Biofilm Disruption and Virulence Attenuation Effects of Essential Oil From Endemic Algerian Cistus munbyi (Cistaceae) Against Clinical Strains of Pseudomonas aeruginosa

Abstract

Background: Pseudomonas aeruginosa is an opportunistic, resistant and highly pathogenic bacteria, responsible for severe nosocomial infections in humans. There is need to search new antimicrobials to target P. aeruginosa strains. Cistus munbyi is used in traditional medicine to manage infections. Objectives: This work aims to investigate the antimicrobial, antibiofilm and other antivirulence effects of essential oil from C. munbyi against P. aeruginosa. Materials and methods: Essential oil (EO) was prepared by hydro-distillation from C. munbyi, characterized by GC–MS and evaluated for its antimicrobial, antibiofilm and anti-virulence effects against clinical isolates of P. aeruginosa. Results: 100% of compounds were identified with Terpinen-4-ol (33.20%), Sabinene (13.20%), α-Thujene (11.30%), and p-Cymene (9.94%) being the major constituents. The EO had good antimicrobial activity determined by diameters of inhibition zones and broth dilution. At minimal inhibitory concentration (MIC), the EO eliminated more that 70% of young biofilms in 19 strains out of 24 tested strains while at 2MIC, only one strain had biofilm inhibition below 70%. The EO eliminated more than 50% of mature biofilms in 13 strains out of 24 tested. Biofilm disruption was concentration-dependent at sub-MIC and indicated good potential of C. munbyi EO as P. aeruginosa antibiofilm agent. Scanning electron microscopy (SEM) images revealed that untreated colonies had a well-developed biofilm while there was significant reduction of biofilms with distorted architecture and cell shrinkage upon treatment with EO. The C. munbyi EO at MIC and sub-MIC was able to reduce quorum-sensing (QS) virulence factors such as pyocyanin production, exopolysaccharides matrix and elastase secretion. Significant QS revealed by reduction of violacein in C. violaceum (CV12472 and CV026) was observed. Conclusion: The overall results show good anti-pseudomonal effects of C. munbyi EO which makes it a potential agent to reduce the spread of infections and resistance to antibiotics from P. aeruginosa strains.