Promising antibacterial agents against multidrug resistant Staphylococcus aureus

Synthesis, crystal structure and Hirshfeld surface analysis of bis-(acetyl-acetonato-κ2 O,O')(2-amino-1-methyl-1H-benzimidazole-κN 3)copper(II)

The title compound, [Cu(C5H7O2)2(C8H9N3)], crystallizes in the ortho-rhom-bic space group Pnma. In the crystal structure, the CuII ion is coordinated by two acetyl-acetonate ligands and one 2-amino-1-methyl-1H-benzimidazole ligand. The crystal structure features intra-molecular N-H⋯O and inter-molecular N-H⋯O hydrogen bonds, which contribute to the overall cohesion of the crystal. Hirshfeld surface analysis and two-dimensional fingerprint plots were utilized to qu-antify the inter-molecular inter-actions, revealing the relative contributions of H⋯H (61.1%), H⋯C/C⋯H (21.3%), and O⋯H/H⋯O (11.3%) contacts to the crystal packing.

Baicalin enhances antioxidant, inflammatory defense, and microbial diversity of yellow catfish (Pelteobagrus fulvidraco) infected with Aeromonas hydrophila

Introduction

The aim of this research was to clarify the mechanism through which baicalin exerts its inhibitory effects on Aeromonas hydrophila infection.

Methods

The antibacterial efficacy of baicalin was assessed by determining its minimum inhibitory concentration (MIC) against A. hydrophila. Various parameters, including the growth curve, cell wall integrity, biofilm formation, AKP content, and morphological alterations of A. hydrophila, were analyzed. In vivo experiments involved the administration of A. hydrophila 4 h postintraperitoneal injection of varying doses of baicalin to induce infection, with subsequent monitoring of mortality rates. After a 3 d period, liver, spleen, and intestinal tissues were harvested to evaluate organ indices, antioxidant and immune parameters, as well as intestinal microbial composition.

Results

The findings indicated that baicalin treatment resulted in the disruption of the cell wall of A. hydrophila, leading to the loss of its normal structural integrity. Furthermore, baicalin significantly inhibited biofilm formation and facilitated the release of intracellular proteins (P < 0.05). In vivo, baicalin enhanced the survival rates of yellow catfish infected with A. hydrophila. Compared to the control group, the liver index of yellow catfish was elevated, while the spleen and intestinal indices were reduced in the baicalin-treated group (P < 0.05). Additionally, baicalin at an appropriate dosage was found to increase levels of SOD, GSH, CAT, ACP, and AKP in yellow catfish (P < 0.05), while simultaneously decreasing MDA accumulation and the mRNA expression of inflammatory markers such as Keap1, IL1, IFN-γ, and TNF-α, (P < 0.05). Moreover, baicalin significantly enhanced the operational taxonomic unit (OTU) count in A. hydrophila-infected yellow catfish (P < 0.05), restoring the abundance of Barnesiellaceae, Enterobacteriaceae, Plesiomonas, and UBA1819 (P < 0.05).

Discussion

In summary, baicalin demonstrates the potential to improve the survival rate of yellow catfish subjected to A. hydrophila infection, augment antioxidant and immune responses, mitigate inflammation, and enhance intestinal microbial diversity.

Computational Screening of T-Muurolol for an Alternative Antibacterial Solution against Staphylococcus aureus Infections: An In Silico Approach for Phytochemical-Based Drug Discovery

Staphylococcus aureus infections present a significant threat to the global healthcare system. The increasing resistance to existing antibiotics and their limited efficacy underscores the urgent need to identify new antibacterial agents with low toxicity to effectively combat various S. aureus infections. Hence, in this study, we have screened T-muurolol for possible interactions with several S. aureus-specific bacterial proteins to establish its potential as an alternative antibacterial agent. Based on its binding affinity and interactions with amino acids, T-muurolol was identified as a potential inhibitor of S. aureus lipase, dihydrofolate reductase, penicillin-binding protein 2a, D-Ala:D-Ala ligase, and ribosome protection proteins tetracycline resistance determinant (RPP TetM), which indicates its potentiality against S. aureus and its multi-drug-resistant strains. Also, T-muurolol exhibited good antioxidant and anti-inflammatory activity by showing strong binding interactions with flavin adenine dinucleotide (FAD)-dependent nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase, and cyclooxygenase-2. Consequently, molecular dynamics (MD) simulation and recalculating binding free energies elucidated its binding interaction stability with targeted proteins. Furthermore, quantum chemical structure analysis based on density functional theory (DFT) depicted a higher energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital (EHOMO-LUMO) with a lower chemical potential index, and moderate electrophilicity suggests its chemical hardness and stability and less polarizability and reactivity. Additionally, pharmacological parameters based on ADMET, Lipinski's rules, and bioactivity score validated it as a promising drug candidate with high activity toward ion channel modulators, nuclear receptor ligands, and enzyme inhibitors. In conclusion, the current findings suggest T-muurolol as a promising alternative antibacterial agent that might be a potential phytochemical-based drug against S. aureus. This study also suggests further clinical research before human application.

In silico exploration of 4(α-l-rhamnosyloxy)-benzyl isothiocyanate: A promising phytochemical-based drug discovery approach for combating multi-drug resistant Staphylococcus aureus

Multidrug-resistant (MDR) Staphylococcus aureus infections significantly threaten global health. With rising resistance to current antibiotics and limited solutions, the urgent discovery of new, effective, and affordable antibacterials with low toxicity is imperative to combat diverse MDR S. aureus strains. Hence, in this study, we introduce an in silico phytochemical-based approach for discovering novel antibacterial agents, underscoring the potential of computational approaches in therapeutic discovery. Glucomoringin Isothiocyanate (GMG-ITC) from Moringa oleifera Lam. is one of the phytochemical compounds with several biological activities, including antimicrobial, anti-inflammatory, and antioxidant activities, and is also effective against S. aureus. This study focuses on screening GMG-ITC as a potential drug candidate to combat MDR S. aureus infections through a molecular docking approach. Moreover, interaction amino acid analysis, in silico pharmacokinetics, compound target prediction, pathway enrichment analysis and molecular dynamics (MD) simulations were conducted for further investigation. Molecular docking and interaction analysis showed strong binding affinity towards S. aureus lipase, dihydrofolate reductase, and other MDR S. aureus proteins, including penicillin-binding protein 2a, MepR, D-Ala:D-Ala ligase, and RPP TetM, through hydrophilic and hydrophobic interactions. GMG-ITC also showed a strong binding affinity to cyclooxygenase-2 and FAD-dependent NAD(P)H oxidase, suggesting that it is a potential anti-inflammatory and antioxidant candidate that may eliminate inflammation and oxidative stress associated with S. aureus infections. MD simulations validated the stability of the GMG-ITC molecular interactions determined by molecular docking. In silico pharmacokinetic analysis highlights its potency as a drug candidate, showing strong absorption, distribution, and excretion properties in combination with low toxicity. It acts as an active protease and enzyme inhibitor with moderate activity against GPCR ligands, ion channels, nuclear receptor ligands, and kinases. Enrichment analysis further elucidated its involvement in important biological, molecular, and cellular functions with potential therapeutic applications in diseases like cancer, hepatitis B, and influenza. Results suggest that GMG-ITC is an effective antibacterial agent that could treat MDR S. aureus-associated infections.

Synthesis and Antibacterial Evaluation of Novel Psoralen Derivatives against Methicillin-Resistant Staphylococcus aureus (MRSA)

Today, the bacterial infections caused by multidrug-resistant pathogens seriously threaten human health. Thereby, there is an urgent need to discover antibacterial drugs with novel mechanism. Here, novel psoralen derivatives had been designed and synthesized by a scaffold hopping strategy. Among these targeted twenty-five compounds, compound ZM631 showed the best antibacterial activity against methicillin-resistant S. aureus (MRSA) with the low MIC of 1 μg/mL which is 2-fold more active than that of the positive drug gepotidacin. Molecular docking study revealed that compound ZM631 fitted well in the active pockets of bacterial S. aureus DNA gyrase and formed a key hydrogen bond binding with the residue ASP-1083. These findings demonstrated that the psoralen scaffold could serve as an antibacterial lead compound for further drug development against multidrug-resistant bacterial infections.

Synergistic Inhibitions of Gram-Negative Bacteria by Combination Treatment with Ciprofloxacin and a Novel Glucolipid

Psychrophilic fungus Pseudogymnoascus sp. OUCMDZ-4032 derived from Antarctica was cultivated under 16 °C to produce a new glucolipid compound (1). Its structure was elucidated by analysis of detailed spectroscopic data, acid hydrolysis and 1-phenyl-3-methyl-5-pyrazolone precolumn derivatization, and 13C NMR quantum chemical calculations. Though compound 1 did not show inhibitory activity against bacteria, it can reduce the minimum inhibitory concentration (MIC) of ciprofloxacin against Gram-negative bacteria Pseudomonas aeruginosa, Escherichia coli, and Salmonella paratyphi by 1024, 256 and 256-fold. Compound 1 showed potential as a synergistically inhibiting adjuvant in co-administration with antibiotic to enhance antibacterial activities.

Antibiotic potentiating effect of Bauhinia purpurea L. against multidrug resistant Staphylococcus aureus

Bauhinia purpurea L. is a medium-sized tree from the family Fabaceae. The plant is traditionally used as medicine by different tribes in Sikkim. The present study aimed to evaluate the modulation in minimum inhibitory concentration (MIC) of the bark methanol extract of Bauhinia purpurea L. against the clinical isolates of multidrug resistant Staphylococcus aureus. The synergistic activity of the test plant extract with different classes of antibiotics was also evaluated. The methanol extract of Bauhinia purpurea exhibited modulation by a 16-fold reduction in the MIC of clindamycin against both resistant and susceptible isolates, followed by penicillin and gentamicin, whereas a maximum of only a 4-fold MIC reduction was observed with ciprofloxacin. The lowest minimum inhibitory concentration and minimum bactericidal concentration showed by the plant extract was 0.48 and 0.97 mg/mL, respectively. The methanol extract of Bauhinia purpurea exhibited synergistic activity with penicillin, gentamicin, ciprofloxacin, and clindamycin against most of the tested isolates of multidrug-resistant Staphylococcus aureus (MDR-SA). Gas chromatography-mass spectrometry analysis of Bauhinia purpurea L. bark methanol extract revealed 16 phytocompounds. The results provide an insight into the potential antibacterial property of the plant extract in terms of its antibiotic MIC modulation and synergistic properties with the selected antibiotics. This is the first report of the antibiotic potentiation property of Bauhinia purpurea L., collected from Sikkim, India.

Biological Activity and Sterilization Mechanism of Marine Fungi-derived Aromatic Butenolide Asperbutenolide A Against Staphylococcus aureus

Marine fungi represent a huge untapped resource of natural products. The bio-activity of a new asperbutenolide A from marine fungus Aspergillus terreus was not well known. In the present study, the minimum inhibitory concentration (MIC) and RNA-Sequencing were used to analyze the bio-activity and sterilization mechanism of asperbutenolide A against clinical pathogenic microbes. The results showed that the MICs of asperbutenolide A against methicillin-resistant Staphylococcus aureus (MRSA) were 4.0-8.0 μg/mL. The asperbutenolide A present poor bio-activity against with candida. The sterilization mechanism of asperbutenolide A against MRSA showed that there were 1426 differentially-expressed genes (DEGs) between the groups of MRSA treated with asperbutenolide A and negative control. Gene Ontology (GO) classification analysis indicated that the DEGs were mainly involved in cellular process, metabolic process, cellular anatomical entity, binding, catalytic activity, etc. Kyoto Encyclopedia of Genes and Genomes (KEGG) classification analysis showed that these DEGs were mainly enriched in amino acid metabolism, carbohydrate metabolism, membrane transport, etc. Moreover, qRT-PCR showed similar trends in the expressions of argF, ureA, glmS and opuCA with the RNA-Sequencing. These results indicated that asperbutenolide A was with ideal bio-activity against with MRSA and could be as a new antibacterial agent.

Can microplastics and disinfectant resistance genes pose conceivable threats to water disinfection process?

Microplastic pollution in the environment has aroused widespread concerns, however, the potential environmental risks caused by excessive use of disinfectants are still unknown. Disinfectants with doses below the threshold can enhance the communication of resistance genes in pathogenic microorganisms, promoting the development and spread of antimicrobial activity. Problematically, the intensification of microplastic pollution and the increase of disinfectant consumption will become a key driving force for the growth of disinfectant resistance bacteria (DRB) and disinfectant resistance genes (DRGs) in the environment. Disinfection plays a crucial role in ensuring water safety, however, the presence of microplastics and DRGs seriously disturb the water disinfection process. Microplastics can reduce the concentration of disinfectant in the local environment around microorganisms and improve their tolerance. Microorganisms can improve their resistance to disinfectants or generate resistance genes via phenotypic adaptation, gene mutations, and horizontal gene transfer. However, very limited information is available on the impact of DRB and DRGs on disinfection process. In this paper, the contribution of microplastics to the migration and transmission of DRGs was analyzed. The challenges posed by the presence of microplastics and DRGs on conventional disinfection were thoroughly discussed. The knowledge gaps faced by relevant current research and further research priorities have been proposed in order to provide a scientific basis in the future.

Molecular Characterization of spa, hld, fmhA, and lukD Genes and Computational Modeling the Multidrug Resistance of Staphylococcus Species through Callindra harrisii Silver Nanoparticles

The problem of multidrug resistance in bacterial pathogens is significant and is related to the high morbidity and death rates of living things due to increased levels of beta-lactamases. Plant-derived nanoparticles have gained a great significance in the field of science and technology to combat bacterial diseases, especially multidrug-resistant bacteria. This study examines the multidrug resistance and virulent genes of identified pathogenic Staphylococcus species obtained from Molecular Biotechnology and Bioinformatics Laboratory (MBBL), culture collection. The polymerase chain reaction-based characterization of Staphylococcus aureus and Staphylococcus argenteus having ON875315.1 and ON876003.1 accession IDs revealed the presence of the spa, LukD, fmhA, and hld genes. The green synthesis of silver nanoparticles (AgNPs) was carried out by utilizing the leaf extract of Calliandra harrisii, of which metabolites act as capping and reducing agents for the precursor of nano-synthesis, i.e., AgNO₃ of 0.25 M. The synthesized AgNPs were characterized via UV-vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis which inferred the bead-like shape of our nanoparticles with the size of 2.21 nm with the existence of aromatic and hydroxyl functional groups at surface plasmon resonance of 477 nm. The antimicrobial activity by AgNPs showed 20 mm inhibition of Staphylococcus species as compared to the vancomycin and cefoxitin antibiotics along with crude plant extract, which showed a minimum zone of inhibition. The synthesized AgNPs were also analyzed for various biological activities like anti-inflammatory with 99.15% inhibition in protein denaturation, antioxidant with 99.8% inhibition in free radical scavenging, antidiabetic with 90.56% inhibition of alpha amylase assay, and anti-haemolytic with 89.9% inhibition in cell lysis which shows good bioavailability and biocompatibility of the nanoparticles with the biological system of the living being. The amplified genes (spa, LukD, fmhA, and hld) were also analyzed for their interaction with AgNPs computationally at the molecular level. The 3-D structure of AgNP and amplified genes was retrieved from ChemSpider (ID: 22394) and Phyre2 online server, respectively. The binding affinities of AgNP with spa, LukD, fmhA, and hld were -7.16, -6.5, -6.45, and -3.3 kJ/mol, respectively, which infers a good docking score except of hld which is -3.3 kJ/mol due to its small size. The salient features of biosynthesized AgNPs proved to be an effective approach in combating the multidrug-resistant Staphylococcus species in the future.

Pyrimirhodomyrtone inhibits Staphylococcus aureus by affecting the activity of NagA

The epidemic of methicillin-resistant Staphylococcus aureus (MRSA) infections has created a critical health threat. The drug resistance of MRSA makes the development of drugs with new modes of action particularly urgent. In this study, we found that a natural product derivative pyrimirhodomyrtone (PRM) exerted antibacterial activity against S. aureus, including MRSA, both in vitro and in vivo. Genetic and biochemical studies revealed the interaction between PRM and N-acetylglucosamine-6-phosphate deacetylase (NagA) and the inhibitory effect of PRM on its deacetylation activity. We also found that PRM causes depolarization and destroys the integrity of the cell membrane. The elucidation of the antibacterial mechanism will inspire the subsequent development of new anti-MRSA drugs based on PRM.

Ultra-Small Silver Nanoparticles: A Sustainable Green Synthesis Approach for Antibacterial Activity

The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antibacterial properties using citrus peel residues (orange, lemon, and grapefruit) as reducing and stabilizing agents, and on assessing their antibacterial activity against multidrug-resistant clinical Staphylococcus aureus. The synthesized AgNPs were analyzed by various techniques, including UV-Vis spectroscopy, SAED, TEM, XRD, FTIR, and Raman. The results demonstrate the formation of ultra-small, monodisperse, quasi-spherical AgNPs with an average particle size of 2.42 nm for AgNPs produced with mixed extracts. XRD analysis indicated that the AgNPs have a crystal size of 9.71 to 16.23 nm. The AgNPs exhibited potent inhibitory activity against resistant S. aureus, with a minimum inhibitory concentration (MIC) of 15.625 to 62.50 ppm. The findings suggest that the ultra-small nanometer size of the AgNPs could be attributed to the synthesis method that employs ambient conditions and the presence of polyphenolic compounds from citrus peel. Consequently, AgNPs obtained through sustainable green synthesis hold significant potential in combating clinical multi-resistant bacterial strains that are challenging to treat and eradicate. This approach also contributes to the revaluation of citrus residues in the region, which is an ongoing environmental issue today.

Antimicrobial efficacy of a hemilabile Pt(II)-NHC compound against drug-resistant S. aureus and Enterococcus

Three platinum(II)-N-heterocyclic carbene (NHC) compounds [Pt(L¹)Cl](PF₆) (1), [Pt(L²)(COD)](PF₆)₂ (2) and [Pt(L²)Cl₂] (3) were synthesized bearing pyridyl-functionalized butenyl-tethered (L¹H) and n-butyl tethered (L²H) NHC ligands, and their antibacterial activity against clinically relevant human pathogens was evaluated. Complex 1 was designed to have one of its metal coordination sites masked with a hemilabile butenyl group. The antibacterial activity spectrum against the ESKAPE panel of pathogens shows superior activity of 1 compared to 2 and 3 against the Gram-positive S. aureus pathogen. Complex 1 showed equipotent activity against clinical drug-resistant S. aureus and Enterococcus isolates. Furthermore, 1 demonstrated concentration-dependent bactericidal activity with a long post-antibiotic effect, eradicated preformed S. aureus biofilm and synergized with gentamicin and minocycline for combinatorial antimicrobial therapy. Under in vivo conditions, 1 displayed potent activity in reducing bacterial load in a murine thigh infection model, similar to vancomycin, albeit at 2.5× less dosage. An array of experiments reveals key characteristics for the hemilabile complex 1 as a potential anti-staphylococcal drug.

Ternary system of sultamicillin tosylate with hydroxypropyl-β-cyclodextrin and L-arginine: susceptibility against methicillin-resistant Staphylococcus aureus

Aim: This study investigated the effect of complex formation between sultamicillin tosylate (ST), hydroxypropyl-β cyclodextrin (HP-βCD) and L-arginine (ARG). Materials & methods: The kneading method was used to prepare the complexes, which were then characterized using SEM, DSC, FT-IR, HPLC, saturation solubility and dissolution studies. The complexes' antibacterial activity against MRSA (ATCC^®-43300TM) was evaluated using ZOI and MIC. Results: Solubility was enhanced in the binary and ternary complexes compared with ST (p < 0.001). MIC and ZOI showed that both complexes have increased antibacterial activity compared with ST (p < 0.001) against MRSA. Conclusion: As a result, the inclusion complex of ST with HP-βCD and ARG can be used to improve the physicochemical properties of ST while also improving antibacterial efficacy against MRSA infections.

The 1,2,3-triazole 'all-in-one' ring system in drug discovery: a good bioisostere, a good pharmacophore, a good linker, and a versatile synthetic tool

INTRODUCTION

The 1,2,3-triazole ring occupies an important space in medicinal chemistry due to its unique structural properties, synthetic versatility and pharmacological potential making it a critical scaffold. Since it is readily available through click chemistry for creating compound collections against various diseases, it has become an emerging area of interest for medicinal chemists.

AREAS COVERED

This review article addresses the unique properties of the1,2,3-triazole nucleus as an intriguing ring system in drug discovery while focusing on the most recent medicinal chemistry strategies exploited for the design and development of 1,2,3-triazole analogs as inhibitors of various biological targets.

EXPERT OPINION

Evidently, the 1,2,3-triazole ring with unique structural features has enormous potential in drug design against various diseases as a pharmacophore, a bioisoster or a structural platform. The most recent evidence indicates that it may be more emerging in drug molecules in near future along with an increasing understanding of its prominent roles in drug structures. The synthetic feasibility and versatility of triazole chemistry make it certainly ideal for creating compound libraries for more constructive structure-activity relationship studies. However, more comparative and target-specific studies are needed to gain a deeper understanding of the roles of the 1,2,3-triazole ring in molecular recognition.[Figure: see text].

Mechanisms of high-level fosfomycin resistance in Staphylococcus aureus epidemic lineage ST5

Objectives

Fosfomycin resistance has become a clinical concern. In this study, we analysed the dynamic change of fosfomycin MIC in the epidemic Staphylococcus aureus lineages in a teaching hospital in Shanghai for 12 years and sought to elucidate the major underlying mechanisms.

Methods

MLST was conducted for 4580 S. aureus isolates recovered from 2008 to 2019. Fosfomycin MIC was determined by the agar dilution method. The genome data of 230 S. aureus epidemic lineage isolates were acquired from a next-generation sequencing (NGS) platform. Gene deletion and corresponding complementation mutants were constructed to confirm the mechanism of fosfomycin resistance.

Results

The predominant S. aureus lineages during the past 12 years were ST5 and ST239 (45.6%; 2090/4580). However, ST5 has been spreading clinically, while ST239 has gradually disappeared recently. Consistent with epidemic trends, fosfomycin-resistant ST5 increased from 19.5% to 67.3%. Most fosfomycin-resistant ST5 isolates (92.7%; 647/698) possessed high-level resistance (MIC > 1024 mg/L) with combined mutations mainly in glpT and uhpT. In contrast, fosfomycin-resistant ST239 isolates (76.8%; 149/194) mainly acquired low-level resistance (MIC = 64–128 mg/L) with mutation primarily in hptA. Deletion of a single resistant gene merely resulted in low-level fosfomycin resistance, while double-gene mutants ΔglpTΔuhpT, ΔglpTΔhptA and ΔglpTΔhptR acquired high-level fosfomycin resistance.

Conclusions

The high-level fosfomycin resistance of S. aureus epidemic lineage ST5 is mainly due to the accumulation of mutations in the resistant genes related to membrane transporter systems, and partly contributes to its persistent prevalence under clinical antibiotic pressure.

The antibacterial potential of ciprofloxacin hybrids against Staphylococcus aureus

Staphylococcus aureus (S. aureus), an important pathogen of both humans and animals, is able to cause a variety of infections at any site of the body. The evolution of S. aureus resistance is notorious, and the widespread of drug-resistant S. aureus, especially methicillin-resistant S. aureus (MRSA), has made the treatment difficult in recent decades. Nowadays, S. aureus is among the leading causes of bacterial infections, creating an urgent need for the development of novel antibacterial agents. Ciprofloxacin, characterized by high clinical efficacy, is a broad-spectrum antibacterial agent with frequency of prescription for various Gram-positive and Gram-negative pathogens, many of which are resistant to a wide range of antibiotics. However, the long-term and widespread use of this antibiotic has led to the emergence of ciprofloxacin-resistant pathogens, and ciprofloxacin-resistant S. aureus has been noted in clinical practice. Ciprofloxacin hybrids have been recognized as advanced chemical entities to simultaneously modulate multiple drug targets in bacteria, so ciprofloxacin hybrids have the potential to overcome drug resistance. The present review provides an overview of ciprofloxacin hybrids with anti-S. aureus potential that have been reported in the last decade with emphasis on their structure-activity relationships and mechanisms of action.

The antibacterial activity of natural-derived flavonoids

Flavonoids, a wide variety of phenolic secondary metabolites, are found in almost all plant families in the leaves, stems, roots, flowers, and seeds. Flavonoids could exert antibacterial activity via damaging the cytoplasmic membrane, inhibiting energy metabolism, and inhibiting the synthesis of nucleic acids, so flavonoids are considered constitutive antibacterial substances. This review aims to outline the recent advances of natural-derived flavonoids, including flavonoid glycosides with antibacterial potential to provide novel antibacterial lead hits/candidates, covering articles published between January 2016 and July 2021.

Total syntheses of ericifolione and its analogues via a biomimetic inverse-electron-demand Diels-Alder reaction

Driven by bioinspiration and appreciation of the structure of ericifolione, a biomimetic tautomerization/intermolecular inverse-electron-demand hetero Diels-Alder reaction cascade sequence promoted by sodium acetate to rapidly construct sterically hindered dihydropyran scaffolds was established, which allowed the first straightforward biomimetic total syntheses of ericifolione and its analogues with high simplicity. Moreover, this methodology set the stage for the preparation of relevant natural products or derivatives.

Bactericidal and antibiofilm properties of Rumex japonicus Houtt. on multidrug-resistant Staphylococcus aureus isolated from milk

Multidrug-resistant (MDR) Staphylococcus aureus and its biofilm formation have been challenging to control in milk and dairy industries. Biofilms formed by Staph. aureus may result in the failure of antibacterial agents and disinfectants to penetrate the biofilm in an attempt to control contamination. Novel natural antibacterial agents are required to combat MDR bacteria and biofilms. In this study, we evaluated the bactericidal, antibiofilm, and antimotility effects of Rumex japonicus Houtt. (RJH) extract on MDR Staph. aureus isolated from milk. The RJH extract exhibited good antibacterial activity against MDR strains with minimum inhibitory concentrations (MIC) ranging from 0.78 to 6.25 mg/mL and minimum bactericidal concentrations ranging from 3.125 to 12.5 mg/mL. The extract showed strong inhibition of biofilm formation (81.9%) at sub-MIC value and eradication of biofilm at higher concentrations. The motility of Staph. aureus was effectively blocked by the extract. Major compounds emodin, chrysophanol, and physcion were identified in RJH extract using HPLC-linear trap quadrupole (LTQ)/Orbitrap-mass spectrometry. The extract was nontoxic to human epithelial cell lines such as Caco-2 and HT-29 cell lines at concentrations ranging from 0.1 to 0.5 mg/mL, and from 0.1 to 0.75 mg/mL, respectively. These findings suggest that RJH extract could be an alternative to synthetic preservatives in milk and dairy products.

A review of the berberine natural polysaccharide nanostructures as potential anticancer and antibacterial agents

Despite the promising medicinal properties, berberine (BBR), due to its relatively poor solubility in plasma, low bio-stability and limited bioavailability is not used broadly in clinical stages. Due to these drawbacks, drug delivery systems (DDSs) based on nanoscale natural polysaccharides, are applied to address these concerns. Natural polymers are biodegradable, non-immunogenic, biocompatible, and non-toxic agents that are capable of trapping large amounts of hydrophobic compounds in relatively small volumes. The use of nanoscale natural polysaccharide improves the stability and pharmacokinetics of the small molecules and, consequently, increases the therapeutic effects and reduces the side effects of the small molecules. Therefore, this paper presents an overview of the different methods used for increasing the BBR solubility and bioavailability. Afterwards, the pharmacodynamic and pharmacokinetic of BBR nanostructures were discussed followed by the introduction of natural polysaccharides of plant (cyclodextrines, glucomannan), the shells of crustaceans (chitosan), and the cell wall of brown marine algae (alginate)-based origins used to improve the dissolution rate of poorly soluble BBR and their anticancer and antibacterial properties. Finally, the anticancer and antibacterial mechanisms of free BBR and BBR nanostructures were surveyed. In conclusion, this review may pave the way for providing some useful data in the development of BBR-based platforms for clinical applications.

Synthesis, biological activities and docking studies of pleuromutilin derivatives with piperazinyl urea linkage

Antibiotics resistance is becoming increasingly common, involving almost all antibiotics on the market. Diseases caused by drug resistant bacteria, such as MRSA, have high mortality and negatively affect public health. The development of new drugs would be an effective means of solving this problem. Modifications based on bioactive natural products could greatly shorten drug development time and improve success rate. Pleuromutilin, a natural product from the basidiomycete bacterial species, is a promising antibiotic candidate. In this study, a series of novel pleuromutilin derivatives possessing piperazinyl urea linkage were efficiently synthesised, and their antibacterial activities and bactericidal properties were evaluated via MIC, MBC and Time-kill kinetics assays. The results showed that all compounds exhibited potent activities against tested strains, especially MRSA strains with MIC values as low as 0.125 μg/mL; 8 times lower than that of marketed antibiotic Tiamulin. Docking studies indicate substituted piperazinyl urea derivatives could provide hydrogen bonds and initiate π-π stacking between molecules and surrounding residues.

A Study on the Synbiotic Composition of Bifidobacterium bifidum and Fructans from Arctium lappa Roots and Helianthus tuberosus Tubers against Staphylococcus aureus

A number of mechanisms have been proposed explaining probiotics and prebiotics benefit human health, in particular, probiotics have a suppression effect on pathogen growth that can be enhanced with the introduction of prebiotics. In vitro models enhanced with computational biology can be useful for selecting a composition with prebiotics from new plant sources with the greatest synergism. Water extracts from burdock root and Jerusalem artichoke tubers were purified by ultrafiltration and activated charcoal and concentrated on a rotary evaporator. Fructans were precipitated with various concentrations of ethanol. Bifidobacterium bifidum 8 VKPM AC-2136 and Staphylococcus aureus ATCC 43300 strains were applied to estimate the synbiotic effect. The growth of bifidobacteria and staphylococci in monocultures and cocultures in broths with glucose, commercial prebiotics, as well as isolated fructans were studied. The minimum inhibitory concentrations (MICs) of lactic and acetic acids for the Staphylococcus strain were determined. A quantitative model joining the formation of organic acids by probiotics as antagonism factors and the MICs of pathogens (as the measure of their inhibition) was tested in cocultures and showed a high predictive value (R2 ≥ 0.86). The synbiotic factor obtained from the model was calculated based on the experimental data and obtained constants. Fructans precipitated with 20% ethanol and Bifidobacterium bifidum have the greater synergism against Staphylococcus.

1,2,3-Triazole-containing hybrids with potential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA), as a classic reason for genuine skin and flimsy tissues diseases, is a worldwide general wellbeing risk and has already tormented humanity for a long history, creating a critical need for the development of new classes of antibacterials. 1,2,3-Triazole moiety, readily interact with diverse enzymes and receptors in organisms through weak bond interaction, is among the most common frameworks present in the bioactive molecules. 1,2,3-Triazole derivatives, especially 1,2,3-triazole-containing hybrids, possess broad-spectrum activity against a panel of clinically important bacteria including drug-resistant pathogens, so rational design of 1,2,3-triazole derivatives may open a door for the opportunities on the development of novel anti-MRSA agents. This review is an endeavour to highlight the current scenario of 1,2,3-triazole-containing hybrids with potential anti-MRSA activity, covering articles published between 2010 and 2020.

Molecular Mechanisms and Epidemiology of Fosfomycin Resistance in Staphylococcus aureus Isolated From Patients at a Teaching Hospital in China

Staphylococcus aureus is a major cause of hospital- and community-acquired infections placing a significant burden on the healthcare system. With the widespread of multidrug-resistant bacteria and the lack of effective antibacterial drugs, fosfomycin has gradually attracted attention as an "old drug." Thus, investigating the resistance mechanisms and epidemiology of fosfomycin-resistant S. aureus is an urgent requirement. In order to investigate the mechanisms of resistance, 11 fosfomycin-resistant S. aureus isolates were analyzed by PCR and sequencing. The genes, including fosA, fosB, fosC, fosD, fosX, and tet38, as well as mutations in murA, glpT, and uhpT were identified. Quantitative real-time PCR (qRT-PCR) was conducted to evaluate the expression of the target enzyme gene murA and the efflux pump gene tet38 under the selection pressure of fosfomycin. Furthermore, multilocus sequence typing (MLST) identified a novel sequence type (ST 5708) of S. aureus strains. However, none of the resistant strains carried fosA, fosB, fosC, fosD, and fosX genes in the current study, and 12 distinct mutations were detected in the uhpT (3), glpT (4), and murA (5) genes. qRT-PCR revealed an elevated expression of the tet38 gene when exposed to increasing concentration of fosfomycin among 8 fosfomycin-resistant S. aureus strains and reference strain ATCC 29213. MLST analysis categorized the 11 strains into 9 STs. Thus, the mutations in the uhpT, glpT, and murA genes might be the primary mechanisms underlying fosfomycin resistance, and the overexpression of efflux pump gene tet38 may play a major role in the fosfomycin resistance in these isolates.

Factors affecting the viability of Staphylococcus aureus and production of enterotoxin during processing and storage of white-brined cheese

Staphylococcus aureus is a major foodborne pathogen that causes severe disease in humans. It is commonly found in milk and dairy products, particularly in fresh brined cheese. Our aim was to investigate the behavior of Staph. aureus and enterotoxin production during the storage of white-brined cheese prepared with or without a starter culture and stored in a 10 or 15% NaCl brine at 10°C and 25°C for 28 d. NaCl concentration, water activity, pH, and number of Staph. aureus and lactic acid bacteria were determined in cheese and brine. Only 1 of 4 Staph. aureus strains (ATCC 439) was positive for enterotoxin production, and its production was detected in unsalted UHT milk, but not in salted milk or in any of the cheese treatments held at 37°C for 1, 3, or 7 d. Staphylococcus aureus grew in the cheese stored in both brines at 10°C and 25°C, regardless of the presence of a starter culture, although the latter significantly reduced Staph. aureus growth in cheese or its brine at 10°C. Staphylococcus aureus numbers were increased by 2.26 and 0.47 log₁₀ cfu/g in cheese stored in 10 and 15% NaCl brine, respectively, in the presence of starter culture, and by 2.78 and 2.96 log₁₀ cfu/g, respectively, in the absence of starter culture at 10°C. Nonetheless, the pathogen grew, but at a lower number in the brines. The salt concentration of cheese stored in 10% brine remained at approximately 5% during storage; however, in 15% brine, the salt concentration increased to almost 8% (wt/wt) by 28 d. The addition of a starter culture, high salt concentration, low temperature, and pH (∼5.2) had inhibitory effects on the growth of Staph. aureus. Moreover, lactic acid bacterial numbers increased considerably in cheese and brine by d 28. The use of starter cultures, salt (15%), and low storage temperature (10°C) reduced the growth of Staph. aureus, and salt may have prevented enterotoxin production in white-brined cheese.

Coumarin-containing hybrids and their antibacterial activities

Infections caused by Gram-positive and -negative bacteria are one of the foremost causes of morbidity and mortality globally. Antibiotics are the mainstay of therapy for bacterial infections, but the emergence and wide spread of drug-resistant pathogens have already become a huge issue for public healthcare systems. The coumarin moiety, which is ubiquitous in nature, could bind to the B subunit of DNA gyrase in bacteria and inhibit DNA supercoiling by blocking the ATPase activity; hence, coumarin derivatives possess potential antibacterial activity. Several coumarin-containing hybrids such as coumermycin A1, clorobiocin, and novobiocin have already been used in clinical practice for the treatment of various bacterial infections; thus, it is conceivable that hybridization of the coumarin moiety with other antibacterial pharmacophores may provide opportunities for the development of novel antibiotics. This review outlines the advances in coumarin-containing hybrids with antibacterial potential in the recent 5 years and the structure-activity relationships are also discussed.

Redox-Channeling Polydopamine-Ferrocene (PDA-Fc) Coating To Confer Context-Dependent and Photothermal Antimicrobial Activities

Microbial disinfection associated with medical device surfaces has been an increasing need, and surface modification strategies such as antibacterial coatings have gained great interest. Here, we report the development of polydopamine-ferrocene (PDA-Fc)-functionalized TiO₂ nanorods (Ti-Nd-PDA-Fc) as a context-dependent antibacterial system on implant to combat bacterial infection and hinder biofilm formation. In this work, two synergistic antimicrobial mechanisms of the PDA-Fc coating are proposed. First, the PDA-Fc coating is redox-active and can be locally activated to release antibacterial reactive oxygen species (ROS), especially ·OH in response to the acidic microenvironment induced by bacteria colonization and host immune responses. The results demonstrate that redox-based antimicrobial activity of Ti-Nd-PDA-Fc offers antibacterial efficacy of over 95 and 92% against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), respectively. Second, the photothermal effect of PDA can enhance the antibacterial capability upon near-infrared (NIR) irradiation, with over 99% killing efficacy against MRSA and E. coli, and even suppress the formation of biofilm through both localized hyperthermia and enhanced ·OH generation. Additionally, Ti-Nd-PDA-Fc is biocompatible when tested with model pre-osteoblast MC-3T3 E1 cells and promotes cell adhesion and spreading presumably due to its nanotopographical features. The MRSA-infected wound model also indicates that Ti-Nd-PDA-Fc with NIR irradiation can effectively eliminate bacterial infection and suppress host inflammatory responses. We believe that this study demonstrates a simple means to create biocompatible redox-active coatings that confer context-dependent antibacterial activities to implant surfaces.