Bacterial Resistance to Antimicrobial Agents

Acinetobacter baumannii biofilm was inhibited by tryptanthrin through disrupting its different stages and genes expression

Biofilm formation plays a significant role in antibiotic resistance, necessitating the search for alternative therapies against biofilm-associated infections. This study demonstrates that 20 μg/mL tryptanthrin can hinder biofilm formation above 50% in various A. baumannii strains. Tryptanthrin impacts various stages of biofilm formation, including the inhibition of surface motility and eDNA release in A. baumannii, as well as an increase in its sensitivity to H202. RT-qPCR analysis reveals that tryptanthrin significantly decreases the expression of the following genes: abaI (19.07%), abaR (33.47%), bfmR (43.41%), csuA/B (64.16%), csuE (50.20%), ompA (67.93%), and katE (72.53%), which are related to biofilm formation and quorum sensing. Furthermore, tryptanthrin is relatively safe and can reduce the virulence of A. baumannii in a Galleria mellonella infection model. Overall, our study demonstrates the potential of tryptanthrin in controlling biofilm formation and virulence of A. baumannii by disrupting different stages of biofilm formation and intercellular signaling communication.

Major facilitator superfamily efflux pumps in human pathogens: Role in multidrug resistance and beyond

The major facilitator superfamily (MFS) of proteins constitutes a large group of related solute transporters found across all known living taxa of organisms. The transporters of the MFS contain an extremely diverse array of substrates, including ions, molecules of intermediary metabolism, and structurally different antimicrobial agents. First discovered over 30 years ago, the MFS represents an important collection of integral membrane transporters. Bacterial microorganisms expressing multidrug efflux pumps belonging to the MFS are considered serious pathogens, accounting for alarming morbidity and mortality numbers annually. This review article considers recent advances in the structure-function relationships, the transport mechanism, and modulation of MFS multidrug efflux pumps within the context of drug resistance mechanisms of bacterial pathogens of public health concerns.

Zwitterion-Modified MXene Quantum Dot as a Nanocarrier for Traditional Chinese Medicine Sanguinarine Delivery and Its Application for Photothermal-Chemotherapy Synergistic Antibacterial and Wound Healing

The nanomaterialization of traditional Chinese medicine (TCM) has aroused widespread interest among researchers. Sanguinarine (SAN) is a kind of TCM with good antibacterial properties, which has important applications in anti-infection of wounds. Additionally, the combination of photothermal therapy and chemotherapy can overcome bacterial resistance, further improving bactericidal and wound healing efficiency. In this paper, we prepared an antibacterial agent by loading SAN on the zwitterion-modified MXene quantum dot nanocarrier (SAN@AHEP@Ta4C3), realizing pH/NIR controlled drug release and photothermal/chemotherapy synergistic antibacterial and wound healing. The particle size of SAN@AHEP@Ta4C3 is about 120 nm, and it has a good water solubility and stability. In addition, it also has excellent photothermal conversion performance (η = 39.2%), which can effectively convert light energy into heat energy under near-infrared (NIR) laser irradiation, further promoting drug release and achieving bactericidal effects by synergistic chemotherapy and photothermal therapy. The in vitro and in vivo experiments show that SAN@AHEP@Ta4C3 exhibits an excellent antibacterial effect against Staphylococcus aureus and Escherichia coli, and it can effectively promote the wound healing of mice. Moreover, the SAN@AHEP@Ta4C3 also has good biocompatibility and has no side effects on normal tissue and organs. This work introduces a multifunctional antibacterial agent based on TCM and hot-spot material MXene, which will have considerable application prospects in biomedical fields.

Exploiting the advantages of cationic copolymers and AgBr nanoparticles to optimize the antibacterial activity of chitosan

Recently, the chitosan (CS)-based composites have attracted increasing attention for controlling and preventing the spread of pathogenic microorganisms. Herein, an amphiphilic copolymer containing epoxy and quaternary ammonium groups (PBGDBr) was synthesized via three common acrylate monomers. The epoxy groups of this copolymer were then crosslinked with the amino groups of CS to synthesize a natural/synthetic (PBGDBr-C) composite to increase the water solubility of CS under alkaline conditions and enhance its antibacterial activity based on chemical contact-type modes. Moreover, silver bromide nanoparticles (AgBr NPs)-decorated PBGDBr-C (AgBr@PBGDBr-C) composite was prepared, which aimed to endow the final AgBr@PBGDBr-C composite with a photodynamic antibacterial mode relying on the formation of Ag/AgBr nanostructures catalyzed by visible light on AgBr NPs. The results showed that the final composite possessed satisfactory bactericidal effects at concentrations higher than 64 and 128 μg/mL against Escherichia coli and Staphylococcus aureus, respectively. Additionally, The L929 cells treated with the final composite retained high cell viability (>80 %) at a concentration of 128 μg/mL, indicating its low toxicity to L929 cells. Overall, our synthetic strategy exploits a multi-modal system that enables chemical-photodynamic synergies to treat infections caused by pathogenic bacteria while delaying the development of bacterial resistance.

Proving the Antimicrobial Therapeutic Activity on a New Copper-Thiosemicarbazone Complex

The misuse and overdose of antimicrobial medicines are fostering the emergence of novel drug-resistant pathogens, providing negative repercussions not only on the global healthcare system due to the rise of long-term or chronic patients and inefficient therapies but also on the world trade, productivity, and, in short, to the global economic growth. In view of these scenarios, novel action plans to constrain this antibacterial resistance are needed. Thus, given the proven antiproliferative tumoral and microbial features of thiosemicarbazone (TSCN) ligands, we have here synthesized a novel effective antibacterial copper-thiosemicarbazone complex, demonstrating both its solubility profile and complex stability under physiological conditions, along with their safety and antibacterial activity in contact with human cellular nature and two most predominant bacterial strains, respectively. A significant growth inhibition (17% after 20 h) is evidenced over time, paving the way toward an effective antibacterial therapy based on these copper-TSCN complexes.

Synthesis, characterization, molecular modeling studies, and biological evaluation of metal piroxicam complexes (M = Ni(II), Pt(IV), Pd(II), Ag(I)) as antibacterial and anticancer agents

Four piroxicam metal complexes; NiL2 , PtL2 , PdL2 , and AgL were synthesized and characterized by different techniques with enhanced antibacterial and anticancer activity. Regarding in vitro antimicrobial activity, complex NiL2 displayed potent antibacterial effect against Escherichia coli and Pseudomonas aeruginosa that was 1.9-folds higher than piroxicam (minimum inhibitory concentration [MIC] = 31.85, 65.32 µM), respectively. In case of G+ve bacteria, complex PtL2 had potent activity on Staphylococcus aureus which was 2.1-folds higher than piroxicam (MIC = 43.12 µM), while activity of complex AgL against Enterococcus faecalis was threefolds higher than piroxicam (MIC = 74.57 µM. Complexes PtL2 and PdL2 exhibited higher inhibition of DNA gyrase than piroxicam (IC50  = 6.21 µM) in the range of 1.9-1.7-folds. The in vitro antiproliferative activity depicted that all investigated complexes showed better cytotoxic effect than piroxicam, specifically Pt and Pd complexes which had lower IC50 values than piroxicam on human liver cancer cell line HepG2 by 1.8 and 1.7-folds, respectively. While Pd and Ag complexes showed 2 and 1.6-folds better effect on human colon cancer cell line HT-29 compared with piroxicam. Molecular modeling studies including docking on Stranded DNA Duplex (1juu) and DNA gyrase enzyme (1kzn) that gave good insight about interaction of complexes with target molecules, calculation of electrostatic potential map and global reactivity descriptors were performed.

A Study of Resistome in Mexican Chili Powder as a Public Health Risk Factor

Chili powder is an important condiment around the world. However, according to various reports, the presence of pathogenic microorganisms could present a public health risk factor during its consumption. Therefore, microbiological quality assessment is required to understand key microbial functional traits, such as antibiotic resistance genes (ARGs). In this study, metagenomic next-generation sequencing (mNGS) and bioinformatics analysis were used to characterize the comprehensive profiles of the bacterial community and antibiotic resistance genes (ARGs) in 15 chili powder samples from different regions of Mexico. The initial bacterial load showed aerobic mesophilic bacteria (AMB) ranging between 6 × 103 and 7 × 108 CFU/g, sporulated mesophilic bacteria (SMB) from 4.3 × 103 to 2 × 109 CFU/g, and enterobacteria (En) from <100 to 2.3 × 106 CFU/g. The most representative families in the samples were Bacillaceae and Enterobacteriaceae, in which 18 potential pathogen-associated species were detected. In total, the resistome profile in the chili powder contained 68 unique genes, which conferred antibiotic resistance distributed in 13 different classes. Among the main classes of antibiotic resistance genes with a high abundance in almost all the samples were those related to multidrug, tetracycline, beta-lactam, aminoglycoside, and phenicol resistance. Our findings reveal the utility of mNGS in elucidating microbiological quality in chili powder to reduce the public health risks and the spread of potential pathogens with antibiotic resistance mechanisms.

Antibiotic action and resistance: updated review of mechanisms, spread, influencing factors, and alternative approaches for combating resistance

Antibiotics represent a frequently employed therapeutic modality for the management of bacterial infections across diverse domains, including human health, agriculture, livestock breeding, and fish farming. The efficacy of antibiotics relies on four distinct mechanisms of action, which are discussed in detail in this review, along with accompanying diagrammatic illustrations. Despite their effectiveness, antibiotic resistance has emerged as a significant challenge to treating bacterial infections. Bacteria have developed defense mechanisms against antibiotics, rendering them ineffective. This review delves into the specific mechanisms that bacteria have developed to resist antibiotics, with the help of diagrammatic illustrations. Antibiotic resistance can spread among bacteria through various routes, resulting in previously susceptible bacteria becoming antibiotic-resistant. Multiple factors contribute to the worsening crisis of antibiotic resistance, including human misuse of antibiotics. This review also emphasizes alternative solutions proposed to mitigate the exacerbation of antibiotic resistance.

Recent Development of DNA Gyrase Inhibitors: An Update

Antibiotic or antimicrobial resistance is an urgent global public health threat that occurs when bacterial or fungal infections do not respond to the drug regimen designed to treat these infections. As a result, these microbes are not evaded and continue to grow. Antibiotic resistance against natural and already-known antibiotics like Ciprofloxacin and Novobiocin can be overcome by developing an agent that can act in different ways. The success of agents like Zodiflodacin and Zenoxacin in clinical trials against DNA gyrase inhibitors that act on different sites of DNA gyrase has resulted in further exploration of this target. However, due to the emergence of bacterial resistance against these targets, there is a great need to design agents that can overcome this resistance and act with greater efficacy. This review provides information on the synthetic and natural DNA gyrase inhibitors that have been developed recently and their promising potential for combating antimicrobial resistance. The review also presents information on molecules that are in clinical trials and their current status. It also analysed the SAR studies and mechanisms of action of enlisted agents.

The potential usage of Caatinga natural products against multi-drug-resistant bacteria

New sources of antibacterial drugs have become urgent with increasing bacterial resistance. Medicinal plants are attractive sources for antimicrobial compounds with fewer side effects and cheaper obtention. Brazil contains six biomes, including Caatinga, a semi-arid tropical vegetation exclusively from Brazil that contains over thousand vascular plant species. This review presents the potential of using Caatinga plant products to treat multidrug-resistant bacteria. This review used the keywords of antimicrobial resistance, resistance profile, multidrug resistance, Caatinga biome, and pathogenic bacteria to search in Scientific Electronic Library Online, the U.S. National Library of Medicine, and Google Scholar. Plant species as Schinopsis brasiliensis Engl., Annona vepretorum Mart., Croton pulegioides Baill., Myracrondruon urundeuva Allemo, Cereus jamacaru DC., Opuntia ficus-indica L., Bauhinia forficata L., Eucalyptus globulus, Croton sonderianus Muell. Arg., Campomanesia pubescens, and Abarema cochliacarpos showed bacteriostatic activity. Encholirium spectabile Mart., Hymenaea courbaril L., Neoglaziovia variegata Mez, Selaginella convoluta Spring, Encholirium spectabile Mart., Bromelia laciniosa Mart., Hymenaea martiana, Commiphora leptophloeos, and Mimosa tenuiflora presented bactericidal activity. Those extracts inhibited clinical-importance bacteria, such as Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Therefore, Caatinga biome plants are a valuable source of active biomolecules against pathogenic bacteria, and their therapeutic potential must be further explored.

Combating Aminoglycoside Resistance: From Structural and Functional Characterisation to Therapeutic Challenges with RKAAT

A comprehensive knowledge of aminoglycoside-modifying enzymes (AMEs) and their role in bacterial resistance mechanisms is urgently required due to the rising incidence of antibiotic resistance, particularly in Klebsiella pneumoniae infections. This study explores the essential features of AMEs, including their structural and functional properties, the processes by which they contribute to antibiotic resistance, and the therapeutic importance of aminoglycosides. The study primarily examines the Recombinant Klebsiella pneumoniae Aminoglycoside Adenylyl Transferase (RKAAT), particularly emphasizing its biophysical characteristics and the sorts of resistance it imparts. Furthermore, this study examines the challenges presented by RKAAT-mediated resistance, an evaluation of treatment methods and constraints, and options for controlling infection. The analysis provides a prospective outlook on strategies to address and reduce antibiotic resistance. This extensive investigation seeks to provide vital insights into the continuing fight against bacterial resistance, directing future research efforts and medicinal approaches.

Antibacterial and Cytotoxic Study of Hybrid Films Based on Polypropylene and NiO or NiFe2O4 Nanoparticles

This study presents an in vitro analysis of the bactericidal and cytotoxic properties of hybrid films containing nickel oxide (NiO) and nickel ferrite (NiFe2O4) nanoparticles embedded in polypropylene (PP). The solvent casting method was used to synthesize films of PP, PP@NiO, and PP@NiFe2O4, which were characterized by different spectroscopic and microscopic techniques. The X-ray diffraction (XRD) patterns confirmed that the small crystallite sizes of NiO and NiFe2O4 NPs were maintained even after they were incorporated into the PP matrix. From the Raman scattering spectroscopy data, it was evident that there was a significant interaction between the NPs and the PP matrix. Additionally, the Scanning Electron Microscopy (SEM) analysis revealed a homogeneous dispersion of NiO and NiFe2O4 NPs throughout the PP matrix. The incorporation of the NPs was observed to alter the surface roughness of the films; this behavior was studied by atomic force microscopy (AFM). The antibacterial properties of all films were evaluated against Pseudomonas aeruginosa (ATCC®: 43636™) and Staphylococcus aureus (ATCC®: 23235™), two opportunistic and nosocomial pathogens. The PP@NiO and PP@ NiFe2O4 films showed over 90% bacterial growth inhibition for both strains. Additionally, the effects of the films on human skin cells, such as epidermal keratinocytes and dermal fibroblasts, were evaluated for cytotoxicity. The PP, PP@NiO, and PP@NiFe2O4 films were nontoxic to human keratinocytes. Furthermore, compared to the PP film, improved biocompatibility of the PP@NiFe2O4 film with human fibroblasts was observed. The methodology utilized in this study allows for the production of hybrid films that can inhibit the growth of Gram-positive bacteria, such as S. aureus, and Gram-negative bacteria, such as P. aeruginosa. These films have potential as coating materials to prevent bacterial proliferation on surfaces.

Mur ligase F as a new target for the flavonoids quercitrin, myricetin, and (-)-epicatechin

MurC, D, E, and F are ATP-dependent ligases involved in the stepwise assembly of the tetrapeptide stem of forming peptidoglycan. As highly conserved targets found exclusively in bacterial cells, they are of significant interest for antibacterial drug discovery. In this study, we employed a computer-aided molecular design approach to identify potential inhibitors of MurF. A biochemical inhibition assay was conducted, screening twenty-four flavonoids and related compounds against MurC-F, resulting in the identification of quercitrin, myricetin, and (-)-epicatechin as MurF inhibitors with IC50 values of 143 µM, 139 µM, and 92 µM, respectively. Notably, (-)-epicatechin demonstrated mixed type inhibition with ATP and uncompetitive inhibition with D-Ala-D-Ala dipeptide and UM3DAP substrates. Furthermore, in silico analysis using Sitemap and subsequent docking analysis using Glide revealed two plausible binding sites for (-)-epicatechin. The study also investigated the crucial structural features required for activity, with a particular focus on the substitution pattern and hydroxyl group positions, which were found to be important for the activity. The study highlights the significance of computational approaches in targeting essential enzymes involved in bacterial peptidoglycan synthesis.

Nanopore Sequencing Assessment of Bacterial Pathogens and Associated Antibiotic Resistance Genes in Environmental Samples

As seen in earlier and present pandemics, monitoring pathogens in the environment can offer multiple insights on their spread, evolution, and even future outbreaks. The present paper assesses the opportunity to detect microbial pathogens and associated antibiotic resistance genes, in relation to specific pathogen sources, by using nanopore sequencing in municipal waters and wastewaters in Romania. The main results indicated that waters collecting effluents from a meat processing facility exhibit altered communities' diversity and abundance, with reduced values (101-108 and 0.86-0.91) of Chao1 and, respectively, Simpson diversity indices and Campylobacterales as main order, compared with other types of municipal waters where the same diversity index had much higher values of 172-214 and 0.97-0.98, and Burkholderiaceae and Pseudomonadaceae were the most abundant families. Moreover, the incidence and type of antibiotic resistance genes were significantly influenced by the proximity of antibiotic sources, with either tetracycline (up to 45% of total reads) or neomycin, streptomycin and tobramycin (up to 3.8% total reads) resistance incidence being shaped by the sampling site. As such, nanopore sequencing proves to be an easy-to-use, accessible molecular technique for environmental pathogen surveillance and associated antibiotic resistance genes.

Beyond Canine Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells Transplantation: An Update on Their Secretome Characterization and Applications

A dog is a valuable animal model and concomitantly a pet for which advanced therapies are increasingly in demand. The characteristics of mesenchymal stem/stromal cells (MSCs) have made cell therapy more clinically attractive. During the last decade, research on the MSC therapeutic effectiveness has demonstrated that tissue regeneration is primarily mediated by paracrine factors, which are included under the name of secretome. Secretome is a mixture of soluble factors and a variety of extracellular vesicles. The use of secretome for therapeutic purposes could have some advantages compared to cell-based therapies, such as lower immunogenicity and easy manufacturing, manipulation, and storage. The conditioned medium and extracellular vesicles derived from MSCs have the potential to be employed as new treatments in veterinary medicine. This review provides an update on the state-of-the-art characterization and applications of canine adipose tissue-derived MSC secretome.

Innovative Phospholipid Carriers: A Viable Strategy to Counteract Antimicrobial Resistance

The overuse and misuse of antibiotics have led to the emergence and spread of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) bacteria strains, usually associated with poorer patient outcomes and higher costs. In order to preserve the usefulness of these life-saving drugs, it is crucial to use them appropriately, as also recommended by the WHO. Moreover, innovative, safe, and more effective approaches are being investigated, aiming to revise drug treatments to improve their pharmacokinetics and distribution and to reduce the onset of drug resistance. Globally, to reduce the burden of antimicrobial resistance (AMR), guidelines and indications have been developed over time, aimed at narrowing the use and diminishing the environmental spread of these life-saving molecules by optimizing prescriptions, dosage, and times of use, as well as investing resources into obtaining innovative formulations with better pharmacokinetics, pharmacodynamics, and therapeutic results. This has led to the development of new nano-formulations as drug delivery vehicles, characterized by unique structural properties, biocompatible natures, and targeted activities such as state-of-the-art phospholipid particles generally grouped as liposomes, virosomes, and functionalized exosomes, which represent an attractive and innovative delivery approach. Liposomes and virosomes are chemically synthesized carriers that utilize phospholipids whose nature is predetermined based on their use, with a long track record as drug delivery systems. Exosomes are vesicles naturally released by cells, which utilize the lipids present in their cellular membranes only, and therefore, are highly biocompatible, with investigations as a delivery system having a more recent origin. This review will summarize the state of the art on microvesicle research, liposomes, virosomes, and exosomes, as useful and effective tools to tackle the threat of antibiotic resistance.

Antibacterial and Toxic Activity of Geopropolis Extracts from Melipona subnitida (Ducke, 1910) (Hymenoptera: Apidae) and Scaptotrigona depilis (Moure, 1942) (Hymenoptera: Apidae)

Bacteria are associated with many infections that affect humans and present antibiotic resistance mechanisms, causing problems in health organisations and increased mortality rates. Therefore, it is necessary to find new antibacterial agents that can be used in the treatment of these microorganisms. Geopropolis is a natural product from stingless bees, formed by a mixture of plant resins, salivary secretions, wax and soil particles, the chemical composition of this natural product is diverse. Thus, this study aimed to evaluate antibacterial activity, antibiotic modulation and the toxicity of geopropolis extracts from the stingless bees, Melipona subnitida (Ducke, 1910) and Scaptotrigona depilis (Moure, 1942) against standard and multi-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacteria. Geopropolis samples were collected in a meliponary located in Camaragibe, Pernambuco, Brazil. To determine the Minimum Inhibitory Concentration (MIC) and antibiotic modulation we performed broth microdilution tests. Mortality tests were used to verify extract toxicity in the model Drosophila melanogaster. The microbiological tests showing that the M. subnitida extracts had better inhibitory effects compared to S. depilis, presenting direct antibacterial activity against standard and multi-resistant strains. The extracts potentialized antibiotic effects, suggesting possible synergy and did not present toxicity in the model used. The information obtained in this study highlights extracts as promising antibacterial agents and is the first study to evaluate bacterial activity in these extracts, in addition to verifying their modulating effects and determining toxicity in the model used.

Characterisation of the essential oil from Iphiona grantioides and investigation of its antibacterial and antioxidant properties

Iphiona grantioides (Boiss) Anderb. is a medicinal plant featuring several traditional uses. Nevertheless, this plant has not been widely investigated by modern medicinal chemistry yet, as also the properties of its extracts.In this study, we report the extraction of the essential oil by hydrodistillation from the leaves of I. grantioides. This was characterised by GC-MS analysis and ten chemical constituents were identified.Our findings demonstrate that the essential oil is effective in inhibiting the growth of bacterial strains, and of Klebsiela pneumonia and Staphylococcus aureus in particular. Additionally, its antioxidant properties were evaluated, and it showed radical scavenging activity in vitro.

Progress in Nanostructured Mechano-Bactericidal Polymeric Surfaces for Biomedical Applications

Bacterial infections and antibiotic resistance remain significant contributors to morbidity and mortality worldwide. Despite recent advances in biomedical research, a substantial number of medical devices and implants continue to be plagued by bacterial colonisation, resulting in severe consequences, including fatalities. The development of nanostructured surfaces with mechano-bactericidal properties has emerged as a promising solution to this problem. These surfaces employ a mechanical rupturing mechanism to lyse bacterial cells, effectively halting subsequent biofilm formation on various materials and, ultimately, thwarting bacterial infections. This review delves into the prevailing research progress within the realm of nanostructured mechano-bactericidal polymeric surfaces. It also investigates the diverse fabrication methods for developing nanostructured polymeric surfaces with mechano-bactericidal properties. We then discuss the significant challenges associated with each approach and identify research gaps that warrant exploration in future studies, emphasizing the potential for polymeric implants to leverage their distinct physical, chemical, and mechanical properties over traditional materials like metals.

Evaluation of the biological responses of silver nanoparticles synthesized using Pelargonium x hortorum extract

Silver nanoparticles (AgNPs) are one of the widely studied nanomaterials for diverse biomedical applications, in particular, as antimicrobial agents to kill bacteria, fungi, and viruses. In this report, AgNPs were synthesized using a geranium (Pelargonium x hortorum) leaves extract and tested for their antimicrobial and cytotoxic activity and reactive oxygen species (ROS) production. Using green biosynthesis, the leaves extract was employed as a reducing and stabilizing agent. Synthesis parameters like reaction time and precursor (silver nitrate AgNO3) volume final were modified, and the products were tested against Streptococcus mutans. For the first time, the metabolomic analysis of extract, we have identified more than 50 metabolites. The UV-Vis analysis showed a peak ranging from 410-430 nm, and TEM confirmed their nearly spherical morphology for all NPs. The antimicrobial activity of the NPs revealed a minimum inhibitory concentration (MIC) of 10 μg mL-1. Concerning cytotoxicity, a dose-time-dependent effect was observed with a 50% cellular cytotoxicity concentration (CC50) of 4.51 μg mL-1 at 24 h. Interestingly, the cell nuclei were visualized using fluorescence microscopy, and no significant changes were observed. These results suggest that synthesized spherical AgNPs are promising potential candidates for medical applications.

Metallic Nanoparticles: A Promising Arsenal against Antimicrobial Resistance-Unraveling Mechanisms and Enhancing Medication Efficacy

The misuse of antibiotics and antimycotics accelerates the emergence of antimicrobial resistance, prompting the need for novel strategies to combat this global issue. Metallic nanoparticles have emerged as effective tools for combating various resistant microbes. Numerous studies have highlighted their potential in addressing antibiotic-resistant fungi and bacterial strains. Understanding the mechanisms of action of these nanoparticles, including iron-oxide, gold, zinc oxide, and silver is a central focus of research within the life science community. Various hypotheses have been proposed regarding how nanoparticles exert their effects. Some suggest direct targeting of microbial cell membranes, while others emphasize the release of ions from nanoparticles. The most compelling proposed antimicrobial mechanism of nanoparticles involves oxidative damage caused by nanoparticles-generated reactive oxygen species. This review aims to consolidate knowledge, discuss the properties and mechanisms of action of metallic nanoparticles, and underscore their potential as alternatives to enhance the efficacy of existing medications against infections caused by antimicrobial-resistant pathogens.

Facial amphiphilic naphthoic acid-derived antimicrobial polymers against multi-drug resistant gram-negative bacteria and biofilms

Inspired by the facial amphiphilic nature and antimicrobial efficacy of many antimicrobial peptides, this work reported facial amphiphilic bicyclic naphthoic acid derivatives with different ratios of charges to rings that were installed onto side chains of poly(glycidyl methacrylate). Six quaternary ammonium-charged (QAC) polymers were prepared to investigate the structure-activity relationship. These QAC polymers displayed potent antibacterial activity against various multi-drug resistant (MDR) gram-negative pathogens such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Polymers demonstrated low hemolysis and high antimicrobial selectivity. Additionally, they were able to eradicate established biofilms and kill metabolically inactive dormant cells. The membrane permeabilization and depolarization results indicated a mechanism of action through membrane disruption. Two lead polymers showed no resistance from MDR-P. aeruginosa and MDR-K. pneumoniae. These facial amphiphiles are potentially a new class of potent antimicrobial agents to tackle the antimicrobial resistance for both planktonic and biofilm-related infections.

Repositioning of HMG-CoA Reductase Inhibitors as Adjuvants in the Modulation of Efflux Pump-Mediated Bacterial and Tumor Resistance

Efflux pump (EP)-mediated multidrug resistance (MDR) seems ubiquitous in bacterial infections and neoplastic diseases. The diversity and lack of specificity of these efflux mechanisms raise a great obstacle in developing drugs that modulate efflux pumps. Since developing novel chemotherapeutic drugs requires large investments, drug repurposing offers a new approach that can provide alternatives as adjuvants in treating resistant microbial infections and progressive cancerous diseases. Hydroxy-methyl-glutaryl coenzyme-A (HMG-CoA) reductase inhibitors, also known as statins, are promising agents in this respect. Originally, statins were used in the therapy of dyslipidemia and for the prevention of cardiovascular diseases; however, extensive research has recently been performed to elucidate the functions of statins in bacterial infections and cancers. The mevalonate pathway is essential in the posttranslational modification of proteins related to vital eukaryotic cell functions. In this article, a comparative review is given about the possible role of HMG-CoA reductase inhibitors in managing diseases of bacterial and neoplastic origin. Molecular research and clinical studies have proven the justification of statins in this field. Further well-designed clinical trials are urged to clarify the significance of the contribution of statins to the lower risk of disease progression in bacterial infections and cancerous diseases.

Inhibition of MurA Enzyme from Escherichia coli by Flavonoids and Their Synthetic Analogues

MurA catalyzes the first step of peptidoglycan (PG) biosynthesis and is a validated target for the development of new antimicrobial agents. In this study, a library of 49 plant flavonoids and their synthetic derivatives were evaluated for their inhibitory properties against MurA fromEscherichia coli. The compounds were tested with and without preincubation and with the addition of DTT to understand the mechanism of inhibition. Thirteen compounds were identified as reversible, time-dependent inhibitors, with inhibition levels ranging from 480 nM to 57 μM, and ampelopsin as the most potent compound. To investigate the major pharmacophore elements responsible for the activity, 2D-QSAR and docking analyzes were performed. The results showed that the catechol moiety and an additional aromatic system were the most important features contributing to the activity of the compounds. However, most of the compounds did not show antibacterial activity againstE. coli andStaphylococcus aureusstrains, suggesting that their inhibitory activity against MurA may not be strong enough to induce antibacterial effects. Nevertheless, our results suggest that flavonoids are a promising starting point to develop new inhibitors of MurA and show great potential for further steps in drug development.

Repurposing Selamectin as an Antimicrobial Drug against Hospital-Acquired Staphylococcus aureus Infections

The emergence of multidrug-resistant strains requires the urgent discovery of new antibacterial drugs. In this context, an antibacterial screening of a subset of anthelmintic avermectins against gram-positive and gram-negative strains was performed. Selamectin completely inhibited bacterial growth at 6.3 μg/mL concentrations against reference gram-positive strains, while no antibacterial activity was found against gram-negative strains up to the highest concentration tested of 50 μg/mL. Given its relevance as a community and hospital pathogen, further studies have been performed on selamectin activity against Staphylococcus aureus (S. aureus), using clinical isolates with different antibiotic resistance profiles and a reference biofilm-producing strain. Antibacterial studies have been extensive on clinical S. aureus isolates with different antibiotic resistance profiles. Mean MIC90 values of 6.2 μg/mL were reported for all tested S. aureus strains, except for the macrolide-resistant isolate with constitutive macrolide-lincosamide-streptogramin B resistance phenotype (MIC90 9.9 μg/mL). Scanning Electron Microscopy (SEM) showed that selamectin exposure caused relevant cell surface alterations. A synergistic effect was observed between ampicillin and selamectin, dictated by an FIC value of 0.5 against methicillin-resistant strain. Drug administration at MIC concentration reduced the intracellular bacterial load by 81.3%. The effect on preformed biofilm was investigated via crystal violet and confocal laser scanning microscopy. Selamectin reduced the biofilm biomass in a dose-dependent manner with minimal biofilm eradication concentrations inducing a 50% eradication (MBEC50) at 5.89 μg/mL. The cytotoxic tests indicated that selamectin exhibited no relevant hemolytic and cytotoxic activity at active concentrations. These data suggest that selamectin may represent a timely and promising macrocyclic lactone for the treatment of S. aureus infections.

Detection of extended-spectrum β-lactamase-producing Escherichia coli genes isolated from cat rectal swabs at Surabaya Veterinary Hospital, Indonesia

Background and Aim

Escherichia coli causes a bacterial illness that frequently affects cats. Diseases caused by E. coli are treated using antibiotics. Because of their proximity to humans, cats possess an extremely high risk of contracting antibiotic resistance genes when their owners touch cat feces containing E. coli that harbor resistance genes. This study was conducted to identify multidrug-resistant E. coli and extended-spectrum β-lactamase (ESBL)-producing genes from cat rectal swabs collected at Surabaya City Veterinary Hospital to determine antibiotic sensitivity.

Materials and Methods

Samples of cat rectal swabs were cultured in Brilliant Green Bile Lactose Broth medium and then streaked on eosin methylene blue agar medium for bacterial isolation, whereas Gram-staining and IMViC tests were conducted to confirm the identification results. The Kirby-Bauer diffusion test was used to determine antibiotic sensitivity, and the double-disk synergy test was used to determine ESBL-producing bacteria. Molecular detection of the genes TEM and CTX-M was performed using a polymerase chain reaction.

Results

Based on morphological culture, Gram-staining, and biochemical testing, the results of sample inspection showed that of the 100 cat rectal swab samples isolated, 71 (71%) were positive for E. coli. Furthermore, 23 E. coli isolates (32.39%) demonstrated the highest resistance to ampicillin. Four isolates were confirmed to be multidurg-resistant and ESBL-producing strains. Molecular examination revealed that three E. coli isolates harbored TEM and CTX-M.

Conclusion

In conclusion, pet owners must be educated on the use of antibiotics to improve their knowledge about the risks of antibiotic resistance.

Green Synthesis of MOF-Mediated pH-Sensitive Nanomaterial AgNPs@ZIF-8 and Its Application in Improving the Antibacterial Performance of AgNPs

Purpose

Herein, an emerging drug delivery system was constructed based on zeolite imidazole backbone (ZIF-8) to improve antibacterial defects of nanosilver (AgNPs), such as easily precipitated and highly cytotoxic.

Methods

The homogeneous dispersion of AgNPs on ZIF-8 was confirmed by UV-Vis spectroscopy, FTIR spectroscopy, particle size analysis, zeta potential analysis, and SEM. The appropriate AgNPs loading ratio on ZIF-8 was screened through the cell and antibacterial experiments based on biosafety and antibacterial performance. The optimal environment for AgNPs@ZIF-8 to exert antibacterial performance was probed in the context of bacterial communities under different acid-base conditions. The potential mechanism of AgNPs@ZIF-8 to inhibit the common clinical strains was investigated by observing the biofilm metabolic activity and the level of reactive oxygen species (ROS) in bacteria.

Results

The successful piggybacking of AgNPs by ZIF-8 was confirmed using UV-Vis spectroscopy, FTIR spectroscopy, particle size analysis, zeta potential analysis, and SEM characterization methods. Based on the bacterial growth curve (0-24 hours), the antibacterial ability of AgNPs@ZIF-8 was found to be superior to AgNPs. When the mass ratio of ZIF-8 and AgNPs was 1:0.25, the selection of AgNPs@ZIF-8 was based on its superior antimicrobial efficacy and enhanced biocompatibility. Notably, under weakly acidic bacterial microenvironments (pH=6.4), AgNPs@ZIF-8 demonstrated a more satisfactory antibacterial effect. In addition, experiments on biofilms showed that concentrations of AgNPs@ZIF-8 exceeding 1×MIC resulted in more than 50% biofilm removal. The nanomedicine was found to increase ROS levels upon detecting the ROS concentration in bacteria.

Conclusion

Novel nanocomposites consisting of low cytotoxicity drug carrier ZIF-8 loaded with AgNPs exhibited enhanced antimicrobial effects compared to AgNPs alone. The pH-responsive nano drug delivery system, AgNPs@ZIF-8, exhibited superior antimicrobial activity in a mildly acidic environment. Moreover, AgNPs@ZIF-8 effectively eradicated pathogenic bacterial biofilms and elevated the intracellular level of ROS.

Nanosilver: An Old Antibacterial Agent with Great Promise in the Fight against Antibiotic Resistance

Antibiotic resistance in bacteria is a major problem worldwide that costs 55 billion USD annually for extended hospitalization, resource utilization, and additional treatment expenditures in the United States. This review examines the roles and forms of silver (e.g., bulk Ag, silver salts (AgNO3), and colloidal Ag) from antiquity to the present, and its eventual incorporation as silver nanoparticles (AgNPs) in numerous antibacterial consumer products and biomedical applications. The AgNP fabrication methods, physicochemical properties, and antibacterial mechanisms in Gram-positive and Gram-negative bacterial models are covered. The emphasis is on the problematic ESKAPE pathogens and the antibiotic-resistant pathogens of the greatest human health concern according to the World Health Organization. This review delineates the differences between each bacterial model, the role of the physicochemical properties of AgNPs in the interaction with pathogens, and the subsequent damage of AgNPs and Ag+ released by AgNPs on structural cellular components. In closing, the processes of antibiotic resistance attainment and how novel AgNP-antibiotic conjugates may synergistically reduce the growth of antibiotic-resistant pathogens are presented in light of promising examples, where antibiotic efficacy alone is decreased.

Electroacoustic Biosensor Systems for Evaluating Antibiotic Action on Microbial Cells

Antibiotics are widely used to treat infectious diseases. This leads to the presence of antibiotics and their metabolic products in the ecosystem, especially in aquatic environments. In many countries, the growth of pathogen resistance to antibiotics is considered a threat to national security. Therefore, methods for determining the sensitivity/resistance of bacteria to antimicrobial drugs are important. This review discusses the mechanisms of the formation of antibacterial resistance and the various methods and sensor systems available for analyzing antibiotic effects on bacteria. Particular attention is paid to acoustic biosensors with active immobilized layers and to sensors that analyze antibiotics directly in liquids. It is shown that sensors of the second type allow analysis to be done within a short period, which is important for timely treatment.

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.

Molecular epidemiology and characterization of antimicrobial-resistant Staphylococcus haemolyticus strains isolated from dairy cattle milk in Northwest, China

Introduction

Non-aureus Staphylococcus (NAS) species are currently the most commonly identified microbial agents causing sub-clinical infections of the udder and are also deemed as opportunistic pathogens of clinical mastitis in dairy cattle. More than 10 NAS species have been identified and studied but little is known about S. haemolyticus in accordance with dairy mastitis. The present study focused on the molecular epidemiology and genotypic characterization of S. haemolyticus isolated from dairy cattle milk in Northwest, China.

Methods

In this study, a total of 356 milk samples were collected from large dairy farms in three provinces in Northwest, China. The bacterial isolation and presumptive identification were done by microbiological and biochemical methods following the molecular confirmation by 16S rRNA gene sequencing. The antimicrobial susceptibility testing (AST) was done by Kirby-Bauer disk diffusion assay and antibiotic-resistance genes (ARGs) were identified by PCR. The phylogenetic grouping and sequence typing was done by Pulsed Field Gel Electrophoresis (PFGE) and Multi-Locus Sequence Typing (MLST) respectively.

Results

In total, 39/356 (11.0%) were identified as positive for S. haemolyticus. The overall prevalence of other Staphylococcus species was noted to be 39.6% (141/356), while the species distribution was as follows: S. aureus 14.9%, S. sciuri 10.4%, S. saprophyticus 7.6%, S. chromogenes 4.2%, S. simulans 1.4%, and S. epidermidis 1.1%. The antimicrobial susceptibility of 39 S. haemolyticus strains exhibited higher resistance to erythromycin (92.3%) followed by trimethoprim-sulfamethoxazole (51.3%), ciprofloxacin (43.6%), florfenicol (30.8%), cefoxitin (28.2%), and gentamicin (23.1%). All of the S. haemolyticus strains were susceptible to tetracycline, vancomycin, and linezolid. The overall percentage of multi-drug resistant (MDR) S. haemolyticus strains was noted to be 46.15% (18/39). Among ARGs, mphC was identified as predominant (82.05%), followed by ermB (33.33%), floR (30.77%), gyrA (30.77%), sul1 (28.21%), ermA (23.08%), aadD (12.82%), grlA (12.82%), aacA-aphD (10.26%), sul2 (10.26%), dfrA (7.69%), and dfrG (5.13%). The PFGE categorized 39 S. haemolyticus strains into A-H phylogenetic groups while the MLST categorized strains into eight STs with ST8 being the most predominant while other STs identified were ST3, ST11, ST22, ST32, ST19, ST16, and ST7.

Conclusion

These findings provided new insights into our understanding of the epidemiology and genetic characteristics of S. haemolyticus in dairy farms to inform interventions limiting the spread of AMR in dairy production.

Inhibition of Multidrug Efflux Pumps Belonging to the Major Facilitator Superfamily in Bacterial Pathogens

Bacterial pathogens resistant to multiple structurally distinct antimicrobial agents are causative agents of infectious disease, and they thus constitute a serious concern for public health. Of the various bacterial mechanisms for antimicrobial resistance, active efflux is a well-known system that extrudes clinically relevant antimicrobial agents, rendering specific pathogens recalcitrant to the growth-inhibitory effects of multiple drugs. In particular, multidrug efflux pump members of the major facilitator superfamily constitute central resistance systems in bacterial pathogens. This review article addresses the recent efforts to modulate these antimicrobial efflux transporters from a molecular perspective. Such investigations can potentially restore the clinical efficacy of infectious disease chemotherapy.

Inhibiting bacterial biofilm formation by stimulating c-di-GMP regulation using citrus peel extract from Jeju Island

Biofilms consist of single or multiple species of bacteria embedded in extracellular polymeric substances (EPSs), which affect the increase in antibiotic resistance by restricting the transport of antibiotics to the bacterial cells. An alternative approach to treatment with antimicrobial agents is using biofilm inhibitors that regulate biofilm development without inhibiting bacterial growth. In this study, we found that citrus peel extract from Jeju Island (CPEJ) can inhibit bacterial biofilm formation. According to the results, CPEJ concentration-dependently reduces biofilm formation without affecting bacterial growth. Additionally, CPEJ decreased the production of extracellular polymeric substances but increased bacterial swarming motility. These results led to the hypothesis that CPEJ can reduce intracellular bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) concentration. The results showed that CPEJ significantly reduced the c-di-GMP level through increased phosphodiesterase activity. Altogether, these findings suggest that CPEJ as a biofilm inhibitor has new potential for pharmacological (e.g. drug and medication) and industrial applications (e.g. ship hulls, water pipes, and membrane processes biofouling control).

Antibiotic resistance profiles on pathogenic bacteria in the Brazilian environments

The present study aimed to elaborate a review of multidrug-resistant (MDR) bacteria in soil, food, aquatic environments, cattle, poultry, and swine farms in Brazil. Initially, the literature database for published papers from 2012 to 2023 was Scientific Electronic Library Online (SciELO), U.S. National Library of Medicine (PubMed), and Google Scholar, through the descriptors: antimicrobial resistance, resistance profile, multidrug resistance, environmental bacteria, and pathogenic bacteria. The studies demonstrated the prevalence of pathogenic and resistant bacteria in environments that favor their rapid dissemination. Bacteria of medical importance, such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes, Salmonella spp., Shigella spp., Vibrio spp., were present in samples from animal farms and foods, including cheese and milk, urban aquatic environments, hospital effluents, and shrimp farms. Studies suggested that important bacteria have been disseminated through different niches with easy contact with humans, animals, and food, demonstrating the danger of the emergence of increasingly difficult conditions for treating and controlling these infections. Thus, better understanding and characterizing the resistance profiles of bacteria in these regions, mainly referring to MDR bacteria, can help develop solutions to prevent the progression of this public health problem.

Design and synthesis of fascaplysin derivatives as inhibitors of FtsZ with potent antibacterial activity and mechanistic study

The increase in antibiotic resistance has made it particularly urgent to develop new antibiotics with novel antibacterial mechanisms. Inhibition of bacterial cell division by disrupting filamentous temperature-sensitive mutant Z (FtsZ) function is an effective and promising approach. A series of novel fascaplysin derivatives with tunable hydrophobicity were designed and synthesized here. The in vitro bioactivity assessment revealed that these compounds could inhibit the tested Gram-positive bacteria including methicillin-resistant S. aureus (MRSA) (MIC = 0.049-25 μg/mL), B. subtilis (MIC = 0.024-12.5 μg/mL) and S. pneumoniae (MIC = 0.049-50 μg/mL). Among them, compounds B3 (MIC = 0.098 μg/mL), B6 (MIC = 0.098 μg/mL), B8 (MIC = 0.049 μg/mL) and B16 (MIC = 0.098 μg/mL) showed the best bactericidal activities against MRSA and no significant tendency to trigger bacterial resistance as well as rapid bactericidal properties. The cell surface integrity of bacteria was significantly disrupted by hydrophobic tails of fascaplysin derivatives. Further studies revealed that these highly active amphiphilic compounds showed low hemolytic activity and cytotoxicity to mammalian cells. Preliminary mechanistic exploration suggests that B3, B6, B8 and B16 are potent FtsZ inhibitors to promote FtsZ polymerization and inhibit GTPase activity of FtsZ, leading to the death of bacterial cells by inhibiting bacterial division. Molecular docking simulations and structure-activity relationship (SAR) study reveal that appropriate increase in the hydrophobicity of fascaplysin derivatives and the addition of additional hydrogen bonds facilitated their binding to FtsZ proteins. These amphiphilic fascaplysin derivatives could serve as a novel class of FtsZ inhibitors, which not only gives new prospects for the application of compounds containing this skeleton but also provides new ideas for the discovery of new antibiotics.

Multidrug-resistant Aeromonas bacteria prevalence in Nile tilapia broodstock

BACKGROUND

Aeromonas hydrophila is an opportunistic pathogen. Thus, it has received significant attention mainly in the fish sectors with high production scales. Nile tilapia broodstock confined in the environment of fish hatcheries can be stressed. Hence, they are vulnerable to A. hydrophila.

RESULTS

Sequencing of the gyr B gene revealed the presence of 18 different A. hydrophila strains (kdy 10,620-10,637), which were deposited in the NCBI under accession numbers ON745861-ON745878. The median lethal doses of the isolates ranged from 2.62 × 10⁴ to 3.02 × 10⁶ CFU/mL. Antibiotic resistant genes, sulfonamide (sul1) and tetracycline (tetA) were found in the eighteen isolates. Approximately 83.3% of A. hydrophila strains were sensitive to ciprofloxacin and florfenicol. Further, eight A. hydrophila strains had high MDR indices at 0.27-0.45. All isolates presented with hemolysin activity. However, only 72.22% of them had proteolytic activity, and only 61.11% could form biofilms. Bacterial isolates harbored different pattern virulence genes, the heat-stable cytotonic enterotoxin (ast), cytotoxic enterotoxin (act), and hemolysin (hly) genes were the most prevalent. Also, a trial to inhibit bacterial growth was conducted using titanium dioxide nanoparticles (TiO₂ NPs) with three sizes (13, 32, and 123 nm). If A. hydrophila strains with a high MDR index were tested against TiO₂ NPs (20 µg/mL) for 1, 12, and 24 h, those with a small size had a greater bactericidal action than large ones. Bacterial strains were inhibited at different percentages in response to TiO₂ NP treatment.

CONCLUSIONS

Nile tilapia broodstock, mortality is associated with different A. hydrophila strains, which harbored virulent and MDR genes. Furthermore, TiO₂ NPs had bactericidal activity, thereby resulting in a considerable reduction in bacterial load.

The Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine, a Complex Phenomenon: A Narrative Review

As warned by Sir Alexander Fleming in his Nobel Prize address: “the use of antimicrobials can, and will, lead to resistance”. Antimicrobial resistance (AMR) has recently increased due to the overuse and misuse of antibiotics, and their use in animals (food-producing and companion) has also resulted in the selection and transmission of resistant bacteria. The epidemiology of resistance is complex, and factors other than the overall quantity of antibiotics consumed may influence it. Nowadays, AMR has a serious impact on society, both economically and in terms of healthcare. This narrative review aimed to provide a scenario of the state of the AMR phenomenon in veterinary medicine related to the use of antibiotics in different animal species; the impact that it can have on animals, as well as humans and the environment, was considered. Providing some particular instances, the authors tried to explain the vastness of the phenomenon of AMR in veterinary medicine due to many and diverse aspects that cannot always be controlled. The veterinarian is the main reference point here and has a high responsibility towards the human–animal–environment triad. Sharing such a burden with human medicine and cooperating together for the same purpose (fighting and containing AMR) represents an effective example of the application of the One Health approach.

Screening of a short chain antimicrobial peptide-FWKFK and its application in wound healing

As a kind of basic polypeptide with antibacterial properties, antimicrobial peptides play an important role in resisting the invasion of foreign microorganisms. Antimicrobial peptides have a wide range of antimicrobial activities against bacteria, fungi, viruses and other microorganisms. They are active against traditional antibiotic-resistant strains and do not easily cause bacterial resistance. In this study, we synthesized an antibacterial peptide library by a Fmoc solid phase synthesis method, and screened the peptide chain FWKFK by modified cell membrane chromatography. The minimum inhibitory concentration of FWKFK against E. coli and S. aureus was 200 μg mL^-1 and 250 μg mL^-1, respectively, and FWKFK also had inhibitory effects on P. aeruginosa, B. subtilis and S. epidermidis. Its biocompatibility and therapeutic effect on mouse wounds were then tested. The results showed that the survival rate of normal cells after FWKFK treatment was more than 95%, the hemolysis rate of red blood cells was as low as 6%, and it had a significant effect on wound healing in mice.

Review of hospital effluents: special emphasis on characterization, impact, and treatment of pollutants and antibiotic resistance

Health care institutions generate large volumes of liquid effluents from specific activities related to healthcare, analysis, and research. Their direct discharge into the environment has various negative effects on aquatic environments and human health, due to their high organic matter charges and the presence of various emerging contaminants such as disinfectants, drugs, bacteria, viruses, and parasites. Moreover, hospital effluents, by carrying antibiotics, contribute to the development of antibiotic-resistant microorganisms in the environment. This resistance has become a global issue that manifests itself variously in different countries, causing the transmission of different infections. In this respect, an effort is provided to protect water resources by current treatment methods that imply physical-chemical processes such as adsorption and advanced oxidation processes, biological processes such as activated sludge and membrane bioreactors and other hybrid techniques. The purpose of this review is to improve the knowledge on the composition and impact of hospital wastewater on man and the environment, highlighting the different treatment techniques appropriate to this type of disposal before discharge into the environment.

The Major Facilitator Superfamily and Antimicrobial Resistance Efflux Pumps of the ESKAPEE Pathogen Staphylococcus aureus

The ESKAPEE bacterial pathogen Staphylococcus aureus has posed a serious public health concern for centuries. Throughout its evolutionary course, S. aureus has developed strains with resistance to antimicrobial agents. The bacterial pathogen has acquired multidrug resistance, causing, in many cases, untreatable infectious diseases and raising serious public safety and healthcare concerns. Amongst the various mechanisms for antimicrobial resistance, integral membrane proteins that serve as secondary active transporters from the major facilitator superfamily constitute a chief system of multidrug resistance. These MFS transporters actively export structurally different antimicrobial agents from the cells of S. aureus. This review article discusses the S. aureus-specific MFS multidrug efflux pump systems from a molecular mechanistic perspective, paying particular attention to structure-function relationships, modulation of antimicrobial resistance mediated by MFS drug efflux pumps, and direction for future investigation.

Comparative Analysis between Salmonella enterica Isolated from Imported and Chinese Native Chicken Breeds

Salmonella enterica is considered a significant threat to the global poultry industry and public health. In recent decades, antimicrobial resistance in Salmonella enterica has attracted increasing concern throughout the world. However, limited information is available on Salmonella enterica among different breeds of breeder chickens. Thus, this study aimed to compare the prevalence, serotype distribution, emergence of extended-spectrum beta-lactamases (ESBLs), antimicrobial resistance, and genetic resistance mechanisms in Salmonella enterica among different breeds of breeder chickens. A total of 693 samples (dead embryos, cloacal swabs, water, feed, environmental swabs, and meconium of newly hatched chicks) were selected and cultured for Salmonella from four breeder chicken farms in Shandong province, China, representing one imported and three native breeds, and the isolates were further serotyped. Of the Salmonella isolates, susceptibility to 11 antimicrobials of 5 classes, ESBL screening, and the presence of 21 antimicrobial resistance genes were determined in the present study. Overall, 94 (13.6%) isolates were recovered, which were divided into 3 serotypes (Salmonella Pullorum (n = 36), Salmonella Thompson (n = 32), and Salmonella Enteritidis (n = 26)). The results showed that the prevalence of Salmonella enterica isolates from the imported breeds was higher compared with the three domestic breeds. Eight of the ninety-four isolates were ESBL-positive strains, which were recovered from a domestic breed chicken farm. These eight ESBL-producing isolates were serotyped to Pullorum. Surprisingly, Salmonella Enteritidis (S. enteritidis) and S. pullorum were simultaneously isolated from a single dead embryo observed among one native breed. Meanwhile, among the Salmonella isolates, 53.2% (50/94) were multidrug-resistant strains, and 44.7% (42/94) of the isolates presented resistance to at least five antibiotics. Nearly all of the isolates (97.9%, 92/94) were resistant to at least one antimicrobial; one isolate of S. Thompson was resistant to seven antimicrobial agents belonging to four different classes. The carriage rate of three resistance genes (tetA, tetB, and sul1) among isolates from the imported breeds (87%, 70%, and 65.2%) was higher than that in those from domestic breeds (35.2%, 36.6, and 14.1%). To our knowledge, this is the first report of ESBLs-producing Salmonella isolated from a Chinese native breed of breeder chickens. Our results also highlight that a high prevalence of multidrug-resistant Salmonella enterica contamination is widespread among different breeds of breeder chickens, which is a major risk of food-borne diseases and public health.

Tuning the Molecular Structure of Corroles to Enhance the Antibacterial Photosensitizing Activity

The increase in the antibiotic resistance of bacteria is a serious threat to public health. Photodynamic inactivation (PDI) of micro-organisms is a reliable antimicrobial therapy to treat a broad spectrum of complex infections. The development of new photosensitizers with suitable properties is a key factor to consider in the optimization of this therapy. In this sense, four corroles were designed to study how the number of cationic centers can influence the efficacy of antibacterial photodynamic treatments. First, 5,10,15-Tris(pentafluorophenyl)corrole (Co) and 5,15-bis(pentafluorophenyl)-10-(4-(trifluoromethyl)phenyl)corrole (Co-CF₃) were synthesized, and then derivatized by nucleophilic aromatic substitution with 2-dimethylaminoethanol and 2-(dimethylamino)ethylamine, obtaining corroles Co-3NMe₂ and Co-CF₃-2NMe₂, respectively. The straightforward synthetic strategy gave rise to macrocycles with different numbers of tertiary amines that can acquire positive charges in an aqueous medium by protonation at physiological pH. Spectroscopic and photodynamic studies demonstrated that their properties as chromophores and photosensitizers were unaffected, regardless of the substituent groups on the periphery. All tetrapyrrolic macrocycles were able to produce reactive oxygen species (ROS) by both photodynamic mechanisms. Uptake experiments, the level of ROS produced in vitro, and PDI treatments mediated by these compounds were assessed against clinical strains: methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae. In vitro experiments indicated that the peripheral substitution significantly affected the uptake of the photosensitizers by microbes and, consequently, the photoinactivation performance. Co-3NMe₂ was the most effective in killing both Gram-positive and Gram-negative bacteria (inactivation > 99.99%). This work lays the foundations for the development of new corrole derivatives having pH-activable cationic groups and with plausible applications as effective broad-spectrum antimicrobial photosensitizers.

An Explorative Review on Advanced Approaches to Overcome Bacterial Resistance by Curbing Bacterial Biofilm Formation

The continuous emergence of multidrug-resistant pathogens evoked the development of innovative approaches targeting virulence factors unique to their pathogenic cascade. These approaches aimed to explore anti-virulence or anti-infective therapies. There are evident concerns regarding the bacterial ability to create a superstructure, the biofilm. Biofilm formation is a crucial virulence factor causing difficult-to-treat, localized, and systemic infections. The microenvironments of bacterial biofilm reduce the efficacy of antibiotics and evade the host's immunity. Producing a biofilm is not limited to a specific group of bacteria; however, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus biofilms are exemplary models. This review discusses biofilm formation as a virulence factor and the link to antimicrobial resistance. In addition, it explores insights into innovative multi-targeted approaches and their physiological mechanisms to combat biofilms, including natural compounds, phages, antimicrobial photodynamic therapy (aPDT), CRISPR-Cas gene editing, and nano-mediated techniques.

Epidemiology of antimicrobial resistance in bacteria isolated from inpatient and outpatient samples, Ecuador, 2018

Objective

To compare the epidemiology of antimicrobial resistance in bacteria isolated from inpatient and outpatient samples in Ecuador.

Methods

A secondary analysis was done of data on bacteria isolated from inpatient and outpatient samples. Data were taken from the 2018 national antimicrobial resistance surveillance database of the National Reference Center for Antimicrobial Resistance. The variables included were: age, sex, inpatient versus outpatient setting, type of specimen, bacterial species identified, pattern of resistance to antibiotics, and geographic area.

Results

Data from 57 305 bacterial isolates were included in the study: 48.8% were from hospitalized patients, 55.7% were from women, and 60.1% were from patients older than 45 years. Urine (42.9%) and blood (12.4%) were the most common clinical samples. Overall, 77.1% of bacterial isolates were gram-negative (83% and 71% in outpatients and inpatients, respectively). The most common gram-positive and gram-negative species were Staphylococcus aureus and Escherichia coli, respectively. Antimicrobial resistance levels were high (up to 80% for some antimicrobial drugs), and were higher in hospitalized patients compared with outpatients. A variety of carbapenemases were found to confer resistance to carbapenems (antibiotics of last resort) in gram-negative bacteria.

Conclusions

The study findings provide an important baseline on antimicrobial resistance in Ecuador. This will allow the strengthening of guidelines of the surveillance system, the creation of public policies for standardization of laboratory methodologies, the proper handling of information, and the development of empirical therapy guidelines based on local epidemiology.

An Enzymatic Antibiotic Adjuvant Modulates the Infectious Microenvironment to Overcome Antimicrobial Resistance of Pathogens

The emergence and evolution of antimicrobial resistance (AMR) pose a significant challenge to the current arsenal to fight infection. Antibiotic adjuvants represent an appealing tactic for tackling the AMR of pathogens, however, their practical applications are greatly constrained by the harsh infectious microenvironment. Herein, it is found that silver nanoclusters (Ag NCs) can possess tunable enzymatic activities to modulate infectious microenvironments. Based on this finding, an enzymatic nanoadjuvant (EnzNA) self-assembled from Ag NCs, which is inert under neutral physiological conditions but can readily disassemble into isolated Ag NCs exhibiting biofilm destructive oxidase-mimetic activity in the acidic biofilm microenvironment, is developed. Once internalized into the neutral cytoplasm of bacteria, Ag NCs switch to reveal the thiol oxidase-mimetic activity to suppress ribosomal biogenesis for AMR reversal and evolution inhibition of pathogens. Consequently, EnzNAs revitalize various existing antibiotics against methicillin-resistant Staphylococcus aureus, and potentiate the antibiotic efficacy against biofilm-mediated skin infection and lethal lung infection in mice. These findings highlight the capability of enzyme-mimetic nanomaterials to modulate the infectious microenvironment and potentiate antibiotics, providing a paradigm shift for anti-infection therapy.

In silico and in vitro evaluation of efflux pumps inhibition of α,β-amyrin

The use of the bacterial efflux pump mechanism to reduce the concentrations of antibiotics in the intracellular to the extracellular region is one of the main mechanisms by which bacteria acquire resistance to antibiotics. The present study aims to evaluate the antibacterial activity of the α,β-amyrin mixture isolated from Protium heptaphyllum against the multidrug-resistant strains of Escherichia coli 06 and Staphylococcus aureus 10, and to verify the inhibition of the efflux resistance mechanisms against the strains of S. aureus 1199B and K2068, carrying the NorA and MepA efflux pumps, respectively. The α,β-amyrin did not show clinically relevant direct bacterial activity. However, the α,β-amyrin when associated with the gentamicin antibiotic presented synergistic effect against the multidrug-resistant bacterial strain of S. aureus 10. In strains with efflux pumps, α,β-amyrin was able to inhibit the action of the efflux protein NorA against Ethidium Bromide. However, this inhibitory effect was not observed in the MepA efflux pump. In addition, when evaluating the effect of standard efflux pump inhibitors, clorptomazine and CCCP, α,β-amyrin showed a decrease in MIC, demonstrating the presence of the efflux mechanism through synergism. Docking studies indicate that α, β-amyrin have a higher affinity energy to MepA, and NorA than ciprofloxacin and norfloxacin. Also, α, β-amyrin bind to the same region of the binding site as these antibiotics. It was concluded that the α, β-amyrin has the potential to increase antibacterial activity with the association of antibiotics, together with the ability to be a strong candidate for an efflux pump inhibitor.Communicated by Ramaswamy H. Sarma.

Nanoparticles for Antimicrobial Agents Delivery-An Up-to-Date Review

Infectious diseases constitute an increasing threat to public health and medical systems worldwide. Particularly, the emergence of multidrug-resistant pathogens has left the pharmaceutical arsenal unarmed to fight against such severe microbial infections. Thus, the context has called for a paradigm shift in managing bacterial, fungal, viral, and parasitic infections, leading to the collision of medicine with nanotechnology. As a result, renewed research interest has been noted in utilizing various nanoparticles as drug delivery vehicles, aiming to overcome the limitations of current treatment options. In more detail, numerous studies have loaded natural and synthetic antimicrobial agents into different inorganic, lipid, and polymeric-based nanomaterials and tested them against clinically relevant pathogens. In this respect, this paper reviews the most recently reported successfully fabricated nanoformulations that demonstrated a great potential against bacteria, fungi, viruses, and parasites of interest for human medicine.

Bacitracin-Engineered BSA/ICG Nanocomplex with Enhanced Photothermal and Photodynamic Antibacterial Activity

To reduce the drug resistance of bacteria and enhance the antibacterial ability in bacterial infection therapy, we designed a new antibacterial nanoagent. In this system, a photosensitizer (indocyanine green, ICG) was loaded in bovine serum albumin (BSA) through hydrophobic-interaction-induced self-assembly to form stable BSA@ICG nanoparticles. Furthermore, a positively charged antibacterial peptide bacitracin (Bac) was physically immobilized onto the surface of BSA@ICG to generate a bacterial-targeted nanomedicine BSA@ICG@Bac through electrostatic interactions. Afterward, its photodynamic and photothermal activities were intensely evaluated. Moreover, its bactericidal efficiency was assessed via in vitro antibacterial assays and bacterial biofilm destruction tests. First, the obtained BSA@ICG@Bac showed both good singlet oxygen generation property and high photothermal conversion efficiency. In addition, it showed enhanced photodynamic and photothermal antibacterial capacities and biofilm-removing ability in vitro due to Bac modification. To sum up, our research provided an economic and less-time-consuming approach to preparing antibacterial nanomedicines with excellent antibacterial ability. Therefore, the prepared antibacterial nanomedicines have great potential to be utilized in clinical trials in the future.