Biosynthesis of gold nanoparticles and inhibition of various stages of bacterial biofilms formed by drug-resistant Aeromonas hydrophila, Escherichia coli, and Klebsiella pneumoniae.

Biofilm development by bacteria is a serious issue in many different sectors, including the food, pharmaceutical, water, petroleum, and others. Because biofilms are difficult to remove due to their capacity to survive in bad environments, attempts were undertaken throughout this work to biologically manufacture gold nanoparticles with possible antibiofilm capabilities. During this study, 19 morphologically distinct fungal cultures were isolated from soil samples and used to synthesize gold nanoparticles. Among 19 fungi, 7 were producing gold nanoparticles and these particles were subjected to antimicrobial activity. Among 7 gold nanoparticles, nanoparticles synthesized from S2-10 isolate of fungi exhibited high antimicrobial activity toward biofilm-forming drug-resistant bacteria including Klebsiella pneumoniae (14.6 ± 0.57 mm), Aeromonas hydrophila (13.3 ± 0.57 mm) and Escherichia coli (10.0 ± 1.0 mm), and was used for further studies. The chosen nanoparticle also shown strong anti-biofilm action against test microorganisms on a variety of material substrates, including plastic, metal, and glass. These nanoparticles also exhibited inhibition of microcolony/initial biofilm, mature and preformed biofilm formed by Klebsiella pneumoniae (53.42 ± 4.45%, 62.14 ± 7.45%, and 24.12 ± 9.87%, respectively), Aeromonas hydrophila (43.89 ± 0.95%, 59.79 ± 1.19%, and 54.85 ± 6.50%, respectively) and Escherichia coli (45.28 ± 6.88%, 45.17 ± 3.94%, and 32.39 ± 4.16%, respectively). The physicochemical characterization of potential nanoparticles was conducted using UV-visible Spectrophotometer, X-ray diffractionSpectroscopy (XRD), Energy Dispersive X-ray (EDX) spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). These physicochemical analyses confirmed the formation of gold nanoparticles which were found to be spherical in shape with the size between 30 and 40 nm. Furthermore, the potential fungal isolate S2-10 was characterized as Aspergillus niger isolate CJ14 with the help of morphological and molecular techniques and deposited at National Center for Biotechnology Information (NCBI) (Accession number MN519438.1). Hence, it can be concluded that the gold nanoparticles produced using A. niger isolate CJ14 contain significant antibiofilm properties and can be used for developing antibiofilm products for future applications.