginosa and pathogenic fungi by essential oils from selected Citrus species

Abstract

Mixed microbial infections caused by Pseudomonas aeruginosa and pathogenic fungi are commonly found in patients with chronic infections and constitute a significant health care burden. The aim of this study was to address the potential polymicrobial antibiofilm activity of pompia and grapefruit essential oils (EOs). The mechanism of antimicrobial activity of EOs was analysed. EOs of pompia and grapefruit inhibited fungal growth with MIC concentrations between 50 and 250 mg L-1, whereas no effect on P. aeruginosa growth was observed. Both citrus EOs inhibited formation of bacterial and fungal monomicrobial biofilms in concentrations of 50 mg L-1 and were efficient in potentiating the activity of clinically used antimicrobials in vitro. The concentration of 10 mg L-1 EOs inhibited mixed biofilm formation composed of P. aeruginosa and Aspergillus fumigatus or Scedosporium apiospermum. Citrus EOs affected quorum sensing in P. aeruginosa and caused fast permeabilisation of Candida albicans membrane. Pompia and grapefruit EOs potently inhibited biofilm formation and could be used for the control of common polymicrobial infections.