Current challenges and advancements towards discovery and resistance of antibiotics

The antibacterial properties of branched peptides based on poly(l-arginine): In vitro antibacterial evaluation and molecular dynamic simulations

The emergence of bacterial strains resistant to antibiotics is a major issue in the medical field. Antimicrobial peptides are widely studied as they do not generate as much resistant bacterial strains as conventional antibiotics and present a broad range of activity. Among them, the homopolypeptide poly(l-arginine) presents promising antibacterial properties, especially in the perspective of its use in biomaterials. Linear poly(l-arginine) has been extensively studied but the impact of its 3D structure remains unknown. In this study, the antibacterial properties of newly synthesized branched poly(l-arginine) peptides, belonging to the family of multiple antigenic peptides, are evaluated. First, in vitro activities of the peptides shows that branched poly(l-arginine) is more efficient than linear poly(l-arginine) containing the same number of arginine residues. Surprisingly, peptides with more arms and more residues are not the most effective. To better understand these unexpected results, interactions between these peptides and the membranes of Gram positive and Gram negative bacteria are simulated thanks to molecular dynamic. It is observed that the bacterial membrane is more distorted by the branched structure than by the linear one and by peptides containing smaller arms. This mechanism of action is in full agreement with in vitro results and suggest that our simulations form a robust model to evaluate peptide efficiency towards pathogenic bacteria.

Toxic effects of lead (Pb), cadmium (Cd) and tetracycline (TC) on the growth and development of Triticum aestivum: A meta-analysis

The environmental issue of lead (Pb), cadmium (Cd), and tetracycline (TC) contamination in cereal crops has become a growing concern worldwide. An in-depth understanding of this issue would be of importance to promote effective management strategies for heavy metals and antibiotics worldwide. The present study was conducted to assess the toxic effects of heavy metals (Cd, Pb) and antibiotics (TC) on Triticum aestivum (T. aestivum, common wheat) based on studies conducted in the past 22 years. Data pertaining to the growth and development of T. aestivum were extracted and analyzed from 89 publications spanning from 2000 to 2022. Our results showed that Pb, Cd and TC significantly reduced growth and development by 11 %, 9 %, and 5 %, respectively. Additionally, significant accumulation of Cd (42 %) and Pb (17 %) was observed in T. aestivum samples, although there was little change in TC accumulation, which showed limited absorption, accumulation, and translocation of TC in wheat plants. Pb had the greatest impact on the yield of T. aestivum, followed by Cd, while TC had no apparent effect. Furthermore, exposure to Cd, Pb and TC reduced the photosynthetic rate due to chlorophyll reduction, with Cd having the most pronounced effect (58 %), followed by Pb (37 %) and TC (8 %). Cd exposure also significantly enhanced gaseous exchange (37 %) compared to TC and Pb, which reduced gaseous exchange by 4 % and 10 %, respectively. However, the treatments with TC (>50-100 mgL-1), Pb (>1000-2000 mg L-1) and Cd (>500-1000 mg L-1) increased the defense system of T. aestivum samples by 38 %, 15 %, and 11 %, respectively. The obtained findings have significant implications for risk assessment, pollution prevention, and remediation strategies to address soil contamination from Pb, Cd and TC in farmland.

Arylidene and amino spacer-linked rhodanine-quinoline hybrids as upgraded antimicrobial agents

Antibiotic resistance associated with various microorganisms such as Gram-positive, Gram-negative, fungal strains, and multidrug-resistant tuberculosis increases the risk of healthcare survival. Preliminary therapeutics becoming ineffective that might lead to noteworthy mortality presents a crucial challenge for the scientific community. Hence, there is an urgent need to develop hybrid compounds as antimicrobial agents by combining two or more bioactive heterocyclic moieties into a single molecular framework with fewer side effects and a unique mode of action. This review highlights the recent advances (2013-2023) in the pharmacology of rhodanine-linked quinoline hybrids as more effective antimicrobial agents. In the drug development process, linker hybrids acquire the top position due to their excellent π-stacking and Van der Waals interaction with the DNA active sites of pathogens. A molecular hybridization strategy has been optimized, indicating that combining these two bioactive moieties with an arylidene and an amino spacer linker increases the antimicrobial potential and reduces drug resistance. Moreover, the structure-activity relationship study is discussed to express the role of various functional groups in improving and decrementing antimicrobial activities for rational drug design. Also, a linker approach may accelerate the development of dynamic antimicrobial agents through molecular hybridization.

Comparative molecular docking and toxicity between carbon-capped metal oxide nanoparticles and standard drugs in cancer and bacterial infections

Introduction

Nanoparticles (NPs) are of great interest in the design of various drugs due to their high surface-to-volume ratio, which result from their unique physicochemical properties. Because of the importance of examining the interactions between newly designed particles with different targets in the case of various diseases, techniques for examining the interactions between these particles with different targets, many of which are proteins, are now very common.

Methods

In this study, the interactions between metal oxide nanoparticles (MONPs) covered with a carbon layer (Ag2O3, CdO, CuO, Fe2O3, FeO, MgO, MnO, and ZnO NPs) and standard drugs related to the targets of Cancer and bacterial infections were investigated using the molecular docking technique with AutoDock 4.2.6 software tool. Finally, the PRO TOX-II online tool was used to compare the toxicity (LD50) and molecular weight of these MONPs to standard drugs.

Results

According to the data obtained from the semi flexible molecular docking process, MgO and Fe2O3 NPs performed better than standard drugs in several cases. MONPs typically have a lower 50% lethal dose (LD50) and a higher molecular weight than standard drugs. MONPs have shown a minor difference in binding energy for different targets in three diseases, which probably can be attributed to the specific physicochemical and pharmacophoric properties of MONPs.

Conclusion

The toxicity of MONPs is one of the major challenges in the development of drugs based on them. According to the results of these molecular docking studies, MgO and Fe2O3 NPs had the highest efficiency among the investigated MONPs.

Selective Determination of Norfloxacin in Pharmaceutical Formulations and Human Urine Samples Using Poly(8-aminonaphthaline-2-sulfonic Acid)-Modified Glassy Carbon Electrodes

In this study, a glassy carbon electrode was modified potentiodynamically with poly(8-aminonaphthaline-2-sulfonic acid) [poly(ANSA)/GCE] for the detection of norfloxacin (NFN) in tablet formulations and human urine samples. Improvement of the effective surface area of the modified electrode and decreased charge-transfer resistance confirmed surface modification of the GCE by a conductive poly(ANSA) film. The appearance of an oxidative peak without a reductive peak in the reverse scan direction showed the irreversibility of the electrochemical oxidation of NFN in both the bare GCE and poly(ANSA)/GCE. A better coefficient of determination for the peak current on the square root of the scan rate (R² = 0.99514) than the scan rate (R² = 0.97109), indicating the oxidation of NFN at the poly(ANSA)/GCE, was predominantly diffusion mass transport-controlled. Under optimized pH and square wave parameters, the voltammetric current response of NFN at the poly(ANSA)/GCE showed linear dependence on the concentration, ranging from 1.0 × 10^-8 to 4.0 × 10^-4 M with a limit of detection of 4.1 × 10^-10. The NFN level in the studied tablet brands was in the range of 90.30-103.3% of their labeled values. Recovery results in tablet and urine samples ranged from 98.35 to 101.20% and 97.75 to 99.60%, respectively, and interference recovery results were less than 2.13% error in the presence of ampicillin, chloroquine phosphate, and cloxacillin. The present method had a better performance for the determination of NFN in tablet formulations and urine samples as compared with recently reported voltammetric methods due to its requirement of a simple electrode modification step, which provides the least limit of detection and a reasonably wider linear dynamic range.

Highly efficient nanocomposite of Y2O3@biochar for oxytetracycline removal from solution: Adsorption characteristics and mechanisms

Nano Y₂O₃-modified biochar composites (Y₂O₃@BC600) were fabricated successfully and exhibited great adsorption toward oxytetracycline (OTC). The Langmuir adsorption capacity of Y₂O₃@BC600-1:4 for OTC reached 223.46 mg/g, 10.52 times greater than that of BC600. The higher dispersion of Y₂O₃ nanoparticles, increased surface area of 175.65 m²/g and expanded porosity of 0.27 cm³/g accounted for higher OTC adsorption by Y₂O₃@BC600-1:4. Y₂O₃@BC600-1:4 could resist the interference of co-existing cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) and anions (Cl^-, NO₃^-, SO₄^2-) on OTC removal. Y₂O₃ coating changed surface charge property of BC600, favoring the contribution of electrostatic interaction. Synchrotron radiation-based Fourier transform infrared spectroscopy detected obvious peak shift and intensity change of surface -OH when OTC adsorption occurred. Accordingly, stronger H-bonding (charge-assisted hydrogen bond, OTC-H₂N⁺···HO-Y₂O₃@BC600-1:4) was proposed for OTC adsorption. Y₂O₃@BC600 exhibited renewability and stability in the adsorptive removal of OTC. Therefore, Y₂O₃@BC600 may be a novel and suitable adsorbent for antibiotic removal.

Size-controlling preparation of covalent organic framework nanospheres for electrochemical impedimetric aptasensing of oxytetracycline

Covalent organic framework (COF) nanospheres with controlled size of ∼500 and ∼1100 nm were successfully prepared by adjusting the HOAc amount in the synthetic system. The as-synthesized COFs have large conjugate aromatic skeleton, excellent stability, abundant pore, and uniform morphology. These advantages of COFs are benefit for immobilizing aptamers to fabricate the targeted electrochemical aptasensor. The commonly used oxytetracycline (OTC) is an analytic model to explore the sensing performance of the COF-based aptasensor, indicating that the smaller COF (∼500 nm) is more conducive to acquiring the sensitive sensor than that of the larger COF (∼1100 nm). Moreover, the limitation of detection of the COF (∼500 nm)-based aptasensor is calculated to be 7.4 fg mL^-1 using the response impedance signal. Additionally, the aptamer-based biosensor has fine reproducibility, good stability, excellent specificity, and available usability even in real samples.

Degradation of antibiotic amoxicillin from pharmaceutical industry wastewater into a continuous flow reactor using supercritical water gasification

In recent years the concern with emerging pollutants in water has become more prominent, especially pharmaceutical residues, such as antibiotics due to the influence to increase antibacterial resistance. Further, conventional wastewater treatment methods have not demonstrated efficiency for the complete degradation of these compounds, or they have limitations to treat a large volume of waste. In this sense, this study aims to investigate the degradation of amoxicillin, one of the most prescribed antibiotics, in wastewater via supercritical water gasification (SCWG) using a continuous flow reactor. For this purpose, the process operating conditions of temperature, feed flow rate, and concentration of H₂O₂ was evaluated using Experimental Design and Response Surface Methodology techniques and optimized by Differential Evolution methodology. Total organic carbon (TOC) removal, chemical oxygen demand (COD) degradability, reaction time, amoxicillin degradation rate, toxicity of degradation by-products, and gaseous products were evaluated. The use of SCWG for treatment achieved 78.4% of the TOC removal for the industrial wastewater. In the gaseous products, hydrogen was the majority component. Furthermore, high-performance liquid chromatography analyses demonstrated that the antibiotic amoxicillin was degraded. For a mass flow rate of 15 mg/min of amoxicillin fed into the reaction system, 14.4 mg/min was degraded. Toxicity tests with microcrustacean Artemia salina showed slight toxicity to treated wastewater. Despite that, the outcomes reveal the SCWG has great potential to degrade amoxicillin and may be applied to treat several pharmaceutical pollutants. Aside from this, carbon-rich effluents may lead to a significant energy gaseous product, especially, hydrogen and syngas.

Discovery and Mechanism of Action of a Novel Antimicrobial Peptide from an Earthworm

The robust innate immune system of the earthworm provides a potential source of natural antimicrobial peptides (AMPs). However, the cost and high rediscovery rate of direct separation and purification limits their discovery. Genome sequencing of numerous earthworm species facilitates the discovery of new antimicrobial peptides. Through predicting potential antimicrobial peptides in the open reading frames of the Eisenia andrei genome and sequence optimization, a novel antimicrobial peptide, named EWAMP-R (RIWWSGGWRRWRW), was identified. EWAMP-R demonstrated good activity against various bacteria, including drug-resistant strains. The antibacterial mechanisms of EWAMP-R were explored through molecular simulation and wet-laboratory experiments. These experiments demonstrated that the bacterial membrane may be one of the targets of EWAMP-R but that there may be different interactions with Gram-negative and Gram-positive bacterial membranes. EWAMP-R can disrupt bacterial membrane integrity; however, at low concentrations, it appears that EWAMP-R may get through the membrane of Escherichia coli instead of damaging it directly, implying the existence of a secondary response. Gene expression studies identified that in E. coli, only the apoptosis-like cell death (ALD) pathway was activated, while in Staphylococcus aureus, the MazEF pathway was also upregulated, limiting the influence of the ALD pathway. The different antimicrobial actions against Gram-positive and -negative bacteria can provide important information on the structure-activity relationship of AMPs and facilitate AMP design with higher specificity. This study identified a new source of antibacterial agents that has the potential to address the increasingly serious issue of antibiotic resistance. IMPORTANCE Drug-resistant bacteria are a great threat to public health and drive the search for new antibacterial agents. The living environment of earthworms necessitates a strong immune system, and therefore, they are potentially a rich resource of novel antibiotics. A novel AMP, EWAMP-R, with high antibacterial activity was found through in silico analysis of the Eisenia andrei genome. Molecular analysis investigating the interactions between EWAMP-R and the cell membrane demonstrated the importance of tryptophan and arginine residues to EWAMP-R activity. Additionally, the different secondary responses found between E. coli and S. aureus were in accordance with a common phenomenon where some antibacterial agents only target specific species of bacteria. These results provided useful molecular information to support further AMP research and design. Our study expands the sources of antimicrobial peptides and also helps to explain the adaptability of earthworms to their environment.

Analytical Determination of Cephalosporin Antibiotics Using Coordination Polymer Based on Cobalt Terephthalate as a Sorbent

In this work, a coordination polymer based on cobalt terephthalate was obtained and characterized by elemental analysis, infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The coordination polymer was tested as a sorbent for the solid-phase extraction of cephalosporin antibiotics, including ceftriaxone, cefotaxime, and cefazolin, from aqueous solutions. The coordination polymer had a high adsorption capacity (520.0 mg/g). Antibiotics adsorption followed pseudo-second order kinetic model and the Freundlich isotherm model. The calculated thermodynamic parameters indicate a spontaneous process. The resulting coordination polymer has good stability and reusability. The possibility of separating the studied cephalosporins on a chromatographic column filled with a coordination polymer was shown. This work opens great prospects for the development and application of a coordination polymer based on cobalt terephthalate for the removal of cephalosporins from ambient water.

Photocatalytic Removal of Antibiotics from Wastewater Using the CeO2/ZnO Heterojunction

CeO₂/ZnO-based photocatalytic materials were synthesized by the sol-gel method in order to establish heterojunctions that increase the degradation efficiency of some types of antibiotics by preventing the recombination of electron-hole pairs. The synthesized materials were analysed by XRD, SEM, EDAX, FTIR, and UV-Vis. After several tests, the optimal concentration of the catalyst was determined to be 0.05 g‧L^-1 and 0.025 g‧L^-1 for chlortetracycline and 0.05 g‧L^-1 for ceftriaxone. CeO₂/ZnO assemblies showed much better degradation efficiency compared to ZnO or CeO₂ tested individually. Sample S3 shows good photocatalytic properties for the elimination of ceftriaxone and tetracycline both from single solutions and from the binary solution. This work provides a different perspective to identify other powerful and inexpensive photocatalysts for wastewater treatment.

Simultaneous screening and analysis of 155 veterinary drugs in livestock foods using ultra-high performance liquid chromatography tandem quadrupole linear-ion-trap mass spectrometry

Veterinary drugs are widely used to improve the health and growth of livestock. The supervision of these residues is necessary to ensure food safety. A high-throughput method based on Oasis PRiME HLB with solid phase extraction for simultaneous qualitative and quantitative analysis of 155 veterinary drugs in livestock foods was developed by the ultra-high performance liquid chromatography tandem quadrupole linear-ion-trap mass spectrometry (UHPLC-QTRAP-MS). The limits of detection and quantification ranged from 0.5 μg/kg to 5 μg/kg and 2 μg/kg to 20 μg/kg, respectively. For over 85% of the analytes, the recoveries were between 60% and 120%. The positive simulated samples perfectly matched with a purity fit value over 70% from the self-built library. The screening results of UHPLC-QTRAP-MS were almost consistent with UHPLC tandem quadrupole-exactive orbitrap mass spectrometry (UHPLC-Q-Exactive Orbitrap/MS). The evaluated UHPLC-QTRAP-MS method was powerful and reliable for the screening and quantification of veterinary drugs in real samples.

New drugs against multidrug-resistant Gram-negative bacteria: a systematic review of patents

Background: Antimicrobial resistance has been a threat to human health ever since the accelerated consumption of antibiotics began. Materials & methods: The present systematic review was carried out using a free and specialized online database - Espacenet - and a survey for patents of antimicrobial agents from 2010 to 2021, selecting 33 recent patents that claimed compounds with antimicrobial activity against resistant strains of Gram-negative bacteria. Results: Some different and new approaches to the development of the patented antibacterial agents were identified, such as antimicrobial peptides, nanomaterials and natural extracts. Conclusion: Some alternatives to modern antibiotics with diminished effectiveness due to antimicrobial resistance were spotted. Nevertheless, many challenges remain to establish a robust and sustainable antibacterial R&D pipeline.

Sulfadiazine inhibits hydrogen production during sludge anaerobic fermentation by affecting pyruvate decarboxylation

The overuse and random discharge of antibiotics can cause serious environmental pollution. Sludge acts as a repository for antibiotics, its anaerobic fermentation process will inevitably be affected. This study investigated the effects of a typical antibiotic contaminant, sulfadiazine (SDZ), on the anaerobic fermentation of sludge for hydrogen production. Results demonstrated that the production of hydrogen was significantly inhibited by SDZ, and the inhibition was enhanced with increasing SDZ content. Within 5 days, the cumulative amount of hydrogen with 500 mg SDZ/kg dry sludge was 8.5 mL, which was only 32.2% of that in the control (26.4 mL). Mechanistic investigation showed that the reduced hydrogen production when SDZ existed was mainly attributed to the suppression of pyruvate decarboxylation during the hydrogen production stage, and the diversity of microorganisms, especially the abundance of microorganisms and the activities of key enzymes closely related to hydrogen production were inhibited with SDZ, resulting in less hydrogen accumulation.

Antistaphylococcal Activities and ADME-Related Properties of Chlorinated Arylcarbamoylnaphthalenylcarbamates

Pattern 1-hydroxy-N-(2,4,5-trichlorophenyl)-2-naphthamide and the thirteen original carbamates derived from it were prepared and characterized. All the compounds were tested against Staphylococcus aureus ATCC 29213 as a reference and quality control strain and in addition against three clinical isolates of methicillin-resistant S. aureus (MRSA). Moreover, the compounds were evaluated against Enterococcus faecalis ATCC 29212, and preliminary in vitro cytotoxicity of the compounds was assessed using the human monocytic leukemia cell line (THP-1). The lipophilicity of the prepared compounds was experimentally determined and correlated with biological activity. While pattern anilide had no antibacterial activity, the prepared carbamates demonstrated high antistaphylococcal activity comparable to the used standards (ampicillin and ciprofloxacin), which unfortunately were ineffective against E. feacalis. 2-[(2,4,5-Trichlorophenyl)carba- moyl]naphthalen-1-yl ethylcarbamate (2) and 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl butylcarbamate (4) expressed the nanomolar minimum inhibitory concentrations (MICs 0.018−0.064 μM) against S. aureus and at least two other MRSA isolates. Microbicidal effects based on the minimum bactericidal concentrations (MBCs) against all the tested staphylococci were found for nine carbamates, while 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl heptylcarbamate (7) and 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl (4-phenylbutyl)carbamate (14) demonstrated MBCs in the range of 0.124−0.461 μM. The selectivity index (SI) for most investigated carbamates was >20 and for some derivatives even >100. The performed tests did not show an effect on the damage to the bacterial membrane, while the compounds were able to inhibit the respiratory chain of S. aureus.

A review on synthetic account of 1,2,4-oxadiazoles as anti-infective agents

Most of the currently marketed drugs consist of heterocyclic scaffolds containing nitrogen and or oxygen as heteroatoms in their structures. Several research groups have synthesized diversely substituted 1,2,4-oxadiazoles as anti-infective agents having anti-bacterial, anti-viral, anti-leishmanial, etc. activities. For the first time, the present review article will provide the coverage of synthetic account of 1,2,4-oxadiazoles as anti-infective agents along with their potential for SAR, activity potential, promising target for mode of action. The efforts have been made to provide the chemical intuitions to the reader to design new chemical entity with potential of anti-infective activity. This review will mark the impact as the valuable, comprehensive and pioneered work along with the library of synthetic strategies for the organic and medicinal chemists for further refinement of 1,2,4-oxadiazole as anti-infective agents.