Abstract
The emergence of antibiotic resistance in Pseudomonas aeruginosa due to biofilm formation has transformed this opportunistic pathogen into a life-threatening one. Biosynthesized nanoparticles are increasingly being recognized as an effective anti-biofilm strategy to counter P. aeruginosa biofilms. In the present study, gold nanoparticles (AuNPs) were biologically synthesized and stabilized using fucoidan, which is an active compound sourced from brown seaweed. Biosynthesized fucoidan-stabilized AuNPs (F-AuNPs) were subjected to characterization using UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission transmission electron microscopy (FE-TEM), dynamic light scattering (DLS), and energy dispersive X-ray diffraction (EDX). The biosynthesized F-AuNPs were then evaluated for their inhibitory effects on P. aeruginosa bacterial growth, biofilm formation, virulence factor production, and bacterial motility. Overall, the activities of F-AuNPs towards P. aeruginosa were varied depending on their concentration. At minimum inhibitory concentration (MIC) (512 µg/mL) and at concentrations above MIC, F-AuNPs exerted antibacterial activity. In contrast, the sub-inhibitory concentration (sub-MIC) levels of F-AuNPs inhibited biofilm formation without affecting bacterial growth, and eradicated matured biofilm. The minimum biofilm inhibition concentration (MBIC) and minimum biofilm eradication concentration (MBEC) were identified as 128 µg/mL. Furthermore, sub-MICs of F-AuNPs also attenuated the production of several important virulence factors and impaired bacterial swarming, swimming, and twitching motilities. Findings from the present study provide important insights into the potential of F-AuNPs as an effective new drug for controlling P. aeruginosa-biofilm-related infections.
Highlights
The formation of biofilm by Pseudomonas aeruginosa contributes to its survival in adverse environmental conditions, defense against the host immune system, and resistance to antimicrobial compounds such as conventional antibiotics, resulting in extreme complications in preventing and eradicating this opportunistic pathogen from infected patients and medical facilities [1,2,3,4]
The maximum absorbance peak was found at 570 nm, which was almost coincident with the peak obtained (566 nm) during the synthesis of AuNPs by Manivasagan et al [30]
Several strategies have been developed in order to combat antibiotic resistance and related infections caused by pathogenic bacteria [44,45,46,47]
Summary
The formation of biofilm by Pseudomonas aeruginosa contributes to its survival in adverse environmental conditions, defense against the host immune system, and resistance to antimicrobial compounds such as conventional antibiotics, resulting in extreme complications in preventing and eradicating this opportunistic pathogen from infected patients and medical facilities [1,2,3,4]. Mar. Drugs 2019, 17, 208; doi:10.3390/md17040208 www.mdpi.com/journal/marinedrugs. P. aeruginosa with biofilm-forming ability, current anti-biofilm and anti-virulence approaches have mainly targeted the following: (1) attachment of planktonic cells, (2) cell-to-cell communication networks and regulatory systems, and (3) eradication of pre-existing matured biofilm structures [6,7]. These modern anti-biofilm approaches highly favor treatments which are bioactive, cost-effective, and less toxic [8,9,10,11]
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