Synthesis of Silver Nanoparticles from Aeromonas caviae for Antibacterial Activity and In Vivo Effects in Rats.

Silver nanoparticles (AgNPs) have excellent antimicrobial properties, as they can inhibit multidrug-resistant (MDR) pathogens. Furthermore, bio-AgNPs have potential applications in medicine due to their low toxicity and high stability. Here, AgNPs were synthesized from the biomass of Aeromonas caviae isolated from a sediment sample and subsequently characterized. The UV-Vis spectra of AgNPs in aqueous medium peaked at 417 nm, matching their plasmon absorption. The X-ray diffraction analysis (XRD) pattern of AgNPs showed four peaks at 2θ values, corresponding to Ag diffraction faces. Absorption band peaks at 3420.16, 1635.54, and 1399.43 cm-1 were identified by Fourier-transform infrared spectroscopy (FTIR) analysis as belonging to functional groups of AgNP-associated biomolecules. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanoparticles are spherical and pseudospherical, with sizes of 15-25 nm. Agar well diffusion minimal inhibitory concentration (MIC) assays were used to assess the antibacterial activity of the nanoparticles against MDR pathogens. AgNPs exhibited antibacterial activity against MDR bacteria. Two groups of albino rats received intraperitoneal injections of AgNPs at 15 mg/kg or 30 mg/kg for 7 days. Blood, kidney, and liver samples were collected to investigate hematological, biochemical, and histopathological alterations. Administered AgNPs in rats fluctuated in liver and kidney function parameters. The ultrastructural impacts of AgNPs were more prominent at higher doses. The results proved the easy, fast, and efficient synthesis of AgNPs using A. caviae isolates and demonstrated the remarkable potential of these AgNPs as antibacterial agents. Nanotoxicological studies are required to identify the specific dose that balances optimal antibacterial activity with minimal toxicity to human health.

Aeromonas sobria as a potential candidate for bioremediation of heavy metal from contaminated environments.

The uncontrolled discharge of industrial wastes causes the accumulation of high heavy metal concentrations in soil and water, leading to many health issues. In the present study, a Gram-negative Aeromonas sobria was isolated from heavily contaminated soil in the Tanjaro area, southwest of Sulaymaniyah city in the Kurdistan Region of Iraq; then, we assessed its ability to uptake heavy metals. A. sobria was molecularly identified based on the partial amplification of 16S rRNA using novel primers. The sequence was aligned with 33 strains to analyze phylogenetic relationships by maximum likelihood. Based on maximum tolerance concentration (MTC), A. sobria could withstand Zn, Cu, and Ni at concentrations of 5, 6, and 8 mM, respectively. ICP-OES data confirmed that A. sobria reduced 54.89% (0.549 mM) of the Cu, 62.33% (0.623 mM) of the Ni, and 36.41% (0.364 mM) of the Zn after 72 h in the culture medium. Transmission electron microscopy (TEM) showed that A. sobria accumulated both Cu and Ni, whereas biosorption was suggested for the Zn. These findings suggest that metal-resistant A. sobria could be a promising candidate for heavy metal bioremediation in polluted areas. However, more broadly, research is required to assess the feasibility of exploiting A. sobria in situ.

Antimicrobial and Antibiofilm Activity of Biosynthesized Silver Nanoparticles Against Beta-lactamase-Resistant Enterococcus faecalis.

Due to the presence of antibiotic-resistant genes, treatment options of clinical isolates are exceedingly limited. This study was aimed to fabricate, optimize, characterize, and evaluate the action of silver nanoparticles (AgNPs) against a clinical isolate of Enterococcus faecalis. A combination of cell-free supernatant (C-FS) of the filamentous fungus Fusarium solani and Gram-negative Comamonas aquatica for AgNP formation was proposed; the antigrowth and antibiofilm of AgNPs against E. faecalis harboring blaTEM and blaCTX-M genes were assessed. The ratio of 1:2 v/v (C-FS:AgNO3) at pH 9.0 for 72 h in 1 mM AgNO3 were the optimal conditions for AgNP formation. UV-vis absorption peak appeared at 425 nm and the crystalline nature of synthesized particles was verified by X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR) analysis confirmed the interaction of protein molecules with the AgNPs. Transmission electron microscopy (TEM) analysis demonstrated that fabricated AgNPs were relatively monodispersed, approximately spherical, and of size 2-7.5 nm. blaTEM and blaCTX-M were detected in E. faecalis; the growth and biofilm of E. faecalis were significantly decreased by the action of 12.5 µg/mL AgNPs. This is the first study proposing alternative sources to form AgNPs via synergistic metabolites of F. solani and C. aquatica. The results here offer a foundation for developing an effective therapy using AgNPs against clinical pathogens.

Synthesis of Silver Nanoparticles by Raoultella Planticola and Their Potential Antibacterial Activity Against Multidrug-Resistant Isolates.

Background: Nanoparticles can be chemically, physically, or biologically synthesized. Biosynthesis of silver nanoparticles (AgNPs) utilizing microbes is a promising process due to the low toxicity and high stability of AgNPs. Here, AgNPs were fabricated by Gram-negative Raoultella planticola. Objectives: This study aimed to assess the ability of Raoultella planticola to produce nanoparticles (NPs) and evaluate their antibacterial potential against multidrug-resistant pathogens (MDR). Additionally, the study aimed to compare the antibacterial activity of biosynthesized nanoparticles to well-known conventional antibiotics Azithromycin and Tetracycline. Materials and Methods: AgNPs were characterized using visual observation, UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The TEM and SEM were used to determine the size and shape of the nanoparticles. The XRD data were recorded in the 2θ ranging from 20-80° to analyze the crystalline structure of nanoparticles. The antibacterial activity was detected using a 96-well microtiter plate. Results: The UV-vis absorption recorded from the 300 - 900 nm spectrum was well defined at 420 nm, and the XRD pattern was compatible with Braggs's reflection of the silver nanocrystals. FTIR showed absorbance bands corresponding to different functional groups. TEM and SEM images showed non-uniform spherical and AgNPs of 10-80 nm. XRD data confirmed that the resultant particles are AgNPs. The AgNPs showed effective activity against multi-drug resistant (MDR) Pseudomonas aeruginosa, Salmonella sp., Shigella sp., E. coli, Enterobacter sp., Staphylococcus aureus, and Bacillus cereus. The AgNPs demonstrated effectiveness in lower concentrations compared to broad-spectrum antibiotics. Conclusion: These data reveal that AgNP generated by R. planticola was more efficient against MDR microorganisms than commercial antibiotics. However, the cytotoxicity of these nanoparticles must be further studied.

Intimate communication between Comamonas aquatica and Fusarium solani in remediation of heavy metal-polluted environments.

Worldwide, humanity is facing a major environmental crisis with the disposal of heavy metal contaminated waste. The current study describes, for the first time, the interactions between gram-negative Comamonas aquatica and filamentous fungus Fusarium solani in removing heavy metal toxicity as an eco-friendly system. When combined, C. aquatica and F. solani grew well in a co-culture setup without showing any antagonistic indications. Monoculture versus co-culture setups were used to determine the metal tolerance concentration (MTC). Based on the metal tolerance concentration (MTC) values, cells of C. aquatica were able to tolerate 4, 5, 6, and 7 mM of Cr, Zn, Cu, and Ni, respectively. Moreover, C. aquatica withstood up to 6 mM of Pb. Although F. solani exhibited sensitivity to high concentrations of heavy metals in monoculture, the MTC of F. solani increased considerably in a co-culture setup. The results presented here revealed that F. solani facilitated the dispersion of C. aquatica and heightened bioavailability, whereas C. aquatica reduced the toxicity of heavy metals and promoted the growth of F. solani. Transmission electron microscopy (TEM) displayed different mechanisms for heavy metal removal by C. aquatica. Biosorption was evident for Cr and Pb, while transformation was recorded for Ni and Zn. Also, C. aquatica was able to reduce and accumulate Cu in cells.

Fusarium mangiferae as New Cell Factories for Producing Silver Nanoparticles.

Finding a safe and broad-spectrum medication is a goal of scientists, pharmacists, and physicians, but developing and fabricating the right medicine can be challenging. The current study describes the formation of silver nanoparticles (AgNPs) by Fusarium mangiferae. It involves the antibiofilm activity of the nanoparticles against Staphylococcus aureus. It also involves cytotoxic effect against mammalian cell lines. Well-dispersed nanoparticles are formed by F. mangiferae. The sizes of the nanoparticles were found to range from 25 to 52 nm, and UV-Vis scan showed absorption around 416-420 nm. SEM, TEM, and AFM results displayed spherical and oval shapes. Furthermore, the FTIR histogram detected amide I and amide II compounds responsible for the stability of AgNPs in an aqueous solution. AgNPs were observed to decrease the formation of biofilm at 75% (v/v). DNA reducing, smearing, and perhaps fragmentation were noticed after treating the bacterial cells with 50% (v/v). Additionally, cell lysis was detected releasing proteins in the supernatant. It was also observed that the AgNPs have the ability to cause 59% cervical cancer cell line (HeLa) deaths at 25% (v/v), however, they showed about 31% toxicity against rat embryo fibroblast transformed cell lines (REF). The results of this study prove the efficiency of AgNPs as an antibiofilm against S. aureus, suggesting that AgNPs could be an alternative to antibiotics. It must also be emphasized that AgNPs displayed cytotoxic behavior against mammalian cell lines. Further studies are needed for assessing risk in relation to the possible benefit of prescribing AgNPs.

Analyzing formation of silver nanoparticles from the filamentous fungus Fusarium oxysporum and their antimicrobial activity.

In recent years much attention has been paid to the biosynthesis of silver nanoparticles (AgNPs) and their important medical applications. The current study employs Fusarium oxysporum for the formation of silver nanoparticles and examines the antimicrobial activity of the particles against some multidrug-resistant (MDR) microbes. Silver nitrate was transformed into silver oxide, forming well-dispersed nanoparticles, by the action of F. oxysporum metabolically. The size of the nanoparticles ranged from 21.3 to 37.3 nm, and UV-spectroscopy showed a peak at 408-411 nm. Moreover, SEM, TEM, and AFM results revealed spherical and oval shapes and showed no sign of aggregation. Furthermore, the FT-IR histogram detected amide I and amide II, which are responsible for the stability of AgNPs in the aqueous solution. The AgNPs halted the growth of MDR bacteria, including some members of Enterobacteriaceae and Staphylococcus species at a concentration of 50% (v/v). The AgNPs also have the ability to inhibit pathogenic yeasts Candida albicans and Candida krusei. The AgNPs displayed antigrowth activity against MDR microbes, suggesting that they might be potential alternatives to antibiotics. However, additional studies may be necessary to substantiate the fact that the benefits of using nanoparticles outweigh the potential risks.