Subinhibitory Concentrations of Biogenic Silver Nanoparticles Affect Motility and Biofilm Formation in Pseudomonas aeruginosa

Abstract

Biogenic silver nanoparticles (bio-AgNPs) are increasingly recognized as an antibiofilm and antivirulence strategy against P. aeruginosa, a bacterium that causes chronic infections in immunocompromised and cystic fibrosis patients. This study aimed to investigate the effects of subinhibitory concentrations of bio-AgNPs on motility and biofilm formation in P. aeruginosa. Bio-AgNPs were synthesized via reduction of ionic silver catalyzed by cell-free culture filtrate from Fusarium oxysporum. A total of 17 P. aeruginosa isolates and strains were evaluated for swarming, swimming, and twitching motility in the presence and absence (control) of bio-AgNPs, including 10 clinical isolates from patients with and without cystic fibrosis, 5 environmental isolates obtained from the public water supply system, and 2 reference strains (PAO1 and PA14). Isolates were identified by biochemical and molecular methods. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. Swarming, swimming, and twitching motility assays were performed in Petri dishes. Biofilm formation capacity was assessed quantitatively by the crystal violet method. MIC values ranged from 15.62 to 62.50 µM. The results showed that subinhibitory concentrations of bio-AgNPs (½ MIC, 7.81–31.25 µM) significantly increased (p < 0.05) swarming, swimming, and twitching motility in 40.0, 40.0, and 46.7% of isolates, respectively. Subinhibitory bio-AgNP treatment enhanced (p < 0.05) biofilm formation capacity in PA14 and a cystic fibrosis isolate (P11). It is concluded that subinhibitory concentrations of bio-AgNPs increased biofilm formation and swarming, swimming, and twitching motility in PA14 and some P. aeruginosa isolates. These virulence factors are directly involved with quorum-sensing systems. Further research should investigate the effects of AgNPs on P. aeruginosa quorum sensing to help elucidate their mechanism of action at subinhibitory concentrations.

Bioinspired Green Synthesis of Silver Nanoparticles Using Three Plant Extracts and Their Antibacterial Activity against Rice Bacterial Leaf Blight Pathogen Xanthomonas oryzae pv. oryzae

“…Thus, we speculate that the three AgNPs can better achieve their antibacterial effects by inhibiting the swimming motility of bacteria. Our study is similar to Saeki et al [ 55 ], who reported that AgNPs can weaken the swimming diameter of Pseudomonas aeruginosa.…”

“…Previous studies showed that bacterial swimming is directly related to bacterial growth, biofilm formation, and pathogenesis [ 55 , 56 ]. In this study, the AgNPs synthesized by three plants showed a strong inhibitory effect on bacterial swimming ( Figure 5 b).…”

No Correlation between Biofilm Formation, Virulence Factors, and Antibiotic Resistance in Pseudomonas aeruginosa: Results from a Laboratory-Based In Vitro Study

“…The study uses a cross-sectional design, with microorganisms that were isolated between 1 Janurary 2019 and 1 Janurary 2020, originating from various types of clinical specimens, being randomly selected to be included in our experiments. During the study, P. aeruginosa ATCC 27853 (MDR isolate, weak biofilm producer) and P. aeruginosa PAE 170022 (susceptible isolate, strong biofilm producer) were used as control strains, obtained from the American Type Culture Collection (Manassas, VI, USA) [ 24 ]. Stock cultures were stored at −80 °C in a cryopreservation medium (700 µL trypticase soy broth + 300 µL 50% glycerol) until use.…”

Understanding the Role of the Antioxidant Drug Erdosteine and Its Active Metabolite on Staphylococcus aureus Methicillin Resistant Biofilm Formation

“…Data demonstrated that Er and Met I at 2 and 5 mg/L promoted biofilm formation, which is characterized by an increased number biofilm-dwelling cells and a reduced ROS level in comparison to the control samples. It is well known that some antimicrobials at sub-inhibitory concentrations can function as signalling molecules and promote biofilm formation while altering bacterial virulence, quorum sensing, gene expression and gene transfer [ 35 , 36 , 37 ]. Furthermore, the antioxidant N -acetylcysteine promoted biofilm growth in S. aureus ATCC25923 and Pseudomonas aeruginosa PAO1 by increasing expression of some biofilm-associated genes and enhanced extracellular polymers production [ 13 ].…”