Synergistic antibacterial and antibiofilm activity of silver nanoparticles biosynthesized by lignin-degrading fungus

Abstract

Background:The fabrication of silver nanoparticles (Ag-NPs) through green chemistry is an emerging area in the field of medical nanotechnology. Ag-NPs were fabricated by enzymatic reduction of AgNO 3 using two lignin-degrading fungus Aspergillus flavus (AfAg-NPs) and Emericella nidulans (EnAg-NPs). The prepared Ag-NPs were characterized by different spectroscopic techniques. Antibacterial activity of prepared Ag-NPs was demonstrated against selected Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus) bacteria in the term of minimum bactericidal concentration (MBC) and susceptibility constant (Z). The synergistic antibacterial activity of Ag-NPs with four conventional antibiotics was also determined by the fractional inhibitory concentration index (FICI) using the checkerboard microdilution method. The antibiofilm potential of Ag-NPs was also tested. Results:The plasmon surface resonance of biosynthesized Ag-NPs shows its characteristic peaks at UV and visible region (~450 and 280 nm). Fourier transform infrared spectrometer (FTIR) analysis confirms the nature of the capping agents as protein (enzyme) and indicates the role of protein (enzyme) in reduction of silver ions. The average particle size and charge of synthesized Ag-NPs was ~100 nm and ~−20 mV, respectively. X-ray diffraction (XRD) and TEM analysis confirmed the purity, shape, and size (quasi-spherical, hexagonal, and triangular) of Ag-NPs. Energy-dispersive X-ray spectroscopy (EDX) data validate the biological synthesis of Ag-NPs. Low MBC and high susceptibility constant indicate the high antimicrobial strength of biosynthesized Ag-NPs. The antibacterial analysis demonstrates the synergistic antimicrobial activity of Ag-NPs with antibiotics. This study also shows that biosynthesized Ag-NPs have ability to inhibit the biofilm formation by 80-90 %. Conclusion:The Aspergillus flavus and Emericella nidulans-mediated biosynthesized Ag-NPs have significant antimicrobial activity and demonstrate synergistic effect in combination with antibiotics. It suggests that nanoparticles can be effectively used in combination with antibiotics to improve the efficacy of antibiotics against pathogenic microbes. The substantial antibiofilm efficiency of biosynthesized Ag-NPs would also be helpful against sensitive and multidrug-resistant strains.

Efficiency of Biosynthesized Silver and Zinc Nanoparticles Against Multi-Drug Resistant Pathogens

“…The report concluded synergistic action of antimicrobial agent can significantly curtail side effects by reducing dosages. Thus, use of nanoparticles combined with antibiotics can improve their efficacy against various pathogenic microbes (Barapatre et al, 2016). The results of synergistic activity of nanoparticles synthesized by P. hibiscicola are in accordance with this report and rightly suggested nanoparticles can indeed be one of the most effective agents in combating serious infections that are rendered untreatable with available antibiotics.…”

Preparation and characterization of ascorbic acid-mediated chitosan–copper oxide nanocomposite for anti-microbial, sporicidal and biofilm-inhibitory activity

“…After drying for 15 min, the stains were solubilized with 100 µL of 70% ethanol and read at 595 nm using an ELISA reader (BioRad-680, USA). The inhibitory percentage of biofilm formation was calculated as done by Bharathi et al [13] and Barapatre et al [14].…”

Microbially synthesized nanoparticles as next generation antimicrobials: scope and applications

“…Ag-NPs produced by the lignin-degrading fungus Emericella nidulans and A. flavus inhibited biofilm formation in Gram-positive (S. aureus) and Gram-negative (P. aeruginosa and E. coli) bacteria. At a concentration of 0.5À64 μg mL 21 , the Ag-NPs significantly decreased 74%À84% biofilm formation as compared with fungal cell-free filtrate (devoid of Ag-NPs) showing 4%À6% antibiofilm activity (Barapatre et al 2016). Zero-valent bismuth nanoparticles completely inhibited growth and formation of biofilm by Streptococcus mutans (Hernandez-Delgadillo et al, 2012).…”

“…On the other hand, a broad range of microorganisms have been studied as potential biofactories for eco-friendly and cost-effective production of metallic nanoparticles, such as silver, titanium oxide, cadmium sulfide, gold, etc. Thus, research in microbial nanotechnology provides a reliable way for large-scale synthesis of nanomaterials (Barapatre et al, 2016). The use metallic preparations of gold, copper, silver, iron, and lead, as well as alloys in healthcare, can be traced back to ancient civilizations.…”