Antiquorum sensing and antibiofilm potential of biosynthesized silver nanoparticles of Myristica fragrans seed extract against MDR Salmonella enterica serovar Typhi isolates from asymptomatic typhoid carriers and typhoid patients.

Globally, Salmonella infection poses a major public health problem. Here, we report antibiofilm activity and quorum sensing inhibition of aqueous seeds extract of Myristica fragrans (nutmeg) and biosynthesized silver nanoparticles (AgNPs) against multidrug resistant (MDR) Salmonella enterica serovar Typhi (S. Typhi) isolated from typhoid patients and asymptomatic carriers. S. Typhi isolates revealed higher percentage (46%) of biofilm production identified by tissue culture plate (TCP) than Congo red agar (CRA) and tube adherence (TA) methods. The inhibition of biofilm-producing MDR S. Typhi isolates and pigment production of Chromobacterium violaceum (indicator bacteria) demonstrated the quorum sensing potential of nutmeg. The aqueous seed extract of nutmeg exhibited 87% of antibiofilm activity, while the biosynthesized AgNPs showed 99.1% of antibiofilm activity. Molecular docking studies of bioactive compounds of nutmeg against transcriptional regulatory protein RcsB and sensor kinase protein RcsC revealed interaction with the target proteins. It is proposed that biosynthesized AgNPs could be used as one of the effective candidates in treating asymptomatic typhoid carriers or typhoid patients and to control the subsistence of biofilm-producing S. Typhi strains or other pathogenic bacteria in the environment or industrial settings.

Syntheses, physicochemical characterization, antibacterial studies on potassium morpholine dithiocarbamate nickel (II), copper (II) metal complexes and their ligands.

Organic molecule dithiocarbamate transition metal complexes are novel and very attractive pharmaceutical targets for the management and control of antibiotic resistant bacteria. The direct reaction has synthesized new transition metal nickel (II), copper (II) complexes of potassium morpholine dithiocarbamate (K+C5H8NOS2 -) ligands and characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), as well as NMR physicochemical techniques. Antibacterial bioefficacy of the ligand and its metal complexes has been investigated in vitro on the growth of Gram-positive (Staphylococcus aureus MTCC 737, Bacillus cereus MTCC 1272) and the Gram-negative (Listeria monocytogenes MTCC 657, Shigella flexeneri MTCC 1457) bacteria. The obtained electronic spectral bands are characteristic and consistent with the proposed composition of the ligand as well as its metal complexes. It also provides a further example of the bidentate coordination of dithiocarbamate ligands. Absorption peak values of FTIR are characteristic of the ligand as well as dithiocarbamate group molecules and exhibit their metal coordination. NMR 1H signal variations also correlate with the coordination mediated chemical shifts. Both the metal complexes showed significant antibacterial activity. However, enhanced antimicrobial activity of the ligands than metal complexes against Gram positive and Gram negative bacteria were observed. Thus, further study on this approach could pave a way for the development of dithiocarbamate-metal complex based antibacterial agent.

Biomimetic synthesis of silver nanoparticles using flower extract of Bauhinia purpurea and its antibacterial activity against clinical pathogens.

In the present study, we have reported an eco-friendly, rapid, and simple method for the synthesis of silver nanoparticles (AgNPs) using Bauhinia purpurea flower extract as non-toxic bioreducing agent. The formation of AgNPs was confirmed by UV-visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The synthesized AgNPs were spherical in shape with an average size of 20 nm. Furthermore, the antibacterial activities of the synthesized AgNPs (2-10 mM) against clinical pathogens, Klebsiella sp. and Staphylococcus sp., were evaluated under in vitro conditions.

Biosynthesis of silver nanoparticles from Spirulina microalgae and its antibacterial activity.

The present work focuses on a low-cost, simple, and green synthesis of silver nanoparticles (AgNPs) by mixing AgNO3 solution with the extract of Spirulina platensis (SP) without any chemical reducing and/or capping agents. The green synthesis of AgNPs was confirmed by the color change from colorless to yellowish brown. The biosynthesis of AgNPs was further confirmed by UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), biological transmission electron microscopy (Bio-TEM), and energy dispersive X-ray analysis (EDX). The UV-vis spectroscopy results showed the surface plasmon resonance (SPR) of AgNPs around 450 nm. Bio-TEM analysis revealed that the Ag nanoparticles were well dispersed with average range of 5-50 nm. XRD results indicated that the green synthetic process produced face-centered cubic structure of AgNPs. FT-IR spectroscopy analysis showed that the bioactive molecules from the SP extract believed to be the responsible for the reduction of Ag ions. Furthermore, the synthesized AgNPs were evaluated against pathogens such as Staphylococcus sp. and Klebsiella sp. The AgNPs (1-4 mM) extensively reduced the growth rate of the pathogens.

Biosynthesis of silver nanoparticles using Myristica fragrans seed (nutmeg) extract and its antibacterial activity against multidrug-resistant (MDR) Salmonella enterica serovar Typhi isolates.

Biosynthesis of nanoparticles has received increasing attention due its effective mode of action, eco-friendly preparation methodology, and less cytotoxicity. In the present study, silver nanoparticles (AgNPs) from aqueous seed extract of Myristica fragrans (nutmeg) were characterized. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of bioactive components acts as effective in reducing and capping agents for converting AgNO3 to AgNPs. The UV-Vis absorption spectrum of the biologically reduced reaction mixture showed the surface plasmon peak at 420 nm, which is the characteristic peak of AgNPs. The functional molecules present in the M. fragrans seed extract and their interaction with the AgNPs were identified by the Fourier transform infrared spectroscopy (FT-IR) analysis. X-ray diffraction (XRD) analysis confirmed the face-centered cubic crystalline structure of metallic silver nanoparticle and diameter was calculated using Scherrer's equation. Transmission electron microscope (TEM) image showed spherical shaped particles with an average size of 25 nm. The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) confirmed the presence of elemental silver. The antibacterial activity of biosynthesized AgNPs was evaluated against multidrug-resistant (MDR) Salmonella enterica serovar Typhi (S. Typhi) according to agar well diffusion, MIC (minimum inhibitory concentration), and IC50 (inhibitory concentration 50%). The results confirm that bacterial growth was significantly reduced in a dose-dependent manner. Further, the cytotoxic effect of biosynthesized AgNPs on rat spleenocytes was analyzed. Thus, it is suggested that the nutmeg-biosynthesized AgNPs could be a lead drug and used effectively to control the MDR S. Typhi, thereby reducing public health issues and environmental pollution.

Optimization of protease production from surface-modified coffee pulp waste and corncobs using Bacillus sp. by SSF.

The aim of the study was to identify new sources of substrate from agro-industrial waste for protease production using Bacillus sp., a local bacteria isolated from an agro-waste dumping site. The strain was identified as Bacillus sp. BT MASC 3 by 16S rRNA sequence followed by phylogenic analysis. Response surface methodology-based Box-Behnken design (BBD) was used to optimize the variables such as pH, incubation time, coffee pulp waste (CPW) and corncob (CC) substrate concentration. The BBD design showed a reasonable adjustment of the quadratic model with the experimental data. Statistics-based contour and 3-D plots were generated to evaluate the changes in the response surface and understand the relationship between the culture conditions and the enzyme yield. The maximum yield of protease production (920 U/mL) was achieved after 60 h of incubation with 3.0 g/L of CPW and 2.0 g/L of CC at pH 8 and temperature 37 °C in this study. The molecular mass of the purified enzyme was 46 kDa. The highest activity was obtained at 50 °C and pH 9 for the purified enzymes.