Search Results (3,670)

The production of β-lactamases is the main mechanism underlying carbapenem resistance. This study combined in silico and in vitro approaches to identify potential polyphenols as carbapenemase inhibitors. Molecular docking, molecular dynamics, and ADMET prediction were performed to assess the binding affinity, stability, and safety of quercetin, kaempferol, caffeic acid, and 3,4-dihydroxybenzoic acid against KPC-2, NDM-1, and OXA-48 carbapenemases. In vitro antibacterial assays and checkerboard analyses were conducted against Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa to assess antibacterial and synergistic effects. Then, the inhibition of the β-lactam hydrolytic activity was confirmed. In silico results showed that quercetin, kaempferol, and caffeic acid exhibited strong binding affinity and consistent stability towards the targets. Therefore, quercetin and kaempferol showed the strongest affinities (−8.0 kcal/mol) and stable interactions with key catalytic residues. ADMET profiles indicated good pharmacokinetic behavior and low acute toxicity. In vitro assays revealed that the polyphenols exhibited MIC values ranging from 12.5 to 25 mg/L and MBC values of 25–50 mg/L. Combined with cefotaxime, they enhanced bacterial susceptibility and inhibited β-lactam hydrolysis, with quercetin achieving complete inhibition at 200 mg/L. These findings highlight the potential of the four polyphenols as natural β-lactamase inhibitors. Further enzyme kinetics and in vivo studies are needed to confirm their therapeutic relevance. Full article

The host microbiome is a promising source of probiotics for aquaculture species including Nile tilapia. In this study, the probiotic potential of autochthonous bacterial isolates from Nile tilapia and carp mid-intestines were screened in vitro. Two isolates (C61 and T70), closely related to Bacillus subtilis, exhibited antagonistic activity against multiple pathogen species and demonstrated multiple digestive enzyme activities. Their antagonistic activity in Aeromonas hydrophila assays remained even under simulated intestinal juice (SIJ) exposure. Subsequently, C61 (PT1) and T70 (PT2) were added to experimental diets at log 7 CFU/g of diet, and fed to Nile tilapia (5.32 ± 0.12 g) for 40 days. There were no significant differences observed in the growth performance across treatments. Despite limited Bacillus intestinal recovery levels, 16S rRNA gene metabarcoding revealed subtle shifts in the intestinal microbial community composition of the probiotic-fed groups. In addition, the PT1 group showed significantly longer mucosal fold length, elevated intestinal and skin goblet cell levels, and higher skin goblet cell coverage compared to the control. These results indicate the potential benefits of the isolates as functional feed additives for enhancing the mucosal health of Nile tilapia, but their benefits were likely achieved through transient activity given the low level of Bacillus recovery in the intestine. Full article

The use of electronic cigarettes has increased in the U.S. with menthol and mint flavors showing notably higher sales. While research on the bacterial microbiome of traditional tobacco products is growing, particularly regarding menthol and nicotine effects, data regarding potential microbial contaminants within electronic liquids (e-liquids) remain limited. Additionally, the potential antibacterial properties of e-liquids remain sparse. To address these gaps, we evaluated the prevalence of viable bacteria in e-liquids; characterized their antimicrobial susceptibility patterns; and tested the antibacterial activity of the e-liquids. Two e-liquid flavors (menthol and non-menthol) across three different nicotine concentrations (0, 6 and 12 mg/mL) were tested using culture-based methods and Sanger sequencing. Antimicrobial susceptibility testing and e-liquid antibacterial activity assays were performed using the Kirby Bauer disc diffusion method. The majority of the isolates (63.15%) were identified as Pseudomonas aeruginosa and Bacillus spp. (B. pumilus, B. megaterium and B. cereus). Notably, P. aeruginosa and P. fluorescens isolates exhibited multidrug resistance against penicillin, tetracyclines, and phenicols. The e-liquids also demonstrated antimicrobial activity, inhibiting the growth of B. cereus, P. aeruginosa, and Staphylococcus aureus, with greater inhibition of P. aeruginosa growth at higher (12 mg/mL) compared to lower (0 mg/mL) nicotine concentrations across the menthol-flavored samples. These findings offer preliminary evidence of viable, multidrug-resistant bacteria and antibacterial properties in e-liquids, underscoring potential public health concerns regarding user exposure risks and microbial interactions, and emphasizing the need for continued surveillance of microbial safety in electronic cigarette products. Full article

Background/Objectives: Biofilm-associated infections pose a major clinical challenge since bacteria within biofilms exhibit highly antibiotic tolerance. Pseudomonas aeruginosa forms persistent biofilms that cause chronic infections in vulnerable patients, including those with cystic fibrosis, burns, or medical implants. Such biofilm-associated chronic infections require prolonged treatments that promote antimicrobial resistance. To address this, recent strategies focus on enhancing biofilm dispersion. Methods: Thirty-six N-arylimino-1,2,3-dithiazoles were screened for their biofilm dispersal activity using a crystal violet assay. Their cytotoxicity was assessed on A549 and HaCat eukaryotic cells. Moreover, their influence on bacterial growth and virulence was investigated. Lastly, fluorescence anisotropy was used to measure membrane fluidity to obtain the first insights on the mechanism of action of these chemicals. Results: Our results showed that quinazoline-derivatives of imino-1,2,3-dithiazoles display biofilm dispersion activity. These compounds do not increase virulence through pyocyanin production, do not modify the growth kinetics of P. aeruginosa, and do not show cytotoxicity towards eucaryotic cells. Conclusions: These findings highlight the potential use of N-arylimino-1,2,3-dithiazole-derived compounds as safe and effective dispersal agents of P. aeruginosa biofilms. Full article

Electrospun fibrous scaffolds based on cellulose acetate (CA), polycaprolactone (PCL), and poly (L-lactic acid) (PLLA) are versatile materials with applications spanning diverse fields, but in their pristine form, they typically lack significant inherent antibacterial properties. To address this limitation and expand their utility, this study explored the incorporation of xylitol, a natural antibacterial sugar alcohol, into these polymer matrices to enhance their physicochemical and antimicrobial properties. Electrospinning was employed to fabricate pristine and xylitol-loaded scaffolds with varying xylitol concentrations. Morphological analysis revealed polymer-dependent changes in fiber diameter and porosity. Mechanical testing assessed the impact of xylitol on tensile properties, while thermal analysis investigated alterations in melting temperature and crystallinity. The antibacterial efficacy against Staphylococcus aureus and Escherichia coli was evaluated using WST assay and live/dead staining. Notably, xylitol significantly enhanced the antibacterial activity against both bacterial species, with a more pronounced and rapid effect observed against S. aureus. The tailored scaffold properties and imparted antimicrobial characteristics highlight the potential of these xylitol-modified electrospun materials: they are easily produced, low-cost, and appropriate for a range of applications (dental applications, filters, masks, wound dressing, and packaging) where preventing bacterial contamination is crucial. Full article

Implant-associated infections remain a major clinical challenge, often leading to implant failure, revision surgery, and increased healthcare burden. Systemic antibiotic administration is limited by poor local bioavailability and systemic side effects, highlighting the need for localized drug-delivery systems that can simultaneously support tissue integration and prevent bacterial colonization. This study aimed to develop and characterize a novel generation of chitosan membranes loaded with hydroxyapatite–clindamycin phosphate (CS/HA-CLY) for localized infection prevention at implantation sites. The composite membranes’ physicochemical characteristics were analyzed using ATR FT-IR, XPS, SEM, XRD, and contact angle measurements. Furthermore, the in vitro biomineralization potential was assessed employing the Taguchi method, while the in vitro release of clindamycin phosphate was examined through UV-Vis spectrophotometry. The CS/HA-CLY membranes exhibited improved wettability, drug release behavior, and biomineralization ability compared to neat CS. These results suggest that the developed composite membranes could successfully combine antibacterial efficacy and biocompatibility, supporting their potential as multifunctional biomaterials for preventing implant-related infections while promoting tissue integration. These findings provide a promising basis for further biological assays and in vitro evaluation. Full article

Bacterial leaf blight (BLB), a destructive disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo), continues to limit rice productivity worldwide. Although biologically synthesized zinc oxide nanoparticles (ZnO NPs) have been extensively investigated, knowledge regarding the antibacterial activity and biocompatibility of commercially available ZnO NPs is still limited. In this study, commercial ZnO NPs were systematically characterized and evaluated for their antibacterial mechanisms and biocompatibility in mammalian cells. FE-SEM and TEM analyses revealed irregular polyhedral, hexagonal, and short rod-like morphologies with an average particle size of ~33 nm, consistent with crystallite sizes estimated by XRD. The nanoparticles exhibited pronounced antibacterial activity against Xoo, with a minimum inhibitory concentration (MIC) of 16 µg/mL and a clear dose-dependent response. Mechanistic assays confirmed multifaceted bactericidal actions involving membrane disruption, ROS generation, Zn²⁺ release, and ultrastructural damage. Biocompatibility testing in human dermal fibroblasts showed enhanced proliferation at 8–32 µg/mL, no cytotoxicity up to 256 µg/mL, and reduced viability only at ≥512 µg/mL. These findings represent the first mechanistic evaluation of commercial ZnO NPs against Xoo, together with cytotoxicity assessment in mammalian cells, highlighting their structural distinctness and dual functionality that combine potent antibacterial activity with minimal mammalian cytotoxicity. Overall, the results underscore their potential as safe nanobiocontrol agents for sustainable rice disease management. Full article

Tomato is one of the most important vegetable crops in Costa Rica, where favorable environmental conditions enabled year-round production but also promote bacterial diseases. In recent years, pith necrosis has been frequently observed; nevertheless, the causal agents remain unidentified in the country. This study evaluated bacteria associated with symptomatic plants collected in the Central Valley of Costa Rica. From 32 plants, 61 bacterial isolates were obtained, described morphologically, and characterized through basic biochemical tests. Partial sequencing of the 16S rRNA gene revealed diverse bacterial taxa, predominantly belonging to the genus Pseudomonas. Thirteen isolates were selected for pathogenicity assays, which confirmed variable virulence levels. Multilocus sequence analysis based on concatenated sequences of the 16S rRNA, gyrB, rpoD, and rpoB genes identified Pseudomonas alliivorans LTM 13.1.2, P. flavescens LTM 14.2.2, and P. capsici LTM 78.3.2 as causal agents of pith necrosis. Additionally, P. straminea LTM 78.2.1 and Cedecea sp. LTM 72.2.1 caused tissue discoloration. Whole-genome sequencing of the two most virulent isolates (LTM 13.1.2 and LTM 78.3.2) supported their taxonomic classification and revealed virulence-associated genes and biosynthetic clusters. This study represents the first report of these Pseudomonas species as tomato pathogens in Costa Rica and expands their known distribution and host ranges. Full article

β-blockers are among the most widely prescribed cardiovascular drugs and are increasingly recognised as emerging pollutants due to their persistence, continuous release into aquatic environments, and potential toxicological effects on aquatic organisms. Their removal in conventional wastewater treatment plants is often inefficient, highlighting the need for biological remediation strategies. This study aimed to identify bacterial strains with the highest potential for the biotransformation of β-blockers. Therefore, we isolated and characterised bacterial strains capable of transforming two commonly used β-blockers—propranolol and metoprolol. The strains BB2 and BB3, which were able to transform propranolol and metoprolol, respectively, were identified as Raoultella terrigena and Stenotrophomonas terrae, respectively. BB2 showed broad metabolic versatility, utilising a wide range of carbon sources, whereas BB3 exhibited limited substrate utilisation. Antibiotic resistance profiling further distinguished the strains, with BB2 resistant across multiple antibiotic classes and BB3 largely sensitive. Co-metabolic assays demonstrated that supplementation with specific carbon and nitrogen sources markedly enhanced β-blocker removal, increasing propranolol biotransformation from 5% to 50% and metoprolol from 4% to 36%. These findings demonstrate the bioremediation potential of newly isolated strains and emphasise the importance of aligning microbial metabolic traits with nutrient conditions to improve pharmaceutical removal in wastewater treatment systems. Full article

The increasing prevalence of the mobile tigecycline resistance gene tet(X) poses a severe global health threat, and the genus Acinetobacter is a major reservoir. This study aimed to develop a rapid and specific multiplex PCR assay for detecting the predominant tet(X)-positive Acinetobacter species. Through pan-genome analyses of 390 tet(X)-positive Acinetobacter genomes, a total of 20 tet(X) variants were identified in 24 Acinetobacter species, including 17 published lineages and seven taxonomically unresolved Taxa. Acinetobacter indicus (30.8%), Acinetobacter amyesii (17.2%), and Acinetobacter towneri (16.1%) were the top three hosts of diverse tet(X) variants. Species-specific signature genes were identified and used for primer design, yielding amplicons of 267 bp (tet(X)), 424 bp (A. indicus), 690 bp (A. amyesii), and 990 bp (A. towneri). The assay was rigorously adjusted for an optimal annealing temperature of 52.8 °C and a primer ratio of 1:1:1:1, demonstrating high sensitivity with a detection limit of 0.3 ng/μL DNA and excellent stability under −20 °C, 4 °C, 20 °C storage conditions. Validation experiments on 151 bacterial strains showed high accuracy for DNA templates (≥97.8%) and bacterial suspensions (≥93.5%) within two hours. This cost-effective and highly accurate multiplex PCR provides a powerful tool for proactive surveillance and control of the critical Acinetobacter sp. pathogens. Full article

Macrolides are crucial for the management and treatment of bovine respiratory disease (BRD). However, antimicrobial resistance (AMR) threatens the efficacy of these and other antimicrobials. We developed real-time recombinase polymerase amplification (RPA) assays targeting three clinically relevant macrolide antimicrobial resistance genes (ARGs)—msrE-mphE and erm42—in ≤30 min using extracted DNA. A set of 199 deep nasopharyngeal swabs (DNPS) collected from feedlot calves near the time of arrival were selected based on bacterial culture (BC) results for Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni and antimicrobial susceptibility testing (AST) for tulathromycin, tilmicosin, tildipirosin, or gamithromycin. Samples were also tested for the same targets using RPA and polymerase chain reaction (PCR). In samples that were culture-positive for one or more macrolide-resistant BRD-associated bacteria (n = 101), msrE-mphE and/or erm42 were detected in 95% of cases using RPA. The remaining 98 samples were either culture-negative, or the recovered bacteria were macrolide-susceptible: 43% of these were RPA-positive for at least one macrolide ARG. Together with BC-AST and PCR, Bayesian latent class modelling estimated the clinical sensitivity of RPA for macrolide ARGs to be 95% and specificity to be 58%, with moderate agreement between RPA and BC-AST (κ = 0.52) or PCR (κ = 0.55). The estimated sensitivity of the RPA multiplex assay for the targeted macrolide ARGs was very good, although estimated specificity was limited. However, Sanger sequencing confirmed RPA detection of msrE-mphE in BC-AST/PCR-negative samples (n = 23), reflecting the presence of this locus in non-target bacteria, as well as potential ARG variants among BRD bacteria. These findings support the potential of RPA for rapid ARG detection from extracted DNA. Continued assay optimization and evaluation for detection of respiratory bacteria and ARGs will further enhance its diagnostic utility. Full article

Background/Objectives: The widespread use of sulfamethoxazole (SMX) has led to increasing antibiotic resistance, and there is a need for improved formulations to enhance its therapeutic effectiveness. In this study, we investigated the biocidal potential of SMX composite crystals incorporated with functionalized poly(lactic-co-glycolic acid) (nfPLGA) and nano-graphene oxide (nGO). Methods: The composites, namely SMX-nfPLGA and SMX-nGO, were synthesized via antisolvent precipitation and evaluated using Kirby–Bauer disk diffusion assays. Results: Incorporation of nfPLGA and nGO significantly improved SMX solubility, increasing it from 0.029 mg/mL to 0.058 mg/mL and 0.063 mg/mL, respectively. Additionally, the log partition coefficient (log P or K_w) also improved from 1.4 to 0.86 for nGO and 0.92 for nfPLGA composites. Both formulations exhibited improved antibacterial activity with distinct time-dependent bactericidal effects. Compared to pure SMX, the SMX-nfPLGA showed 60% and 53% greater bacterial inhibition at concentrations of 50 mg/mL and 100 mg/mL, respectively. Although SMX-nGO was slightly less potent, it still surpassed pure SMX, with 50% and 33% higher inhibition at the same concentrations. Conclusions: Importantly, neither nfPLGA nor nGO showed any biocidal effects, confirming that the observed enhancement was due to improved SMX solubility caused by their incorporation. These findings suggest that embedding solubility-enhancing nanoparticles into the existing crystal structure of the antibiotic is a promising strategy for enhancing the effectiveness. Full article

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), poses a serious threat to the global kiwifruit industry. Although flavonoids are widely recognized as natural antibacterial compounds, the transcriptional regulatory networks controlling their synthesis in kiwifruit and their relationship with production of downstream antibacterial metabolites remain poorly understood. In this study, we identified the transcription factor AcMYB5 as a key mediator of salicylic acid (SA) signaling that activates flavonoid biosynthesis and enhances resistance to Psa. Comparative analysis between the resistant cultivar ‘Jinkui’ and the susceptible cultivar ‘Hongyang’ revealed that Psa infection induced a rapid accumulation of endogenous SA, accompanied by a decrease in jasmonic acid (JA) levels in ‘Jinkui’. From a pool of SA-induced candidate genes, we identified AcMYB5, which is rapidly up-regulated by SA and encodes a nuclear localization protein. Overexpression of AcMYB5 in susceptible kiwifruit significantly enhanced resistance to Psa. Mechanistically, AcMYB5 directly binds to and activates the promoter of the chalcone isomerase (AcCHI), a key structural gene in the flavonoid pathway, leading to a marked increase in total flavonoid content. Notably, AcMYB5 did not activate any other genes in the flavonoid synthesis pathway in our assays, underscoring its target specificity. Our findings reveals a novel AcMYB5-AcCHI module that finely tunes flavonoid-mediated defense responses, offering valuable genetic targets and strategic insights for kiwifruit-resistant breeding. Full article

Essential oils (EOs) are complex plant-derived products known for their broad-spectrum antibacterial activity. This study aims to evaluate the chemical composition of eight essential oils-EOs (Caryophylli aetheroleum, Menthae aetheroleum, Origani aetheroleum, Rosmarini aetheroleum, Salviae aetheroleum, Melaleucae aetheroleum, Limonis aetheroleum, and Curcumae aetheroleum) and to evaluate their antibacterial and antibiofilm activity against five opportunistic pathogens with biofilm-forming potential (methicillin-susceptible and methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli, and Klebsiella pneumoniae). GC-MS was used to determine the chemical composition of the EOs, and antibacterial activity was evaluated using broth microdilution to determine the minimum inhibitory concentration and minimum bactericidal concentration. Biofilm inhibition was assessed by a crystal violet assay. Oxygenated monoterpenes and phenolic compounds were dominant in Origani, Menthae, Rosmarinus, Melaleucae, and Caryophylli aetheroleum. Potent inhibitory effects against the tested bacterial strains were observed for clove, tea tree, oregano, and rosemary EOs. The antimicrobial efficacy of EOs is closely linked to their chemical composition. Tea tree and oregano EOs exhibited the broadest spectrum of antimicrobial activity, while peppermint and curcuma oils were the least potent. Cytotoxicity thresholds from the literature suggest that some effective EO concentrations exceed safe mucosal limits, particularly in continuous high-dose applications, but short-contact delivery systems or adjunctive use with different agents may mitigate safety concerns. These findings support further investigation into their therapeutic applications in oral health products. Full article

Essential oils (EOs) from aromatic plants are valuable sources of bioactive compounds with potential applications as natural antimicrobials and antioxidants. This study investigated the chemical composition, antimicrobial and antioxidant activities, and in silico pharmacological properties of EOs extracted from Laurus nobilis, Thymbra capitata, and Mentha piperita, three medicinal species traditionally used in northern Morocco. Hydrodistillation yielded 1.12–1.53% oils, and GC–MS analysis revealed distinct chemotypes: L. nobilis was rich in eucalyptol, linalool, methyleugenol, and α-terpinyl acetate; T. capitata was dominated by carvacrol (80.95%), and M. piperita contained high proportions of linalool (57.37%) and linalyl acetate (28.56%). Antimicrobial assays demonstrated strong activity of all oils against Gram-positive and Gram-negative bacteria as well as Candida species, with T. capitata showing the most potent and broad-spectrum effects (MIC 0.073–9.47 mg/mL), attributed to its high carvacrol content. Antioxidant assays (DPPH and ferric reducing power) identified L. nobilis as the most active radical scavenger (IC₅₀ = 0.037 mg/mL), followed by T. capitata, whereas M. piperita displayed weaker activity. PCA confirmed that phenolic monoterpenes drive both antimicrobial and antioxidant potency, while oxygenated terpenes and sesquiterpenes contribute more selectively. ADMET predictions indicated generally favorable absorption and low toxicity, although o-cymene and carvacrol presented potential safety concerns. Molecular docking revealed α-terpinyl acetate as the most versatile ligand, with strong binding to bacterial, fungal, and oxidative enzymes, whereas other compounds exhibited more selective affinities. Collectively, these findings highlight the potential of Moroccan EOs, particularly T. capitata and L. nobilis, as promising natural alternatives to synthetic antimicrobial and antioxidant agents. Full article