Gram-positive Research Articles

Biological Effects of Green Synthesized Al-ZnO Nanoparticles Using Leaf Extract from Anisomeles indica (L.) Kuntze on Living Organisms

The synthesis of Al-ZnO nanoparticles (NPs) was achieved using a green synthesis approach, utilizing leaf extract from Anisomeles indica (L.) in a straightforward co-precipitation method. The goal of this study was to investigate the production of Al-ZnO nanoparticles through the reduction and capping method utilizing Anisomeles indica (L.) leaf extract. The powder X-ray diffraction, UV spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy with EDAX analysis were used to analyze the nanoparticles. X-ray diffraction analysis confirmed the presence of spherical structures with an average grain size of 40 nm in diameter, while UV–visible spectroscopy revealed a prominent absorption peak at 360 nm. FTIR spectra demonstrated the presence of stretching vibrations associated with O-H, N-H, C=C, C-N, and C=O as well as C-Cl groups indicating their involvement in the reduction and stabilization of nanoparticles. SEM image revealed the presence of spongy, spherical, porous agglomerated nanoparticles, confirming the chemical composition of Al-ZnO nanoparticles through the use of the EDAX technique. Al-ZnO nanoparticles showed increased bactericidal activity against both Gram-positive and Gram-negative bacteria. The antioxidant property of the green synthesized Al-ZnO nanoparticles was confirmed by DPPH radical scavenging with an IC50 value of 23.52 indicating excellent antioxidant capability. Green synthesized Al-ZnO nanoparticles were shown in in vivo studies on HeLa cell lines to be effective for cancer treatment. Additionally, α-amylase inhibition assay and α-glucosidase inhibition assay demonstrated their potent anti-diabetic activities. Moving forward, the current methodology suggests that the presence of phenolic groups, flavonoids, and amines in Al-ZnO nanoparticles synthesized with Anisomeles indica (L.) extract exhibit significant promise for eliciting biological responses, including antioxidant and anti-diabetic effects, in the realms of biomedical and pharmaceutical applications.

Crystal structure of the Rib domain of the cell-wall-anchored surface protein from Limosilactobacillus reuteri.

The immunoglobulin (Ig)-like domain is found in a broad range of proteins with diverse functional roles. While an essential β-sandwich fold is maintained, considerable structural variations exist and are critical for functional diversity. The Rib-domain family, primarily found as tandem-repeat modules in the surface proteins of Gram-positive bacteria, represents another significant structural variant of the Ig-like fold. However, limited structural and functional exploration of this family has been conducted, which significantly restricts the understanding of its evolution and significance within the Ig superclass. In this work, a high-resolution crystal structure of a Rib domain derived from the probiotic bacterium Limosilactobacillus reuteri is presented. This protein, while sharing significant structural similarity with homologous domains from other bacteria, exhibits a significantly increased thermal resistance. The potential structural features contributing to this stability are discussed. Moreover, the presence of two copper-binding sites, with one positioned on the interface, suggests potential functional roles that warrant further investigation.

Specific Response of Bacterial Cells to β-Ionone

The biological activity and mechanisms of action of the unsaturated ketone β-ionone, a volatile compound of significantinterest for biotechnology, medicine, and agriculture, were studied. Using specific lux biosensors basedon Escherichia coli MG1655, we found that β-ionone causes oxidative stress in E. coli cells by inducing expression from the PkatG and Pdps promoters, but not from the PsoxS promoter. The effects of β-ionone on the heat shock induction (expression from the PibpA and PgrpE promoters) and on DNA damage (expression from the PcolD and PdinI promoters, SOS response) in E. coli cells were significantly weaker. β-Ionone did not cause oxidative stress in the cells of the gram-positive bacterium Bacillus subtilis.

Long-term mold resistance strategy of laccase-catalyzed eugenol-modified bamboo and its antimicrobial mechanism derived from lignin

Bamboo, which has excellent physical properties and environmental credentials, is widely used in the construction industry and furniture manufacturing. Bamboo is, however, susceptible to attack by molds and bacteria; protection by natural phenolic antimicrobial agents would be a green and environmentally friendly solution to this problem. The application of such protection has, so far, been hampered by poor stability and ease of volatilization of the antimicrobial agent. Here, an innovative strategy that uses the catalytic action of the laccase to chemically attach a natural antimicrobial agent, eugenol (EU), to bamboo, is described. This modification endows bamboo with both long-lasting and extensive mold resistance and antibacterial activity. Laccase-catalyzed covalent bonding of EU to bamboo reduces the volatilization rate of the EU from 1.72 % to 0.29 %. The outstanding mold resistance and antimicrobial activity of bamboo treated using this modified process is retained during a 50-day mold resistance test, with mold growth inhibited by as much as 87.5 %. The treated bamboo is also able to inhibit the growth of both Gram-positive and Gram-negative bacteria. The antimicrobial mechanism results shown that the bamboo lignin is the primary reaction site during laccase-catalyzed EU modification of bamboo, and the long-term mold resistance derived from modified lignin. Furthermore, we analyzed bacterial morphology through SEM, and the results demonstrated that modified enzymatic hydrolysis lignin (EHL) significantly disrupts bacterial morphology, including membrane invagination and collapse. This study provides a new direction for the green development of mold- and bacteria-resistant bamboo, which has potential for use in a wide range of application.

Asian Spice Nanotech: Illicium verum made Metal Nanoparticles for Potent Antibacterial and Catalytic Applications

Introduction: Asian spices are globally recognized for their rich phytochemical composition. The bioactive compounds of Asian spices have significant potential to extend the biological applications of metal nanomaterials by increasing their surface area, stability, dispersion, and ecofriendliness. Method: The present study is designed to prepare novel iron oxide (Fe2O3) and copper oxide (CuO) nanoparticles using an aqueous extract of Illicium verum (star anise), a traditional Asian spice as a reducing, capping & stabilizing agent. The synthesized nanoparticles have been characterized to study their molecular environment using Fourier-transform infrared spectroscopy (FTIR). Elemental composition was examined through the Energy dispersive X-ray Spectroscopy (EDS). Scanning Electron Microscopy (SEM) revealed the size, shape, and other morphological characteristics of nanoparticles. The optical properties have been tested through Ultraviolet-Visible (UV) spectroscopy and the band gap energies of both Fe2O3 and CuO nanoparticles have been calculated by using the Tauc plot method, which explores its semiconductor applications. The catalytic applications of obtained nanoparticles have shown significant potential in the degradation of aqueous methyl orange dye (MO). Results: Results revealed that Fe2O3 and CuO nanoparticles significantly increased the rate of reaction by decreasing the reaction time to 45 mins and 40 mins, respectively in comparison to the NaBH4 (60 mins). This shows that CuO has a larger surface area and more absorption capacity than Fe2O3 NPs. To examine the cause of value healthcare, the obtained materials have also been applied against various Gram-positive and Gram-negative bacteria. The bactericidal activity was compared with gentamicin, which showed both nanometals are moderate to strongly active against tested microbes. Conclusion: The successful eco-friendly synthesis of metallic nanoparticles by using Asian spices and their applications in physical and biological sciences opens the door for the scientific community to develop and apply more novel and green nanomaterials in industrial and commercial areas.

Combination of High-Dose Daptomycin and Ceftriaxone for Cardiac Implantable Electronic Device Infections: A 10-Year Experience

PurposeCardiac implantable electronic device (CIED) infections are increasingly common. Gram-positive bacteria such as coagulase negative staphylococci and Staphylococcus aureus are the most commonly involved pathogens. The aim of this study was to describe the characteristics and outcome of patients with CIED infections who underwent device removal and were empirically treated with high dose (8–12 mg/kg daily) daptomycin (DAP) in combination with ceftriaxone (CRO). MethodsRetrospective, single center study including patients admitted at IRCCS San Raffaele Hospital (Milan, Italy), from June 2011 to June 2021, who underwent device removal for CIED infection and were empirically treated with DAP/CRO. FindingsOverall, 147 patients were included in this study. Median duration of therapy was 16 days (IQR 14–26). Empirical treatment with DAP/CRO was confirmed as definitive treatment in 140 patients (95.2%). In 7 (4.8%) patients DAP/CRO were discontinued according to the definite microbiological isolates: Corynebacterium spp. (4), Pseudomonas aeruginosa (2), Enterobacter cloacae (1). Ten patients (6.8%) underwent treatment simplification to narrow-spectrum antibiotics. One patient (0.6%) interrupted DAP-CRO due to pancytopenia.6-month follow-up was available for 123/147 patients (83.7%): 9 patients recurred with a CIED infection (7.3%), and 9 died (7.3%). ImplicationsIn our 10-year experience, high-dose DAP in combination with CRO represented a good option for empirical therapy of CIED infections. DAP-CRO combination was safe and effective, showing no significant drug-related adverse events and low rates of 6-month recurrence and mortality.

Chemical composition, antimicrobial and antibiofilm activities of essential oil from Turkish endemic Prangos hulusii fruits

ABSTRACT The chemical composition, antimicrobial, and antibiofilm activities of the essential oil from the fruits of Turkish endemic Prangos hulusii were studied. Essential oil was analyzed by GC and GC/MS. Thirty-nine compounds were identified, which represent 98.6% of the total composition of the essential oil. Monoterpene hydrocarbons and sesquiterpene hydrocarbons were the most represented classes of volatiles with 49.8% and 21.0%, respectively. The main constituents of the essential oil were (E)-methyl cinnamate (22.9%), α-phellandrene (13.8%), and (E)-β-ocimene (12.9%). (E)-methyl cinnamate was detected in Prangos spp. for the first time. Antimicrobial activities against three Gram-positive bacteria, three Gram-negative bacteria, and three yeast strains were evaluated using disk diffusion test and microdilution method. Antibiofilm experiments were done by spectrophotometric microplate method and the results of Staphylococcus aureus, Escherichia coli, and Candida albicans were visualized via scanning electron microscopy. The essential oil had an antimicrobial effect and showed an antibiofilm effect on these strains.

Antibacterial Efficacy and Characterization of Silver Nanoparticles Synthesized via Methanolic Extract of Fomes fomentarius L. Fr.

Green synthesis employs environmentally friendly, biodegradable substances for the production of nanomaterials. This study aims to develop an innovative method for synthesizing silver nanoparticles (AgNPs) using a methanolic extract of Fomes fomentarius L. Fr. as the reducing agent and to assess the potential antibacterial properties of the resulting nanoparticles. The successful synthesis of AgNPs was confirmed through characterization techniques such as UV-visible (UV-Vis) spectrophotometry, Fourier-transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (PXRD). The UV-Vis analysis revealed an absorption peak at 423 nm, while FT-IR identified key phytochemical compounds involved in the reduction process. PXRD analysis indicated a face-centered cubic (fcc) structure with prominent peaks observed at 2θ = 38°, 44.6°, 64.6°, and 78°, confirming the crystalline nature of the AgNPs, with a crystallite diameter of approximately 24 nm, consistent with TEM analysis. The synthesized AgNPs demonstrated significant antibacterial activity, particularly against S. aureus, with higher efficacy against gram-positive bacteria.

Phytochemical Study of Ethanol Extract of Gnaphalium uliginosum L. and Evaluation of Its Antimicrobial Activity.

This study evaluates the antibacterial and antifungal effects of ethanol extracts from Gnaphalium uliginosum L. derived from freshly harvested plant biomass, including stems, leaves, flowers, and roots. The extract was analyzed using gas chromatography-mass spectrometry (GC-MS) to determine its antimicrobial activity against phytopathogenic bacteria and fungi. Two methods were used in the experiments: agar well diffusion and double serial dilution. Extraction was carried out using the maceration method with different temperature regimes (25 °C, 45 °C, and 75 °C) and the ultrasonic method at various powers (63-352 W) for different durations (5 and 10 min). It was found that the 70% ethanol extract obtained through the ultrasonic experiment at 189 W power for 10 min and at 252 W power for 5 min had the highest antimicrobial activity compared to the maceration method. The most sensitive components of the extracts were the Gram-positive phytopathogenic bacteria Clavibacter michiganensis and the Gram-negative phytopathogenic bacteria Erwinia carotovora spp., with MIC values of 156 μg/mL. Among the fungi, the most sensitive were Rhizoctonia solani and Alternaria solani (MIC values in the range of 78-156 µg/mL). The evaluation of the antimicrobial activity of extracts using the diffusion method established the presence of a growth suppression zone in the case of C. michiganensis (15-17 mm for flowers, leaves, and total biomass), which corresponds to the average level of antimicrobial activity. These findings suggest that G. uliginosum has potential as a source of biologically active compounds for agricultural use, particularly for developing novel biopesticides.

Exploring the feasibility of biodegradable films for antimicrobial absorbent sachets and CO2 emitters as sustainable active packaging

The use of biodegradable polymer films for packaging materials as eco-friendly alternatives to traditional plastics is limited by their water sensitivity and poor gas barrier properties. This study developed a multifunctional supplemental packaging system using poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) blend film incorporated with 3% and 5% zinc oxide (ZnO) nanoparticles. The system targets the triple-active packaging displayed antimicrobial activity with water absorption and CO2 emission properties. ZnO incorporation effectively reduced water solubility of the PBAT/TPS film (from 16% to 7%), and exhibited excellent antimicrobial activity against Gram-positive and Gram-negative bacteria (>99% reduction). Well-dispersed ZnO, verified by scanning electron microscopy, decreased water vapor and CO2 gas permeation. A PBAT/TPS-ZnO sachet was fabricated, comprising carboxymethyl cellulose as the absorbent function and CO2 precursors (sodium bicarbonate and citric acid). The 3% ZnO loading achieved optimal performance, balancing water absorption (2.48 g weight gain after 144 h) and CO2 emission (35% in headspace at equilibrium). Kinetic studies suggested diffusion as the dominant mechanism for CO2 release, driven by concentration differences between the sachet and headspace. This system showed potential as active modified atmosphere packaging to extend product shelf life.

UV-ozone treated glass fiber based lateral flow DNA extraction platform integrated with LAMP for rapid detection of pathogen bacteria in whole blood

The need for a fast and reliable platform for the detection of pathogens in point-of-care (POC) applications is increasing day by day. Molecular detection of pathogens is made possible by a good DNA isolation method, which allows for efficient and pure extraction from the cell. To address this need, our work presents a new lateral flow platform based on UV ozone-treated glass fiber pads for high-throughput DNA isolation from very low volumes of bacterial samples. The platform we developed mainly consists of UV ozone-treated glass fiber, which serves as the essential component binding DNA, and a cellulose-based absorbent pad acting as a reservoir for washing buffers and undesired substances from bacterial cells. UV ozone treatment increased the DNA recovery efficiency of glass fiber by 2.5 times compared to untreated glass fiber. qPCR results confirmed the isolation of pure DNA from both gram-negative and gram-positive bacteria samples performed on the developed platform. For five different bacteria concentrations (10–109 cfu/mL), a good linearity between Cq values and bacteria concentrations was obtained. A minimum concentration of 10 cfu/mL could be detected for both bacterial samples of 10 µL. The developed DNA extraction platform was also integrated with a portable heater for the LAMP-based detection application. We successfully demonstrated that the proposed extraction platform, combined with the colorimetric LAMP-based system, can detect Staphylococcus aureus bacteria spiked in whole blood samples in under one hour, including both extraction and detection processes. Our simplified paper-based platform will be a good alternative for the DNA extraction and molecular detection of pathogens without the need for complex laboratory equipment in POC applications.

Exploring the Multifaceted Biological Activities of Anthocyanins Isolated from Two Andean Berries.

Natural pigments extracted from plant species are used in foods, cosmetics, and pharmaceuticals. This study evaluates the comprehensive biological activities of anthocyanins isolated from Andean blueberry (Vaccinium floribundum Kunth) and Andean blackberry (Rubus glaucus Benth), focusing on their antimicrobial, antioxidant, antitumoral, anti-inflammatory, and hemolytic properties. Chemical characterization revealed significant anthocyanin content with complex mass spectrometric profiles indicating diverse glycosylation patterns that may influence their bioactivity. The antimicrobial assays showed that the extracts were particularly effective against Gram-positive bacteria, with minimal inhibitory concentrations (MICs) as low as 1 mg/mL for Rubus glaucus, indicating strong potential for therapeutic use. The antioxidant capacity of the berries was substantial, albeit slightly lower than that of ascorbic acid. The extracts also exhibited notable antitumoral activity in various cancer cell lines, showing promise as adjunctive or preventive treatments. The anti-inflammatory effects were confirmed by inhibiting nitric oxide production in macrophage cells, highlighting their potential in managing inflammatory diseases. In terms of hemolytic activity, Rubus glaucus exhibited dose-dependent effects, potentially attributable to anthocyanins and phenolics, while Vaccinium floribundum demonstrated no significant hemolytic activity, underscoring its safety. These findings suggest that anthocyanins from Andean berries possess potent biological activities, which could be leveraged for health benefits in pharmaceutical and nutraceutical applications. Further studies are needed to isolate specific bioactive compounds and investigate their synergistic effects in clinical and real-world contexts.

Anti-Inflammatory, Antibacterial, Anti-Biofilm, and Anti-Quorum Sensing Activities of the Diterpenes Isolated from Clinopodium bolivianum.

This study reports for the first time the isolation of four diterpenoid compounds: 15-Hydroxy-12-oxo-abietic acid (1), 12α-hydroxyabietic acid (2), (-)-Jolkinolide E (3), and 15-Hydroxydehydroabietic acid (4) from Clinopodium bolivianum (C. bolivianum). The findings demonstrate that both the dichloromethane/methanol (DCMECB) extract of C. bolivianum and the isolated compounds exhibit significant anti-inflammatory (inhibition of NF-κB activation), antibacterial (primarily against Gram-positive bacteria), and anti-biofilm (primarily against Gram-negative bacteria) activities. Among the isolated diterpenes, compounds 3 and 4 showed notable anti-inflammatory effects, with IC50 values of 17.98 μM and 23.96 μM for compound 3, and 10.79 μM and 17.37 μM for compound 4, in the HBEC3-KT and MRC-5 cell lines. Regarding their antibacterial activity, compounds 3 and 4 were particularly effective, with MIC values of 0.53-1.09 μM and 2.06-4.06 μM, respectively, against the S. pneumoniae and S. aureus Gram-positive bacteria. Additionally, these compounds demonstrated significant anti-biofilm and anti-quorum sensing activities, especially against Gram-negative bacteria (H. influenzae and L. pneumophila). We also explain how compound 3 (BIC = 1.50-2.07 μM, Anti-QS = 0.31-0.64 μM) interferes with quorum sensing due to its structural homology with AHLs, while compound 4 (BIC = 4.65-7.15 μM, Anti-QS = 1.21-2.39 μM) destabilises bacterial membranes due to the presence and position of its hydroxyl groups. These results support the traditional use of C. bolivianum against respiratory infections caused by both Gram-positive and Gram-negative bacteria. Furthermore, given the increasing antibiotic resistance and biofilm formation by these bacteria, there is a pressing need for the development of new, more active compounds. In this context, compounds 3 and 4 isolated from C. bolivianum offer promising potential for the development of a library of new, more potent, and selective drugs.

Design, synthesis and biological evaluation of amphiphilic benzopyran derivatives as potent antibacterial agents against multidrug-resistant bacteria

Antimicrobial resistance has emerged as a significant threat to global public health. To develop novel, high efficiency antibacterial alternatives to combat multidrug-resistant bacteria, A total of thirty-two novel amphiphilic benzopyran derivatives by mimicking the structure and function of antimicrobial peptides were designed and synthesized. Among them, the most promising compounds 4h and 17e displayed excellent antibacterial activity against Gram-positive bacteria (MICs = 1–4 μg/mL) with weak hemolytic activity and good membrane selectivity. Additionally, compounds 4h and 17e had rapid bactericidal properties, low resistance frequency, good plasma stability, and strong capabilities of inhibiting and eliminating bacterial biofilms. Mechanistic studies revealed that compounds 4h and 17e could effectively disrupt the integrity of bacterial cell membranes, and accompanied by an increase in intracellular reactive oxygen species and the leakage of proteins and DNA, ultimately leading to bacterial death. Notably, compound 4h exhibited comparable in vivo antibacterial potency in a mouse septicemia model infected by Staphylococcus aureus ATCC43300, as compared to vancomycin. These findings indicated that 4h might be a promising antibacterial candidate to combat antimicrobial resistance.

Eco-friendly synthesis of CuO/NiO nanocomposite and their enhanced photocatalytic organic dyes degradation, antimicrobial, cytotoxicity and antioxidant applications

In this study, Macroptilium lathyroides leaf extract was used as a reducing and capping agent to prepare the biogenic CuO-NiO nanocomposite. The synthesized samples were analyzed using UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy with energy-dispersive X-ray (EDX) analysis, Dynamic light scattering, and Zeta potential. The structure, surface morphology, elemental compositions, and stability of the particles were determined. The average size of the particles from TEM was found to be 10.6 nm with a cubic structure. Furthermore, CuO-NiO nanocomposite was used to study the methylene blue dye degradation when exposed to sunlight for 90 min, about 98.1 % of the dye degraded. The nanocomposite showed high antimicrobial activity against both Gram-positive bacteria Staphylococcus aureus (18 mm), Streptococcus pyogenes (20 mm) and Gram-negative strains Klebsiella pneumonia (16 mm), Escherichia coli (18 mm) at 30 µg/mL. The antifungal activity against Trichoderma viride (14 mm), Candida albicans (13 mm) and excellent antioxidant properties with an IC50 value of 184.52 µg/mL were observed. Furthermore, it shows potent cytotoxic effects against the lung cancer cell line A549, and breast cancer cell line MCF 7 with an IC50 value of 59.8 µg/mL, 42.90 µg/mL, respectively.

Secretion of the arthrodial membrane gland of a harvester (Arachnida: Opiliones): Antimicrobial activity

Because of the exoskeleton, arthropods must have flexible areas to be able to move. Such regions are called arthrodial membranes and are particularly vulnerable to bacteria and fungi. Here, we analyzed the secretion in the glands underneath it in a Neotropical harvester Mischonyx squalidus (Arachnida: Opiliones) and tested whether it has antiseptical properties. Wepuncturedthemembrane,collectedand quantified ina spectrophotometer. We also fractionated and analyzed the samples in reversed-phase high-performance liquid chromatography (RP-HPLC) and then incubated the treated fractions and determined growth inhibition by measuring absorbance. The secretions resulted in 100 fractions, among which two had activity against the Gram-positive bacteria Micrococcus luteus and against the yeast Candida albicans. The low concentrations at which the secretions were active are relevant from a biotechnological point of view. For the organism, the secretions possibly prevent infections, including when they are attacked in these regions by predators that pick that spot to bite.

Positive-Charge-Based Small Molecule Dyes for Gut Microbiota Fluorescent Imaging.

As one of the research hotspots in recent years, gut microbiota have been proven to be closely related to host metabolism, nutrient absorption, and immune regulation. However, there are still many urgent issues in the research of gut microbiota, such as the localization and tracking of gut microbiota. In this research, two new fluorescent probes, EF and 6F, were developed by optimizing the structure of the positron salt small molecule probe F16. In vitro labeling experiments showed that EF and 6F can quickly label Gram-positive bacteria, Staphylococcus aureus and Lactobacillus reuteri, as well as Gram-negative bacteria, Escherichia coli and Salmonella pullorum. Meanwhile, EF and 6F have little bacterial toxicity and are used at a maximum concentration of 200 μM. Compared with EF, 6F has better hydrophilicity and stronger fluorescence characteristics in aqueous solutions, making it more suitable for imaging within gut microbiota populations. The results of in vivo imaging experiments indicate that EF and 6F can label and image the intestinal microbiota colonized by the mouse intestinal mucosal epithelium without causing any damage to intestinal tissue. Compared with commercially available MitoTracker dyes and fluorescein 5-isothiocyanate (FITC) dyes, EF and 6F exhibit better biocompatibility. Therefore, the compounds EF and 6F synthesized in this study are novel small molecule probes suitable for imaging gut microbiota, providing a better probe selection for exploring complex gut microbiota.

Synthesis and Antimicrobial Activity of Newly Synthesized Nicotinamides.

Antioxidants are promising compounds with antimicrobial activity against drug-resistant pathogens, especially when combined with conventional antimicrobials. Our study aimed to characterize the structure of nicotinamides synthesized from nicotinic acid and thiocarbohydrazones and to evaluate their antibacterial and antifungal activity. Seven nicotinic acid hydrazides (NC 1-7) were synthesized using mono-thiocarbohydrazones with hydroxyl group substituents, along with quinolone, phenolic, and pyridine rings known for their antimicrobial activity. The in vitro antimicrobial activity of NC 1-7, at concentrations ranging from 0.001 to 1 mM, was tested against Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (NCIMB 9111), and Candida albicans (ATCC 24433) using the broth microdilution method per EUCAST 2024 guidelines. Microorganism survival percentages were calculated based on optical density, and target fishing using the PharmMapper database identified potential molecular targets. The results showed that P. aeruginosa was most susceptible to the compounds, while C. albicans was the least susceptible. NC 3 significantly inhibited P. aeruginosa and K. pneumoniae growth at 0.016 mM, while higher concentrations were required for S. aureus, E. faecalis, and C. albicans. NC 5 was most effective against gram-positive bacteria at 0.03 mM. Only NC 4 completely inhibited C. albicans below 1 mM. NC 3, with the lowest concentration for 50% growth inhibition (0.016-0.064 mM), showed promising antibacterial potential against specific AMR-related proteins (bleomycin resistance protein, HTH-type transcriptional regulator QacR, and streptogramin A acetyltransferase), suggesting that this class of compounds could enhance or restore the activity of established antibiotics.

Mechanistic insights and in vivo efficacy of thiosemicarbazones against methicillin-resistant Staphylococcus aureus

Staphylococcus aureus poses a significant threat in both community and hospital settings due to its infective and pathogenic nature combined with its ability to resist the action of chemotherapeutic agents. Methicillin-resistant S. aureus (MRSA) poses a critical challenge. Metal-chelating thiosemicarbazones (TSCs) have shown promise in combating MRSA and while previous studies hinted at the antimicrobial potential of TSCs, their mechanisms of action against MRSA are still under investigation. We screened a chemical library for anti-staphylococcal compounds and identified a potent molecule named R91 that contained the NNSN structural motif found within TSCs. We identified that R91 and several structural analogs exhibited antimicrobial activity against numerous S. aureus isolates as well as other Gram-positive bacteria. RNAseq analysis revealed that R91 induces copper and oxidative stress responses. Checkerboard assays demonstrated synergy of R91 with copper, nickel, and zinc. Mutation of the SrrAB two-component regulatory system sensitizes S. aureus to R91 killing, further linking the oxidative stress response to R91 resistance. Moreover, R91 was found to induce hydrogen peroxide production, which contributed to its antimicrobial activity. Remarkably, no mutants with elevated R91 resistance were identified, despite extensive attempts. We further demonstrate that R91 can be used to effectively treat an intracellular reservoir of S. aureus in cell culture and can reduce bacterial burdens in a murine skin infection model. Combined, these data position R91 as a potent TSC effective against MRSA and other Gram-positive bacteria, with implications for future therapeutic development.

Chemical, antimicrobial, antioxidant, and molecular dynamic studies of spiro[chromane-3',2''-thiopyran]-4'-one 1''-oxide and spiro[chromane-3',2''-thiopyran]-4'-one 1'',1''-dioxide

Some of spiro[chromane-3',2''-thiopyran]-4'-ones were oxidized via m-chloroperbenzoic acid and/or hydrogen peroxide to afford the corresponding nine spiro[chromane-3',2''-thiopyran]-4'-one 1''-oxides and three spiro[chromane-3',2''-thiopyran]-4'-one 1'',1''-dioxides, which were confirmed by spectral data (IR, 1H NMR, 13C NMR, MS-ESI, and MS-EI). Whereas, the yield of oxidation using hydrogen peroxide is higher than that of oxidation using m-chloroperbenzoic acid. Moreover, Gram-negative bacteria (Escherichia coli ATCC 25922), and Gram-positive bacteria (Staphylococcus aureus ATCC 6538) were adopted to test the antimicrobial activity of 12 newly synthesized compounds (7a, 8a-c, 9a, 10a-c, 11a, 12a-c). The three sulfoxide derivatives 8b, 10b, and 10c showed antimicrobial activity. Also, antioxidant activity was evaluated for the newly synthesized compounds and shows that, all newly synthesized compounds (7a, 8a-c, 9a, 10a-c, 11a, 12a-c) have antioxidant activity. Molecular dynamic and system stability, Binding interaction mechanism based on binding free energy calculation, Identification of the critical residues responsible for ligands binding, Ligand–residue interaction network profiles, and In silico ADMET properties prediction were studied for the new compounds. The results of molecular dynamic studies were consistent with the in vitro antibacterial and antioxidant activity.