Evaluation of novel compounds as anti-bacterial or anti-virulence agents.

Antimicrobial resistance is a global threat, leading to an alarming increase in the prevalence of bacterial infections that can no longer be treated with available antibiotics. The World Health Organization estimates that by 2050 up to 10 million deaths per year could be associated with antimicrobial resistance, which would equal the annual number of cancer deaths worldwide. To overcome this emerging crisis, novel anti-bacterial compounds are urgently needed. There are two possible approaches in the fight against bacterial infections: a) targeting structures within bacterial cells, similar to existing antibiotics; and/or b) targeting virulence factors rather than bacterial growth. Here, for the first time, we provide a comprehensive overview of the key steps in the evaluation of potential new anti-bacterial and/or anti-virulence compounds. The methods described in this review include: a) in silico methods for the evaluation of novel compounds; b) anti-bacterial assays (MIC, MBC, Time-kill); b) anti-virulence assays (anti-biofilm, anti-quorum sensing, anti-adhesion); and c) evaluation of safety aspects (cytotoxicity assay and Ames test). Overall, we provide a detailed description of the methods that are an essential tool for chemists, computational chemists, microbiologists, and toxicologists in the evaluation of potential novel antimicrobial compounds. These methods are cost-effective and have high predictive value. They are widely used in preclinical studies to identify new molecular candidates, for further investigation in animal and human trials.

Correlation of Short Leukocyte Telomeres and Oxidative Stress with the Presence and Severity of Lung Cancer Explored by Principal Component Analysis.

Lung cancer (LC) is the second most common malignancy and leading cause of cancer death. The potential "culprit" for local and systemic telomere shortening in LC patients is oxidative stress. We investigated the correlation between the peripheral blood leukocyte (PBL) telomere length (TL) and the presence/severity of LC and oxidative stress, and its usefulness as LC diagnostic marker. PBL TL was measured in 89 LC patients and 83 healthy subjects using the modified Cawthon RTq-PCR method. The relative PBL TL, found to be a potential diagnostic marker for LC with very good accuracy (P < 0.001), was significantly shorter in patients compared to the control group (CG) (P < 0.001). Significantly shorter telomeres were found in patients with LC TNM stage IV than in patients with stages I-III (P = 0.014), in patients without therapy compared to those on therapy (P = 0.008), and in patients with partial response and stable/progressive disease compared to those with complete response (P = 0.039). The total oxidant status (TOS), advanced oxidation protein products (AOPP), prooxidant-antioxidant balance (PAB) and C-reactive protein (CRP) were significantly higher in patients compared to CG (P < 0.001) and correlated negatively with TL in both patients and CG (P < 0.001). PCA showed a relation between PAB and TL, and between the EGFR status and TL. Oxidative stress and PBL telomere shortening are probably associated with LC development and progression.

Ex vivo and in vivo antioxidant activity of ß-hydroxy-ß-arylalkanoic acids.

The interplay between oxidative stress and inflammation is implicated in many chronic diseases including Alzheimer`s disease, cardiovascular diseases, diabetes and cancer. Thirteen ß-hydroxy-ß-arylalkanoic acids were previously synthesized and evaluated for their anti-inflammatory activity. The aim of this study was to asses ex vivo antioxidant activity of synthesized acids, as well as ibuprofen and to identify the compounds with the most promising results for further investigation on their capacity to counteract in vivo oxidative stress triggered by inflammation. The antioxidant potential of tested compounds was evaluated by determining the concentrations of total antioxidative status, total oxidative status, prooxidant antioxidant balance and the total sulfhydryl groups. Z score statistics were used to calculate the summary scores for antioxidative activity, prooxidative activity and oxy score. The tested compounds and ibuprofen demonstrated mild prooxidative activity ex vivo. Seven acids with substituents on one benzene ring exhibited better results than ibuprofen and were selected for in vivo testing. In vivo results demonstrated better antioxidant protection compared to ex vivo results. Compound g which contains nitro group on the benzene ring demonstrated the lowest oxy score, and four compounds exhibited better results than ibuprofen.

Targeting outer membrane protein A (OmpA) - inhibitory effect of 2'-hydroxychalcone derivatives on Acinetobacter baumannii and Candida albicans dual-species biofilm formation.

Biofilm production facilitates microbial colonization of wounds and catheters. Acinetobacter baumannii produces high levels of biofilm and causes difficult-to-treat nosocomial infections. Candida albicans is another strong biofilm producer which may facilitate A. baumannii adhesion by providing hyphae-mediated OmpA-binding sites. Here we tested the potential of 2'-hydroxychalcones to inhibit dual-species biofilm production of A. baumannii and Candida spp., and further predicted the mechanism of structure-related difference in activity. The results suggest that 2'-hydroxychalcones exhibit potent activity against Candida spp./A. baumannii dual-species biofilm production. Particularly active was trifluoromethyl-substituted derivative (p-CF3), which decreased C. albicans/A. baumannii biomass produced on vein-indwelling parts of the central venous catheterization set by up to 99%. Further, higher OmpA-binding affinity was also calculated for p-CF3, which together with demonstrated significant ompA-downregulating activity, suggests that superior antibiofilm activity of this chalcone against the tested dual-species community of A. baumannii is mediated through the OmpA.

In vitro colistin susceptibility of pandrug-resistant Ac. baumannii is restored in the presence of selenium nanoparticles.

AIMS: To investigate the synergistic activity of colistin and selenium nanoparticles (SeNPs) against pandrug-resistant (PDR) Ac. baumannii. METHODS AND RESULTS: Chequerboard and time-kill assays were employed to explore the potential synergistic interactions between colistin and SeNPs against Ac. baumannii isolates (8), previously determined as colistin-resistant (MIC range 16-256 µg ml-1 ). Also, whole-genome sequencing (WGS) and gene expression analyses were used to elucidate the mechanisms of colistin resistance. Exceptionally strong synergistic activity (FICI range 0.004-0.035) of colistin and SeNPs against colistin-resistant isolates was revealed. Colistin (0.5 or 1 µg ml-1 ) used in combination with SeNPs (0.5 µg ml-1 ) was able to reduce initial inoculum during the first 4 h of incubation, in contrast to colistin (0.5, 1 or 2 µg ml-1 ) alone. CONCLUSIONS: These findings propose colistin/SeNPs combination as a new option to fight PDR Ac. baumannii, the therapeutic possibilities of which should be proved in future in vivo studies. SIGNIFICANCE AND IMPACT OF STUDY: Here we present the first evidence of synergy between colistin and selenium compounds against bacteria in general. Also, WGS and gene expression analyses provide some new insights into Ac. baumannii colistin resistance mechanisms.

Antimicrobial Susceptibility Testing: A Comprehensive Review of Currently Used Methods.

Antimicrobial resistance (AMR) has emerged as a major threat to public health globally. Accurate and rapid detection of resistance to antimicrobial drugs, and subsequent appropriate antimicrobial treatment, combined with antimicrobial stewardship, are essential for controlling the emergence and spread of AMR. This article reviews common antimicrobial susceptibility testing (AST) methods and relevant issues concerning the advantages and disadvantages of each method. Although accurate, classic technologies used in clinical microbiology to profile antimicrobial susceptibility are time-consuming and relatively expensive. As a result, physicians often prescribe empirical antimicrobial therapies and broad-spectrum antibiotics. Although recently developed AST systems have shown advantages over traditional methods in terms of testing speed and the potential for providing a deeper insight into resistance mechanisms, extensive validation is required to translate these methodologies to clinical practice. With a continuous increase in antimicrobial resistance, additional efforts are needed to develop innovative, rapid, accurate, and portable diagnostic tools for AST. The wide implementation of novel devices would enable the identification of the optimal treatment approaches and the surveillance of antibiotic resistance in health, agriculture, and the environment, allowing monitoring and better tackling the emergence of AMR.

Comparison of the Standard vs. Thoracoscopic Extrapleural Modification of the Nuss Procedure-Two Centers' Experiences.

Pectus excavatum is the most common congenital anterior chest wall deformity, with an incidence of 1:400 to 1:1000. Surgical strategy has evolved with the revolutionary idea of Donald Nuss, who was a pioneer in the operative correction of this deformity using minimally invasive surgery. The aim of this paper is to compare the preliminary results of pectus excavatum repair in two University Centers with a moderate number of patients using the standard Nuss procedure and its modification, the extrapleural thoracoscopic approach. The statistical analysis showed no significant difference for the patient's age (14.52 ± 3.70 vs. 14.57 ± 1.86; p = 0.95) and the CT Haller index (4.17 ± 1.58 vs. 3.78 ± 0.95; p = 0.32). A statistically significant difference was noted for the duration of a pectus bar implant (2.16 ± 0.24 vs. 2.48 ± 0.68; p = 0.03) between the Maribor and Novi Sad Center. We report 14 complications (28%), including dislocation of the pectus bar (10%), pleural effusion (8%), wound inflammation (6%), pericarditis (2%) and an allergic reaction to the pectus bar (2%). Standard and thoracoscopic extrapleural Nuss procedures are both safe and effective procedures used to correct a pectus excavatum deformity. The choice of surgical procedure should be made according to a surgeon's reliability in performing a particular procedure. Our study found no advantages of one procedure over the other.

Spasmolytic, Gastroprotective and Antioxidant Activities of Dry Methanol Extract of Ferula heuffelii Underground Parts.

Dry MeOH extract of Ferula heuffelii (Apiaceae) underground parts was tested for spasmolytic, gastroprotective and antioxidant activities. HPLC analysis revealed that chlorogenic acid (CGA; 34.6 mg/g) was its main constituent. Extract in vitro exhibited notable total antioxidant activity (FRAP value=1.0 µmol Fe2+ /mg), and scavenging of DPPH (SC50 =62.5 µg/ml) and • OH radicals (49.5 % at 20 µg/ml in 2-deoxyribose assay). In vitro on isolated rat ileum, extract exhibited significant spasmolytic activity, i. e., it showed 124.6 % of maximal atropine effect on spontaneous contractions (at 100 µg/ml), and reduced spasmogenic effect of KCl (80 mm) to 44.4 % (at 60 µg/ml) and of highest applied concentration of ACh to 26.3 % (at 120 µg/ml). In parallel experiments, spasmolytic effect of CGA was also demonstrated. In acute EtOH-induced gastric ulceration model in rats, extract (100 mg/kg p.o.) showed significant gastroprotective effect (gastric damage score 0.50), similar to ranitidine (20 mg/kg p.o.). Obtained results showed that tested F. heuffelii polar extract represents new herbal preparation with potential use against some gastrointestinal complaints.

Synthesis and characterization of a collagen-based composite material containing selenium nanoparticles.

Multidrug-resistant bacterial strains represent an emerging global health threat and a great obstacle for bone tissue engineering. One of the major components of the extracellular matrix of the bone is a collagen protein, while selenium is an element that has antimicrobial potential, and is also important for bone metabolism and bone health. Here we represent the incorporation of selenium nanoparticles (SeNPs) synthesized by the green chemical reduction method into collagen gels to produce a composite material, collagen/SeNPs, with antimicrobial properties. The samples were comprehensively characterized by zeta potential measurements, dynamic light scattering inductively coupled plasma-mass spectrometry (ICP-MS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), optical microscopy, field-emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry The cytotoxicity of the SeNPS, as well as collagen/SeNPs, was tested on the MRC-5 cells. It was revealed that collagen/SeNPS expressed a lower cytotoxic effect. Collagen/SeNPs showed significant antibacterial activity against all tested Gram-positive strains, the major causative agents of orthopedic infections as well as Candida albicans. Furthermore, three-dimensional ß-tricalcium phosphate (3D-TCP) scaffolds were fabricated by a well-established 3D printing (lithography) method, and afterward preliminary coated by newly-synthesized SeNPs or collagen/SeNPs. In addition, uncoated 3D-TCP scaffolds as well as coated by collagen/SeNPs were subjected to biofilm formation. The production of Staphylococcus aureus biofilm on coated scaffolds by collagen/SeNPs was significantly reduced compared to the uncoated ones.

Predictive Value of Red Blood Cell Distribution Width, Mean Platelet Volume and Platelet Distribution Width in Children with Acute Appendicitis.

BACKGROUND AND OBJECTIVES: Acute appendicitis in pediatric patients is one of the most common surgical emergencies, but the early diagnosis still remains challenging. The aim of this study was to determine the predictive value of Red blood cell distribution width (RDW), Mean platelet volume (MPV) and Platelet distribution width (PDW) in children with acute appendicitis. MATERIALS AND METHODS: This study was a retrospective assessment of laboratory findings (RDW, MPV, PDW) of patients who underwent surgical treatment for acute appendicitis from January 2019 to December 2020. RESULT: During this period, 223 appendectomies were performed at our Institute. In 107 (43%) cases appendicitis was uncomplicated, while in 116 (46.6%) it was complicated. WBC and RDW/MPV ratio were significant parameters for the diagnosis of acute appendicitis with cut-off values of 12.86 (susceptibility: 66.3%; specificity: 73.2%) and 1.64 (susceptibility: 59.8%; specificity: 71.9%), respectively. WBC and RDW/RBC ratio were independent variables for the diagnosis of complicated appendicitis. The cut-off values were 15.05 for WBC (sensitivity: 60.5%; specificity: 70.7%) and 2.5 for RDW/RBC ratio (sensitivity: 72%; specificity: 52.8%). CONCLUSIONS: WBC is an important predictor of appendicitis and complicated appendicitis. RDW, MPV and PDW alone have no diagnostic value in pediatric acute appendicitis or predicting the degree of appendix inflammation. However, the RDW/MPV ratio can be an important predictor of appendix inflammation, with higher values in patients with more severe appendix inflammation. RDW/RBC ratio may be an important predictor of complicated appendicitis.

Factors associated with poor self-reported function and quality of life in patients with end-stage knee or hip osteoarthritis immediately prior to total joint arthroplasty.

INTRODUCTION: The aim was to evaluate patients' perception of function and physical and mental dimensions of health-related quality of life (HRQoL) in patients with end-stage knee or hip osteoarthritis (OA) immediately prior to surgery and to identify the factors associated with the outcomes. MATERIAL AND METHODS: The study included 200 patients with end-stage OA (100 knee OA and 100 hip OA patients). Self-reported physical function was assessed using the Oxford Knee Score or Oxford Hip Score. Physical and mental dimensions of HRQoL were assessed using the physical and mental component summary scores of the 36-Item Short-Form Health Survey. Multivariate linear regression analysis was used to identify the sociodemographic, clinical and psychological factors associated with self-reported function and physical and mental dimensions of HRQoL. RESULTS: End-stage knee or hip OA patients had poor function and physical dimension of HRQoL, while the mental dimension of HRQoL was not impaired. In knee OA, pain, flexion range of motion (ROM), catastrophizing, and anxiety were significantly associated with self-reported function (explained 56% of the variance), whereas catastrophizing explained 10% of the variance of the physical dimension of HRQoL. In hip OA, flexion ROM, catastrophizing and being employed were significantly associated with self-reported function (explained 44% of the variance), whereas catastrophizing and flexion ROM explained 34% of the variance of the physical dimension of HRQoL. CONCLUSIONS: Many investigated factors were associated with poor self-reported function and HRQoL in knee and hip OA. However, the most important factors for both knee and hip OA were catastrophizing and flexion ROM.

Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite.

The present research aims to enhance the antimicrobial activity of kaolinite surfaces by a one-step cost-effective and energy-efficient dry thermal reaction, producing an antibacterial and antifungal silver-kaolinite (Ag-Kao) nanocomposite agent. Pharmaceutical grade kaolin powder samples, with variable kaolinite structural order-disorder degree, were homogeneously mixed with silver nitrate in a proportion 1:4 AgNO3:kaolin (w/w) and sintered at 400 °C for 30 min. The composition, microstructure, microtexture and surface characteristics of the pyro-fabricated nanocomposites were characterized by XRD/XRF diffractometry, differential scanning calorimetry DSC, FT-IR spectroscopy, TEM/EDX, zeta potential (mV) measured within the 2-12 pH range, and BET method. Physicochemical stability was evaluated by silver dissociation testing under close-neutral and acidic conditions with Ag content assay using ICP-OES. The resulting Ag-Kao nanocomposites exhibited bulk silver contents ranging from 9.29% to 13.32% with high physicochemical stability in both neutral and acidic mediums (Ag dissociation rate <0.5% in 5 days). Ag nanocrystals exhibited particle sizes ranging from 5 to 30 nm, which were embedded and reinforced within the kaolinite matrix. The sizes of the Ag nanocrystals and their distribution patterns on the edges and faces of kaolinite platelets were controlled by the structural order-disorder degree. Highly ordered kaolinites (Hinckley Index, HI > 1) produced platelet edge-clustered silver nanocrystals due to the abundance of the dangling hydroxyls on platelet edges, while the highly disordered kaolinite (HI < 1) provided homogeneous platelet basal-doped silver nanocrystals due to the presence of some residual charges by exposed basal hydroxyl groups with interplatelet silver diffusivity. At pH 2, the magnitude of the positive surface charge was influenced by the silver nanocrystal size. Nanocomposites with the smallest silver nanocrystals (10-5 nm) exhibited the highest positive zeta potential (+15.2 mV to +17.0 mV), while those with larger silver nanocrystals (up to 30 nm) indicated lower positive zeta potential values (+9.5 mV to +3.6 mV). Under the same testing conditions using the Mueller-Hinton broth microdilution method, the raw kaolin samples did not show any significant antimicrobial activity, while all the pyro-fabricated Ag-Kao nanocomposite samples showed potent antibacterial and antifungal activity at low doses (MIC range 0.1-0.0125 mg/mL). Therefore, modulation of the effective electrostatic surface charge of the kaolinite platelets, via thermal doping of silver within their basal planes and edges, was found to be strongly dependent on the pH as well as the size and microtexture of the silver nanocrystals (mainly controlled by the order-disorder degree HI). The resulting modified nanostructure, with physicochemical stability and the efficient surface properties of the designed pyro-fabricated nanocomposite, led to an enhanced synergistic biophysical antimicrobial activity.

Methoxy-Substituted Hydroxychalcone Reduces Biofilm Production, Adhesion and Surface Motility of Acinetobacter baumannii by Inhibiting ompA Gene Expression.

An increasing lack of available therapeutic options against Acinetobacter baumannii urged researchers to seek alternative ways to fight this extremely resistant nosocomial pathogen. Targeting its virulence appears to be a promising strategy, as it offers considerably reduced selection of resistant mutants. In this study, we tested antibiofilm potential of four synthetic chalcone derivatives against A. baumannii. Compound that showed the greatest activity was selected for further evaluation of its antivirulence properties. Real-time PCR was used to evaluate mRNA expression of biofilm-associated virulence factor genes (ompA, bap, abaI) in treated A. baumannii strains. Also, we examined virulence properties related to the expression of these genes, such as fibronectin- and collagen-mediated adhesion, surface motility, and quorum-sensing activity. The results revealed that the expression of all tested genes is downregulated together with the reduction of adhesion and motility. The conclusion is that 2'-hydroxy-2-methoxychalcone exhibits antivirulence activity against A. baumannii by inhibiting the expression of ompA and bap genes, which is reflected in reduced biofilm formation, adhesion, and surface motility.

Synthesis, characterization, antimicrobial and cytotoxic activity of novel half-sandwich Ru(II) arene complexes with benzoylthiourea derivatives.

Three new ruthenium(II)-arene complexes, [Ru(η6-p-cymene)(L1)Cl2] (C1) where L1 is N-((4 methoxyphenyl)carbamothioyl)benzamide; [Ru(η6-p-cymene)(L2)Cl2] (C2) where L2 is 4-(3-benzoylthioureido)benzoic acid and [Ru(η6-p-cymene)(L3)Cl2] (C3) where L3 is methyl 4-(3- benzoylthioureido)benzoate have been synthetized, characterized and evaluated for their antimicrobial and anticancer activity. Characterization was performed using 1H and 13C NMR, IR spectroscopy, mass spectrometry, electrical conductivity measurements and X-Ray diffraction analysis. X-Ray diffraction analysis of C1 showed typical expected "piano-stool" geometry with ruthenium coordinated to ligand via nitrogen and sulfur atoms of benzoylthiourea derivatives. Interesting, in herein described complex, upon coordination the four-membered ring was formed, instead of six-membered chelate common for this type of ligands. Cytotoxic activity was determined in human cervix adenocarcinoma (HeLa) cell line and IC50 values ranged from 29.68 to 52.36 µM and the complexes were more active than related ligands (except in case of C2 where it is found that IC50 value is close to IC50 value of related ligand). Complex [Ru(η6-p-cymene)(L1)Cl2] (C1) expressed the highest cytotoxic activity with IC50 value of 29.7 µM. Complexes and ligands were tested against nine Gram-positive and Gram-negative bacteria and one yeast- Candida albicans. Clinical Candida spp. strains from microbiological laboratories were included in testing processes as well. Minimum inhibitory concentrations values ranged from 62.5 µg/ml for complexes against Candida albicans to over 1000 µg/ml for several bacterial species.

Double active BEA zeolite/silver tungstophosphates - Antimicrobial effects and pesticide removal.

Novel composites of BEA zeolite and silver tungstophosphate were prepared by different procedures: two-step impregnation, ion-exchange, and as physical mixtures with varying component mass ratios. Composites were characterized using Atomic force microscopy, Infrared, Raman and Atomic absorption spectroscopy, and results were related to adsorption properties and antimicrobial efficiencies of the composites. Prepared samples were tested as antimicrobial agents for fungal and different bacterial strains, as well as for adsorbents for pesticide nicosulfuron in aqueous solutions by using High-performance liquid chromatography. Experimental conditions for batch adsorption testing were optimized in order to efficiently eliminate nicosulfuron from aqueous solutions, while enabling antimicrobial activity of these advanced materials. Antimicrobial efficiency of composites was verified, and indicated that silver ion persistence in the solid phase is of utmost significance for the antimicrobial activity. Spectroscopic investigation revealed interaction of the silver tungstophosphate active phase and the zeolite framework, giving evidence of uniform distribution of active sites in the synthesized materials that proved to be essential for adsorption application. The best obtained adsorption capacity, as well as highest antimicrobial efficiency, is found for composite samples prepared by two-step impregnation with (BEA: silver tungstophosphate) mass ratio 2:1. The amount of nicosulfuron removed from water suspension was 38.2 mg per gram of composite, and the minimum inhibitory concentration determined for all investigated gram-negative bacteria was 125 µg mL-1.

Methodology for determining ecological benefits of advanced tolling systems.

Toll plazas are places on the road network where increased emissions of exhaust gases occur due to changes in vehicle driving regime in their corresponding impact areas. Therefore, they provide a great potential in terms of the ability to significantly reduce the emission of pollutants by using advanced technologies. In light of this, this paper aims at getting the most accurate quantification of pollutant emission (CO, CO2, HC and NOx) for the various vehicle categories which use Manuel System (MS), Electronic toll collection (ETC) with mechanical barriers and Multi Lane Free Flow (MLFF) system, for determining ecological benefits that can be achieved using advanced tolling systems. The measurement of the emission of harmful gases was carried out in real field conditions for the five most common classes of passenger cars, light truck and semi-trailer-truck. Vehicle speed, fuel consumption and emission of pollutants were recorded every second, in various driving processes in the impact areas of toll plazas, as well as in numerous scenarios that involve a different number of vehicles in a queue. The obtained results show that the use of the MLFF system, compared to the MS, can achieve a reduction in CO2 in the range of 25%-45% and the reduction in NOx in the range of 32%-98%, depending on the type of vehicle and the considered scenario. The case study of the tolling system in the Republic of Serbia, on a sample of 77,408,112 vehicles, has shown that moving from the existing to an advanced MLFF tolling system allows for annual ecological benefits ranging from 1,349,862 € to 1,491,391 €.

Comparative Study of the Antimicrobial Activity of Selenium Nanoparticles With Different Surface Chemistry and Structure.

Although selenium nanoparticles (SeNPs) have gained attention in the scientific community mostly through investigation of their anticancer activity, a great potential of this nanomaterial was recognized recently regarding its antimicrobial activity. The particle form, size, and surface chemistry have been recognized as crucial parameters determining the interaction of nanomaterials with biological entities. Furthermore, considering a narrow boundary between beneficial and toxic effects for selenium per se, it is clear that investigations of biomedical applications of SeNPs are very demanding and must be done with great precautions. The goal of this work is to evaluate the effects of SeNPs surface chemistry and structure on antimicrobial activity against several common bacterial strains, including Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Bacillus subtilis (ATCC 6633), and Kocuria rhizophila (ATCC 9341), as well as Escherichia coli (ATCC 8739), Salmonella Abony (NCTC 6017), Klebsiella pneumoniae (NCIMB 9111) and Pseudomonas aeruginosa (ATCC 9027), and the standard yeast strain Candida albicans (ATCC 10231). Three types of SeNPs were synthesized by chemical reduction approach using different stabilizers and reducing agents: (i) bovine serum albumin (BSA) + ascorbic acid, (ii) chitosan + ascorbic acid, and (iii) with glucose. A thorough physicochemical characterization of the obtained SeNPs was performed to determine the effects of varying synthesis parameters on their morphology, size, structure, and surface chemistry. All SeNPs were amorphous, with spherical morphology and size in the range 70-300 nm. However, the SeNPs obtained under different synthesis conditions, i.e. by using different stabilizers as well as reducing agents, exhibited different antimicrobial activity as well as cytotoxicity which are crucial for their applications. In this paper, the antimicrobial screening of the selected systems is presented, which was determined by the broth microdilution method, and inhibitory influence on the production of monomicrobial and dual-species biofilm was evaluated. The potential mechanism of action of different systems is proposed. Additionally, the cytotoxicity of SeNPs was examined on the MRC-5 cell line, in the same concentration interval as for antimicrobial testing. It was shown that formulation SeNPs-BSA expressed a significantly lower cytotoxic effect than the other two formulations.

Novel nano-composite hydrogels with honey effective against multi-resistant clinical strains of Acinetobacter baumannii and Pseudomonas aeruginosa.

Novel alginate hydrogels with silver nanoparticles (AgNPs) and honey components were produced with the aim to target multidrug-resistant bacterial strains causing nosocomial wound infections. AgNP synthesis was optimized in highly concentrated honey solutions so that a 5-month stable, colloid solution with 50% of honey and ~ 8 nm AgNPs at neutral pH was obtained. The colloid solution was further used to produce nano-composite Ag/alginate hydrogels in different forms (microbeads, microfibers and discs) that retained all AgNPs and high fractions of honey components (40-60%) as determined by the phenol-sulfuric acid and Folin-Ciocalteu methods. The hydrogels were characterized by UV-Vis spectroscopy and Fourier-transform infrared-attenuated total reflectance spectroscopy while the antibacterial activity was investigated against a broad spectrum of Gram-negative and Gram-positive bacteria, including 13 multi-resistant clinical strains of Acinetobacter baumannii, one clinical strain of Pseudomonas aeruginosa and one clinical strain of Staphylococcus aureus. At the total released silver concentration of ~ 9 µg/ml, the hydrogels exhibited strong bactericidal activity against standard and most of the investigated multi-resistant hospital strains with the exemption of 3 clinical strains of A. baumannii in which antibacterial effects were absent. These results reveal the need for further in-depth studies of bacterial resistance mechanisms and, in the same time, potentials of the novel Ag/alginate hydrogels with honey components to combat wound infections and enhance healing as non-sticky, antibacterial, and bioactive dressings.