Multidrug-resistant Clinical Isolates Research Articles

Antimicrobial Delivery Using Metallophore-Responsive Dynamic Nanocarriers.

The increasing prevalence of multidrug-resistant (MDR) pathogens has promoted the development of innovative approaches, such as drug repurposing, synergy, and efficient delivery, in complement to traditional antibiotics. In this study, we present an approach based on biocompatible nanocarriers containing antimicrobial cations and known antibiotics. The matrices were prepared by coordinating GaIII or InIII to formulations of chitosan/tripolyphosphate or catechol-functionalized chitosan with or without encapsulated antibiotics, yielding particles of 100-200 nm in hydrodynamic diameter. MDR clinical isolates of Pseudomonas aeruginosa were found to be effectively inhibited by the nanocarriers under nutrient-limiting conditions. Fractional inhibitory concentration (FIC) indices revealed that cation- and antibiotic-encapsulated nanomatrices were effective against both Gram-negative and Gram-positive pathogens. Metallophores, such as deferoxamine (DFO), were probed to facilitate the sequestration and transport of the antimicrobial cations GaIII or InIII. Although the antimicrobial activities were less significant with DFO, the eradication of biofilm-associated bacteria showed promising trends against P. aeruginosa and Staphylococcus epidermidis. Interestingly, indium-containing compounds showed enhanced activity on biofilm formation and eradication, neutralizing P. aeruginosa under Fe-limiting conditions. In particular, InIII-cross-linked catechol-modified chitosan matrices were able to inhibit pathogenic growth together with DFO. The nanocarriers showed low cytotoxicity toward A549 cells and improvable CC50 values with NIH/3T3 cells.

A New Guanidine-Core Small-Molecule Compound as a Potential Antimicrobial Agent against Resistant Bacterial Strains

The guanidine core has been one of the most studied functional groups in medicinal chemistry, and guanylation reactions are powerful tools for synthesizing this kind of compound. In this study, a series of five guanidine-core small molecules were obtained through guanylation reactions. These compounds were then evaluated against three different strains of Escherichia coli, one collection strain from the American Type Culture Collection (ATCC) of E. coli ATCC 35218, and two clinical extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates (ESBL1 and ESBL2). Moreover, three different strains of Pseudomonas aeruginosa were studied, one collection strain of P. aeruginosa ATCC 27853, and two clinical multidrug-resistant isolates (PA24 and PA35). Among Gram-positive strains, three different strains of Staphylococcus aureus, one collection strain of S. aureus ATCC 29213, and two clinical methicillin-resistant S. aureus (MRSA1 and MRSA2) were evaluated. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) experiments were reported, and the drop plate (DP) method was used to determine the number of viable suspended bacteria in a known beaker volume. The results from this assessment suggest that guanidine-core small molecules hold promise as therapeutic alternatives for treating infections caused by clinical Gram-negative and Gram-positive bacteria, highlighting the need for further studies to explore their potential.

Efficacy of Cefiderocol, a Novel Siderophore Cephalosporin, against Multidrug Resistant Acinetobacter baumannii Clinical Isolates in Japan.

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important pathogen that causes nosocomial infections and is resistant to almost all antibiotics, including carbapenems. Cefiderocol is a novel siderophore cephalosporin active against a broad spectrum of gram-negative bacteria. However, the susceptibility of MDRAB to cefiderocol has not yet been reported in Japan. In this study, we measured the minimum inhibitory concentrations (MICs) of antibiotics including cefiderocol against MDRAB clinical isolates collected during a nosocomial outbreak between 2009 and 2010 at the Teikyo University Hospital in Japan. We found that all 10 MDRAB clinical isolates tested were susceptible to cefiderocol, with an MIC range of 0.12 to 1 μg/mL. All the isolates also exhibited resistance to ampicillin-sulbactam and an intermediate resistance to colistin, whereas nine of them were susceptible to tigecycline. DNA sequencing revealed that all strains harbored an OXA-51-like carbapenemase, a major cause of carbapenem resistance in A. baumannii in Japan. In conclusion, this study showed that the cefiderocol susceptibility of MDRAB clinical isolates in Japan was equivalent to that to colistin or tigecycline, and thus cefiderocol is a potential treatment option for MDRAB infections.

A Gram-negative-selective antibiotic that spares the gut microbiome.

Infections caused by Gram-negative pathogens are increasingly prevalent and are typically treated with broad-spectrum antibiotics, resulting in disruption of the gut microbiome and susceptibility to secondary infections1-3. There is a critical need for antibiotics that are selective both for Gram-negative bacteria over Gram-positive bacteria, as well as for pathogenic bacteria over commensal bacteria. Here we report the design and discovery of lolamicin, a Gram-negative-specific antibiotic targeting the lipoprotein transport system. Lolamicin has activity against a panel of more than 130 multidrug-resistant clinical isolates, shows efficacy in multiple mouse models of acute pneumonia and septicaemia infection, and spares the gut microbiome in mice, preventing secondary infection with Clostridioides difficile. The selective killing of pathogenic Gram-negative bacteria by lolamicin is a consequence of low sequence homology for the target in pathogenic bacteria versus commensals; this doubly selective strategy can be a blueprint for the development of other microbiome-sparing antibiotics.

AdeIJK Pump-Specific Inhibitors Effective against Multidrug Resistant Acinetobacter baumannii.

Multidrug-resistant Acinetobacter baumannii is a serious threat pathogen rapidly spreading in clinics and causing a range of complicated human infections. The major contributor to A. baumannii antibiotic resistance is the overproduction of AdeIJK and AdeABC multidrug efflux pumps of the resistance-nodulation-division (RND) superfamily of proteins. The dominant role of efflux in antibiotic resistance and the relatively high permeability of the A. baumannii outer membrane to amphiphilic compounds make this pathogen a promising target for the discovery of clinically relevant efflux pump inhibitors. In this study, we identified 4,6-diaminoquoniline analogs with inhibitory activities against A. baumannii AdeIJK efflux pump and followed up on these compounds with a focused synthetic program to improve the target specificity and to reduce cytotoxicity. We identified several candidates that potentiate antibacterial activities of antibiotics erythromycin, tetracycline, and novobiocin not only in the laboratory antibiotic susceptible strain A. baumannii ATCC17978 but also in multidrug-resistant clinical isolates AB5075 and AYE. The best analogs potentiated the activities of antibiotics in low micromolar concentrations, did not have antibacterial activities on their own, inhibited AdeIJK-mediated efflux of its fluorescent substrate ethidium ion, and had low cytotoxicity in A549 human lung epithelial cells.

The Effect of Combinations of Antibiotics and Natural Products on the Antimicrobial Resistance of Staphylococcus aureus and Pseudomonas aeruginosa

Introduction/Background The steadily increasing bacterial resistance to existing antimicrobial drugs is a significant issue, hence, it is imperative to look out for new approaches to bacterial therapy Occasionally, effective inhibitory action is not produced when antibiotics are used alone. To overcome this problem, a combination of drugs is often used. One approach to treat infectious diseases is the use of a combination of antibiotics together with plant extracts or phytochemicals. For patients with serious infections caused by pathogens resistant to drugs, combination therapy is beneficial and useful. Materials and Methods Seven antibiotics were obtained from a local pharmacy (gentamicin, ceftazidime, ciprofloxacin, doxycycline, amoxicillin, ceftriaxone, and azithromycin). Minimum inhibitory concentrations (MIC) were determined by broth micro-dilution method, and different antimicrobial combinations were studied on 20 Multidrug-resistant (MDR) clinical isolates (10 S. aureus and 10 P. aeruginosa). Moreover, the antibacterial activity of some volatile oils (limonene, rosemary, salvia, thymus, and black pepper), plant extracts (moringa seed, curcumin, and capsicum), and phytochemicals (thymol, and chitosan) was detected against S. aureus and P. aeruginosa isolates using broth micro-dilution method. Results According to our findings, ceftriaxone and ciprofloxacin or gentamicin together exhibited a substantial synergistic effect against S. aureus. Moreover, the combination of amoxicillin with ceftazidime was synergistic to reduce MIC by five to six times. Regarding MDR clinical isolates of P. aeruginosa, the combination of azithromycin with doxycycline exhibited a decrease of MIC of azithromycin by about five to sixfold. The combination of gentamicin with ceftriaxone was significant. For natural compounds, thymol, rosemary oil, curcumin, capsicum, and moringa seed extract exhibited the highest synergistic activity with the tested antibiotics against S. aureus and P. aeruginosa. Conclusion In conclusion, the lack of new antibiotics necessitates the improvement of existing ones. Our study shows that antibiotic combinations and antibiotic-natural plant combinations are very promising strategies for combating complex bacterial resistance.

CATH-2-derived antimicrobial peptide inhibits multidrug-resistant Escherichia coli infection in chickens.

Avian colibacillosis (AC), caused by infection with Escherichia coli (E. coli), is a major threat to poultry health, food safety and public health, and results in high mortality and significant economic losses. Currently, new drugs are urgently needed to replace antibiotics due to the continuous emergence and increasing resistance of multidrug-resistant (MDR) strains of E. coli caused by the irrational use of antibiotics in agriculture and animal husbandry. In recent years, antimicrobial peptides (AMPs), which uniquely evolved to protect the host, have emerged as a leading alternative to antibiotics in clinical settings. CATH-2, a member of the antimicrobial cathelicidin peptide family, has been reported to have antibacterial activity. To enhance the antimicrobial potency and reduce the adverse effects on animals, we designed five novel AMPs, named C2-1, C2-2, C2-3, C2-4 and C2-5, based on chicken CATH-2, the secondary structures of these AMPs were consistently α-helical and had an altered net charge and hydrophobicity compared to those of the CATH-2 (1-15) sequences. Subsequently, the antimicrobial activities of CATH-2 (1-15) and five designed peptides against MDR E. coli were evaluated in vitro. Specifically, C2-2 showed excellent antimicrobial activity against either the ATCC standard strain or veterinary clinical isolates of MDR E. coli, with concentrations ranging from 2-8 μg/mL. Furthermore, C2-2 maintained its strong antibacterial efficacy under high temperature and saline conditions, demonstrating significant stability. Similarly, C2-2 retained a high level of safety with no significant hemolytic activity on chicken mature red blood cells or cytotoxicity on chicken kidney cells over the concentration range of 0-64 μg/mL. Moreover, the administration of C2-2 improved the survival rate and reduced the bacterial load in the heart, liver and spleen during MDR E. coli infection in chickens. Additionally, pathological damage to the heart, liver and intestine was prevented when MDR E. coli infected chickens were treated with C2-2. Together, our study showed that C2-2 may be a promising novel therapeutic agent for the treatment of MDR E. coli infections and AC.

A hit expansion of 3-benzamidopyrazine-2-carboxamide: Towardinhibitors of prolyl-tRNA synthetase with antimycobacterial activity.

This study presents an exploration of the chemical space around derivatives of 3-benzamidopyrazine-2-carboxamides, previously identified as potent antimycobacterial compounds with predicted binding to mycobacterial prolyl-transfer RNA synthetase. New urea derivatives (Series-1) were generally inactive, probably due to their preference for cis-trans conformation (confirmed by density functional theory calculations and experimentally by nuclear overhauser effect spectroscopy NMR). Series-2 (3-benzamidopyrazine-2-carboxamides with disubstituted benzene ring) demonstrated that substituents larger than fluorine are not tolerated in the ortho position of the benzene ring. This series brought two new compounds (21: R = 2-F, 4-Cl and 22: R = 2-F, 4-Br) with in vitro activity against Mycobacterium tuberculosis H37Rv as well as multidrug-resistant clinical isolates, with minimum inhibitory concentration ranging from 6.25 to 25 μg/mL. The lactone-type derivatives 4H-pyrazino[2,3-d][1,3]oxazin-4-ones (Series-3) were inactive, but solvent stability studies of compound 29 indicated that they might be developed to usable lactone prodrugs of inhibitors of mycobacterial aspartate decarboxylase (PanD).

Phytosynthesis of Nickel Oxide Nanoparticles and Their Antioxidant and Antibacterial Efficacy Studies.

Multidrug-resistant (MDR) bacteria are widely acknowledged as a significant and pressing public health concern. Tribulus terrestris has been used as a health tonic in traditional medicine since ancient Vedic times. It was also utilized to synthesize small, well-dispersed metal nanoparticles (NPs). Thebiosynthesized nickel oxidenanoparticles (NiO-NPs) have a broad spectrum of biomedical uses. The objective of the research was to utilize a green synthesis method to synthesizeNiO-NPsusing Tribulus terrestris, subsequently characterize, and this study aimed to assess the antioxidant and antibacterial effectiveness of these NPs against wound isolates that are resistant to multiple drugs. The synthesis of NiO-NPs was achieved through the titration method, which is a green synthesis approach, and it was characterized by using techniques such as ultraviolet-visible spectroscopy (UV), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM),X-ray diffraction (XRD) analysis, andenergy dispersive X-ray (EDX). The antioxidant activity of theNPs was evaluated using the 2,2-diphenyl-1-picrylhydrazyl(DPPH) assay, and antibacterial activity was done using the agar well diffusion method. IBM SPSS Statistics for Windows, Version 21 (Released 2012; IBM Corp., Armonk, New York, United States)is used for statistical analysis. The biosynthesized NiO-NPs exhibited acolor change from dark brown to dark green, indicating the successful reduction of the NPs.UV analysis peaks were observed at 310-350 nm, whileFT-IRanalysis showed the peaks at various wavelengths such as 629.31cm-1(halo compound; C-Br stretching), 957.80cm-1(aromatic phosphates; P-O-C stretch), 1004.65cm-1 (aliphatic phosphates; P-O-C stretch), 1094.93cm-1(organic siloxane or silicone; Si-O-Si), 1328.38cm-1(dialkyl/aryl sulfones), 1604.88cm-1(open-chainazo-N=N-), 2928.68cm-1 (methylene C-H asym/sym stretch), 3268.65cm-1(normal polymeric "OH" stretch). The crystallinity of the NPs was determined to be 24.7%, while the remaining 75.6% exhibited an amorphous structure. The SEM image revealed a spherically agglomeratedstructure of the nano-ranged size NiO-NPs.TheEDX analysis indicated the presence of elemental compositions Ni (7.4%), O (39.4%), and C (53.3%)in the biosynthesized NiO-NPs. These NPs demonstrated significant antibacterial activity against Pseudomonas aeruginosa and Klebsiella pneumoniae, moderate antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), and the lowest antibacterial activity against Enterococcus faecalis. Our in vitro results demonstrate that the biosynthesized NiO-NPsexhibit significant antioxidant and antibacterial activity. These NPs can be used as a future antimicrobial medication, particularly against MDR clinical wound isolates ofK. pneumoniae, P. aeruginosa, and MRSA.

Functionalization of Chlorotonils: Dehalogenil as Promising Lead Compound for In Vivo Application.

The natural product chlorotonil displays high potency against multidrug-resistant Gram-positive bacteria and Plasmodium falciparum. Yet, its scaffold is characterized by low solubility and oral bioavailability, but progress was recently made to enhance these properties. Applying late-stage functionalization, we aimed to further optimize the molecule. Previously unknown reactions including a sulfur-mediated dehalogenation were revealed. Dehalogenil, the product of this reaction, was identified as the most promising compound so far, as this new derivative displayed improved solubility and in vivo efficacy while retaining excellent antimicrobial activity. We confirmed superb activity against multidrug-resistant clinical isolates of Staphylococcus aureus and Enterococcus spp. and mature transmission stages of Plasmodium falciparum. We also demonstrated favorable in vivo toxicity, pharmacokinetics and efficacy in infection models with S. aureus. Taken together, these results identify dehalogenil as an advanced lead molecule.

Complete genome sequences and multidrug resistance genotypes of nontuberculous mycobacteria isolates from the Central Tuberculosis Reference Laboratory Muhimbili Tanzania

Background: Nontuberculous mycobacteria (NTM) usually comprise a group of environmental bacteria, with emerging but elusive coinfection with tuberculous mycobacteria, causing pulmonary tuberculosis. Whole genome sequencing may give insight into potential antimicrobial resistance genotypes, giving clinicians and policymakers proper directions in clinical applications and management regimens. Methods: WGS was performed on twenty-four gDNA isolates from archival samples at the Central Tuberculosis Reference Laboratory using the MinION Oxford Nanopore Sequencing approach. Out of twenty-four, two were confirmed to belong to the NTM group. Further analysis was done to resolve the complete genomes of two nontuberculous mycobacteria strains isolated from tuberculosis patients. We then combined phylogenomics, reference-based scaffolding and average nucleotide identity (ANI) analysis to delineate each strain's taxonomic position and corresponding features. Results: Our findings reveal that the two strains fit into the genus Mycolicibacterium, and the closest relative is Mycolicibacterium novocastrense. Coupling BacAnt and CARD-based antibiotic resistance analyses revealed multidrug-resistant genotypes of diverse spectra and mechanisms. While the BC02 strain is genetically resistant to beta-lactams, macrolides and rifamycins, the BC05 strain portrays an extended drug resistance genotype encompassing beta-lactams, macrolides, polyamines, and aminoglycosides. Both strains possess a single nucleotide polymorphism (SNP) of the RNA polymerase beta-subunit (rpoB), representing resistance to the first-line rifampicin. Additionally, the BC05 strain genetically portrays resistance to ethambutol, isoniazid and fosfomycin through mechanisms involving target alteration through SNPs, drug inactivation and efflux. Conclusion: Our findings strongly suggest the potential implication of multidrug-resistant NTM clinical isolates in the pathogenesis of pulmonary tuberculosis.

Evaluation of Copper Nanoparticle Synthesis by Fusarium oxysporum Antibacterial Activity Against Staphylococcus aureus

The creation of effective, environmentally friendly antimicrobial alternatives is becoming more and more important in light of the development of antibiotic resistance. The objective of the present study was to illustrate the biosynthetic process of copper (II) carbonate nanoparticles, CuCo3 NPs, by using Fusarium oxysporum culture filtrate as an antibacterial activity against multidrug-resistant (MDR) clinical bacterial isolates, Staphylococcus aureus. Fusarium oxysporum isolate was diagnosed by PCR. One hundred and sixty specimens of pathogenic bacteria were collected from different sources (wounds, urine, sputum) then the bacterial isolates were diagnosed as Staphylococcus aureus by conventional morphological examination, biochemical tests, and the Vitek-2 system. Fusarium oxysporum culture filtrate was prepared by a culture of the fungus on Czapek Dox broth media modified by adding cornmeal and incubated for 14 days with shaking at 27±2°C and filtered in the last stages using a Millipore. The biosynthesis of CuCo3 NPs was done by adding 1g of CuCo3 Cu (OH)2 to 10 ml of Fusarium oxysporum culture filtrate. The NPs were diagnosed using modern methods, including UV-VIS, FT-IR, AFM, FE-SEM, and EDX techniques. Multidrug-resistant Staphylococcus aureus was tested on the produced Cu NPs. The results indicated that the prepared CuCo3 NPs inhibited pathogenic bacterial isolates of Staphylococcus aureus at concentration of 500, 250, 125, and 62.5 mg/ml.

Escherichia coli has an undiscovered ability to inhibit the growth of both Gram-negative and Gram-positive bacteria

The ability for bacteria to form boundaries between neighboring colonies as the result of intra-species inhibition has been described for a limited number of species. Here, we report that intra-species inhibition is more common than previously recognized. We demonstrated that swimming colonies of four Escherichia coli strains and six other bacteria form inhibitory zones between colonies, which is not caused by nutrient depletion. This phenomenon was similarly observed with non-flagellated bacteria. We developed a square-streaking pattern assay which revealed that Escherichia coli BW25113 inhibits the growth of other E. coli, and surprisingly, other Gram-positive and negative bacteria, including multi-drug resistant clinical isolates. Altogether, our findings demonstrate intra-species inhibition is common and might be used by E. coli to inhibit other bacteria. Our findings raise the possibility for a common mechanism shared across bacteria for intra-species inhibition. This can be further explored for a potential new class of antibiotics.

The Moraxella catarrhalis AdhC–FghA system is important for formaldehyde detoxification and protection against pulmonary clearance

Multidrug-resistant clinical isolates of Moraxella catarrhalis have emerged, increasing the demand for the identification of new treatment and prevention strategies. A thorough understanding of how M. catarrhalis can establish an infection and respond to different stressors encountered in the host is crucial for new drug-target identification. Formaldehyde is a highly cytotoxic compound that can be produced endogenously as a by-product of metabolism and exogenously from environmental sources. Pathways responsible for formaldehyde detoxification are thus essential and are found in all domains of life. The current work investigated the role of the system consisting of the S-hydroxymethyl alcohol dehydrogenase (AdhC), a Zn-dependent class III alcohol dehydrogenase, and the S-formyl glutathione hydrolase (FghA) in the formaldehyde detoxification process in M. catarrhalis. Bioinformatics showed that the components of the system are conserved across the species and are highly similar to those of Streptococcus pneumoniae, which share the same biological niche. Isogenic mutants were constructed to study the function of the system in M. catarrhalis. A single fghA knockout mutant did not confer sensitivity to formaldehyde, while the adhC–fghA double mutant is formaldehyde-sensitive. In addition, both mutants were significantly cleared in a murine pulmonary model of infection as compared to the wild type, demonstrating the system’s importance for this pathogen’s virulence. The respective phenotypes were reversed upon the genetic complementation of the mutants. To date, this is the first study investigating the role of the AdhC–FghA system in formaldehyde detoxification and pathogenesis of M. catarrhalis.

Characterization of Bacteriophage vB_PaeS_TUMS_P6 Infecting Pseudomonas aeruginosa

Background: Pseudomonas aeruginosa is an important pathogen in healthcare settings that poses significant challenges due to its ability to rapidly develop antibiotic resistance. Its propensity to form biofilms and adapt to host defenses makes it even more difficult to treat, leading to prolonged and debilitating illnesses. So, it is vital to prioritize efforts to develop new strategies for treating infections caused by this pathogen. In the present work, morphological and biological characteristics of vB_PaeS_TUMS_P6 (P6), a lytic phage against P. aeruginosa, belonging to the genus Luzseptimavirus were fully described.
 Methods: P. aeruginosa ATCC 27853 was used for propagation and biological characterization of P6. Its morphology was assessed using transmission electron microscopy (TEM). Adsorption rate assay, one-step growth curve analysis and time-kill experiment were analyzed. Host Range of P6, as well as pH and thermal stability were also determined.
 Results: The results showed that it was of classic podovirus morphology and had a short latent period. It could kill bacteria at multiplicity of infection as low as 0.01 and also infect some multidrug-resistant clinical isolates. Stability data suggested that P6 remained stable in various temperatures and pH levels, which is a beneficial characteristic for phage therapy in different situations
 Conclusion: This study presents promising data supporting the future use of P6 as a candidate for phage therapy.

Pharmacological Potential Effects of Algerian Propolis Against Oxidative Stress, Multidrug-Resistant Pathogens Biofilm and Quorum-Sensing.

This study sought to examine the chemical profile, antioxidant, antimicrobial, antibiofilm, and anti-quorum sensing potential of two propolis ethanolic extracts (PEEs) collected from northeast Algeria. To achieve the main objectives of this study, multiple in vitro tests were employed. The phenolic and flavonoid contents were analyzed, and the chemical composition of both PEE was determined by high-performance liquid chromatography. The antioxidant properties of the propolis extracts were investigated using six complementary tests. The inhibitory effects of propolis extracts were evaluated against multidrug-resistant (MDR) clinical isolates using agar well diffusion and microdilution methods, whereas their antibiofilm and quorum-sensing disruption effects were determined by spectrophotometric microplate methods. The results demonstrated that phenolic and flavonoid contents were higher in propolis from the Guelma (PEEG) region (PEEG; 188.50 ± 0.33 μg GAE/mg E, 144.23 ± 1.03 μg QE/mg E), respectively. Interestingly, different components were identified, and cynarin was the major compound detected. The PEEG sample exhibited potential antioxidant effects in scavenging ABTS•+ radicals with minimal inhibitory concentration values equal to 10.46 ± 1.40 µg/mL. Furthermore, the highest antibacterial activity was recorded by PEEG against Gram-positive Staphylococcus aureus MDR1. Similarly, PEEG effectively inhibited the biofilm formation of S. aureus MDR1 and the degradation of biofilm was up to 60%. In addition, quorum sensing disruption revealed that both extracts have a moderate capacity for violacein inhibition by the Chromobacterium violaceum ATCC 12472 strain in a concentration-dependent manner. These findings indicate that propolis can be regarded as a natural therapeutic agent for health problems associated with MDR bacteria and oxidative stress.

Alkyl deoxyglycoside-polymyxin combinations against critical priority carbapenem-resistant gram-negative bacteria

The escalating antimicrobial resistance crisis urges the development of new antibacterial treatments with innovative mechanisms of action, particularly against the critical priority carbapenem-resistant Acinetobacter baumannii (CRAB), Pseudomonas aeruginosa (CRPA) and Enterobacteriaceae (CRE). Membrane-disrupting dodecyl deoxyglycosides have been reported for their interesting phosphatidylethanolamine-associated bactericidal activity against Gram-positive strains; however, their inability to penetrate the Gram-negative outer membrane (OM) renders them useless against the most challenging pathogens. Aiming to repurpose alkyl deoxyglycosides against Gram-negative bacteria, this study investigates the antimicrobial effects of five reference compounds with different deoxygenation patterns or anomeric configurations in combination with polymyxins as adjuvants for enhanced OM permeability. The generation of the lead 4,6-dideoxy scaffold was optimized through a simultaneous dideoxygenation step and applied to the synthesis of a novel alkyl 4,6-dideoxy C-glycoside 5, herein reported for the first time. When combined with subtherapeutic colistin concentrations, most glycosides demonstrated potent antimicrobial activity against several multidrug-resistant clinical isolates of CRAB, CRE and CRPA exhibiting distinct carbapenem resistance mechanisms, together with acceptable cytotoxicity against human HEK-293T and Caco-2 cells. The novel 4,6-dideoxy C-glycoside 5 emerged as the most promising prototype structure for further development (MIC 3.1 μg/mL when combined with colistin 0.5 μg/mL against CRPA or 0.25 μg/mL against several CRE and CRAB strains), highlighting the potential of C-glycosylation for an improved bioactive profile. This study is the first to show the potential of IM-targeting carbohydrate-based compounds for the treatment of infections caused by MDR Gram-negative pathogens of clinical importance.

Engineering of a decellularized bovine skin coated with antibiotics-loaded electrospun fibers with synergistic antibacterial activity for the treatment of infectious wounds.

An ideal antibacterial wound dressing with strong antibacterial behavior versus highly drug-resistant bacteria and great wound-healing capacity is still being developed. There is a clinical requirement to progress the current clinical cares that fail to fully restore the skin structure due to post-wound infections. Here, we aim to introduce a novel two-layer wound dressing using decellularized bovine skin (DBS) tissue and antibacterial nanofibers to design a bioactive scaffold with bio-mimicking the native extracellular matrix of both dermis and epidermis. For this purpose, polyvinyl alcohol (PVA)/chitosan (CS) solution was loaded with antibiotics (colistin and meropenem) and electrospun on the surface of the DBS scaffold to fabricate a two-layer antibacterial wound dressing (DBS-PVA/CS/Abs). In detail, the characterization of the fabricated scaffold was conducted using biomechanical, biological, and antibacterial assays. Based on the results, the fabricated scaffold revealed a homogenous three-dimensional microstructure with a connected pore network, a high porosity and swelling ratio, and favorable mechanical properties. In addition, according to the cell culture result, our fabricated two-layer scaffold surface had a good interaction with fibroblast cells and provided an excellent substrate for cell proliferation and attachment. The antibacterial assay revealed a strong antibacterial activity of DBS-PVA/CS/Abs against both standard strain and multidrug-resistant clinical isolates of Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Our bilayer antibacterial wound dressing is strongly suggested as an admirable wound dressing for the management of infectious skin injuries and now promises to advance with preclinical and clinical research.

Honey mediated synthesis of zinc oxide nanoparticles, and evaluation of antimicrobial, antibiofilm activities against multidrug resistant clinical bacterial isolates

The present work aims to synthesize zinc oxide nanoparticles (ZnONPs) via a greener approach using honey as a bio-reductant and stabilizing agent. The prepared nanoparticles were analysed by using UV–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), crystalline nature by X-ray diffraction (XRD), field electron scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), size distribution and zeta potential by dynamic light scattering (DLS) analysis. XRD patterns demonstrate the polycrystalline wurtzite structure for ZnONPs with an average zeta potential value of − 2.61 mV. Spherical and square-shaped nanostructures were affirmed using FE-SEM and TEM micrographs. The DPPH and ABTS assays revealed that ZnONPs possess antioxidant activity with an IC50 value of 38 µg/mL and 6.38 µg/mL, respectively. Additionally, the antimicrobial activity of ZnONPs performed against clinical strains of Gram negative bacteria such as Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli), and Gram positive bacteria Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa (P. aeruginosa), and Staphylococcus aureus (S. aureus) was assessed along with their antibiofilm activity. The evaluation of the integrity of the bacterial cell membrane with the leakge of cellular components, including nucleic acids and proteins, into the culture medium indicated that honey synthesized ZnONPs could function as potential antimicrobial agents.

Genomic and functional insights into antibiotic resistance genes floR and strA linked with the SXT element of Vibrio cholerae non-O1/non-O139.

The emergence and spread of antibiotic-resistant bacterial pathogens are a critical public health concern across the globe. Mobile genetic elements (MGEs) play an important role in the horizontal acquisition of antimicrobial resistance genes (ARGs) in bacteria. In this study, we have decoded the whole genome sequences of multidrug-resistant Vibrio cholerae clinical isolates carrying the ARG-linked SXT, an integrative and conjugative element, in their large chromosomes. As in others, the SXT element has been found integrated into the 5'-end of the prfC gene (which encodes peptide chain release factor 3 involved in translational regulation) on the large chromosome of V. cholerae non-O1/non-O139 strains. Further, we demonstrate the functionality of SXT-linked floR and strAB genes, which confer resistance to chloramphenicol and streptomycin, respectively. The floR gene-encoded protein FloR belongs to the major facilitator superfamily efflux transporter containing 12 transmembrane domains (TMDs). Deletion analysis confirmed that even a single TMD of FloR is critical for the export function of chloramphenicol. The floR gene has two putative promoters, P1 and P2. Sequential deletions reveal that P2 is responsible for the expression of the floR. Deletion analysis of the N- and/or C-terminal coding regions of strA established their importance for conferring resistance against streptomycin. Interestingly, qPCR analysis of the floR and strA genes indicated that both of the genes are constitutively expressed in V. cholerae cells. Further, whole genome-based global phylogeography confirmed the presence of the integrative and conjugative element SXT in non-O1/non-O139 strains despite being non-multidrug resistant by lacking antimicrobial resistance (AMR) gene cassettes, which needs monitoring.