Broad-spectrum Antimicrobial Agents Research Articles

Effect of Triclosan and Silver Nanoparticles on DNA Damage Investigated with DNA-Based Biosensor.

Triclosan (TCS) is a broad-spectrum antimicrobial agent widely used in personal care, healthcare, and clinical practice. One of the most important aspects of toxicological profiling of compounds is their interaction with DNA. In human cells, TCS causes a significant reduction in DNA methylation. The involvement of TCS in chromosomal aberrations, DNA damage, and strand breaks, as well as DNA damage from TCS degradation products, was reported. AgNPs share similarities with TCS in terms of antimicrobial properties, enter the body after exposure, and are used even together with TCS in oral care products. Therefore, their mutual effect on the DNA is of interest. In this study, the electrochemical behavior of TCS on a glassy carbon electrode (GCE) and the biosensor with salmon sperm dsDNA (DNA/GCE), DNA damage by TCS present in phosphate buffer solution pH 7.4 and an additional effect of the immobilized AgNP layer on such DNA damage have been investigated. Two different sizes of AgNPs (about 15 and 37 nm) were tested. Using square-wave voltammetric signals of nucleobases, the portion of survived DNA was 64% in the presence of 15 nm AgNPs compared to 55% in its absence. The protective effect of AgNPs on DNA against TCS-induced DNA damage was found.

Triclosan: A Small Molecule with Controversial Roles.

Triclosan (TCS), a broad-spectrum antimicrobial agent, has been widely used in personal care products, medical products, plastic cutting boards, and food storage containers. Colgate Total® toothpaste, containing 10 mM TCS, is effective in controlling biofilm formation and maintaining gingival health. Given its broad usage, TCS is present ubiquitously in the environment. Given its strong lipophilicity and accumulation ability in organisms, it is potentially harmful to biohealth. Several reports suggest the toxicity of this compound, which is inserted in the class of endocrine disrupting chemicals (EDCs). In September 2016, TCS was banned by the U.S. Food and Drug Administration (FDA) and the European Union in soap products. Despite these problems, its application in personal care products within certain limits is still allowed. Today, it is still unclear whether TCS is truly toxic to mammals and the adverse effects of continuous, long-term, and low concentration exposure remain unknown. Indeed, some recent reports suggest the use of TCS as a repositioned drug for cancer treatment and cutaneous leishmaniasis. In this scenario it is necessary to investigate the advantages and disadvantages of TCS, to understand whether its use is advisable or not. This review intends to highlight the pros and cons that are associated with the use of TCS in humans.

Novel macrolide-lincosamide-streptogramin B resistance gene erm(54) in MRSA ST398 from Germany.

Macrolides are important broad-spectrum antimicrobial agents in human and veterinary medicine. Macrolide resistance genes are often located on mobile genetic elements (MGEs) in staphylococci, which can be horizontally transferred across strain, species or genus boundaries.1 The erm genes encode 23S rRNA methylases, which confer combined resistance to macrolide, lincosamide and streptogramin B (MLS) compounds by adding one or two methyl groups to the adenine A2058 in the 23S rRNA.1,2 Livestock-associated MRSA (LA-MRSA) are often multiresistant and mainly associated with ST398 in many parts of the world.3 They have their main reservoir in food-producing animals and, therefore, represent a considerable health risk for humans, especially for those having frequent contact with livestock.3 Macrolides are commonly used to treat bacterial infections in livestock and, consequently, different erm genes, including erm(A), erm(B), erm(C) and erm(T), have so far been detected on MGEs among LA-MRSA ST398.1,4,5 LA-MRSA ST398 isolate 3860 was obtained from the nasal swab of a pig suffering from respiratory disease in the German National Resistance Monitoring programme GERM-Vet in 2007. WGS on Illumina MiSeq and PacBio Sequel II platforms, followed by hybrid assembly and consecutive sequence analysis, revealed the presence of a novel erm gene, designated erm(54) by the Nomenclature Center for MLS Resistance Genes (https://faculty.washington.edu/marilynr), on the non-conjugative 36 929 bp plasmid pHKS3860 (GenBank accession number OM362497) (Figure 1a). Upstream of the erm(54) gene, a regulatory region, known as translational attenuator, was identified. This regulatory region was more complex compared with the corresponding regions of other known staphylococcal erm genes.1,6,7 Besides an open reading frame for a 30 amino acid (aa) regulatory peptide, seven pairs of inverted repeats (IRs), IR1a,b to IR7a,b, were detected. A putative stable mRNA secondary structure formed by the IR sequences was identified, in which the IR7b sequence, which covered in part the erm(54)-associated ribosome binding site and the start of the erm(54) gene, was freely accessible to ribosomes and thereby allowed the translation of the erm(54) transcript.6 Screening for inducible macrolide/lincosamide resistance by agar disc diffusion8 using erythromycin (15 μg), clindamycin (2 μg) and pirlimycin (2 μg) discs confirmed the constitutive expression of erm(54).

Studies on the Transmission of a Tigecycline Resistance-Mediating tet(A) Gene Variant from Enterobacter hormaechei via a Two-Step Recombination Process.

ABSTRACTTo investigate the contribution of a tet(A) variant to tigecycline resistance in Enterobacter hormaechei and the recombination events that occurred during transmission of this variant. MICs were determined by broth microdilution. E. hormaechei G17 was characterized by PCR, transfer assay, S1-PFGE, Southern blot hybridization, and WGS analysis. A tet(A) variant conferring resistance to tigecycline was present in E. hormaechei G17. This strain harbored two resistance plasmids (pG17-1, 264,084 bp and pG17-2, 68,610 bp) and its E. coli transformant Tm-G17TGC one resistance plasmid (pTm-G17, 93,013 bp). The comparative analysis of pG17-1, pG17-2, and pTm-G17 showed that a tet(A) variant-carrying multiresistance gene cluster (~23 kb) originating from pG17-1 had integrated into pG17-2, forming the novel plasmid pTm-G17. In a first step, this multiresistance gene cluster was excised from pG17-1 by recombination of homologous sequences, including △TnAs1 at both termini, thereby generating an unconventional circularizable structure (UCS). In a second step, this UCS integrated into pG17-2 via recombination between homologous sequences, including IS26 present on both, the UCS and pG17-2, thereby giving rise to the new plasmid pTm-G17. In summary, a tet(A) variant conferring resistance to tigecycline was reported in E. hormaechei. Transfer of a tet(A) variant-carrying multiresistance gene cluster between plasmids occurred in a two-step recombination process, in which homologous sequences, including either △TnAs1 or IS26, were involved.IMPORTANCE Tigecycline is an important last-resort broad spectrum antimicrobial agent. This study describes the two-step recombination processes resulting in the transfer of the tet(A) variant gene between different plasmids in E. hormaechei, which depicts the role of recombination processes in the generation of UCSs and new plasmids, both carrying a tet(A) variant conferring resistance to tigecycline. Such processes enhance the dissemination of resistance genes, which is of particular relevance for resistance genes, such as the tet(A) variant. The presence and transmission of a tet(A) variant in E. hormaechei will compromise the efficacy of tigecycline treatment for E. hormaechei associated infection.

In vitro activities of N-acetyl cysteine and levofloxacin as a catheter lock therapy against catheter-associated infections.

Since management of catheter-associated infections, which are generally biofilm-based, is attempted in certain patients such as older and frail patients by using a catheter lock solution (CLS), we examined the combination of N-acetyl cysteine (NAC), an antibiofilm agent, and levofloxacin, a broad-spectrum antimicrobial agent, for this purpose. Intravascular catheters were colonized with methicillin-resistant Staphylococcus epidermidis, levofloxacin-sensitive/methicillin-resistant Staph. aureus, levofloxacin-resistant/methicillin-resistant Staph. aureus, vancomycin-resistant Enterococcus, Escherichia coli, Klebsiella pneumoniae or Pseudomonas aeruginosa and treated with a CLS containing normal saline, NAC, levofloxacin or NAC plus levofloxacin (NACLEV) and then cultured to assess their antimicrobial activities. We also examined antibiofilm and antimicrobial activities of each CLS by scanning electron microscopy (SEM) and the mechanical integrity of catheters exposed to CLS. Treatment of colonized catheters with NACLEV-CLS significantly reduced colonization (p<0.005) against all pathogens. SEM images also indicate reduction in colonization with NACLEV-CLS with considerable reduction in both visible bacteria and the associated biofilm. Mean tensile strength of catheters exposed to CLS was not significantly different compared to controls (p>0.05). These in vitro results suggest that NACLEV-CLS can significantly reduce all bacterial colonization and potentially help salvage infected catheters without affecting the catheter's mechanical integrity. This study presents a novel CLS with a broad spectrum of antimicrobial activity against catheter-associated infections, particularly in long-term catheters.

Gold Nanoparticles as Antimicrobial Agents: A Mini-Review

Metal nanoparticles, such as gold nanoparticles, have abundant unusual chemical and physical properties owing to the effects of their quantum size and their large surface area, in comparison with other metal atoms. Gold nanoparticles (AuNPs), in particular, are becoming increasingly popular due to their biocompatibility, multifunctional and aqueous solubility. Many scientific reports described the important antimicrobial properties possessed by the gold nanoparticles. Therefore, the present mini-review summarizes an overview of gold nanoparticles as broad spectrum antimicrobial agents for biomedical applications.

Inhibitory effects of reuterin on biofilm formation, quorum sensing and virulence genes of Clostridium perfringens

Clostridium perfringens (C. perfringens) have been considered as one of the most common causes of human and veterinary gastrointestinal diseases. Reuterin is a broad-spectrum antimicrobial agent produced by certain Lactobacillus reuteri (L. reuteri) strains. The present study showed that bioconversion reuterin from isolated probiotic L. reuteri (LR) 21 strain significantly inhibited bacterial growth and downregulated expression of virulence genes (p < 0.05). The DCFH-DA staining assays exhibited ROS are essential mediators of reuterin bactericidal activity. Reuterin at subinhibitory dose also inhibited Cp 13124 biofilm formation, which is probably owing its inhibitory effects on bacterial mobility. Besides, the interaction of Cp 13124 and LR 21 was investigated during co-cultures with or without glycerol. LR 21 combined with in situ reuterin production can induce more reductions (p < 0.05) in medium pH, cellular number, and alpha toxin production of Cp 13124 than that using probiotic LR 21 alone. In summary, this study showed great potential of reuterin as natural antibacterial and antibiofilm agent to address the contamination and infection caused by Cp 13124 and highlighted the positive effects of glycerol for L. reuteri strains to reduce C. perfringens infection.

Nitric Oxide-Releasing Lock Solution for the Prevention of Catheter-Related Infection and Thrombosis.

Although frequently used, venous catheters are often associated with serious complications such as infection and thrombosis. Lock solution therapies are clinically used to deter these issues but generally address only infection or thrombosis with limited success. Here, we report the development of a dual-functional lock therapy using nitric oxide (NO) donor molecule, S-nitrosoglutathione (GSNO). NO is a potent, broad-spectrum antimicrobial agent that also temporarily inhibits platelet activation, preventing thrombosis. Furthermore, NO has antibiofilm actions, an ability that traditional antibiotic lock solutions lack, thus limiting their efficacy. In this work, different concentrations of GSNO were characterized via NO analysis to determine a range of NO-releasing lock solution (NOreLS) concentrations to investigate and to demonstrate prolonged potential efficacy. Tested against clinically used vancomycin and gentamicin lock solutions, GSNO-based NOreLS repeatedly outperformed in models of different stages of catheter infections. NOreLS also prevented clot formation when exposed to whole blood, showing increased efficacy compared to a heparin lock solution. Moreover, NOreLS was demonstrated to be biocompatible via hemolysis and cytotoxicity assays. NOreLS has excellent potential for safely and effectively preventing infection and thrombosis related to catheter usage.

Broad-Spectrum Antimicrobial ZnMintPc Encapsulated in Magnetic-Nanocomposites with Graphene Oxide/MWCNTs Based on Bimodal Action of Photodynamic and Photothermal Effects.

Microbial diseases have been declared one of the main threats to humanity, which is why, in recent years, great interest has been generated in the development of nanocomposites with antimicrobial capacity. The present work studied two magnetic nanocomposites based on graphene oxide (GO) and multiwall carbon nanotubes (MWCNTs). The synthesis of these magnetic nanocomposites consisted of three phases: first, the synthesis of iron magnetic nanoparticles (MNPs), second, the adsorption of the photosensitizer menthol-Zinc phthalocyanine (ZnMintPc) into MWCNTs and GO, and the third phase, encapsulation in poly (N-vinylcaprolactam-co-poly(ethylene glycol diacrylate)) poly (VCL-co-PEGDA) polymer VCL/PEGDA a biocompatible hydrogel, to obtain the magnetic nanocomposites VCL/PEGDA-MNPs-MWCNTs-ZnMintPc and VCL/PEGDA-MNPs-GO-ZnMintPc. In vitro studies were carried out using Escherichia coli and Staphylococcus aureus bacteria and the Candida albicans yeast based on the Photodynamic/Photothermal (PTT/PDT) effect. This research describes the nanocomposites’ optical, morphological, magnetic, and photophysical characteristics and their application as antimicrobial agents. The antimicrobial effect of magnetics nanocomposites was evaluated based on the PDT/PTT effect. For this purpose, doses of 65 mW·cm−2 with 630 nm light were used. The VCL/PEGDA-MNPs-GO-ZnMintPc nanocomposite eliminated E. coli and S. aureus colonies, while the VCL/PEGDA-MNPs-MWCNTs-ZnMintPc nanocomposite was able to kill the three types of microorganisms. Consequently, the latter is considered a broad-spectrum antimicrobial agent in PDT and PTT.

Amphiphilic cyclic peptide [W4KR5]-Antibiotics combinations as broad-spectrum antimicrobial agents

Linear and cyclic amphiphilic peptides, (W4KR5) and [W4KR5], were evaluated as antibacterial agents against Gram-positive and Gram-negative bacteria, including four multi-drug resistant strains and the corresponding four non-resistant strains. Cyclic peptide [W4KR5] showed higher antibacterial activity than the linear (W4KR5) counterpart. Cyclic [W4KR5] was subjected to combination (physical mixture or covalent conjugation) with meropenem as a model antibiotic to study the impact of the combination on antimicrobial activity. A physical mixture of meropenem and [W4KR5] showed synergistic antibacterial activity against Gram-negative P. aeruginosa (ATCC BAA-1744) and P. aeruginosa (ATCC 27883) strains. [W4KR5] was further subjected to extensive antibacterial studies against additional 10 bacteria strains, showing significant antibacterial efficacy against Gram-positive bacteria strains. Combinations studies of [W4KR5] with an additional 9 commercially available antibiotics showed significant enhancement in antibacterial activity for all tested combinations, especially with tetracycline, tobramycin, levofloxacin, clindamycin, daptomycin, polymyxin, kanamycin, and vancomycin. Time-kill kinetics assay and flow cytometry results exhibited that [W4KR5] had a time-dependent synergistic effect and membrane disruption property. These data indicate that [W4KR5] improves the antibacterial activity, presumably by facilitating the internalization of antibiotics and their interaction with the intracellular targets. This study introduces a potential strategy for treating multidrug-resistant pathogens by combining [W4KR5] and a variety of classical antibiotics to improve the antibacterial effectiveness.

Bacterial and fungal co-infections with SARS-CoV-2 in solid organ recipients: a retrospective study

BackgroundSARS-CoV-2, a novel corona virus, has caused clusters of fatal pneumonia worldwide. Immune compromised patients are among the high risk groups with poor prognosis of the disease. The presence of bacterial or fungal co-infections with SARS-CoV-2 is associated with increased mortality.MethodsThe electronic data of the liver and kidney recipients, hospitalized in COVID-19 intensive care unit in an 8-month period in 2020 were retrospectively assessed. The documented bacterial or fungal infections alongside with outcome and risk factors were recorded and analyzed by binary logistic regression model and multivariate analyses.ResultsSixty-Six liver and kidney recipients with positive RT-PCR for SARS-CoV-2 were included this study. Twenty one percent of the patients had at least one episode of co-infection during their COVID-19 course. Bacterial and fungal co-infections contributed to a significantly higher mortality. Urine and sputum were the most common sites of pathogen isolation (45.45% and 36.36%; respectively). The majority of infections were caused by vancomycin- resistant Enterococci (30%). Escherichia coli stood in the next position with 23.3%. Prior hospitalization and high doses of corticosteroids were associated with co-infections (p < 0.001 and p = 0.02; respectively.)ConclusionsBacterial and fungal co-infections with COVID-19 are more prevalent in solid organ recipients compared to the general population. Prior hospitalizations and use of broad-spectrum antimicrobial agents lead to emergence of multi-drug resistant pathogens in this susceptible patient population. Early detection and treatment of co-infections as well as antibiotic stewardship is recommended in solid organ recipients.

Novel Biogenic Synthesis of a Ag@Biochar Nanocomposite as an Antimicrobial Agent and Photocatalyst for Methylene Blue Degradation.

The conventional synthesis of nanomaterials employing physical and chemical methods usually requires high cost and toxic chemicals. Thus, a facile, ecofriendly, cost-effective, novel, and sustainable route for the synthesis of a silver-loaded biochar nanocomposite (Ag@biochar) using Chenopodium ambrosioides leaf extract and biomass is reported for the first time in this study to advocate many of the principles of green chemistry such as safer solvents and auxiliaries. UV spectroscopic analysis at 420 nm indicated the formation of silver nanoparticles (AgNPs). The band gap energy of Ag@biochar was 1.9 eV, confirming its potential use as a photocatalyst. Ag@biochar was found to be photoluminescent at 425 nm. AgNPs on the surface of biochar were predominantly spherical with a size range of 25–35 nm and a surface area of 47.61 m2/g. A zeta potential of −5.87 mV designated the stability of Ag@biochar. Testing the photocatalytic potential of Ag@biochar to remove methylene blue from wastewater demonstrated its high removal efficiency that reached 88.4% due to its high efficiency of electron transfer confirmed via electrochemical impedance spectroscopy analysis and retained 70.65% after six cycles of reuse. Ag@biochar was shown to be a powerful broad-spectrum antimicrobial agent as it completely prevented the growth of Escherichia coli and also inhibited the growth of Pseudomonas aeruginosa, Klebsiella pneumoniae, Bacillus subtilis, and Candida albicans with the inhibition zones of 19, 18, 22, and 16 mm, respectively.

Inactivation of Polymicrobial Biofilms of Foodborne Pathogens Using Epsilon Poly-L-Lysin Conjugated Chitosan Nanoparticles.

A mixed culture (polymicrobial) biofilm provides a favorable environment for pathogens to persist in the food processing environment and to contaminate food products. Inactivation and eradication of such biofilms from food processing environments are achieved by using harsh disinfectants, but their toxicity and environmentally hostile characteristics are unsustainable. This study aims to use food-grade natural nanoparticulated antimicrobials to control mixed-culture biofilms. Chitosan, a natural broad-spectrum antimicrobial biopolymer (polysaccharide) from crustaceans, was derivatized to produce chitosan nanoparticles (ChNP) as a carrier for another broad-spectrum antimicrobial agent, ε-poly-L-lysine (PL), to synthesize ChNP-PL conjugate. The antimicrobial activity of ChNP and ChNP-PL was tested against mixed-culture biofilms. ChNP-PL (~100 nm) exhibited a synergistic antimicrobial and anti-biofilm effect against mono or mixed-culture biofilms of five foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. ChNP-PL treatment prevented biofilm formation by mono or mixed cultures of L. monocytogenes, P. aeruginosa, and E. coli O157:H7, and bacterial counts were either below the detection limit or caused 3.5–5 log reduction. ChNP-PL also inactivated preformed biofilms. In monoculture biofilm, ChNP-PL treatment reduced L. monocytogenes counts by 4.5 logs, S. Enteritidis by 2 logs, E. coli by 2 logs, and S. aureus by 0.5 logs, while ChNP-PL had no inhibitory effect on P. aeruginosa. In vitro mammalian cell-based cytotoxicity analysis confirmed ChNP-PL to have no deleterious effect on intestinal HCT-8 cell line. In conclusion, our results show ChNP-PL has strong potential to prevent the formation or inactivation of preformed polymicrobial biofilms of foodborne pathogens.

The Role of Topical Povidone-Iodine in the Management of Infectious Keratitis: A Pilot Study.

The aim of this prospective explorative study was to evaluate the safety and the effectiveness of topical polyvinylpyrrolidone-iodine (PVP-I) administered during the time-to-results period for pathogen identification and susceptibility testing in patients with infectious keratitis (IK). A corneal swab (CS) for antimicrobial evaluation was performed at enrollment (T0) and topical 0.66%-PVP-I was administered until the laboratory results were available (T1). Ulcer and infiltrate areas and infiltrate depths were compared between T0 and T1 (i.e., time-to-result period). Patients were then shifted to a specific antimicrobial therapy and followed up until resolution of their infiltrates (Tlast-TL). Twenty-five eyes were enrolled, and none showed clinical worsening leading to protocol withdrawal. At T1, ulcer and infiltrate areas showed significant improvement in Gram-positive IK (n = 13–52%; p = 0.027 and p = 0.019, respectively), remained stable in fungal IK (n = 5–20%; both p = 0.98) and increased in those with Gram-negative bacteria (n = 4–16%; p = 0.58 and p = 0.27). Eyes with negative cultures (n = 3–12%) showed complete resolution at T1 and did not initiate any additional antimicrobial therapy. The administration of 0.66% PVP-I during the time-to-result period seems to be a safe strategy in patients with IK while often sparing broad-spectrum antimicrobial agents. In addition, it showed to be effective in eyes with a Gram-positive bacterial infection.

Multicomponent Crystal of Trimethoprim and Citric Acid: Solid State Characterization and Dissolution Rate Studies

BACKGROUND: Trimethoprim is a broad spectrum antimicrobial agent with low solubility in water which causes low bioavailability in systemic circulation.&#x0D; AIM: The purpose of this study was to prepare multicomponent crystals of trimethoprim and citric acid to increase the solubility and dissolution rate of trimethoprim.&#x0D; MATERIALS AND METHODS: Multicomponent crystals were prepared by solvent evaporation method. Characterizations of multicomponent crystalline solid phase properties were carried out by powder X-ray diffraction (PXRD) analysis, differential scanning calorimetry (DSC), FT-IR spectroscopy, scanning electron microscopy (SEM). Solubility and dissolution rate tests were carried out in aqueous medium.&#x0D; RESULTS: The PXRD characterization results showed a new X-ray diffraction pattern in the multicomponent crystal phase. DSC analysis showed the formation of a new endothermic peak. This indicates the formation of a multicomponent crystal phase between trimethoprim and citric acid. The results of the SEM analysis indicate the formation of a new crystal habit. Solubility of multi-component crystal phase of trimethoprim increased 7 times compared to intact trimethoprim. The dissolution of trimethoprim and multicomponent crystals in 0.1 N HCl medium at 60 minutes was 56.36% and 95.57% and CO2-free distilled water medium was 43.03% and 88.26%, respectively.&#x0D; CONCLUSIONS: From the results of the study, it can be concluded that the multicomponent phase of trimethoprim crystals with citric acid successfully increase the solubility and dissolution rate of trimethoprim significantly.

Pharmacokinetic profiles of antifungal drugs during extracorporeal membrane oxygenation life support

Extracorporeal membrane oxygenation (ECMO), a kind of life support technology that can replace lung and heart function, is widely used in critical respiratory and circulatory exhaustion. Because of the serious diseases and the use of interventional catheters, patients receiving ECMO life support are often administrated with broad-spectrum antimicrobial agents, which increase the risk of fungal infection. Fungal infection during ECMO can increase mortality. How to effectively control fungal infection is a thorny problem faced by clinicians. During the treatment of ECMO, the patient's physiological status, ECMO oxygenation membrane, circulation pipeline and other factors may change the pharmacokinetic profiles of antifungal drugs, thereby affect the clinical efficacy of drugs. This artical reviews the pharmacokinetic characteristics of antifungal drugs during ECMO support, in order to provide references for clinical antifungal treatment.

Functional silver nanoparticles as broad-spectrum antimicrobial agents

Indole-functionalized silver nanoparticles were prepared by a simple one-pot method, which exhibited efficient antibacterial activity against Gram-positive and Gram-negative bacteria.

Effects of free radicals from doxycycline hyclate and minocycline hydrochloride under blue light irradiation on the deactivation of Staphylococcus aureus, including a methicillin-resistant strain

Doxycycline hyclate (DCH) and minocycline hydrochloride (MH) are tetracycline antibiotics and broad-spectrum antimicrobial agents. The changes in DCH and MH under blue light (λ=462nm) irradiation in alkaline conditions (BLIA) were investigated. Deactivation caused by superoxide anion radical (O2•-) and deactivation from DCH and MH during photolysis on Staphylococcus aureus (S. aureus), including methicillin-resistant S. aureus (MRSA), were studied. DCH is relatively unstable compared to MH under BLIA. The level of O2•- generated from the MH-treated photoreaction is lower than that from DCH photolysis, and the DCH-treated photoreaction is more efficient at inactivating S. aureus and MRSA at the same radiant intensity. DCH subjected to BLIA decreased the viability of S. aureus and MRSA by 3.84 and 5.15 log, respectively. Two photolytic products of DCH (PPDs) were generated under BLIA. The mass spectra of the PPDs featured molecular ions at m/z 460.8 and 458.8. The molecular formulas of the PPDs were C21H22N2O10 and C22H24N2O9, and their exact masses were 462.44 and 460.44g/mol, respectively. These results bolster the photolytic oxidation that leads to DCH-enhanced deactivation of S. aureus and MRSA. Photochemical treatment of DCH could be applied as a supplement in hygienic processes.

Synergistic actions of phytonutrient capped nanosilver as a novel broad-spectrum antimicrobial agent: unveiling the antibacterial effectiveness and bactericidal mechanism

Bactericidal action of cogon grass extract mediated AgNPs and LDI-MS analysis revealed the putative phytochemicals capped on the AgNP surface.

Synthesis of silver nanoparticles using Nigella sativa seed extract and its efficacy against some multidrug-resistant uropathogens

Background: Urinary tract infection (UTI) is one of the most chronic infections in humans, as well as the most common cause of multidrug-resistant (MDR) pathogen emergence, necessitating the quest for stringent antibiotic treatment. In the imperative search for effective drugs to combat MDR, silver nanoparticles (AgNPs) are given priority. The objective of this study was to synthesize, characterize, and evaluate the antimicrobial activity of AgNPs synthesized using Nigella sativa on MDR uropathogens. Methods: Urine samples of suspected UTI patients were collected using sterile sample bottles and cultured on different agar media to isolate and identify uropathogens using conventional method. All isolates were screened for multidrug resistance by disk diffusion method following the Clinical and Laboratory Standards Institute guideline with slight modification. N. sativa seed extract was used to synthesize AgNPs from aqueous solution of silver nitrate (AgNO3). AgNPs formed were characterized using ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscope (SEM), dynamic light scattering, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy (XRD). Antibacterial activities of synthesized AgNPs were assessed (in vitro) by disc diffusion method against MDR isolates, and cytotoxicity was evaluated using brine shrimp lethality assay. The formed AgNPs were characterized using UV-Vis, and antibacterial activity of synthesized AgNPs was assessed (in vitro) by impregnated disc diffusion method against MDR isolates. Results: Escherichia coli, Klebsiella sp., and Staphylococcus aureus were isolated. Multiple antibiotic-resistant indexes of the isolates ranged between 0.4 and 0.75 against the different standard antibiotics tested. The color change from pale yellow to dark brown was indicative of AgNP formation. UV-Vis spectrum of solution containing AgNPs exhibited peak wavelengths of 378 nm. Fourier transform infrared spectroscopic analysis showed that terpenoids, flavonoid, and phenols played an important role in the biosynthesis. Irregular shapes within nanoscale range were detected using SEM. XRD showed that the particles were crystalline in structure with an average size of 32 nm. The mean diameter zone of inhibition (in mm) for the different isolates at the dose of 100 μg/mL concentration showed maximum for E. coli (18 mm) followed by both Klebsiella sp. and S. aureus at 17 mm. Conclusion: The study underscores the efficacy of the plant-mediated nanoparticles as well as their potential for use as broad-spectrum antimicrobial agents for the management of MDR uropathogens.