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Acylphloroglucinols are well-known Eucalyptus secondary metabolites which exhibit a variety of structures and bioactivities. The investigation of a crude acetone extract of Eucalyptus camaldulensis leaves led to the isolation of two new acylphloroglucinols, eucalypcamals O and P ( 1 and 2 ) together with seven phloroglucinols ( 3 - 9 ), and a benzene derivative ( 10 ). Their chemical structures were elucidated by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and mass spectroscopy. The absolute configurations of compounds 1 and 2 were established by comparison of experimental and calculated electronic circular dichroism (ECD) data. In the putative biosynthetic pathway, eucalypcamals O and P should be derived from hetero-Diels-Alder reaction between grandinol and trans -isoeugenol.

Aims: Quercus infectoria (Qi), a traditional herbal plant with a broad spectrum of activities on multidrug-resistant bacteria, has been developed for hand sanitizer applications., Methods and Results: Antimicrobial activity was evaluated using agar-well diffusion and broth microdilution method. Bactericidal activity was determined following the European Standard 1276 antibacterial suspension test. Neutralization assay was performed to assess antirespiratory syncytial virus. Safety, stability, and skin permeation of Qi hand gel was investigated. Qi hand sanitizer gel inhibited microorganisms ranging from 99.9% to 99.999% against Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant Staph. aureus, Staph. epidermidis, Staph. pseudintermedius, Staph. saprophyticus, Streptococcus pyogenes, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Candida albicans. A significant reduction in main human dermatophytes including Microsporum canis, M. gypseum, and Talaromyces marneffei of ∼50% was observed (P < .05). Qi hand sanitizer gel inactivated >99% viral particles entering human laryngeal epidermoid carcinoma cells in a dose-dependent manner. Scanning electron micrographs further illustrated that Qi hand sanitizer gel disrupted microbial cell membrane after 1-min contact time resulting in cell death. Qi hand sanitizer gel delivered emollient compounds through simulated human skin layers and showed no cytotoxicity on fibroblast cells. Moreover, Qi hand sanitizer gel demonstrated stability under extreme conditions., Conclusions: Qi hand sanitizer gel was able to inhibit various microorganisms including bacteria, dermatophytes, and virus., (© The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.)

Biofilm-associated infections are a critical element in infectious diseases and play an important role in antibiotic resistance. Biosynthesized gold nanoparticles (AuNPs) using ethanolic extract of Musa sapientum unripe fruit were performed. The nanoparticles demonstrated an absorption peak at 554 nm with particle sizes ranging from 5.45 to 104.44 nm. High negative zeta potential value of -33.97 mV confirmed the high stability of AuNPs. The presence of bioconstituents responsible for capping and stabilization was indicated by intensity changes of several peaks from Fourier-transform infrared spectroscopy analysis. The minimum inhibitory concentrations (MIC) of the biosynthesized AuNPs against important pathogens ranged from 10 to 40 μg mL -1 . Synthesized nanoparticles at 0.062 to 0.5 × MIC significantly inhibited biofilm formation in all the tested microorganisms (p < 0.05). Scanning electron microscopy and confocal scanning laser microscopy images clearly illustrated in disruption and architectural changes of microbial biofilms at sub-MIC of biosynthesized AuNPs. Excellent antioxidant and antityrosinase activities of AuNPs were observed. The biosynthesized AuNPs at 20 μg mL -1 significantly inhibited nitric oxide production by 93% in lipopolysaccharide-stimulated RAW 264.7 cells, compared with control (p < 0.05). The biosynthesized AuNPs at 0.6 to 40 μg mL -1 demonstrated no toxic effects on L929 fibroblast cells., (© 2023 Wiley-VCH GmbH.)

COVID-19 patients have often required prolonged endotracheal intubation, increasing the risk of developing ventilator-associated pneumonia (VAP). A preventive strategy is proposed based on an endotracheal tube (ETT) modified by the in situ deposition of eucalyptus-mediated synthesized silver nanoparticles (AgNPs). The surfaces of the modified ETT were embedded with AgNPs of approximately 28 nm and presented a nanoscale roughness. Energy dispersive X-ray spectroscopy confirmed the presence of silver on and inside the coated ETT, which exhibited excellent antimicrobial activity against Gram-positive and Gram-negative bacteria, and fungi, including multidrug-resistant clinical isolates. Inhibition of planktonic growth and microbial adhesion ranged from 99 to 99.999% without cytotoxic effects on mammalian cells. Kinetic studies showed that microbial adhesion to the coated surface was inhibited within 2 h. Cell viability in biofilms supplemented with human tracheal mucus was reduced by up to 95%. In a porcine VAP model, the AgNPs-coated ETT prevented adhesion of Pseudomonas aeruginosa and completely inhibited bacterial invasion of lung tissue. The potential antimicrobial efficacy and safety of the coated ETT were established in a randomized control trial involving 47 veterinary patients. The microbial burden was significantly lower on the surface of the AgNPs-coated ETT than on the uncoated ETT (p < 0.05). KEY POINTS: • Endotracheal tube surfaces were modified by coating with green-synthesized AgNPs • P. aeruginosa burden of endotracheal tube and lung was reduced in a porcine model • Effective antimicrobial activity and safety was demonstrated in a clinical trial., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Catheter-associated urinary tract infections (CAUTIs) are significant complications among catheterized patients, resulting in increased morbidity, mortality rates, and healthcare costs. Foley urinary catheters coated with synthesized silver nanoparticles (AgNPs) using Eucalyptus camaldulensis leaf extract were developed using a green chemistry principle. In situ-deposited AgNPs with particle size ranging between 20 and 120 nm on the catheter surface were illustrated by scanning electron microscopy. Atomic force microscopy revealed the changes in surface roughness after coating with nanoparticles. The coated catheter could significantly inhibit microbial adhesion and biofilm formation performed in pooled human urine-supplemented media to mimic a microenvironment during infections ( p 0.05). AgNPs-coated catheter exhibited broad-spectrum antimicrobial activity against important pathogens, causing CAUTIs with no cytotoxic effects on HeLa cells. A reduction in microbial viability in biofilms was observed under confocal laser scanning microscopy. A catheter bridge model demonstrated complete prevention of Proteus mirabilis migration by the coated catheter. Significant inhibition of ascending motility of Escherichia coli and P. mirabilis along the AgNPs-coated catheter was demonstrated in an in vitro bladder model ( p 0.05). The results suggested that the AgNPs-coated urinary catheter could be applied as an alternative strategy to minimize the risk of CAUTIs by preventing bacterial colonization and biofilm formation.

Failure in the prevention of cross-transmission from contaminated gloves has been recognized as an important factor that contributes to the spread of several healthcare-associated infections. Ex situ coating process with silver nanoparticles (AgNPs) using Eucalyptus citriodora ethanolic leaf extract as reducing and capping agents to coat glove surfaces has been developed to prevent this mode of transmission. Elemental analysis of coated gloves showed 24.8 Wt% silver densely adhere on the surface. The coated gloves fully eradicated important hospital-acquired pathogens including Gram-positive bacteria, Gram-negative bacteria, and yeasts within 1 h. The coated gloves showed significant reduction, an average of five logs when tested against all standard strains and most clinical isolates (p < 0.01). Following prolonged exposure, the coating significantly reduced the numbers of most adhered pathogenic species, compared with uncoated gloves (p < 0.0001). AgNPs-coated gloves reduced microbial adhesion of mixed-species biofilms. A series of contamination and transmission assays demonstrated no transmission of viable organisms. Biocompatibility analysis confirmed high viability of HaCaT and L929 cells at all concentrations of AgNPs tested. The coated gloves were non-toxic with direct contact with L929 cells. The highly efficacious AgNPs-coated gloves potentially provide additional protection against transmission of healthcare-associated infections., (© 2021 Wiley-VCH GmbH.)

Bionanotechnology has increasingly gained attention in biomedical fields as antifungal and antibiofilm agents. In this study, biosynthesized silver nanoparticles (bio-AgNPs) using aqueous Eucalyptus camaldulensis leaf extract were successfully performed by a one-step green approach. Spherical-shaped nanoparticles, approximately 8.65 nm, exhibited noncytotoxicity to erythrocytes, HeLa, and HaCaT cells. The synthesized nanoparticles showed strong fungicidal activity ranging from 0.5 to 1 µg/ml. The nanoparticles affected Candida adhesion and invasion into host cells by reduced germ tube formation and hydrolytic enzyme secretion. Inhibitory effects of bio-AgNPs on Candida biofilms were evaluated by the prevention of yeast-to-hyphal transition. A decrease in cell viability within mature biofilm demonstrated the ability of bio-AgNPs to penetrate into the extracellular matrix and destroy yeast cell morphology, leading to cell death. Molecular biology study on biofilms confirmed downregulation in the expression of genes ALS3, HWP1, ECE1, EFG1, TEC1, ZAP1, encoding hyphal growth and biofilm development and PLB2, LIP9, SAP4, involved in hydrolytic enzymes. In addition to candida treatment, the bio-AgNPs could be applied as an antioxidant to protect against oxidative stress-related human diseases. The findings concluded that bio-AgNPs could be used as an antifungal agent for candida treatment, as well as be incorporated in medical devices to prevent biofilm formation., (© 2021 Wiley Periodicals LLC.)

Surgical site infection arising from microbial contamination of surgical wounds is a major cause of surgical complications and prolong hospital stay. In this study, silver nanoparticles (AgNPs) biosynthesized using Eucalyptus camaldulensis extract were deposited on silk surgical sutures by ex situ method. Adherence of AgNPs to the surface of sutures was observed, with significantly reduced surface roughness (323.7 ± 16.64 nm), compared with uncoated sutures (469.3 ± 7.31 nm) (P < .001). Elasticity of AgNPs-coated (13 ± 1.485%) and uncoated (8 ± 0.728%) sutures was also significantly different (P < .05). Quantification of AgNPs demonstrated release of 3.88, 5.33, 5.44, 6.14% on day 1, 3, 5, 7, respectively from total Ag + concentration (6.14 ± 0.14 μg/mL). The coated sutures produced a strong bacteriostatic effect on Staphylococcus aureus, an important wound pathogen with approximately 99% reduction in growth. In contrast, bactericidal effects were observed with Gram-negative pathogens including Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Cytocompatibility tested on human keratinocyte cells exhibited approximately 80% cell viability. The coated sutures revealed stable antibacterial properties up to 12 weeks. This work suggested the potency of AgNPs-coated sutures as a suitable biocompatible medical device for the management of surgical site infections., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Pathogen resistance to conventional antibiotics has become a serious clinical and public health problem, making the development of an alternative mean a very urgent issue. Recently, biosynthesis of silver nanoparticles (AgNPs) was successfully accomplished in the presence of Eucalyptus citriodora leaf extract as a reducing agent. In this study, the antimicrobial mechanisms of AgNPs against important hospital-acquired pathogens, including Gram-positive, Gram-negative bacteria, and fungi were further assessed. The results indicated that AgNPs could enhance a broad antimicrobial spectrum against drug-resistant organisms, with a range of minimum inhibitory concentration from 0.02 to 0.36 μg/mL. Time-kill assay showed that AgNPs produced bactericidal effects on the microorganisms. AgNPs could significantly reduce biofilm production in pathogens without affecting growth of the pathogens (p < 0.05). AgNPs inhibited cell viability and biofilm formation in a dose-dependent manner. Cell membrane damage in microorganisms resulting from effects of AgNPs was observed. A significant increase in per cent uptake of crystal violet was observed in all isolates treated with AgNPs when compared with the control (p < 0.05). Upon treatment with AgNPs, the surface charge of the reference strains and clinical isolates of pathogens moved towards neutral. The alteration of surface potential after exposure to AgNPs could contribute to membrane disruption and cell viability. Scanning electron microscopy further confirmed morphological cell changes and disrupted the cell membrane. Increasing resistance to AgNPs was not induced by stepwise isolation of the bacteria after 45 passages on Luria-Bertani agar supplemented with AgNPs. Furthermore, AgNPs was not toxic to red blood cells., (© 2019 APMIS. Published by John Wiley & Sons Ltd.)

Biological synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. This study aimed to synthesize silver nanoparticles (AgNPs) using Senna alata bark extract as reducing and capping agents, and to evaluate their antimicrobial activities. AgNPs was characterized using UV-vis spectrophotometry, transmission electron microscopy, and Fourier transform infrared spectroscopy (FTIR). The formation of AgNPs was monitored by recording the surface plasmon resonance peak observed at 425 nm. High-resolution TEM images elucidated the formation of spherical AgNPs with an average diameter of 10-30 nm. Energy dispersive spectroscopy (EDS) revealed the presence of silver. The functional groups of biomolecules present in the extract and their interaction with AgNPs were identified through FTIR analysis. Biosynthesized AgNPs displayed antimicrobial activity against different microorganisms, including Gram-positive and Gram-negative bacteria as well as fungi, as indicated by the diameter of inhibition zones between 11.37 and 14.87 mm. Minimum inhibitory concentration of AgNPs for the tested microorganisms was in the range from 31.25 to 125 μg/mL. Potassium leakage is a primary indicator of membrane damage which is a significant mode of action of AgNPs against the tested microorganisms. The amount of potassium ions leaked from the microbial cells after 4 h contact time ranged between 0.97 and 3.05 ppm. Morphological changes were observed in all AgNPs-treated microorganisms. The green synthesized AgNPs with high antimicrobial activity has potential to be used in food packaging and biomedical research areas., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Endotracheal tubes (ETTs) are a common source of bacterial colonization, leading to ventilator-associated pneumonia (VAP). This research developed a biofilm-resistant ETT, following the principles of green chemistry. Using an aqueous layer-by-layer (LbL) technique, a thick polyelectrolyte multilayered film was deposited on a ventilation tube. The polyelectrolyte multilayered film accommodated silver nanoparticles (AgNPs) formed in situ by reducing Ag + ions with Eucalyptus citriodora leaf extract. The multilayered film coating conformed to the curved surfaces of the ETT. Film thickness and silver content increased exponentially with the number of polyelectrolyte bilayer pairs, and a sufficiently high AgNPs content of 10-30%w/w was obtained at 75 to 125 bilayer films. Adhesion of the Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa was prevented by 99.9 and 99.99%, respectively, without cytotoxic effects against human lung epithelial cells (p < 0.05)., (Copyright © 2019. Published by Elsevier B.V.)

The increasing multidrug resistance of Acinetobacter baumannii has been highlighted as a worldwide therapeutic problem. Despite the wide range of studies on green synthesis of silver nanoparticles, there is currently no alternative treatment for MDR A. baumannii infection. This study investigated the potential of silver nanoparticles synthesized with Eucalyptus critriodora leaf extract as an inhibitor of MDR A. baumannii infection. The results demonstrated that silver nanoparticles synthesized with E. critriodora leaf extract triggered MDR A. baumannii DNA condensation, induced bacterial cell death and had a significant effect on biofilm formation, biofilm-grown cells, bacterial attachment and invasion of human lung cells in a concentration dependent manner. Silver nanoparticles synthesized with E. critriodora leaf extract had no obvious effects on the viability of human lung cells. The synthesized silver nanoparticles inhibited MDR A. baumannii infection by approximately 90% without cytotoxicity with a 50% effective concentration of 0.028 μg/ml. Thus silver nanoparticles with E. critriodora leaf extract had the potential to be a promising anti-MDR A. baumannii agent for effective treatment and they point the way to further development of a wide range of effective biomedical applications., (Copyright © 2018. Published by Elsevier Ltd.)

Increasing rates of infections caused by multidrug resistant Acinetobacter baumannii (MDRAB) and extensively drug resistant A. baumannii (XDRAB) have caused the need for searching alternative agents. The purposed of this project was to search plant-derived natural products that act as resistant modifying agents (RMAs) against A. baumannii. In this study, we further evaluated the activity of Holarrhena antidysenterica that has been previously proposed as RMA of novobiocin for a model strain, A. baumannii ATCC 19606 on clinically isolated non-MDRAB, MDRAB, and XDRAB. Effects of H. antidysenterica on outer membrane permeability and efflux pumps of the pathogen were conducted to preliminary elucidate mechanisms of this resistant modifier. Novobiocin was selected as a model antibiotic because it is well-established as an effective agent against Gram-positive pathogens. But, it possessed low level of antibacterial activity against Gram-negative pathogens due to an effective permeability barrier of these pathogens. H. antidysenterica ethanol extract possessed weak intrinsic antibacterial activity with minimum inhibitory concentration (MIC) more than 1000 μg/mL. The extract, at concentrations of 250, 125, and 62.5 μg/mL, remarkably enhanced the inhibitory effects of novobiocin (1/4 × MIC; 1-4 μg/mL) against XDRAB isolates. Synergistic effects of novobiocin at 1/4 × MIC and 1/8 × MIC in combination with H. antidysenterica either at 31.2, 15.6, or 7.8 μg/mL against clinical isolates non-MDRAB, MDRAB, and XDRAB were evidenced for 80% of the combinations (189 out of 234 combinations). Although, no enhancement of the accumulation of ethidium bromide was observed after treated with H. antidysenterica, this plant extract weakened the outer membrane of the pathogen as indicated by an increase in the N-phenyl-1-naphthylamine uptake. Our results suggested that H. antidysenterica which primarily interrupts membrane permeability should be further investigated as a promising resistant modifier for A. baumannii., (Copyright © 2013 Elsevier GmbH. All rights reserved.)