Phage-induced efflux down-regulation boosts antibiotic efficacy.

The interactions between a virus and its host vary in space and time and are affected by the presence of molecules that alter the physiology of either the host or the virus. Determining the molecular mechanisms at the basis of these interactions is paramount for predicting the fate of bacterial and phage populations and for designing rational phage-antibiotic therapies. We study the interactions between stationary phase Burkholderia thailandensis and the phage ΦBp-AMP1. Although heterogeneous genetic resistance to phage rapidly emerges in B. thailandensis, the presence of phage enhances the efficacy of three major antibiotic classes, the quinolones, the beta-lactams and the tetracyclines, but antagonizes tetrahydrofolate synthesis inhibitors. We discovered that enhanced antibiotic efficacy is facilitated by reduced antibiotic efflux in the presence of phage. This new phage-antibiotic therapy allows for eradication of stationary phase bacteria, whilst requiring reduced antibiotic concentrations, which is crucial for treating infections in sites where it is difficult to achieve high antibiotic concentrations.

Natural products as anthelmintics: safeguarding animal health.

Covering literature to December 2022This review provides a comprehensive account of all natural products (500 compounds, including 17 semi-synthetic derivatives) described in the primary literature up to December 2022, reported to be capable of inhibiting the egg hatching, motility, larval development and/or the survival of helminths (i.e., nematodes, flukes and tapeworms). These parasitic worms infect and compromise the health and welfare, productivity and lives of commercial livestock (i.e., sheep, cattle, horses, pigs, poultry and fish), companion animals (i.e., dogs and cats) and other high value, endangered and/or exotic animals. Attention is given to chemical structures, as well as source organisms and anthelmintic properties, including the nature of bioassay target species, in vivo animal hosts, and measures of potency.

In Vitro Activity of Vancapticin MCC5145 against Methicillin-Resistant Staphylococcus aureus from Periprosthetic Joint Infection.

MRSA periprosthetic 1 joint infection (PJI) can be challenging to treat due to biofilm formation, alongside sometimes limited vancomycin activity (1-3).….

The Antimicrobial Properties of PdII - and RuII -pyta Complexes.

Infections associated with antimicrobial resistance (AMR) are poised to become the leading cause of death in the next few decades, a scenario that can be ascribed to two phenomena: antibiotic over-prescription and a lack of antibiotic drug development. The crowd-sourced initiative Community for Open Antimicrobial Drug Discovery (CO-ADD) has been testing research compounds contributed by researchers around the world to find new antimicrobials to combat AMR, and during this campaign has found that metallodrugs might be a promising, yet untapped source. To this end, we submitted 18 PdII - and RuII -pyridyl-1,2,3-triazolyl complexes that were developed as catalysts to assess their antimicrobial properties. It was found that the Pd complexes, especially Pd1, possessed potent antifungal activity with MICs between 0.06 and 0.125 µg mL-1 against Candida glabrata. The in-vitro studies were extended to in-vivo studies in Galleria mellonella larvae, where it was established that the compounds were nontoxic. Here, we effectively demonstrate the potential of PdII -pyta complexes as antifungal agents.

Use of Antiviral Agents and other Therapies for COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic led to a remarkably rapid development of a range of effective prophylactic vaccines, including new technologies that had not previously been approved for human use. In contrast, the development of new small molecule antiviral therapeutics has taken years to produce the first approved drugs specifically targeting severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), with the intervening years filled with attempts to repurpose existing drugs and the development of biological therapeutics. This review will discuss the reasons behind this variation in timescale and provide a survey of the many new treatments that are progressing through the clinical pipeline.

Leveraging the potential of silver nanoparticles-based materials towards sustainable water treatment.

Increasing demand of pure and accessible water and improper disposal of waste into the existing water resources are the major challenges for sustainable development. Nanoscale technology is an effective approach that is increasingly being applied to water remediation. Compared to conventional water treatment processes, silver nanotechnology has been demonstrated to have advantages due to its anti-microbial and oligodynamic (biocidal) properties. This review is focused on environmentally friendly green syntheses of silver nanoparticles (AgNPs) and their applications for the disinfection and microbial control of wastewater. A bibliometric keyword analysis is conducted to unveil important keywords and topics in the utilisation of AgNPs for water treatment applications. The effectiveness of AgNPs, as both free nanoparticles (NPs) or as supported NPs (nanocomposites), to deal with noxious pollutants like complex dyes, heavy metals as well as emerging pollutants of concern is also discussed. This knowledge dataset will be helpful for researchers to identify and utilise the distinctive features of AgNPs and will hopefully stimulate the development of novel solutions to improve wastewater treatment. This review will also help researchers to prepare effective water management strategies using nano silver-based systems manufactured using green chemistry.

Amino Alcohols as Potential Antibiotic and Antifungal Leads.

Five focused compound libraries (forty-nine compounds), based on prior studies in our laboratory were synthesized and screened for antibiotic and anti-fungal activity against S. aureus, E. coli, K. pneumoniae, P. aeruginosa, A. baumannii, C. albicans and C. neoformans. Low levels of activity, at the initial screening concentration of 32 µg/mL, were noted with analogues of (Z)-2-(3,4-dichlorophenyl)-3-phenylacrylonitriles which made up the first two focused libraries produced. The most promising analogues possessing additional substituents on the terminal aromatic ring of the synthesised acrylonitriles. Modifications of the terminal aromatic moiety were explored through epoxide installation flowed by flow chemistry mediated ring opening aminolysis with discreet sets of amines to the corresponding amino alcohols. Three new focused libraries were developed from substituted anilines, cyclic amines, and phenyl linked heterocyclic amines. The aniline-based compounds were inactive against the bacterial and fungal lines screened. The introduction of a cyclic, such as piperidine, piperazine, or morpholine, showed >50% inhibition when evaluated at 32 µg/mL compound concentration against methicillin-resistant Staphylococcus aureus. Examination of the terminal aromatic substituent via oxirane aminolysis allowed for the synthesis of three new focused libraries of afforded amino alcohols. Aromatic substituted piperidine or piperazine switched library activity from antibacterial to anti-fungal activity with ((Z)-2-(3,4-dichlorophenyl)-3-(4-(2-hydroxy-3-(4-methylpiperazin-1-yl)propoxy)phenyl)acrylonitrile), ((Z)-2-(3,4-dichlorophenyl)-3-(4-(2-hydroxy-3-(4-(4-hydroxyphenyl)piperazin-1-yl)propoxy)-phenyl)acrylonitrile) and ((Z)-3-(4-(3-(4-cyclohexylpiperazin-1-yl)-2-hydroxypropoxy)-phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile) showing >95% inhibition of Cryptococcus neoformans var. grubii H99 growth at 32 µg/mL. While (Z)-3-(4-(3-(cyclohexylamino)-2-hydroxypropoxy)phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile, (S,Z)-2-(3,4-dichlorophenyl)-3-(4-(2-hydroxy-3-(piperidin-1-yl)propoxy)phenyl)acrylonitrile, (R,Z)-2-(3,4-dichlorophenyl)-3-(4-(2-hydroxy-3-(piperidin-1-yl)propoxy)phenyl)acrylonitrile, (Z)-2-(3,4-dichlorophenyl)-3-(4-(2-hydroxy-3-(D-11-piperidin-1-yl)propoxy)phenyl)-acrylonitrile, and (Z)-3-(4-(3-(4-cyclohexylpiperazin-1-yl)-2-hydroxypropoxy)-phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile 32 µg/mL against Staphylococcus aureus.

Antimicrobial and Anticancer Properties of Synthetic Peptides Derived from the Wasp Parachartergus fraternus.

Agelaia-MPI and protonectin are antimicrobial peptides isolated from the wasp Parachartergus fraternus that show antimicrobial and neuroactive activities. Previously, two analogues of these peptides, neuroVAL and protonectin-F, were designed to reduce nonspecific toxicity and improve potency. Here, the three-dimensional structures of neuroVAL, protonectin and protonectin-F were determined by using circular dichroism and NMR spectroscopy. Antibacterial, antifungal, cytotoxic and hemolytic activities were tested for the parent peptides and analogues. All peptides showed moderate antimicrobial activity against Gram-positive bacteria, with agelaia-MPI being the most active. Protonectin and protonectin-F were found to be toxic to cancerous and noncancerous cell lines. Internalization experiments revealed that these peptides accumulate inside both cell types. By contrast, neuroVAL was nontoxic to all tested cells and was able to enter cells without accumulating. In summary, neuroVAL has potential as a nontoxic cell-penetrating peptide, while protonectin-F needs further modification to realize its potential as an antitumor peptide.

Nontoxic Cobalt(III) Schiff Base Complexes with Broad-Spectrum Antifungal Activity.

Resistance to currently available antifungal drugs has quietly been on the rise but overshadowed by the alarming spread of antibacterial resistance. There is a striking lack of attention to the threat of drug-resistant fungal infections, with only a handful of new drugs currently in development. Given that metal complexes have proven to be useful new chemotypes in the fight against diseases such as cancer, malaria, and bacterial infections, it is reasonable to explore their possible utility in treating fungal infections. Herein we report a series of cobalt(III) Schiff base complexes with broad-spectrum antifungal activity. Some of these complexes show minimum inhibitory concentrations (MIC) in the low micro- to nanomolar range against a series of Candida and Cryptococcus yeasts. Additionally, we demonstrate that these compounds show no cytotoxicity against both bacterial and human cells. Finally, we report the first in vivo toxicity data on these compounds in Galleria mellonella, showing that doses as high as 266 mg kg-1 are tolerated without adverse effects, paving the way for further in vivo studies of these complexes.

Bio-Potency and Molecular Docking Studies of Isolated Compounds from Grewia optiva J.R. Drumm. ex Burret.

In the study, two novel compounds along with two new compounds were isolated from Grewia optiva. The novel compounds have never been reported in any plant source, whereas the new compounds are reported for the first time from the studied plant. The four compounds were characterized as: 5,5,7,7,11,13-hexamethyl-2-(5-methylhexyl)icosahydro-1H-cyclopenta[a]chrysen-9-ol (IX), docosanoic acid (X), methanetriol mano formate (XI) and 2,2'-(1,4-phenylene)bis(3-methylbutanoic acid (XII). The anticholinesterase, antidiabetic, and antioxidant potentials of these compounds were determined using standard protocols. All the isolated compounds exhibited a moderate-to-good degree of activity against acetylcholinesterases (AChE) and butyrylcholinesterase (BChE). However, compound XII was particularly effective with IC50 of 55 µg/mL (against AChE) and 60 µg/mL (against BChE), and this inhibitory activity is supported by in silico docking studies. The same compound was also effective against DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid) radicals with IC50 values of 60 and 62 µg/mL, respectively. The compound also significantly inhibited the activities of α-amylase and α-glucosidase in vitro. The IC50 values for inhibition of the two enzymes were recorded as 90 and 92 µg/mL, respectively. The in vitro potentials of compound XII to treat Alzheimer's disease (in terms of AchE and BChE inhibition), diabetes (in terms of α-amylase and α-glucosidase inhibition), and oxidative stress (in terms of free radical scavenging) suggest further in vivo investigations of the compound for assessing its efficacy, safety profile, and other parameters to proclaim the compound as a potential drug candidate.

Formulation of Quaternized Aminated Chitosan Nanoparticles for Efficient Encapsulation and Slow Release of Curcumin.

An effective drug nanocarrier was developed on the basis of a quaternized aminated chitosan (Q-AmCs) derivative for the efficient encapsulation and slow release of the curcumin (Cur)-drug. A simple ionic gelation method was conducted to formulate Q-AmCs nanoparticles (NPs), using different ratios of sodium tripolyphosphate (TPP) as an ionic crosslinker. Various characterization tools were employed to investigate the structure, surface morphology, and thermal properties of the formulated nanoparticles. The formulated Q-AmCs NPs displayed a smaller particle size of 162 ± 9.10 nm, and higher surface positive charges, with a maximum potential of +48.3 mV, compared to native aminated chitosan (AmCs) NPs (231 ± 7.14 nm, +32.8 mV). The Cur-drug encapsulation efficiency was greatly improved and reached a maximum value of 94.4 ± 0.91%, compared to 75.0 ± 1.13% for AmCs NPs. Moreover, the in vitro Cur-release profile was investigated under the conditions of simulated gastric fluid [SGF; pH 1.2] and simulated colon fluid [SCF; pH 7.4]. For Q-AmCs NPs, the Cur-release rate was meaningfully decreased, and recorded a cumulative release value of 54.0% at pH 7.4, compared to 73.0% for AmCs NPs. The formulated nanoparticles exhibited acceptable biocompatibility and biodegradability. These findings emphasize that Q-AmCs NPs have an outstanding potential for the delivery and slow release of anticancer drugs.

Light-Activated Rhenium Complexes with Dual Mode of Action against Bacteria.

New antibiotics and innovative approaches to kill drug-resistant bacteria are urgently needed. Metal complexes offer access to alternative modes of action but have only sparingly been investigated in antibacterial drug discovery. We have developed a light-activated rhenium complex with activity against drug-resistant S. aureus and E. coli. The activity profile against mutant strains combined with assessments of cellular uptake and synergy suggest two distinct modes of action.

Hydroxyl substituted benzoic acid/cinnamic acid derivatives: Tyrosinase inhibitory kinetics, anti-melanogenic activity and molecular docking studies.

The inhibition of tyrosinase is an established strategy for treating hyperpigmentation. Our previous findings demonstrated that cinnamic acid and benzoic acid scaffolds can be effective tyrosinase inhibitors with low toxicity. The hydroxyl substituted benzoic and cinnamic acid moieties of these precursors were incorporated into new chemotypes that displayed in vitro inhibitory effect against mushroom tyrosinase. The most active compound, (2-(3-methoxyphenoxy)-2-oxoethyl (E)-3-(4-hydroxyphenyl) acrylate) 6c, inhibited tyrosinase with an IC50 of 5.7 µM, while (2-(3-methoxyphenoxy)-2-oxoethyl 2, 4-dihydroxybenzoate) 4d had an IC50 of 23.8 µM. In comparison, the positive control, kojic acid showed tyrosinase inhibition with an IC50 = 16.7 µM. Analysis of enzyme kinetics revealed that 6c and 4d displayed noncompetitive reversible inhibition of the second tyrosinase enzymatic reaction with Ki values of 11 µM and 130 µM respectively. In silico docking studies with mushroom tyrosinase (PDB ID 2Y9X) predicted possible binding modes in the catalytic site for these active compounds. The phenolic para-hydroxy group of the most active compound 6c is predicted to interact with the catalytic site Cu++ ion. The methoxy part of this compound is predicted to form a hydrogen bond with Arg 268. Compound 6c had no observable toxic effects on cell morphology or cell viability at the highest tested concentration of 91.4 µM. When dosed at 91.4 µM onto B16F10 melanoma cells in vitro6c showed anti-melanogenic effects equivalent to kojic acid at 880 µM. 6c displayed no PAINS (pan-assay interference compounds) alerts. Our results show that compound 6c is a more potent tyrosinase inhibitor than kojic acid and is a candidate for further development. Our exposition of the details of the interactions between 6c and the catalytic pocket of tyrosinase provides a basis for rational design of additional potent inhibitors of tyrosinase, built on the cinnamic acid scaffold.

Effects of Microplate Type and Broth Additives on Microdilution MIC Susceptibility Assays.

The determination of antibiotic potency against bacterial strains by assessment of their minimum inhibitory concentration normally uses a standardized broth microdilution assay procedure developed more than 50 years ago. However, certain antibiotics require modified assay conditions in order to observe optimal activity. For example, daptomycin requires medium supplemented with Ca2+, and the lipoglycopeptides dalbavancin and oritavancin require Tween 80 to be added to the growth medium to prevent the depletion of free drug via adsorption to the plastic microplate. In this report, we examine systematically the effects of several different plate types on microdilution broth MIC values for a set of antibiotics against Gram-positive and Gram-negative bacteria, both in medium alone and in medium supplemented with the commonly used additives Tween 80, lysed horse blood, and 50% human serum. We observed very significant differences in measured MICs (up to 100-fold) for some lipophilic antibiotics, such as the Gram-positive lipoglycopeptide dalbavancin and the Gram-negative lipopeptide polymyxins, and found that nonspecific binding plates can replace the need for surfactant additives. Microtiter plate types and any additives should be specified when reporting broth dilution MIC values, as results can vary dramatically for some classes of antibiotics.

Octapeptin C4 and polymyxin resistance occur via distinct pathways in an epidemic XDR Klebsiella pneumoniae ST258 isolate.

BACKGROUND: Polymyxin B and E (colistin) have been pivotal in the treatment of XDR Gram-negative bacterial infections; however, resistance has emerged. A structurally related lipopeptide, octapeptin C4, has shown significant potency against XDR bacteria, including polymyxin-resistant strains, but its mode of action remains undefined. OBJECTIVES: We sought to compare and contrast the acquisition of resistance in an XDR Klebsiella pneumoniae (ST258) clinical isolate in vitro with all three lipopeptides to potentially unveil variations in their mode of action. METHODS: The isolate was exposed to increasing concentrations of polymyxins and octapeptin C4 over 20 days. Day 20 strains underwent WGS, complementation assays, antimicrobial susceptibility testing and lipid A analysis. RESULTS: Twenty days of exposure to the polymyxins resulted in a 1000-fold increase in the MIC, whereas for octapeptin C4 a 4-fold increase was observed. There was no cross-resistance observed between the polymyxin- and octapeptin-resistant strains. Sequencing of polymyxin-resistant isolates revealed mutations in previously known resistance-associated genes, including crrB, mgrB, pmrB, phoPQ and yciM, along with novel mutations in qseC. Octapeptin C4-resistant isolates had mutations in mlaDF and pqiB, genes related to phospholipid transport. These genetic variations were reflected in distinct phenotypic changes to lipid A. Polymyxin-resistant isolates increased 4-amino-4-deoxyarabinose fortification of lipid A phosphate groups, whereas the lipid A of octapeptin C4-resistant strains harboured a higher abundance of hydroxymyristate and palmitoylate. CONCLUSIONS: Octapeptin C4 has a distinct mode of action compared with the polymyxins, highlighting its potential as a future therapeutic agent to combat the increasing threat of XDR bacteria.

Structure-Function Studies of Polymyxin B Lipononapeptides.

The emerging threat of infections caused by highly drug-resistant bacteria has prompted a resurgence in the use of the lipodecapeptide antibiotics polymyxin B and colistin as last resort therapies. Given the emergence of resistance to these drugs, there has also been a renewed interest in the development of next generation polymyxins with improved therapeutic indices and spectra of action. We report structure-activity studies of 36 polymyxin lipononapeptides structurally characterised by an exocyclic FA-Thr²-Dab³ lipodipeptide motif instead of the native FA-Dab¹-Thr²-Dab³ tripeptide motif found in polymyxin B, removing one of the positively charged residues believed to contribute to nephrotoxicity. The compounds were prepared by solid phase synthesis using an on-resin cyclisation approach, varying the fatty acid and the residues at position 2 (P2), P3 and P4, then assessing antimicrobial potency against a panel of Gram-negative bacteria, including polymyxin-resistant strains. Pairwise comparison of N-acyl nonapeptide and decapeptide analogues possessing different fatty acids demonstrated that antimicrobial potency is strongly influenced by the N-terminal L-Dab-1 residue, contingent upon the fatty acid. This study highlights that antimicrobial potency may be retained upon truncation of the N-terminal L-Dab-1 residue of the native exocyclic lipotripeptide motif found in polymyxin B. The strategy may aid in the design of next generation polymyxins.

Surface Ligand Density of Antibiotic-Nanoparticle Conjugates Enhances Target Avidity and Membrane Permeabilization of Vancomycin-Resistant Bacteria.

Many bacterial pathogens have now acquired resistance toward commonly used antibiotics, such as the glycopeptide antibiotic vancomycin. In this study, we show that immobilization of vancomycin onto a nanometer-scale solid surface with controlled local density can potentiate antibiotic action and increase target affinity of the drug. Magnetic nanoparticles were conjugated with vancomycin and used as a model system to investigate the relationship between surface density and drug potency. We showed remarkable improvement in minimum inhibitory concentration against vancomycin-resistant strains with values of 13-28 µg/mL for conjugated vancomycin compared to 250-4000 µg/mL for unconjugated vancomycin. Higher surface densities resulted in enhanced affinity toward the bacterial target compared to that of unconjugated vancomycin, as measured by a competition experiment using a surrogate ligand for bacterial Lipid II, N-Acetyl-l-Lys-d-Ala-d-Ala. High density vancomycin nanoparticles required >64 times molar excess of ligand (relative to the vancomycin surface density) to abrogate antibacterial activity compared to only 2 molar excess for unconjugated vancomycin. Further, the drug-nanoparticle conjugates caused rapid permeabilization of the bacterial cell wall within 2 h, whereas no effect was seen with unconjugated vancomycin, suggesting additional modes of action for the nanoparticle-conjugated drug. Hence, immobilization of readily available antibiotics on nanocarriers may present a general strategy for repotentiating drugs that act on bacterial membranes or membrane-bound targets but have lost effectiveness against resistant bacterial strains.

Synthesis of octapeptin C4 and biological profiling against NDM-1 and polymyxin-resistant bacteria.

The first synthesis of octapeptin C4 was achieved using a combination of solid phase synthesis and off-resin cyclisation. Octapeptin C4 displayed antibiotic activity against multi-drug resistant, NDM-1 and polymyxin-resistant Gram-negative bacteria, with moderate activity against Staphylococcus aureus. The linear analogue of octapeptin C4 was also prepared, which showed reduced activity.

Short cationic lipopeptides as effective antibacterial agents: Design, physicochemical properties and biological evaluation.

The spread of drug-resistant bacteria has imparted a sense of urgency in the search for new antibiotics. In an effort to develop a new generation of antibacterial agents, we have designed de novo charged lipopeptides inspired by natural antimicrobial peptides. These short lipopeptides are composed of cationic lysine and hydrophobic lipoamino acids that replicate the amphiphilic properties of natural antimicrobial peptides. The resultant lipopeptides were found to self-assemble into nanoparticles. Some were effective against a variety of Gram-positive bacteria, including strains resistant to methicillin, daptomycin and/or vancomycin. The lipopeptides were not toxic to human kidney and liver cell lines and were highly resistant to tryptic degradation. Transmission electron microscopy analysis of bacteria cells treated with lipopeptide showed membrane-damage and lysis with extrusion of cytosolic contents. With such properties in mind, these lipopeptides have the potential to be developed as new antibacterial agents against drug-resistant Gram-positive bacteria.

Mucin Binding Reduces Colistin Antimicrobial Activity.

Colistin has found increasing use in treating drug-resistant bacterial lung infections, but potential interactions with pulmonary biomolecules have not been investigated. We postulated that colistin, like aminoglycoside antibiotics, may bind to secretory mucin in sputum or epithelial mucin that lines airways, reducing free drug levels. To test this hypothesis, we measured binding of colistin and other antibiotics to porcine mucin, a family of densely glycosylated proteins used as a surrogate for human sputum and airway mucin. Antibiotics were incubated in dialysis tubing with or without mucin, and concentrations of unbound antibiotics able to penetrate the dialysis tubing were measured over time using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The percentage of antibiotic measured in the dialysate after 4 h in the presence of mucin, relative to the amount without mucin, was 15% for colistin, 16% for polymyxin B, 19% for tobramycin, 52% for ciprofloxacin, and 78% for daptomycin. Antibiotics with the strongest mucin binding had an overall polybasic positive charge, whereas those with comparatively little binding were less basic. When comparing MICs measured with or without added mucin, colistin and polymyxin B showed >100-fold increases in MICs for multiple Gram-negative bacteria. Preclinical evaluation of mucin binding should become a standard procedure when considering the potential pulmonary use of new or existing antibiotics, particularly those with a polybasic overall charge. In the airways, mucin binding may reduce the antibacterial efficacy of inhaled or intravenously administered colistin, and the presence of sub-MIC effective antibiotic concentrations could result in the development of antibiotic resistance.