Multidrug-resistant Bacterial Strains Research Articles

Correction: Bucki et al. Bactericidal Properties of Rod-, Peanut-, and Star-Shaped Gold Nanoparticles Coated with Ceragenin CSA-131 against Multidrug-Resistant Bacterial Strains. Pharmaceutics 2021, 13, 425

Correction: Bucki et al. Bactericidal Properties of Rod-, Peanut-, and Star-Shaped Gold Nanoparticles Coated with Ceragenin CSA-131 against Multidrug-Resistant Bacterial Strains. Pharmaceutics 2021, 13, 425

Subduing the Inflammatory Cytokine Storm

The inflammatory cytokine response is essential for protective immunity, yet bacterial and viral pathogens often elicit an exaggerated response (“cytokine storm”) harmful to the host that can cause multi-organ damage and lethality. Much has been published recently on the cytokine storm within the context of the coronavirus pandemic, yet bacterial sepsis, severe wound infections and toxic shock provide other prominent examples. The problem of the cytokine storm is compounded by the increasing incidence of multidrug-resistant bacterial strains. We created an incisive molecular tool for analyzing the role of the B7/CD28 costimulatory axis in the human inflammatory response. To attenuate the cytokine storm underlying infection pathology, yet preserve host defenses, we uniquely targeted the engagement of CD28 with its B7 co-ligands by means of short peptide mimetics of the human CD28 and B7 receptor homodimer interfaces. These peptides are not only effective tools for dissecting mechanism but also serve to attenuate the inflammatory response as a broad host-oriented therapeutic strategy against the cytokine storm. Indeed, such peptides protect mice from lethal Gram-positive bacterial superantigen-induced toxic shock even when dosed in molar amounts well below that of the superantigen and show promise in protecting humans from the severe inflammatory disease necrotizing soft tissue infections (‘flesh-eating’ bacterial sepsis) following traumatic wound injuries.

Antibacterial and anticancer potential of bioactive compounds and secondary metabolites of endophytic fungi isolated from Anethum graveolens.

Fungal endophytes are known to produce bioactive chemicals and secondary metabolites that are often identical to those produced by their host plants. The main objective of the current study was to isolate and identify endophytic fungi associated with the medicinal plant Anethum graveolens, and to investigate their potential antibacterial and anticancer properties. The ethyl acetate extracts from the isolated endophytic fungi, as well as the host plant A. graveolens, were subjected to bioactivity assays to evaluate their antibacterial and anticancer potential against multi-drug resistant bacterial strains and the human hepatocellular carcinoma cell line HepG2. The endophytic fungi isolated and identified from the A. graveolens samples included Diaporthe, Auxarthron, Arthrinium, Aspergillus, Microsporum, Dothiorella, Trichophyton, Lophiostoma, Penicillium, and Trichoderma species. The minimum inhibitory concentration (MIC) assay revealed that the A. graveolens extract exhibited the strongest antibacterial activity, with an MIC value of 4 μg/ml, followed by the Trichoderma sp. (5 μg/ml) and Penicillium sp. (6 μg/ml) extracts. Additionally, the crude extracts of Trichoderma sp., Penicillium sp., and Fusarium sp. demonstrated high anticancer activity against HepG2 cells, with inhibition rates ranging from 89 to 92% at a concentration of 50 μg/ml. Interestingly, the A. graveolens extract showed the most potent anticancer activity, with a 95% inhibition rate against HepG2 cells at the same concentration. These findings highlight the significant potential of endophytic fungi associated with A. graveolens, as a source of bioactive compounds with promising antibacterial and anticancer properties. The results reinforce the hypothesis that medicinal plants and their endophytic fungi can serve as an attractive alternative for the development of novel therapeutic agents, potentially offering a more sustainable and less harmful approach to disease management compared to traditional chemical-based methods.

Discovery of clinical isolation of drug-resistant Klebsiella pneumoniae with overexpression of OqxB efflux pump as the decisive drug resistance factor.

Background emergence of multidrug-resistant (MDR) bacterial strains is a public health concern that threatens global and regional security. Efflux pump-overexpressing MDR strains from clinical isolates are the best subjects for studying the mechanisms of MDR caused by bacterial efflux pumps. A Klebsiella pneumoniae strain overexpressing the OqxB-only efflux pump was screened from a clinical strain library to explore reverse OqxB-mediated bacterial resistance strategies. We identified non-repetitive clinical isolated K. pneumoniae strains using a matrix-assisted laser desorption/ionization time-of-flight (TOF) mass spectrometry clinical TOF-II (Clin-TOF-II) and susceptibility test screening against levofloxacin and ciprofloxacin. And the polymorphism analysis was conducted using pulsed-field gel electrophoresis. Efflux pump function of resistant strains is obtained by combined drug sensitivity test of phenylalanine-arginine beta-naphthylamide (PaβN, an efflux pump inhibitor) and detection with ethidium bromide as an indicator. The quantitative reverse transcription PCR was performed to assess whether the oqxB gene was overexpressed in K. pneumoniae isolates. Additional analyses assessed whether the oqxB gene was overexpressed in K. pneumoniae isolates and gene knockout and complementation strains were constructed. The binding mode of PaβN with OqxB was determined using molecular docking modeling. Among the clinical quinolone-resistant K. pneumoniae strains, one mediates resistance almost exclusively through the overexpression of the resistance-nodulation-division efflux pump, OqxB. Crystal structure of OqxB has been reported recently by N. Bharatham, P. Bhowmik, M. Aoki, U. Okada et al. (Nat Commun 12:5400, 2021, https://doi.org/10.1038/s41467-021-25679-0). The discovery of this strain will contribute to a better understanding of the role of the OqxB transporter in K. pneumoniae and builds on the foundation for addressing the threat posed by quinolone resistance.IMPORTANCEThe emergence of antimicrobial resistance is a growing and significant health concern, particularly in the context of K. pneumoniae infections. The upregulation of efflux pump systems is a key factor that contributes to this resistance. Our results indicated that the K. pneumoniae strain GN 172867 exhibited a higher oqxB gene expression compared to the reference strain ATCC 43816. Deletion of oqxB led a decrease in the minimum inhibitory concentration of levofloxacin. Complementation with oqxB rescued antibiotic resistance in the oqxB mutant strain. We demonstrated that the overexpression of the OqxB efflux pump plays an important role in quinolone resistance. The discovery of strain GN 172867 will contribute to a better understanding of the role of the OqxB transporter in K. pneumoniae and promotes further study of antimicrobial resistance.

Antioxidant, antibacterial and antibiofilm activities of Pittosporum napaulense (DC.) against drug-resistant Staphylococcus aureus and Shigella sp

Gandhamardan has a rich heritage of floristic diversity with undocumented medicinal plants, called Anukta Dravya having immense pharmacological values. Among them, Pittosporum napaulense (DC.) Rehder & E. H. Wilson is an important medicinal plant with widespread pharmacological importance. The antioxidant potential, antibacterial and antibiofilm activities of P. napaulense (DC.) were evaluated. The ethanolic extract showed the highest share of phenolic and flavonoid contents responsible for DPPH and ABTS radical scavenging activity with an IC50 of 5.58 and 5.28 µg/ml, respectively. In addition, the extracts also showed antibacterial and antibiofilm properties against multidrug-resistant bacterial strains, Staphylococcus aureus and Shigella sp. The biological activities of P. napaulense (DC.) bark could be attributed to the presence of phytoconstituents such as Malabaricone C, Borapetoside B, Kanzonol R. as evident from UPLC-Q-TOF-MS analysis. Based on the bioactivities; this plant could be explored for the development of potential therapeutic drug candidates against severe bacterial diseases.

Preparation of Zinc Oxide Nanoparticles and the Evaluation of their Antibacterial Effects.

Nosocomial bacterial infections have become increasingly challenging due to their inherent resistance to antibiotics. The emergence of multidrug-resistant bacterial strains in hospitals has been attributed to the extensive and varied use of antibiotics, further exacerbating the problem of antibiotic resistance. Metal nanomaterials have been widely studied as an alternative solution for eradicating antibiotic-resistant bacterial cells. Metallic nanoparticles attack bacterial cells through various mechanisms, such as the release of antibacterial ions, generation of reactive oxygen species, or physical disruption, against which bacteria cannot develop resistance. Among the actively researched antimicrobial metal nanoparticles, zinc oxide nanoparticles, which are FDA-approved, are known for their biocompatibility and antibacterial properties. In this study, we focused on successfully developing a precipitation method for synthesizing zinc oxide nanoparticles, analyzing the properties of these nanoparticles, and conducting antimicrobial tests. Zinc oxide nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), ultraviolet/visible spectroscopy, and X-ray diffraction (XRD). Antibacterial tests were conducted using the broth microdilution test with the multidrug-resistant strains of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. This study demonstrated the potential of zinc oxide nanoparticles in inhibiting the proliferation of antibiotic-resistant bacteria.

Synergistic antibacterial activity of biogenic AgNPs with antibiotics against multidrug resistant bacterial strains

The prevalence of hospital-acquired infections caused by drug resistant bacterial pathogens is a major health risk, leading to a considerable number of deaths and illnesses globally. Therefore, it is essential to develop new combinations of antimicrobial agents to effectively manage drug-resistant bacteria that are responsible for nosocomial infections. A current study aims to synthesize silver nanoparticles (AgNPs) from the seeds of Trigonella foenum-graecum (fenugreek). The AgNPs exhibited a spherical morphology and had an average particle size of 29.75 nm. In addition, XRD examination verified the presence of a face-centered cubic (fcc) lattice structure in the biosynthesized AgNPs, while FTIR study demonstrated the existence of several functional groups such as phenols, alkanes, and amines. The biogenic AgNPs exhibited the most potent antibacterial effect against E. coli strain, with relative inhibitory zone of 18.43 ± 0.35 mm and a minimum inhibitory concentration (MIC) of 50 µg/ml. In addition, the most potent antibacterial effect of AgNPs combined with colistin was observed against Acinetobacter baumannii strain, while the greatest combined efficacy of AgNPs with norfloxacin was found against Pseudomonas aeruginosa, resulting in a relative increase in the fold of inhibition area (IFA) of 0.53 and 0.35, respectively. In conclusion, the potent antibacterial and synergistic effect of AgNPs with antibiotics highlights their potential application of this combination in controlling nosocomial infections in health care settings.

Bioactive potential of Mentha arvensis L. essential oil

The aim of this study was to evaluate the phytotoxic, genotoxic, cytotoxic and antimicrobial effects of the Mentha arvensis L. essential oil (EO). The biological activity of M. arvensis EO depended on the analyzed variable and the tested oil concentration. Higher concentrations of EO (20 and 30 µg mL−1) showed a moderate inhibitory effect on the germination and growth of seedlings of tested weed species (Bellis perennis, Cyanus segetum, Daucus carota, Leucanthemum vulgare, Matricaria chamomilla, Nepeta cataria, Taraxacum officinale, Trifolium repens and Verbena × hybrida). The results obtained also indicate that the EO of M. arvensis has some genotoxic, cytotoxic and proliferative potential in both plant and human in vitro systems. Similar results were obtained for antimicrobial activity against eight bacteria, including multidrug-resistant (MDR) strains [Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, extended-spectrum beta-lactamase-producing (ESBL) E. coli, Pseudomonas aeruginosa and Salmonella enterica subsp. enterica serovar Enteritidis], with the effect on multidrug-resistant bacterial strains. Research indicates that the EO of M. arvensis shows phytotoxic, genotoxic, cytotoxic and antimicrobial effects, as well as its potential application as a herbicide and against various human diseases.

Eugenia Pohliana Leaves Essential Oil Inhibits Fungal Virulence and Restores Antibiotic Efficacy in Multidrug-Resistant Bacterial Strains.

This study aims to investigate the essential oil from leaves of Eugenia pohliana (EOEP) in regard to its chemical composition, antimicrobial and drug-enhancing activity, as well as the reduction of fungal virulence capacity. Chemical characterization using GC-MS showed as major components the sesquiterpenes δ-cadinene, Epi-α-Muurolol, and bicyclogermacrene. The results of antibacterial tests indicated that Staphylococcus aureus was more sensitive to EOEP, that also enhanced the efficacy of gentamicin, erythromycin, and norfloxacin. EOEP exhibited antifungal properties against Candida albicans, in addition to potentiating the effectiveness of fluconazole against Candida tropicalis. It showed anti-virulence effects in all fungal strains. These findings underscore E. pohliana as a potential candidate for the prospection of novel therapeutic agents to treat infectious diseases caused by resistant microbes.

Facile one-pot synthesis of N-pyridinylaminonaphthol derivatives and their antibacterial evaluation against multidrug-resistant Staphylococcus aureus.

The escalating severity of the menace posed by bacterial resistance has rendered the existing antibiotics less effective, thus necessitating the discovery of new antibacterial agents. The current study reports the exploration of substituted N-pyridinylaminonaphthols produced by a straightforward, one-pot multicomponent reaction process as antibacterial agents. The synthesized derivatives were assessed in vitro for their antibacterial properties against a panel of bacterial pathogens. The analogs 4b, 4g, 4h, 4i, 4j, 4l, 4r, and 4t exhibited potent inhibitory activity with minimum inhibitory concentration (MIC) values of 1-2 µg/mL. Notably, 4b, 4l, and 4t displayed an excellent selectivity index. Additionally, they were active against the multidrug-resistant bacterial strains, with 4l exhibiting the best activity against methicillin-resistant Staphylococcus aureus and vancomycin resistant staphylococcus aureus with a MIC of 1 µg/mL. 4l showed synergism with gentamycin and showed bactericidal property in a concentration-dependent manner. Furthermore, the molecule 4l inhibited the DNA gyrase supercoiling activity. Absorption, distribution, metabolism, excretion/toxicity parameters and pharmacokinetic properties were assessed via in silico techniques, which elucidate the potential mode of action. These findings demonstrate the potential of the N-pyridinylaminonaphthol derivatives as antibacterial agents against multidrug-resistant S. aureus.

Bioinspired green synthesis of copper, nickel, and hybrid nanoparticles using Myristica Fragrans seeds: Biomedical applications and beyond

Nanotechnology focuses on materials at the molecular and atomic levels, with sizes ranging from 0.1 to 100 nm. This study explores the synthesis and characterization of copper oxide (CuO), nickel oxide (NiO), and hybrid nanoparticles using an aqueous seed extract from Myristica fragrans. The nanomaterials underwent comprehensive characterization employing various techniques: UV analysis, FTIR spectroscopy, XRD, TGA, EDX and SEM. We explored their biological applications through antioxidant and antibacterial assays. UV analysis determined the optical absorption spectra values for CuO, NiO and hybrid nanoparticles. FTIR analysis confirmed functional groups in the plant extract responsible for capping and reducing the reaction medium. XRD and SEM analysis demonstrated the crystalline nature and morphology of the nanoparticles. CuO nanoparticles exhibited polyhedral morphology, while NiO nanoparticles were primarily spherical with some agglomeration. The CuO-NiO hybrid nanoparticles showed a wurtzite morphology with significant agglomeration and larger mean size than CuO and NiO nanoparticles. EDX indicated higher quantities of Cu and Ni. XRD spectra revealed the average particle sizes of nanoparticles. TGA indicated the thermal stability of the nanoparticles, with hybrid nanoparticles being the most stable. The nanoparticles exhibited excellent antioxidant activity, with hybrid nanoparticles showing the highest values in measuring total antioxidant capacity, total reducing power (TRP), ABTS assay, and DPPH-free radical scavenging assay at 400 μg/mg. Antibacterial assays against multidrug-resistant bacterial strains demonstrated that antibiotics-coated hybrid nanoparticles exhibited potent antibacterial properties against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. In conclusion, CuO, NiO, and CuO-NiO hybrid nanoparticles mediated by Myristica fragrans showcase promising characteristics for various applications, especially in biomedical and clinical settings. The nanoparticles eco-friendly synthesis and biocompatible nature make them attractive candidates for future research and development.

Exploring synergistic and antagonistic interactions in phage-antibiotic combinations against ESKAPE pathogens.

In the era of antimicrobial resistance, phage-antibiotic combinations offer a promising therapeutic option, yet research on their synergy and antagonism is limited. This study aims to assess these interactions, focusing on protein synthesis inhibitors and cell envelope-active agents against multidrug-resistant bacterial strains. We evaluated synergistic and antagonistic interactions in multidrug-resistant Staphylococcus aureus, Enterococcus faecium, and Pseudomonas aeruginosa strains. Phages were combined with protein synthesis inhibitors [linezolid (LZD), minocycline (MIN), gentamicin (GEN), and azithromycin (AZM)] or cell envelope-active agents [daptomycin (DAP), ceftaroline (CPT), and cefepime (FEP)]. Modified checkerboard minimum inhibitory concentration assays and 24-h time-kill analyses were conducted, alongside one-step growth curves to analyze phage growth kinetics. Statistical comparisons used one-way analysis of variance (ANOVA) and the Tukey test (P < 0.05). In the checkerboard and 24-h time-kill analyses (TKA) of S. aureus and E. faecium, phage-LZD and phage-MIN combinations were antagonistic (FIC > 4) while phage-DAP and phage-CPT were synergistic (FIC 0.5) (ANOVA range of mean differences 0.52-2.59 log10 CFU/mL; P < 0.001). For P. aeruginosa, phage-AZM was antagonistic (FIC > 4), phage-GEN was additive (FIC = 1), and phage-FEP was synergistic (ANOVA range of mean differences 1.04-1.95 log10 CFU/mL; P < 0.001). Phage growth kinetics were altered in the presence of LZD and MIN against S. aureus and in the presence of LZD against a single E. faecium strain (HOU503). Our findings indicate that select protein synthesis inhibitors may induce phage-antibiotic antagonism. However, this antagonism may not solely stem from changes in phage growth kinetics, warranting further investigation into the complex interplay among strains, phage attributes, and antibiotic mechanisms affecting bacterial inhibition.IMPORTANCEIn the face of escalating antimicrobial resistance, combining phages with antibiotics offers a promising avenue for treating infections unresponsive to traditional antibiotics. However, while studies have explored synergistic interactions, less attention has been given to potential antagonism and its impact on phage growth kinetics. This research evaluates the interplay between phages and antibiotics, revealing both synergistic and antagonistic patterns across various bacterial strains and shedding light on the complex dynamics that influence treatment efficacy. Understanding these interactions is crucial for optimizing combination therapies and advancing phage therapy as a viable solution for combating antimicrobial resistance.

Synthesis and antibacterial properties under blue LED light of conjugates between the siderophore desferrioxamine B (DFOB) and an Iridium(III) complex

The decline of antibiotics efficacy worldwide has recently reached a critical point urging for the development of new strategies to regain upper hand on multidrug resistant bacterial strains. In this context, the raise of photodynamic therapy (PDT), initially based on organic photosensitizers (PS) and more recently on organometallic PS, offers promising perspectives. Many PS exert their biological effects through the generation of reactive oxygen species (ROS) able to freely diffuse into and to kill surrounding bacteria. Hijacking of the bacterial iron-uptake systems with siderophore-PS conjugates would specifically target pathogens. Here, we report the synthesis of unprecedented conjugates between the siderophore desferrioxamine B (DFOB) and an antibacterial iridium(III) PS. Redox properties of the new conjugates have been determined at excited states and compared to that of an antibacterial iridium PS previously reported by our groups. Tested on nosocomial pathogen Pseudomonas aeruginosa and other bacteria, these conjugates demonstrated significant inhibitory activity when activated with blue LED light. Ir(III) conjugate and iridium free DFOB-2,2′-dipyridylamine ligands were crystallized in complex with FoxA, the outer membrane transporter involved in DFOB uptake in P. aeruginosa and revealed details of the binding mode of these unprecedented conjugates.

Novel insights from financial analysis of the failure to commercialise plazomicin: Implications for the antibiotic investment ecosystem

The need for novel antibiotics to combat emerging multi-drug resistant bacterial strains is widely acknowledged. The development of new therapeutic agents relies on small and medium-sized biotechnology enterprises (SMEs), representing 75% of the late-stage pipeline. However, most SME sponsors of an antibacterial approved by the FDA since 2010 have gone bankrupt, or exited at a loss, below investment cost. Uncovering financial flows related to the development and commercialisation of a single drug is complex and typically untransparent. There is therefore a lack of empirical research on the financial vulnerabilities of these critical SMEs. The development of plazomicin by Achaogen (2004–2019) entailed financial disclosures as a public company enabling application of financial analysis methods to: determine quantum and timing of public and private investments; quantify development costs; and provide a deeper understanding of the role of capital market dependency in exacerbating pipeline fragility. Achaogen’s widely cited bankruptcy, and plazomicin’s commercialisation failure, created a perception that novel antibiotics have zero market value, causing investors to question the SME developer business model. Our analysis of Achaogen’s inability to fund commercialisation suggests three key implications for the antibiotic investment ecosystem: (1) novel antibiotics with narrow approval for small patient populations affected by severe resistant infections cannot be successfully commercialised in the current US antibiotic market; (2) SMEs need incentive payments structured to enable them to survive the commercialisation cashflow drought, and (3) these changes are necessary to restore industry and financial investor confidence in the antibiotic SME development model. Achaogen’s demise demonstrates that proposals to incentivise innovation, e.g. by providing one-off payments at registration, may be insufficient to ensure access to novel antibiotics developed by SMEs. In plazomicin’s case, moreover, US government biosecurity investments have not resulted in access, as the Indian and Chinese companies which bought post-bankruptcy rights have not widely commercialised the drug. This study is timely as new market-based incentives are currently being proposed by the US, EU, Canada and Japan. In order to make further government funding effective, ensuring access, not only innovation, these must support sustainable financial models for the SMEs critical to novel antibiotic development.

Harnessing Plant-Based Nanoparticles for Combatting Multidrug-Resistant Bacteria

The emergence of multidrug-resistant organisms poses a significant challenge to public health worldwide. In response, plant-based nanoparticles have garnered attention for their potential as novel antimicrobial agents. These nanoparticles are derived from various plant sources and exhibit inherent antimicrobial properties due to their phytochemical composition. Nanoparticles synthesized from spinach (Spinacia oleracea) and orange (Citrus sinensis) extracts, loaded with salts of Cu and Zn, were evaluated for their antimicrobial activity against multidrug-resistant bacteria. Antimicrobial efficacy was assessed through agar well diffusion assays against clinically relevant multidrug-resistant bacterial strains of Pseudomonas aeruginosa MTCC 74, Staphylococcus aureus MTCC 902, Klebsiella pneumoniae MTCC 661. The nanoparticles exhibited potent antimicrobial effects, significantly inhibiting the growth of tested bacteria even when compared to commercially available antibiotics. These findings highlight the potential of plant-based nanoparticles loaded with Cu and Zn salts as effective agents against multidrug-resistant bacteria, offering a promising avenue for future antimicrobial therapies.

Humanized Mouse Models of Bacterial Infections.

Bacterial infections continue to represent a significant healthcare burden worldwide, causing considerable mortality and morbidity every year. The emergence of multidrug-resistant bacterial strains continues to rise, posing serious risks to controlling global disease outbreaks. To develop novel and more effective treatment and vaccination programs, there is a need for clinically relevant small animal models. Since multiple bacterial species have human-specific tropism for numerous virulence factors and toxins, conventional mouse models do not fully represent human disease. Several human disease characteristic phenotypes, such as lung granulomas in the case of Mycobacterium tuberculosis infections, are absent in standard mouse models. Alternatively, certain pathogens, such as Salmonella enterica serovar typhi and Staphylococcus aureus, can be well tolerated in mice and cleared quickly. To address this, multiple groups have developed humanized mouse models and observed enhanced susceptibility to infection and a more faithful recapitulation of human disease. In the last two decades, multiple humanized mouse models have been developed to attempt to recapitulate the human immune system in a small animal model. In this review, we first discuss the history of immunodeficient mice that has enabled the engraftment of human tissue and the engraftment methods currently used in the field. We then highlight how humanized mouse models successfully uncovered critical human immune responses to various bacterial infections, including Salmonella enterica serovar Typhi, Mycobacterium tuberculosis, and Staphylococcus aureus.

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Heterostructure Nanozyme with Hyperthermia-Amplified Enzyme-Like Activity and Controlled Silver Release for Synergistic Antibacterial Therapy.

Heterostructure nanozymes as antibiotic-free antimicrobial agents exhibit great potential for multidrug-resistant (MDR) bacterial strains elimination. However, realization of heterostructure antimicrobials with enhanced interfacial interaction for synergistically amplified antibacterial therapy is still a great challenge. Herein, oxygen-vacancy-enriched glucose modified MoOx (G-MoOx) is exploited as a reducing agent to spontaneously reduce Ag (I) into Ag (0) that in situ grows onto the surface of G-MoOx. The resultant Ag doped G-MoOx (Ag/G-MoOx) heterostructure displays augmenting photothermal effect and NIR-enhanced oxidase-like activity after introducing Ag nanoparticles. What's more, NIR hyperthermia accelerate Ag+ ions release from Ag nanoparticles. Introduction of Ag greatly enhances antimicrobial activities of Ag/G-MoOx against MDR bacteria, especially the hybrid loading with 1 wt% Ag NPs exhibiting antibacterial efficacy up to 99.99% against Methicillin-resistant Staphylococcus aureus (MRSA, 1×106 CFU mL-1).

Synthesis and characterization of Spirulina-mediated titanium dioxide nanoparticles: Antimicrobial activity against multidrug-resistant bacteria

Nanotechnology, particularly the use of nanoparticles, has garnered significant interest due to their unique properties and diverse applications, notably in antimicrobial research. This study focuses on the synthesis of titanium dioxide (TiO2) nanoparticles mediated by Spirulina using green synthesis methods and explores their antibacterial effectiveness against multidrug-resistant bacteria, including Methicillin Resistance Staphylococcus aeruginosa, Pseudomonas aeruginosa, E. coli, and Enterococcus faecalis. The synthesis process involved the reduction of a titanium precursor using Spirulina biomass extract. Various characterization techniques, such as UV analysis, SEM imaging, FTIR spectroscopy, EDX analysis, and XRD, were employed to assess the physicochemical properties of the synthesized TiO2 nanoparticles. Results showed a prominent absorbance peak at 322 nm and a band gap energy of 3.850 eV. SEM imaging revealed spherical morphology with aggregation, while XRD analysis indicated 61.4 % crystallinity with anatase phase. FTIR spectroscopy identified functional groups present in the nanoparticles, and EDX analysis confirmed the presence of titanium and oxygen elements. The antibacterial efficacy of Spirulina-mediated TiO2 nanoparticles was evaluated using the Agar well diffusion method against multidrug-resistant bacteria. The nanoparticles exhibited significant inhibitory zones of 22 ±3, 17±4, 11±2, and 15±3 nm at 80 μg/ml against MRSA, P. aeruginosa, E. coli, and E. faecalis, respectively. Minimal microbial inhibition was observed at concentrations of 3.906, 15.625, 15.625, and 31.25 μg/ml for MRSA, Pseudomonas aeruginosa, Enterococcus faecalis, and E. coli, respectively. The minimum bactericidal concentrations (MBC) were found to be 7.812, 31.25, 31.25, and 62.5 μg/ml for the respective bacteria. This study highlights the effectiveness of Spirulina-mediated TiO2 nanoparticles against multidrug-resistant bacterial strains in a bactericidal mode of action. Further research is warranted to investigate the molecular interactions between TiO2 nanoparticles and multidrug-resistant bacteria.

Chemical analysis of Moringa oleifera (Moringaceae) seed oil and potentiation of antibiotic activity against standard and multidrug-resistant bacterial strains

Moringa oleifera (“moringa”) seeds are sources of fixed oil with a composition of fatty acids important for their biological properties. This work aimed to verify the fixed oil of seed, regarding chemical composition, antibacterial activity alone and in association with antibiotics against standard and multidrug resistant bacterial strains. In the chemical composition of the fixed oil, the unsaturated fatty acids (78.26 %) predominated in relation to saturated fatty acids (17.34 %). The palmitic acid (5.88 %), behenic acid (4.27 %), stearic acid (4.17 %) and oleic acid (74.15 %) were the main constituents. Physicalchemical analyzes for moisture, acidity, pH, relative density, peroxide index and refractive index indicated chemical quality of the oil. We performed docking calculation to prioritize low affinity major molecules present in the chemical composition. The docking result of the all compounds showed that highest binding energy type Hydrogen bond, water hydrogen bond and hydrophobic interaction. The fixed oil did not show antibacterial activity alone with a minimum inhibitory concentration (MIC ≥ 1024 μg/mL) for the analyzed bacterial strains. Synergistic effects were verified in the association of the fixed oil with gentamicin, ofloxacin and penicillin against multiresistant strains, with reductions in MICs.