Antimicrobial Efficacy and Synergy of Metal Ions against Enterococcus faecium, Klebsiella pneumoniae and Acinetobacter baumannii in Planktonic and Biofilm Phenotypes

The critical role of organic matter for cadmium-lead interactions in soil: Mechanisms and risks

Understanding the interaction mechanisms between complex heavy metals and soil components is a prerequisite for effectively forecasting the mobility and availability of contaminants in soils. Soil organic matter (SOM), with its diverse functional groups, has long been a focal point of research interest. In this study, four soils with manipulated levels of SOM, cadmium (Cd) and lead (Pb) were subjected to a 90-day incubation experiment. The competitive interactions between Cd and Pb in soils were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray adsorption near-edge structure (XANES) analysis. Our results indicate that Pb competed with Cd for adsorption sites on the surface of SOM, particularly on carboxyl and hydroxyl functional groups. Approximately 22.6 % of Cd adsorption sites on humus were occupied by Pb. The use of sequentially extracted exchangeable heavy metals as indicators for environment risk assessments, considering variations in soil physico-chemical properties and synergistic or antagonistic effects between contaminants, provides a better estimation of metal bioavailability and its potential impacts. Integrating comprehensive contamination characterization of heavy metal interactions with the soil organic phase is an important advancement to assess the environmental risks of heavy metal dynamics in soil compared to individual contamination assessments.

Evolution of copper coupons resistance in Enterobacteriaceae strains isolated from high-contact surfaces in hospital

Objective

Metallic copper alloys have gained attention recently as a cutting-edge antibacterial weapon for areas where surface hygiene is crucial. The present study aimed to assess copper coupons (99% Cu) for their potential to decrease the viability of various Enterobacteriaceae strains from inanimate hospital surfaces.

Methods

This in vitro-experimental study was conducted at the Microbiology Laboratory, Faculty of Natural and Life Sciences and Earth and Universe Sciences, University of Guelma, and Khodja Ahmed Public Hospital Establishment, Algeria, for a period of six months from January to May 2022. A total of 85 samples were collected from patient room door handles and bed rails at the government hospital in Guelma State, from which 12 enterobacterial isolates were obtained. These isolates were evaluated for susceptibility to copper and polyvinyl chloride (PVC) coupons using plate counts to determine bacterial viability after 72 hours of incubation at 37°C or room temperature (25°C). Antibiotic sensitivity testing was then carried out using a modified Kirby-Bauer disc diffusion method. Copper coupons' ability to either select for or create antibiotic resistance is also determined.

Results

Copper showed a bactericidal effect after three hours for Serratia odorifera and six hours for Escherichia coli. Whereas it was shown that within three days of selection, 83.33% of Enterobacteriaceae strains are capable of rapidly acquiring Cu resistance. Indeed, the increase in temperature reduced the effects of Cu (p<0.05; Student's t-test). Antimicrobial susceptibility testing revealed that the copper-resistant bacteria were less sensitive than their predecessors. Citrobacter freundii strains showed the highest incidence of multidrug resistance. The most significant findings included widespread resistance to beta-lactams (100%-75%) and chloramphenicol (66.67%).

Conclusion

These results suggest that prolonged copper usage may contribute to the development of antibiotic resistance, which could have significant ramifications.

Exploration of Variable Solvent Directed Self-Healable Supramolecular M(II)-Metallogels (M = Co, Ni, Zn) of Azelaic Acid: Investigating Temperature-Dependent Ion Conductivity and Antibacterial Efficiency

Molecular self-assembly assisted self-healing supramolecular metallogels of azelaic acid with cobalt(II)-, nickel(II)-, and zinc(II)-based metal acetate salts were successfully fabricated. Individually, N,N'-dimethylformamide and dimethyl sulfoxide were immobilized within these distinctly synthesized soft-scaffolds of metallogels to attain their semisolid viscoelastic nature. Rheological experiments such as amplitude sweep, frequency sweep, and thixotropic measurements were executed for these metallogels to ratify their gel features. The different extents of supramolecular interactions operating within these solvent-directed metallogels were clearly reflected in terms of their distinct morphological patterns as investigated through field emission scanning electron microscopy. Comparative infrared (IR) spectral properties of metallogels along with individual metal salts and azelaic acid were analyzed. These experimental data clearly depict the significant shifting of Fourier transform (FT)-IR peaks of xerogel samples of different metallogels from the gel-forming precursors. The networks present within the soft-scaffold are evidently illustrated by the electrospray ionization-mass experimental data. The temperature-dependent ionic conductivity studies with these solvent-directed versatile metallogel systems were investigated through impedance spectroscopy. The temperature-dependent impedance spectroscopic studies clearly demonstrate that the ion-transportation within the gel matrix depends not only on the types of cations but also on the dielectric properties of the immobilized solvents. The antipathogenic effect of these metallogel systems has also been explored by testing their effectiveness against human pathogenic Gram-negative bacteria Klebsiella pneumoniae (MTCC 109) and Vibrio parahemolyticus, and Gram-positive bacteria like Bacillus cereus (MTCC 1272). These gel soft-scaffolds show no significant cytotoxicity against both the human neuroblastoma cell line-SH-SY5Y and the human embryonic kidney cell line-HEK 293.

Antimicrobial activity of silver-copper coating against aerosols containing surrogate respiratory viruses and bacteria

The transmission of bacteria and respiratory viruses through expelled saliva microdroplets and aerosols is a significant concern for healthcare workers, further highlighted during the SARS-CoV-2 pandemic. To address this issue, the development of nanomaterials with antimicrobial properties for use as nanolayers in respiratory protection equipment, such as facemasks or respirators, has emerged as a potential solution. In this study, a silver and copper nanolayer called SakCu® was deposited on one side of a spun-bond polypropylene fabric using the magnetron sputtering technique. The antibacterial and antiviral activity of the AgCu nanolayer was evaluated against droplets falling on the material and aerosols passing through it. The effectiveness of the nanolayer was assessed by measuring viral loads of the enveloped virus SARS-CoV-2 and viability assays using respiratory surrogate viruses, including PaMx54, PaMx60, PaMx61 (ssRNA, Leviviridae), and PhiX174 (ssDNA, Microviridae) as representatives of non-enveloped viruses. Colony forming unit (CFU) determination was employed to evaluate the survival of aerobic and anaerobic bacteria. The results demonstrated a nearly exponential reduction in SARS-CoV-2 viral load, achieving complete viral load reduction after 24 hours of contact incubation with the AgCu nanolayer. Viability assays with the surrogate viruses showed a significant reduction in viral replication between 2-4 hours after contact. The simulated viral filtration system demonstrated inhibition of viral replication ranging from 39% to 64%. The viability assays with PhiX174 exhibited a 2-log reduction in viral replication after 24 hours of contact and a 16.31% inhibition in viral filtration assays. Bacterial growth inhibition varied depending on the species, with reductions ranging from 70% to 92% for aerobic bacteria and over 90% for anaerobic strains. In conclusion, the AgCu nanolayer displayed high bactericidal and antiviral activity in contact and aerosol conditions. Therefore, it holds the potential for incorporation into personal protective equipment to effectively reduce and prevent the transmission of aerosol-borne pathogenic bacteria and respiratory viruses.

Co-regulation of biofilm formation and antimicrobial resistance in Acinetobacter baumannii: from mechanisms to therapeutic strategies

In recent years, multidrug-resistant Acinetobacter baumannii has emerged globally as a major threat to the healthcare system. It is now listed by the World Health Organization as a priority one for the need of new therapeutic agents. A. baumannii has the capacity to develop robust biofilms on biotic and abiotic surfaces. Biofilm development allows these bacteria to resist various environmental stressors, including antibiotics and lack of nutrients or water, which in turn allows the persistence of A. baumannii in the hospital environment and further outbreaks. Investigation into therapeutic alternatives that will act on both biofilm formation and antimicrobial resistance (AMR) is sorely needed. The aim of the present review is to critically discuss the various mechanisms by which AMR and biofilm formation may be co-regulated in A. baumannii in an attempt to shed light on paths towards novel therapeutic opportunities. After discussing the clinical importance of A. baumannii, this critical review highlights biofilm-formation genes that may be associated with the co-regulation of AMR. Particularly worthy of consideration are genes regulating the quorum sensing system AbaI/AbaR, AbOmpA (OmpA protein), Bap (biofilm-associated protein), the two-component regulatory system BfmRS, the PER-1 β-lactamase, EpsA, and PTK. Finally, this review discusses ongoing experimental therapeutic strategies to fight A. baumannii infections, namely vaccine development, quorum sensing interference, nanoparticles, metal ions, natural products, antimicrobial peptides, and phage therapy. A better understanding of the mechanisms that co-regulate biofilm formation and AMR will help identify new therapeutic targets, as combined approaches may confer synergistic benefits for effective and safer treatments.

Development of antibacterial neural stimulation electrodes via hierarchical surface restructuring and atomic layer deposition

Miniaturization and electrochemical performance enhancement of electrodes and microelectrode arrays in emerging long-term implantable neural stimulation devices improves specificity, functionality, and performance of these devices. However, surgical site and post-implantation infections are amongst the most devastating complications after surgical procedures and implantations. Additionally, with the increased use of antibiotics, the threat of antibiotic resistance is significant and is increasingly being recognized as a global problem. Therefore, the need for alternative strategies to eliminate post-implantation infections and reduce antibiotic use has led to the development of medical devices with antibacterial properties. In this work, we report on the development of electrochemically active antibacterial platinum-iridium electrodes targeted for use in neural stimulation and sensing applications. A two-step development process was used. Electrodes were first restructured using femtosecond laser hierarchical surface restructuring. In the second step of the process, atomic layer deposition was utilized to deposit conformal antibacterial copper oxide thin films on the hierarchical surface structure of the electrodes to impart antibacterial properties to the electrodes with minimal impact on electrochemical performance of the electrodes. Morphological, compositional, and structural properties of the electrodes were studied using multiple modalities of microscopy and spectroscopy. Antibacterial properties of the electrodes were also studied, particularly, the killing effect of the hierarchically restructured antibacterial electrodes on Escherichia coli and Staphylococcus aureus-two common types of bacteria responsible for implant infections.

BBD optimized antioxidants of Crotalaria candicans and its nanoconjugates, exert potent in vivo anti-biofilm effects against MRSA

Crotalaria genus is extensively dispersed in tropical and subtropical provinces, and it is found to harbor antioxidant flavonoids. Response surface methodology-based optimization was carried out for the purpose of efficient extraction involving a suitable solvent which can maximize the yield along with higher total phenolic content and total flavonoid content (TFC). Optimization conditions for extraction of C.candicans flavonoids (CCF) based on variables such as solvent, solid-solvent ratio and extraction temperature were evaluated. The optimized conditions were found as Solvent i.e., Aqueous-ethanol (53.42%), Solid-solvent ratio (1:15.83 w/v) and temperature (44.42 °C) and resulted to obtain the TFC as 176.23 mg QRET/g C. candicans extract with the yield 27.42 mg CCF/g (C. candicans dry weight). LC-MS analysis of CCF, revealed the presence of seven major flavonoids. The antioxidant flavonoids were further used to functionalize the zero-valent silver (ZVAgF) and copper (ZVCuF) nanoparticles. The ZVAgF and ZVCuF were investigated using UV-Vis spectrophotometry, FT-IR spectroscopy and X-ray diffractometry to confirm the presence of the zero valent metals and possible functional groups which capped the elemental metal. Further transmission electron microscopy, dynamic light scattering method and zeta-potential studies were done to understand their respective structural and morphological properties. The efficacy of the as-prepared ZVAgF/ZVCuF as antibiofilm agents on Methicillin-resistant Staphylococcus aureus (MRSA) with the mechanism studies have been explored. The MRSA-colony count from the infection zebrafish (in vivo) model, portrayed a reduction of > 1.9 fold for ZVCuF and > twofold for ZVAgF, with no alteration in liver morphology when treated with ZVAgF, implying that the nanoparticles were safe and biocompatible.

Synergistic antibacterial effect of copper and silver nanoparticles and their mechanism of action

Bacterial infections are one of the leading causes of death worldwide. In the case of topical bacterial infections such as wound infections, silver (Ag) has historically been one of the most widely used antibacterials. However, scientific publications have demonstrated the adverse effects of silver on human cells, ecotoxicity and insufficient antibacterial effect for the complete elimination of bacterial infections. The use of Ag in the form of nanoparticles (NPs, 1-100 nm) allows to control the release of antibacterial Ag ions but is still not sufficient to eliminate infection and avoid cytotoxicity. In this study, we tested the potency of differently functionalized copper oxide (CuO) NPs to enhance the antibacterial properties of Ag NPs. The antibacterial effect of the mixture of CuO NPs (CuO, CuO-NH₂ and CuO-COOH NPs) with Ag NPs (uncoated and coated) was studied. CuO and Ag NP combinations were more efficient than Cu or Ag (NPs) alone against a wide range of bacteria, including antibiotic-resistant strains such as gram-negative Escherichia coli and Pseudomonas aeruginosa as well as gram-positive Staphylococcus aureus, Enterococcus faecalis and Streptococcus dysgalactiae. We showed that positively charged CuO NPs enhanced the antibacterial effect of Ag NPs up to 6 times. Notably, compared to the synergy of CuO and Ag NPs, the synergy of respective metal ions was low, suggesting that NP surface is required for the enhanced antibacterial effect. We also studied the mechanisms of synergy and showed that the production of Cu⁺ ions, faster dissolution of Ag⁺ from Ag NPs and lower binding of Ag⁺ by proteins of the incubation media in the presence of Cu²⁺ were the main mechanisms of the synergy. In summary, CuO and Ag NP combinations allowed increasing the antibacterial effect up to 6 times. Thus, using CuO and Ag NP combinations enables to retain excellent antibacterial effects due to Ag and synergy and enhances beneficial effects, since Cu is a vital microelement for human cells. Thus, we suggest using combinations of Ag and CuO NPs in antibacterial materials, such as wound care products, to increase the antibacterial effect of Ag, improve safety and prevent and cure topical bacterial infections.

The antimicrobial efficacy of copper, cobalt, zinc and silver nanoparticles: alone and in combination

With the advent of nanotechnology, there has been an extensive interest in the antimicrobial potential of metals. The rapid and widespread development of antimicrobial-resistant and multidrug-resistant bacteria has prompted recent research into developing novel or alternative antimicrobial agents. In this study, the antimicrobial efficacy of metallic copper, cobalt, silver and zinc nanoparticles was assessed againstEscherichia coli(NCTC 10538),S. aureus(ATCC 6538) along with three clinical isolates ofStaphylococcus epidermidis(A37, A57 and A91) and three clinical isolates ofE. coli(Strains 1, 2 and 3) recovered from bone marrow transplant patients and patients with cystitis respectively. Antimicrobial sensitivity assays, including agar diffusion and broth macro-dilution to determine minimum inhibitory and bactericidal concentrations (MIC/MBC) and time-kill/synergy assays, were used to assess the antimicrobial efficacy of the agents. The panel of test microorganisms, including antibiotic-resistant strains, demonstrated a broad range of sensitivity to the metals investigated. MICs of the type culture strains were in the range of 0.625-5.0 mg ml^-1. While copper and cobalt exhibited no difference in sensitivity between Gram-positive and Gram-negative microorganisms, silver and zinc showed strain specificity. A significant decrease (p< 0.001) in the bacterial density ofE. coliandS. aureuswas demonstrated by silver, copper and zinc in as little as two hours. Furthermore, combining metal nanoparticles reduced the time required to achieve a complete kill.

New Palladium(II) Complexes Containing Methyl Gallate and Octyl Gallate: Effect against Mycobacterium tuberculosis and Campylobacter jejuni

This work describes the preparation, characterization and antimicrobial activity of four palladium(II) complexes, namely, [Pd(meg)(1,10-phen)] 1, [Pd(meg)(PPh₃)₂] 2, [Pd(og)(1,10-phen)] 3 and [Pd(og)(PPh₃)₂] 4, where meg = methyl gallate, og = octyl gallate, 1,10-phen = 1,10-phenanthroline and PPh₃ = triphenylphosphine. As to the chemical structures, spectral and physicochemical studies of 1-4 indicated that methyl or octyl gallate coordinates a palladium(II) ion through two oxygen atoms upon deprotonation. A chelating bidentate phenanthroline or two triphenylphosphine molecules complete the coordination sphere of palladium(II) ion, depending on the complex. The metal complexes were tested against the Mycobacterium tuberculosis H37Rv strain and 2 exhibited high activity (MIC = 3.28 μg/mL). As to the tests with Campylobacter jejuni, complex 1 showed a significant effect in reducing bacterial population (greater than 7 log CFU) in planktonic forms, as well as in the biomass intensity (IBF: 0.87) when compared to peracetic acid (IBF: 1.11) at a concentration of 400 μg/mL. The effect provided by these complexes has specificity according to the target microorganism and represent a promising alternative for the control of microorganisms of public health importance.

Analysis of Cellular Damage Resulting from Exposure of Bacteria to Graphene Oxide and Hybrids Using Fourier Transform Infrared Spectroscopy

With the increase in antimicrobial resistance, there is an urgent need to find new antimicrobials. Four particulate antimicrobial compounds, graphite (G), graphene oxide (GO), silver-graphene oxide (Ag-GO) and zinc oxide-graphene oxide (ZnO-GO) were tested against Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. The antimicrobial effects on the cellular ultrastructure were determined using Fourier transform infrared spectroscopy (FTIR), and selected FTIR spectral metrics correlated with cell damage and death arising from exposure to the GO hybrids. Ag-GO caused the most severe damage to the cellular ultrastructure, whilst GO caused intermediate damage. Graphite exposure caused unexpectedly high levels of damage to E. coli, whereas ZnO-GO exposure led to relatively low levels of damage. The Gram-negative bacteria demonstrated a stronger correlation between FTIR metrics, indicated by the perturbation index and the minimal bactericidal concentration (MBC). The blue shift of the combined ester carbonyl and amide I band was stronger for the Gram-negative varieties. FTIR metrics tended to provide a better assessment of cell damage based on correlation with cellular imaging and indicated that damage to the lipopolysaccharide, peptidoglycan and phospholipid bilayers had occurred. Further investigations into the cell damage caused by the GO-based materials will allow the development of this type of carbon-based multimode antimicrobials.

Synthesis, spectral characterization of pyrazole derived Schiff base analogs: molecular dynamic simulation, antibacterial and DNA binding studies

We have synthesized the pyrazole-bearing Schiff base derivatives (5a-5e) and (6a-6h) then the structural confirmation was supported by various spectral analyses. The antibacterial activity of all analogs was screened against bacterial strains Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis, Escherichia coli, Klebsiella pneumonieae and Pseudomonas aeruginosa. In comparison to the reference drug ciprofloxacin, the lead analogs 5c and 6c showed potent activity, with MIC values of 64 µg/mL against E. coli and B. subtilis. Compound 5c showed a moderate effect with a MIC value of 128 µg/mL against B. subtilis, P. aeruginosa and K. pneumonieae, while compound 6c was against E. coli and P. aeruginosa. Furthermore, the compounds 5c and 6c displayed groove binding mode towards CT-DNA by absorption, emission, competitive fluorescence studies using EtBr, CD and time-resolved fluorescence studies. Thermodynamic parameters of analogs 5c and 6c with CT-DNA were also calculated at 298, 303 and 308K temperatures by UV-visible spectroscopy. The molecular docking studies give the docking score for all compounds with PDB codes: 1BNA and 2XCT. The MD simulation study of analogs 5c and 6c was also carried out. The pharmacokinetic and ADME properties were calculated for all of the synthesized analogs (5a-5e) and (6a-6h).Communicated by Ramaswamy H. Sarma.

Overview of Antimicrobial Biodegradable Polyester-Based Formulations

As the clinical complications induced by microbial infections are known to have life-threatening side effects, conventional anti-infective therapy is necessary, but not sufficient to overcome these issues. Some of their limitations are connected to drug-related inefficiency or resistance and pathogen-related adaptive modifications. Therefore, there is an urgent need for advanced antimicrobials and antimicrobial devices. A challenging, yet successful route has been the development of new biostatic or biocide agents and biomaterials by considering the indisputable advantages of biopolymers. Polymers are attractive materials due to their physical and chemical properties, such as compositional and structural versatility, tunable reactivity, solubility and degradability, and mechanical and chemical tunability, together with their intrinsic biocompatibility and bioactivity, thus enabling the fabrication of effective pharmacologically active antimicrobial formulations. Besides representing protective or potentiating carriers for conventional drugs, biopolymers possess an impressive ability for conjugation or functionalization. These aspects are key for avoiding malicious side effects or providing targeted and triggered drug delivery (specific and selective cellular targeting), and generally to define their pharmacological efficacy. Moreover, biopolymers can be processed in different forms (particles, fibers, films, membranes, or scaffolds), which prove excellent candidates for modern anti-infective applications. This review contains an overview of antimicrobial polyester-based formulations, centered around the effect of the dimensionality over the properties of the material and the effect of the production route or post-processing actions.

The effects of palladium coordination complex speciation and concentration upon the ubiquitous bacterial species Pseudomonas aeruginosa

The toxicity of three different palladium (Pd) species to Pseudomonas aeruginosa, an environmentally ubiquitous bacterial species, is reported. Palladium was added to chemically-defined minimal media as three complex ion salts, namely sodium tetrachloropalladate (Na₂[PdCl₄]), tetraamminepalladium(II) chloride ([Pd(NH₃)₄]Cl₂), and potassium hexachloropalladate(IV) (K₂[PdCl₆]), inoculated with log-phase cultures and incubated for 24 h at 25 °C. Toxicity was tested for Pd concentrations ranging from 6.55 μg/L (0.06 μM Pd) to 250 μg/L (2.33 μM Pd). Minimum inhibitory concentrations (MICs) were determined and growth tracked via optical absorption at 600 nm. Viability and minimum bactericidal concentrations (MBCs) were measured in parallel with dilution, plating and colony forming unit (CFU) counting. MICs for all forms of Pd were 62.5 μg Pd/L, approximately 1000 times lower than previously reported values. The MBCs for PdCl₄^2- and Pd(NH₃)₄²⁺ were 62.5 μg Pd/L and 125 μg Pd/L for PdCl₆^2-. Pd(NH₃)₄²⁺ and PdCl₆^2- culture viability at 7.8-31.3 μg Pd/L was not different from controls. However, PdCl₄^2- culture viability was different from the other additives, with decreasing viability at sub-MBC concentrations down to 6.55 μg Pd/L. To understand the possible effect of speciation upon toxicity, the equilibrium speciation of Pd was modeled for all solutions using PHREEQC and found to be dominated by Pd(NH₃)₃Cl⁺ (65.6 % of total Pd) and Pd(NH₃)₄²⁺ (34.2 % total Pd). The juxtaposition of the equilibrium calculations and the toxicity results indicates that the kinetics of ligand exchange between the palladium complexes and the growth medium could influence bacterial response.

Metal-Organic Frameworks and Their Biodegradable Composites for Controlled Delivery of Antimicrobial Drugs

Antimicrobial resistance (AMR) is a growing global crisis with an increasing number of untreatable or exceedingly difficult-to-treat bacterial infections, due to their growing resistance to existing drugs. It is predicted that AMR will be the leading cause of death by 2050. In addition to ongoing efforts on preventive strategies and infection control, there is ongoing research towards the development of novel vaccines, antimicrobial agents, and optimised diagnostic practices to address AMR. However, developing new therapeutic agents and medicines can be a lengthy process. Therefore, there is a parallel ongoing worldwide effort to develop materials for optimised drug delivery to improve efficacy and minimise AMR. Examples of such materials include functionalisation of surfaces so that they can become self-disinfecting or non-fouling, and the development of nanoparticles with promising antimicrobial properties attributed to their ability to damage numerous essential components of pathogens. A relatively new class of materials, metal-organic frameworks (MOFs), is also being investigated for their ability to act as carriers of antimicrobial agents, because of their ultrahigh porosity and modular structures, which can be engineered to control the delivery mechanism of loaded drugs. Biodegradable polymers have also been found to show promising applications as antimicrobial carriers; and, recently, several studies have been reported on delivery of antimicrobial drugs using composites of MOF and biodegradable polymers. This review article reflects on MOFs and polymer-MOF composites, as carriers and delivery agents of antimicrobial drugs, that have been studied recently, and provides an overview of the state of the art in this highly topical area of research.

Advanced photocatalytic sterilization for recalcitrant Enterococcus sp. contaminated water by newly developed Z-scheme Bi2WO6 based composites under solar light

Pathogenic contamination is one of the major causes of clean water shortage, which poses great risk to human health. Herein, g-C₃N₄ (CN) was firstly introduced to Ag/Ag₂O/BiPO₄/Bi₂WO₆ (Ag/P/BWO) to construct a novel Z-scheme composite CN-Ag/P/BWO for disinfecting Enterococcus sp. contaminated water. CN-Ag/P/BWO showed excellent disinfection performance toward recalcitrant Enterococcus sp. under simulated solar light irradiation, achieving complete inactivation of 1.5 × 10⁷ cfu mL^-1 of bacterial cells only within 60 min, which was mainly attributed to the improved light absorption ability, charge carries separation/transfer efficiency and surface wettability. Additionally, the disinfection mechanism of CN-Ag/P/BWO toward Enterococcus sp. was systematically investigated. Photogenerated active species h⁺, ·OH and ·O₂^- worked together and played crucial roles in photocatalytic inactivation. The antioxidant system enabled Enterococcus sp. self-protection ability at the beginning of disinfection through secreting more antioxidant enzymes. However, with accumulation of active species, bacterial cell membrane and energy system were damaged, which further led to leakage of intracellular components and decomposition of bacteria. Besides, CN-Ag/P/BWO exhibited high practicability for different environmental factors and also performed well for real lake water disinfection. The high stability further confirmed its practicability for water disinfection. This work not only systematically revealed the disinfection mechanism toward Enterococcus sp., but also provided an efficient method for water disinfection.

The Study of Nanosized Silicate-Substituted Hydroxyapatites Co-Doped with Sr2+ and Zn2+ Ions Related to Their Influence on Biological Activities

Nanosized silicate-substituted hydroxyapatites, characterized by the general formula Ca_9.8-x-nSr_nZn_x(PO₄)_6-y(SiO₄)_y(OH)₂ (where: n = 0.2 [mol%]; x = 0.5-3.5 [mol%]; y = 4-5 [mol%]), co-doped with Zn²⁺ and Sr²⁺ ions, were synthesized with the help of a microwave-assisted hydrothermal technique. The structural properties were determined using XRD (X-ray powder diffraction) and Fourier-transformed infrared spectroscopy (FT-IR). The morphology, size and shape of biomaterials were detected using scanning electron microscopy techniques (SEM). The reference strains of Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa were used to assess bacterial survivability and the impact on biofilm formation in the presence of nanosilicate-substituted strontium-hydroxyapatites. Safety evaluation was also performed using the standard cytotoxicity test (MTT) and hemolysis assay. Moreover, the mutagenic potential of the materials was assessed (Ames test). The obtained results suggest the dose-dependent antibacterial activity of nanomaterials, especially observed for samples doped with 3.5 mol% Zn²⁺ ions. Moreover, the modification with five SiO₄ groups enhanced the antibacterial effect; however, a rise in the toxicity was observed as well. No harmful activity was detected in the hemolysis assay as well as in the mutagenic assay (Ames test).

Antimicrobial Resistance Challenged with Platinum(II) and Palladium(II) Complexes Containing 1,10-Phenanthroline and 5-Amino-1,3,4-Thiadiazole-2(3H)-Thione in Campylobacter jejuni

This work describes the synthesis and characterization of two metal complexes of the type [M(L1)2(phen)], where M = Pt2+ (complex I) or Pd2+ (complex II), L1 = 5-amino-1,3,4-thiadiazole-2(3H)-thiolate and phen = 1,10-phenanthroline. The in vitro antibacterial activity of these complexes was investigated in isolation and synergistically with ciprofloxacin (CIP) and erythromycin (ERY) in three strains of Campylobacter jejuni (MIC = 32 mg/L for CIP and ERY), selected from a bank of 235 strains representative of three poultry exporting states of the country (A, B and C), previously analyzed for epidemiology and resistance to CIP and ERY. A total of 53/235 (22.55%) strains showed co-resistance to CIP and ERY. Isolated resistance to CIP was higher than to ERY. Epidemiological analysis showed that resistance to CIP was more evident in state B (p < 0.0001), as well as a higher susceptibility to ERY in state C (p = 0.0028). Co-resistance was expressive in state A and in the spring and fall seasons. The evaluation of I alone and in synergy with CIP and ERY found values up to 0.25 mg/L not significant for ERY. Complex II did not show an antimicrobial effect on the three strains of tested C. jejuni. The effect provided by complex I represents a promising alternative for control of resistant strains of C. jejuni.

Amoxicillin encapsulated in the N-2-hydroxypropyl trimethyl ammonium chloride chitosan and N,O-carboxymethyl chitosan nanoparticles: Preparation, characterization, and antibacterial activity

This is a report on the encapsulation amoxicillin (AMX) in the N-2-Hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC) and N,O-carboxymethyl chitosan (CMCS) nanoparticles (NPs) for biomedical applications. The N-2-HACC/CMCS NPs have broad-spectrum antibacterial properties. In order to achieve sustained and slow drug release, improve drug transport efficiency and bioavailability, prolong drug residence time, and reduce pollution, we synthesized highly efficient, easily absorbed and rapidly degradable nano-formulation veterinary antibiotics in this study. The N-2-HACC/CMCS NPs were used for the encapsulation of AMX, and the cytocompatibility, in vitro release, in vivo drug release kinetics and antimicrobial activity of N-2-HACC/CMCS/AMX NPs were investigated. The NPs displayed a round shape and smooth surface, and the NPs allowed the sustained release of AMX at a much slower rate than that of non-coated AMX. The NPs exhibited excellent cytocompatibility and the antimicrobial activity against Escherichia coli, Acinetobacter baumannii, Streptococcus pneumoniae and Staphylococcus aureus. Moreover, the NPs could store at 4 °C, -20 °C and 25 ± 5 °C for 30 d. These results suggested that the N-2-HACC/CMCS NPs could be availed as a candidate for drug delivery carrier to achieve sustained and slow release, improve bioavailability, prolong residence time at the target site, and reduce the dosage of drug.

Effect of Cu Modified Textile Structures on Antibacterial and Antiviral Protection

Textile structures with various bioactive and functional properties are used in many areas of medicine, special clothing, interior textiles, technical goods, etc. We investigated the effect of two different textile woven structures made of 90% polyester with 10% polyamide (PET) and 100% cotton (CO) modified by magnetron sputtering with copper (Cu) on bioactive properties against Gram-positive and Gram-negative bacteria and four viruses and also on the some comfort parameters. PET/Cu and CO/Cu fabrics have strong antibacterial activity against Staphylococcus aureus and Klebsiella pneumonia. CO/Cu fabric has good antiviral activity in relation to vaccinia virus (VACV), herpes simplex virus type 1 (HSV-1) and influenza A virus H1N1 (IFV), while its antiviral activity against mouse coronavirus (MHV) is weak. PET/Cu fabric showed weak antiviral activity against HSV-1 and MHV. Both modified fabrics showed no significant toxicity in comparison to the control medium and pristine fabrics. After Cu sputtering, fabric surfaces became hydrophobic and the value of the surface free energy was over four times lower than for pristine fabrics. The modification improved thermal conductivity and thermal diffusivity, facilitated water vapour transport, and air permeability did not decrease.

Novel Fusidic Acid Cream Containing Metal Ions and Natural Products against Multidrug-Resistant Bacteria

Background: Drug design and development to overcome antimicrobial resistance continues to be an area of research due to the evolution of microbial resistance mechanisms and the necessity for new treatments. Natural products have been used since the dawn of medicine to heal skin infections. The antimicrobial properties of fusidic acid, zinc sulfate, and copper sulfate have been studied and are well known. Furthermore, these compounds have different mechanisms of action in targeting microorganisms, either by inhibiting protein synthesis or bacterial cell walls. Therefore, their combination is expected to have synergistic activity in killing bacteria. However, the synergistic antimicrobial activity has not been evaluated in a cream formulation. Therefore, the objectives of this in vitro study were to develop and evaluate the synergistic efficacy of fusidic acid in combinations with natural products, including oleuropein, thyme oil, zinc sulfate, and copper sulfate, as a cream to eradicate fusidic-acid-resistant microorganisms in skin infections. Methods: Three different cream formulations were developed, compared, and labeled F1, F2, and F3. The compounds were studied for their antibacterial activity. In addition, the stability of the cream was investigated at 25 °C and 40 °C in plastic jars over three months. Results: The F2 formula has adequate physicochemical properties. Furthermore, it displays stable and better results than the marketed trade product and has potential inhibition zones (ZOI). Interestingly, considerable numbers (9.5%) of fusidic-acid-resistant Staphylococcus aureus (FRSA) isolates possessed a high resistance pattern with MIC ≥ 128 μg/mL. In contrast, most tested FRSA isolates (90.5%) had a low resistance pattern with MIC ≤ 8 μg/mL. Conclusion: In conclusion, the F2 cream made with fusidic acid, oleuropein, thyme oil, zinc sulfate, and copper sulfate in the right amounts has stable physical and chemical properties and has potential against FRSA as an antimicrobial agent.

Gallium containing calcium phosphates: potential antibacterial agents or fictitious truth

Amidst an ever-increasing demand for the enhancement of the lifestyle and the modulation of modern diseases, the functionalization of biomaterials is of utmost importance. One of the leading materials for the aforementioned purpose have been calcium phosphates (CaPs). They have been widely used in bone regeneration displaying favourable regenerative potential and biological properties. Many studies have placed their entire focus on facilitating the osteogenic differentiation of stem cells and bone progenitor cells, while the aspect of antibacterial properties has been surmounted. Nevertheless, increasing antibiotic resistance of bacteria requires the development of new materials and the usage of alternative approaches such as ion doping. Gallium (Ga) has been the potential star on the rise among the ions. However, the obstacle that accompanies gallium is the scarcity of research performed and the variety of amalgamations. The question that imposes itself is how a growing field of therapeutics can be further entwined with advances in material science, and how will the incorporation of gallium bring a new outlook. The present study offers a comprehensive overview of state-of-the-art gallium containing calcium phosphates (GaCaPs), their synthesis methods, antibacterial properties, and biocompatibility. Considering their vast potential as antibacterial agents, the need for a methodical perspective is highly necessary to determine if it is a direction on the brink of recognition or a fruitless endeavour. STATEMENT OF SIGNIFICANCE: : Although several studies have been published on various metal ions-containing calcium phosphates, to this date there is no systematic overview pointing out the properties and benefits of gallium containing calcium phosphates. Here we offer a critical overview, including synthesis, structure and biological properties of gallium containing calcium phosphates.

Metal nanoparticles functionalized with nutraceutical Kaempferitrin from edible Crotalaria juncea, exert potent antimicrobial and antibiofilm effects against Methicillin-resistant Staphylococcus aureus

Kaempferitrin (KF), a flavonol glycoside, was isolated from the edible plant Crotalaria juncea. Optimization for the synthesis of silver (AgNPs) and copper (CuNPs) nanoparticles using C. juncea extract and kaempferitrin were attempted for the first time. A detailed study on size and stability analysis have been reported. Efficacy of KF@AgNPs and KF@CuNPs against biofilm formation and planktonic mode of growth on methicillin-resistant Staphylococcus aureus (MRSA) along with possible mechanisms has been explored. Release of Cu(II) upon prolonged treatment with KF@CuNPs in the presence of MRSA was quantified through Alizarin red test, indicating the antibacterial effect is initiated by the CuNPs itself. Time kill curve depicted both the NPs have similar kill kinetics to curtail the pathogen and imaging with Crystal violet assay, Fluorescent live dead imaging and SEM analysis revealed a 60% reduction in biofilm formation at the Sub-MIC concentration of KF@AgNPs and KF@CuNPs. Furthermore, the membrane permeability and cell surface hydrophobicity were altered in the presence of both the NPs. The colony count from the in vivo infection zebrafish model in the treatment group showed a decline of > 1.8 fold for KF@AgNPs and > two fold for KF@CuNPs. Toxicity studies did not reveal any abnormality in liver and brain enzyme levels. Liver morphology images show no severe cytological alterations when treated with KF@AgNPs and were almost similar to the normal liver. Thus, KF@AgNPs was nontoxic and caused significant reduction in biofilm formation in MRSA, also reduced bacterial bioburden in the infected zebrafish, which has the potential to be explored in higher animal models.

Field and Laboratory Assessment of a New Electrolytic Point-of-Use Water Treatment Technology

This research creates and implements a new electrolytic point-of-use water treatment (POUWT) device. Device development began by applying two voltages common to commercially available batteries to an apparatus with either two silver or copper wires submerged into synthetic groundwater. The effects of wire diameter, ionic strength of groundwater, and other POUWT parameters on metallic ion release were analyzed. We determined that the silver wire apparatus need only to be run for 2 min at 9 V to yield the target 50 µg/L concentration for water treatment. The 50 µg/L silver yielded up to a 5-log reduction in E. coli bacteria. The copper wire apparatus was excluded in prototype fabrication because it required 62 min to release the target 500 µg/L for disinfection when nine volts were applied to the system and was less effective in disinfection than silver wires. The electrolytic prototype was evaluated in 20 households in Limpopo, South Africa, over a four-week period. The device achieved a 2-log reduction in total coliform bacteria in household drinking water, which is comparable to the field performance of other POUWT devices in low-resource settings. The device also consistently released enough silver sufficient for disinfection while remaining below the WHO drinking water guideline.

Insights into the Antibacterial Activity of Prolactin-Inducible Protein against the Standard and Environmental MDR Bacterial Strains

Background: Prolactin inducible protein (PIP) is a small secretary glycoprotein present in most biological fluids and contributes to various cellular functions, including cell growth, fertility, antitumor, and antifungal activities. Objectives: The present study evaluated the antibacterial activities of recombinant PIP against multiple broad-spectrum MDR bacterial strains. Methods: The PIP gene was cloned, expressed and purified using affinity chromatography. Disk diffusion, broth microdilution, and growth kinetic assays were used to determine the antibacterial activities of PIP. Results: Disk diffusion assay showed that PIP has a minimum and maximum zone of inhibition against E. coli and P. aeruginosa, respectively, compared to the reference drug ampicillin. Furthermore, growth kinetics studies also suggested that PIP significantly inhibited the growth of E. coli and P. aeruginosa. The minimum inhibitory concentration of PIP was 32 µg/mL for E. coli (443), a standard bacterial strain, and 64 µg/mL for Bacillus sp. (LG1), an environmental multidrug-resistant (MDR) strain. The synergistic studies of PIP with ampicillin showed better efficacies towards selected bacterial strains having MDR properties. Conclusion: Our findings suggest that PIP has a broad range of antibacterial activities with important implications in alleviating MDR problems.

Scalable Hybrid Antibacterial Surfaces: TiO2 Nanoparticles with Black Silicon

With the increase of drug resistance, there is a need for surface coatings that inhibit microbes without antibiotics. Nanostructured photocatalysts, like TiO₂-coated nanotubes, are promising alternatives to antibiotics. Nanostructures rupture the cell wall by impaling the bacteria. Photocatalysts generate reactive oxygen species (ROS) in the presence of light, which oxidize organic matter. The combined effect of photocatalysts and nanostructures is better than the addition of individual components, as nanostructures also enhance the ROS production by trapping light. The synergetic effect is remarkably effective in reducing the growth of bacterial colonies, but scalability still remains a challenge. Conventional techniques like atomic layer deposition (ALD) are excellent for proof of concept but are not scalable to hundreds of square meters, as needed for practical applications. This report demonstrates two scalable and cost-effective techniques for synthesizing photocatalytic nanostructures: spray- and spin-coating TiO₂ nanoparticles. Unlike ALD, spray- and spin-coated TiO₂ nanoparticles do not reduce the roughness of a structured surface, which improves antibacterial performance by 23%. Integration of nanostructures with spray-coated TiO₂ is potentially a low-cost and scalable technology for large-area antibacterial surfaces.

Gemini-Mediated Self-Disinfecting Surfaces to Address the Contact Transmission of Infectious Diseases

According to both the Center for Disease Control and the World Health Organization, contact transmission is the primary transmission route of infectious diseases worldwide. Usually, this is mitigated by a schedule of repeated regular sanitization, yet surfaces are easily re-contaminated in the interim between cleanings. One solution to this problem is to generate self-disinfecting surfaces that can display sustained virucidal/antimicrobial properties against pathogens that settle upon them. Quaternary ammonium organosilicon compounds are ideal candidates to achieve this; cationic surfactants are safe and well-established surface disinfectants, while organosilanes are used broadly to form durable coatings with altered surface properties on many different materials. Despite their potential to circumvent the disadvantages of traditional disinfection methods, extant commercially available quaternary ammonium silanes do not display comparable efficacy to the standard surface disinfectants, nor have their respective coatings been demonstrated to meet the Environmental Protection Agency's guidelines for residual/extended efficacy. Inspired by the powerful surface activity of double-headed "gemini" surfactants, here, we present gemini-diquaternary silanes (GQs) with robust residual germicidal efficacy on various surfaces by incorporating a second cationic "head" to the structure of a conventional monoquaternary ammonium silane (MQ). Aqueous solutions of GQs were tested in suspension- and surface-antimicrobial assays against an array of pathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). GQ performance was benchmarked against the common disinfectants, ethanol, hydrogen peroxide, hypochlorite, as well as MQ. Solutions of GQs were efficacious when used for immediate disinfection (>10⁶-fold reduction in 15 s). Additionally, GQs were demonstrated to impart durable self-disinfecting properties to a variety of porous and nonporous surfaces, effective after repeated cycles of abrasion and repeated contaminations, and with superior coating ability and activity (>10⁸ higher activity) than that of MQs. GQs as surface treatments show great promise to overcome the limitations of traditional disinfectants in preventing the spread of infectious diseases.

The Enclosed Intestinal Microbiome: Semiochemical Signals from the Precambrian and Their Disruption by Heavy Metal Pollution

It is increasingly likely that many non-communicable diseases of humans and associated animals are due to the degradation of their intestinal microbiomes, a situation often referred to as dysbiosis. An analysis of the resultant diseases offers an opportunity to probe the function of these microbial partners of multicellular animals. In our view, it now seems likely that vertebrate animals and their microbiomes have coevolved throughout the Ediacaran–Cambrian transition and beyond, operating by semiochemical messaging between the multicellular host and its microbial community guest. A consideration of the overall role of the mutualistic intestinal microbiome as an enclosed bioreactor throws up a variety of challenging concepts. In particular: the significance of the microbiome with respect to the immune system suggests that microeukaryotes could act as microbial sentinel cells; the ubiquity of bacteriophage viruses implies the rapid turnover of microbial composition by a viral-shunt mechanism; and high microbial diversity is needed to ensure that horizontal gene transfer allows valuable genetic functions to be expressed. We have previously postulated that microbes of sufficient diversity must be transferred from mother to infant by seemingly accidental contamination during the process of natural birth. We termed this maternal microbial inheritance and suggested that it operates alongside parental genetic inheritance to modify gene expression. In this way, the adjustment of the neonate immune system by the microbiome may represent one of the ways in which the genome of a vertebrate animal interacts with its microbial environment. The absence of such critical functions in the neonate may help to explain the observation of persistent immune-system problems in affected adults. Equally, granted that the survival of the guest microbiome depends on the viability of its host, one function of microbiome-generated semiochemicals could be to facilitate the movement of food through the digestive tract, effectively partitioning nutrition between host and guest. In the event of famine, downregulation of microbial growth and therefore of semiochemical production would allow all available food to be consumed by the host. Although it is often thought that non-communicable diseases, such as type 2 diabetes, are caused by consumption of food containing insufficient dietary fibre, our hypothesis suggests that poor-quality food is not the prime cause but that the tendency for disease follows the degradation of the intestinal microbiome, when fat build-up occurs because the relevant semiochemicals can no longer be produced. It is the purpose of this paper to highlight the possibility that the origins of the microbiome lie in the Precambrian and that the disconnection of body and microbiome gives rise to non-communicable disease through the loss of semiochemical signalling. We further surmise that this disconnect has been largely brought about by heavy metal poisoning, potentially illuminating a facet of the exposome, the sum total of environmental insults that influence the expression of the genetic inheritance of an animal.

Biocides as Biomedicines against Foodborne Pathogenic Bacteria

Biocides are currently considered the first line of defense against foodborne pathogens in hospitals or food processing facilities due to the versatility and efficiency of their chemical active ingredients. Understanding the biological mechanisms responsible for their increased efficiency, especially when used against foodborne pathogens on contaminated surfaces and materials, represents an essential first step in the implementation of efficient strategies for disinfection as choosing an unsuitable product can lead to antibiocide resistance or antibiotic–biocide cross-resistance. This review describes these biological mechanisms for the most common foodborne pathogens and focuses mainly on the antipathogen effect, highlighting the latest developments based on in vitro and in vivo studies. We focus on biocides with inhibitory effects against foodborne bacteria (e.g., Escherichia spp., Klebsiella spp., Staphylococcus spp., Listeria spp., Campylobacter spp.), aiming to understand their biological mechanisms of action by looking at the most recent scientific evidence in the field.

Attenuation of Enterococcus faecalis biofilm formation by Rhodethrin: A combinatorial study with an antibiotic

The nosocomial pathogen Enterococcus faecalis critically implicated in the hospital environment. Its major virulence attributes biofilm formation and antibiotic resistance. The novel therapeutics are required to inhibit E. faecalis biofilm formation and virulence. Thus combinatorial and drug repurposing has been promising approaches to tackling biofilm-associated infections. Here, we have used a bacterium that produced indole terpenoid Rhodethrin (Rdn) with a combination of known antibiotic chloramphenicol (Chpl) against E. faecalis (ATCC 19433). The fractional inhibitory concentration index (FICI) values showed between 0.25 and 0.33 synergistic activities. The exopolysaccharides (EPSs) production significant decrease with Rdn (34.6 ± 4.6%), Chpl (31.0 ± 5.2%), and combination (Rdn-Chpl) (76.0 ± 4.5%) (p > 0.05). However, the biofilm interruption can attenuate of total biofilm was shown with Rdn (39.7 ± 5.1%), Chpl (32.6 ± 4.7%), and Rdn-Chpl (69.0 ± 5.3%), (p > 0.05). The microscopic observations reveal that the gradually unstructured biofilm architecture in E. faecalis. Furthermore, in silico, studies on biofilm-associated proteins (GelE, LuxS), virulence regulating (SprE), and cell division (FtsZ) have resulted in high and reasonable binding affinity, respectively. Thus, our results suggested that the synergism of Rdn-Chpl has the potential to function as a combinatorial antibiotic accelerates in treating vancomycin-resistant Enterococcus faecalis infections.

Heteroleptic pincer palladium(II) complex coated orthopedic implants impede the AbaI/AbaR quorum sensing system and biofilm development by Acinetobacter baumannii

Implant-associated infections mediated by Acinetobacter baumannii biofilms have become a major concern in the healthcare sector. As biofilm formation by this important pathogen is mediated by quorum sensing, quorum sensing inhibitors (QSI) have gained much attention. The present study confirms that novel thiazolinyl-picolinamide based palladium(II) complexes had good biofilm disruptive and QSI properties against A. baumannii. Key QS-mediated virulence factors like pili mediated surface motility and polysaccharide production were inhibited by the best Pd(II) complex (E). This also showed potent inhibitory activity against both the standard and clinical strains of A. baumannii. Molecular docking analysis also proved the potent binding affinity of Pd(II)-E with the virulence targets. The Pd(II) complex also disrupted preformed biofilms and down-regulated the expression of QS mediated virulence genes in the biofilms established on implant material (titanium plates). As a whole, the present study showed that the novel thiazolinyl-picolinamide based Pd(II) complexes offer a promising anti-infective strategy to combat biofilm-mediated implant infections.

Using nano technology for imparting PET/C blended fabric new functional performance properties

This article, discuss the effect of finishing polyester/cotton blended fabric (PET/C) with alkali and Titanium dioxide nanoparticles (TiO2 NPs) simultaneously. The treatment conditions such as NaOH and TiO2 NPs concentrations, reaction temperature and duration will be investigated. The effect of addition NPs on alkaline treatment conditions will prove through weight loss and carboxylic content. The ability of PET/C fabrics for loading with NPs during alkaline treatment was investigated by using SEM, EDX, and FTIR measurements. The effect of finishing of PET/C blended fabric with the suggested method on antimicrobial activity and ultraviolet protection was investigated. The simultaneous finishing of PET/C blended fabrics with alkali and TiO2 NPs showed excellent ultraviolet protection and high antimicrobial activity against Gram-positive ( Bacillus mycoides), Gram-negative ( Escherichia coli), and nonfilamentous fungus ( Candida albicans). The functional performance imparted to PET/C fabrics by the suggested approach are durable in repeated laundering processes, even after five Launder-Ometer washes.

Newly synthesized palladium(II) complexes with aminothiazole derivatives: in vitro study of antimicrobial activity and antitumor activity on the human prostate cancer cell line

Five new complexes of the palladium(II) ion (C1-C5) having the general formula [(PdL₂)]Cl₂ with some 2-aminothiazoles (L1-L5), where L1 = 2-amino-4-(3,4-difluorophenyl)thiazole, L2 = 2-amino-5-methyl-4-phenylthiazole, L3 = 2-amino-4-phenylthiazole, L4 = 2-amino-4-(4-chlorophenyl)thiazole, and L5 = 2-amino-4-(2,4-difluorophenyl)thiazole, have been synthesized and characterized by elemental microanalysis and infrared, ¹H NMR and ¹³C NMR spectroscopy. The in vitro antimicrobial activity of the five ligands and the corresponding Pd(II) complexes is investigated. Testing is performed by the microdilution method and the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) have been determined. Testing is conducted against 11 microorganisms (nine strains of pathogenic bacteria and two yeast species). The tested ligands and palladium(II) complexes show selective, high and moderate activity. There is a difference in antimicrobial activity between the ligands and the corresponding palladium(II) complexes. The complexes have significant anti-staphylococcal activity and activity on Pseudomonas aeruginosa which is better than the positive control. The interactions of newly synthesized palladium(II) complexes with calf thymus DNA (CT-DNA) were investigated using UV-Vis absorption and fluorescence spectroscopy. Analysis of UV-absorption and fluorescence spectra indicates the formation of a complex between the palladium(II) complexes and DNA. The high values of intrinsic binding constants, K_b, of the order 10⁴ M^-1 and Stern-Volmer quenching constants, K_SV, of the order 10⁵ M^-1 indicated very good binding of all complexes to CT-DNA. Also, the new Pd(II) complexes show high cytotoxic activity towards the human prostate cancer cell line and insignificant activity towards non-cancerous human fibroblasts. Future research could additionally explore the biological activity of Pd(II) complexes presented in this paper and investigate the possibility of their implementation in clinical practice.

Liquid metal polymer composite: Flexible, conductive, biocompatible, and antimicrobial scaffold

Gallium and its alloys, such as eutectic gallium indium alloy (EGaIn), a form of liquid metal, have recently attracted the attention of researchers due to their low toxicity and electrical and thermal conductivity for biomedical application. However, further research is required to harness EGaIn-composites advantages and address their application as a biomedical scaffold. In this research, EGaIn-polylactic acid/polycaprolactone composites with and without a second conductive filler, MXene, were prepared and characterized. The addition of MXene, into the EGaIn-composite, can improve the composite's electrochemical properties by connecting the liquid metal droplets resulting in electrically conductive continuous pathways within the polymeric matrix. The results showed that the composite with 50% EGaIn and 4% MXene, displayed optimal electrochemical properties and enhanced mechanical and radiopacity properties. Furthermore, the composite showed good biocompatibility, examined through interactions with fibroblast cells, and antibacterial properties against methicillin-resistant Staphylococcus aureus. Therefore, the liquid metal (EGaIn) polymer composite with MXene provides a first proof-of-concept engineering scaffold strategy with low toxicity, functional electrochemical properties, and promising antimicrobial properties.

Current approaches for the exploration of antimicrobial activities of nanoparticles

Infectious diseases of bacterial and viral origins contribute to substantial mortality worldwide. Collaborative efforts have been underway between academia and the industry to develop technologies for a more effective treatment for such diseases. Due to their utility in various industrial applications, nanoparticles (NPs) offer promising potential as antimicrobial agents against bacterial and viral infections. NPs have been established to possess potent antimicrobial activities against various types of pathogens due to their unique characteristics and cell-damaging ability through several mechanisms. The recently accepted antimicrobial mechanisms possessed by NPs include metal ion release, oxidative stress induction, and non-oxidative mechanisms. Another merit of NPs lies in the low likelihood of the development of microbial tolerance towards NPs, given the multiple simultaneous mechanisms of action against the pathogens targeting numerous gene mutations in these pathogens. Moreover, NPs provide a fascinating opportunity to curb microbial growth before infections: this outstanding feature has led to their utilization as active antimicrobial agents in different industrial applications, e.g. the coating of medical devices, incorporation in food packaging, promoting wound healing and encapsulation with other potential materials for wastewater treatment. This review discusses the progress and achievements in the antimicrobial applications of NPs, factors contributing to their actions, mechanisms underlying their efficiency, and risks of their applications, including the antimicrobial action of metal nanoclusters (NCs). The review concludes with a discussion of the restrictions on present studies and future prospects of nanotechnology-based NPs development.

Hemostatic materials in wound care

Blood plays an essential role in the human body. Hemorrhage is a critical cause of both military and civilian casualties. The human body has its own hemostatic mechanism that involves complex processes and has limited capacity. However, in emergency situations such as battlefields and hospitals, when the hemostatic mechanism of the human body itself cannot stop bleeding effectively, hemostatic materials are needed for saving lives. In this review, the hemostatic mechanisms and performance of the most commonly used hemostatic materials, (including fibrin, collagen, zeolite, gelatin, alginate, chitosan, cellulose and cyanoacrylate) and the commercial wound dressings based on these materials, will be discussed. These materials may have limitations, such as poor tissue adhesion, risk of infection and exothermic reactions, that may lessen their hemostatic efficacy and cause secondary injuries. High-performance hemostatic materials, therefore, have been designed and developed to improve hemostatic efficiency in clinical use. In this review, hemostatic materials with advanced performances, such as antibacterial capacity, superhydrophobicity/superhydrophilicity, superelasticity, high porosity and/or biomimicry, will be introduced. Future prospects of hemostatic materials will also be discussed in this review.

Diversity of metal and antibiotic resistance genes in Enterococcus spp. from the last century reflects multiple pollution and genetic exchange among phyla from overlapping ecosystems

Arsenic (As), mercury (Hg), and copper (Cu) are among the major historical and contemporary metal pollutants linked to global anthropogenic activities. Enterococcus have been considered indicators of fecal pollution and antibiotic resistance for years, but its largely underexplored metallome precludes understanding their role as metal pollution bioindicators as well. Our goal was to determine the occurrence, diversity, and phenotypes associated with known acquired genes/operons conferring tolerance to As, Hg or Cu among Enterococcus and to identify their genetic context (381 field isolates from diverse epidemiological and genetic backgrounds; 3547 enterococcal genomes available in databases representing a time span during 1900-2019). Genes conferring tolerance to As (arsA), Hg (merA) or Cu (tcrB) were used as biomarkers of widespread metal tolerance operons. Different variants of metal tolerance (MeT) genes (13 arsA, 6 merA, 1 tcrB) were more commonly recovered from the food-chain (arsA, tcrB) or humans (merA), and were shared with 49 other bacterial taxa. Comparative genomics analysis revealed that MeT genes occurred in heterogeneous operons, at least since the 1900s, with an increasing accretion of antibiotic resistance genes since the 1960's, reflecting diverse antimicrobial pollution. Multiple MeT genes were co-located on the chromosome or conjugative plasmids flanked by elements with high potential for recombination, often along with antibiotic resistance genes. Phenotypic analysis of some isolates carrying MeT genes revealed up to 128× fold increase in the minimum inhibitory concentrations to metals. The main distribution of functional MeT genes among Enterococcus faecium and Enterococcus faecalis from different sources, time spans, and clonal lineages, and their ability to acquire diverse genes from multiple taxa bacterial communities places these species as good candidates to be used as model organisms in future projects aiming at the identification and quantification of bioindicators of metal polluted environments by anthropogenic activities.

Whole-genome analysis of Klebsiella pneumoniae from bovine mastitis milk in the U.S

Dairy cattle mastitis has long been one of the most common and costly diseases in the dairy industry worldwide, due to its significant impact on milk production and animal welfare. Among all mastitis causing bacterial pathogens, Klebsiella pneumoniae causes the largest milk loss. To better understand the genomic features of this population, 180 K. pneumoniae strains isolated from dairy cattle mastitis milk in 11 U.S. states were sequenced. The phylogenetic analysis classified all mastitis-causing K. pneumoniae into two major phylogroups, with exclusive predominance in phylogroup KpI. Analysis of more than 61 sequence types, 51 capsular types and 12 lipopolysaccharide O-antigen types revealed great genomic diversity of this K. pneumoniae population. Approximately 100 gene units in accessory genomes were detected with significantly higher prevalence in bovine mastitis strains, compared to human-sourced or dairy environmental strains. The most notable genes were identified associated with ferric citrate uptake, lactose fermentation and resistance to heavy metals. The acquired antimicrobial resistance genes were identified in sporadic mastitis strains. This comprehensive genomic epidemiological study provides insights for a better understanding of the virulence of mastitis-causing K. pneumoniae strains and may lead to the development of novel diagnostic tools and preventive strategies.

Ionic gold demonstrates antimicrobial activity against Pseudomonas aeruginosa strains due to cellular ultrastructure damage

Due to the ever-increasing rise of antimicrobial resistant (AMR) bacteria, the development of alternative antimicrobial agents is a global priority. The antimicrobial activity of ionic gold was explored against four Pseudomonas aeruginosa strains with different AMR profiles in order to determine the antimicrobial activity of ionic gold and elucidate the mechanisms of action. Disc diffusion assays (zone of inhibition: ZoI) coupled with minimum inhibitory/bactericidal concentrations (MIC/MBC) were conducted to determine the antimicrobial efficacy of ionic gold. Scanning electron microscopy (SEM) was used to visualise morphological changes to the bacterial cell ultrastructure. Strains with increased AMR were slower to grow which is likely a fitness cost due to the enhanced AMR activity. Although greater concentrations of ionic gold were required to promote antimicrobial activity, ionic gold demonstrated similar antimicrobial values against all strains tested. Lowry assay results indicated that protein leakage was apparent following incubation with ionic gold, whilst SEM revealed cellular ultrastructure damage. This study suggests that the application of ionic gold as an alternative antimicrobial is promising, particularly against AMR P. aeruginosa. The antimicrobial activity of ionic gold against P. aeruginosa could potentially be utilised as an alternative therapeutic option in wound management, an approach that could benefit healthcare systems worldwide.

Observation of synergistic antibacterial properties of prodigiosin from Serratia marcescens jx-1 with metal ions in clinical isolates of Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a major global health problem, and novel and effective antimicrobial drugs are urgently required to combat this life-threatening pathogen. Prodigiosin (PG) is a bacterial secondary metabolite with excellent anticancer and antibacterial properties. However, little is known about the antibacterial function of PG against MRSA. Therefore, the antibacterial efficacy of PG alone and PG in combination with different metal ions against clinic isolates of MRSA and methicillin-sensitive S. aureus (MSSA) strain was evaluated in the present study. The minimum inhibitory concentration of PG against both MRSA and MSSA was 0.25 μg/mL. However, 0.1 μg/mL PG showed a stronger inhibitory effect on MSSA cell growth (47.12%) than on MRSA cell growth (35.87%). Surprisingly, we observed a significant difference (p < 0.01) in membrane integrity between PG-treated MRSA and MSSA using the propidium iodide staining assay. Further, we found that in combination with PG, Zn²⁺, Al³⁺, and Cu²⁺ showed synergistic antibacterial effects against MRSA and MSSA. Our results could increase the current knowledge regarding the efficacy of PG in inhibiting the growth of different types of S. aureus clinical isolates and also offer a novel strategy for developing efficient antibacterial agents.

The antimicrobial activity of silver acetate against Acinetobacter baumannii in a Galleria mellonella infection model

Background

The increasing prevalence of bacterial infections that are resistant to antibiotic treatment has caused the scientific and medical communities to look for alternate remedies aimed at prevention and treatment. In addition to researching novel antimicrobials, there has also been much interest in revisiting some of the earliest therapies used by man. One such antimicrobial is silver; its use stretches back to the ancient Greeks but interest in its medicinal properties has increased in recent years due to the rise in antibiotic resistance. Currently antimicrobial silver is found in everything from lunch boxes to medical device implants. Though much is claimed about the antimicrobial efficacy of silver salts the research in this area is mixed.

Methods

Herein we investigated the efficacy of silver acetate against a carbapenem resistant strain of Acinetobacter baumannii to determine the in vitro activity of this silver salt against a World Health Organisation designated category I critical pathogen. Furthermore, we use the Galleria mellonella larvae model to assess toxicity of the compound and its efficacy in treating infections in a live host.

Results

We found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival. This demonstrates the selective toxicity of silver acetate for bacterial pathogens but also highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment.

Emerging Concern for Silver Nanoparticle Resistance in Acinetobacter baumannii and Other Bacteria

The misuse of antibiotics combined with a lack of newly developed ones is the main contributors to the current antibiotic resistance crisis. There is a dire need for new and alternative antibacterial options and nanotechnology could be a solution. Metal-based nanoparticles, particularly silver nanoparticles (NAg), have garnered widespread popularity due to their unique physicochemical properties and broad-spectrum antibacterial activity. Consequently, NAg has seen extensive incorporation in many types of products across the healthcare and consumer market. Despite clear evidence of the strong antibacterial efficacy of NAg, studies have raised concerns over the development of silver-resistant bacteria. Resistance to cationic silver (Ag+) has been recognised for many years, but it has recently been found that bacterial resistance to NAg is also possible. It is also understood that exposure of bacteria to toxic heavy metals like silver can induce the emergence of antibiotic resistance through the process of co-selection. Acinetobacter baumannii is a Gram-negative coccobacillus and opportunistic nosocomial bacterial pathogen. It was recently listed as the "number one" critical level priority pathogen because of the significant rise of antibiotic resistance in this species. NAg has proven bactericidal activity towards A. baumannii, even against strains that display multi-drug resistance. However, despite ample evidence of heavy metal (including silver; Ag+) resistance in this bacterium, combined with reports of heavy metal-driven co-selection of antibiotic resistance, little research has been dedicated to assessing the potential for NAg resistance development in A. baumannii. This is worrisome, as the increasingly indiscriminate use of NAg could promote the development of silver resistance in this species, like what has occurred with antibiotics.

Microbial Biofilms in the Food Industry-A Comprehensive Review

Biofilms, present as microorganisms and surviving on surfaces, can increase food cross-contamination, leading to changes in the food industry’s cleaning and disinfection dynamics. Biofilm is an association of microorganisms that is irreversibly linked with a surface, contained in an extracellular polymeric substance matrix, which poses a formidable challenge for food industries. To avoid biofilms from forming, and to eliminate them from reversible attachment and irreversible stages, where attached microorganisms improve surface adhesion, a strong disinfectant is required to eliminate bacterial attachments. This review paper tackles biofilm problems from all perspectives, including biofilm-forming pathogens in the food industry, disinfectant resistance of biofilm, and identification methods. As biofilms are largely responsible for food spoilage and outbreaks, they are also considered responsible for damage to food processing equipment. Hence the need to gain good knowledge about all of the factors favouring their development or growth, such as the attachment surface, food matrix components, environmental conditions, the bacterial cells involved, and electrostatic charging of surfaces. Overall, this review study shows the real threat of biofilms in the food industry due to the resistance of disinfectants and the mechanisms developed for their survival, including the intercellular signalling system, the cyclic nucleotide second messenger, and biofilm-associated proteins.

Antimicrobial Properties of the Ag, Cu Nanoparticle System

Microbes, including bacteria and fungi, easily form stable biofilms on many surfaces. Such biofilms have high resistance to antibiotics, and cause nosocomial and postoperative infections. The antimicrobial and antiviral behaviors of Ag and Cu nanoparticles (NPs) are well known, and possible mechanisms for their actions, such as released ions, reactive oxygen species (ROS), contact killing, the immunostimulatory effect, and others have been proposed. Ag and Cu NPs, and their derivative NPs, have different antimicrobial capacities and cytotoxicities. Factors, such as size, shape and surface treatment, influence their antimicrobial activities. The biomedical application of antimicrobial Ag and Cu NPs involves coating onto substrates, including textiles, polymers, ceramics, and metals. Because Ag and Cu are immiscible, synthetic AgCu nanoalloys have different microstructures, which impact their antimicrobial effects. When mixed, the combination of Ag and Cu NPs act synergistically, offering substantially enhanced antimicrobial behavior. However, when alloyed in Ag-Cu NPs, the antimicrobial behavior is even more enhanced. The reason for this enhancement is unclear. Here, we discuss these results and the possible behavior mechanisms that underlie them.

Trimetallic Nanoparticles: Greener Synthesis and Their Applications

Nanoparticles (NPs) and multifunctional nano-sized materials have significant applications in diverse fields, namely catalysis, sensors, optics, solar energy conversion, cancer therapy/diagnosis, and bioimaging. Trimetallic NPs have found unique catalytic, active food packaging, biomedical, antimicrobial, and sensing applications; they preserve an ever-superior level of catalytic activities and selectivity compared to monometallic and bimetallic nanomaterials. Due to these important applications, a variety of preparation routes, including hydrothermal, microemulsion, selective catalytic reduction, co-precipitation, and microwave-assisted methodologies have been reported for the syntheses of these nanomaterials. As the fabrication of nanomaterials using physicochemical methods often have hazardous and toxic impacts on the environment, there is a vital need to design innovative and well-organized eco-friendly, sustainable, and greener synthetic protocols for their assembly, by applying safer, renewable, and inexpensive materials. In this review, noteworthy recent advancements relating to the applications of trimetallic NPs and nanocomposites comprising these NPs are underscored as well as their eco-friendly and sustainable synthetic preparative options.

Au, Pd and maghemite nanofunctionalized hydroxyapatite scaffolds for bone regeneration

Nanotechnology plays a key role in the development of innovative scaffolds for bone tissue engineering (BTE) allowing the incorporation of nanomaterials able to improve cell proliferation and differentiation. In this study, Mg-HA-Coll type I scaffolds (Mg-HA-based scaffolds) were nanofunctionalized with gold nanorods (Au NRs), palladium nanoparticles (Pd NPs) and maghemite nanoparticles (MAG NPs). Nanofunctionalized Mg-HA-based scaffolds (NF-HA-Ss) were tested for their ability to promote both the proliferation and the differentiation of adipose-derived mesenchymal stem cells (hADSCs). Results clearly highlight that MAG nanofunctionalization substantially improves cell proliferation up to 70% compared with the control (Mg-HA-based scaffold), whereas both Au NRs and Pd NPs nanofunctionalization induce a cell growth inhibition of 94% and 89%, respectively. Similar evidences were found for the osteoinductive properties showing relevant calcium deposits (25% higher than the control) for MAG nanofunctionalization, while a decreasing of cell differentiation (20% lower than the control) for both Au NRs and Pd NPs derivatization. These results are in agreement with previous studies that found cytotoxic effects for both Pd NPs and Au NRs. The excellent improvement of both osteoconductivity and osteoinductivity of the MAG NF-HA-S could be attributed to the high intrinsic magnetic field of superparamagnetic MAG NPs. These findings may pave the way for the development of innovative nanostructured scaffolds for BTE.

Copper-Polyurethane Composite Materials: Particle Size Effect on the Physical-Chemical and Antibacterial Properties

In this work, thermoplastic polyurethane (TPU) composites incorporated with 1.0 wt% Cu particles were synthesized by the melt blending method. The effect of the incorporated copper particle size on the antibacterial, thermal, rheological, and mechanical properties of TPU was investigated. The obtained results showed that (i) the addition of copper particles increased the thermal and mechanical properties because they acted as co-stabilizers of polyurethane (PU) (ii) copper nanoparticles decreased the viscosity of composite melts, and (iii) microparticles > 0.5 µm had a tendency to easily increase the maximum torque and formation of agglomerates. SEM micrographics showed that a good mixture between TPU and copper particles was obtained by the extrusion process. Additionally, copper-TPU composite materials effectively inhibited the growth of the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus. Considering that the natural concentration of copper in the blood is in the range of 0.7-0.12 mg/L and that the total migration value of copper particles from TPU was 1000 times lower, the results suggested that TPU nanocomposites could be adequately employed for biomedical applications without a risk of contamination.

Bismuth Nanoantibiotics Display Anticandidal Activity and Disrupt the Biofilm and Cell Morphology of the Emergent Pathogenic Yeast Candida auris

Candida auris is an emergent multidrug-resistant pathogenic yeast, which forms biofilms resistant to antifungals, sanitizing procedures, and harsh environmental conditions. Antimicrobial nanomaterials represent an alternative to reduce the spread of pathogens-including yeasts-regardless of their drug-resistant profile. Here we have assessed the antimicrobial activity of easy-to-synthesize bismuth nanoparticles (BiNPs) against the emergent multidrug-resistant yeast Candida auris, under both planktonic and biofilm growing conditions. Additionally, we have examined the effect of these BiNPs on cell morphology and biofilm structure. Under planktonic conditions, BiNPs MIC values ranged from 1 to 4 µg mL-1 against multiple C. auris strains tested, including representatives of all different clades. Regarding the inhibition of biofilm formation, the calculated BiNPs IC50 values ranged from 5.1 to 113.1 µg mL-1. Scanning electron microscopy (SEM) observations indicated that BiNPs disrupted the C. auris cell morphology and the structure of the biofilms. In conclusion, BiNPs displayed strong antifungal activity against all strains of C. auris under planktonic conditions, but moderate activity against biofilm growth. BiNPs may potentially contribute to reducing the spread of C. auris strains at healthcare facilities, as sanitizers and future potential treatments. More research on the antimicrobial activity of BiNPs is warranted.