Search for new antimicrobials: spectroscopic, spectrometric, and in vitro antimicrobial activity investigation of Ga(III) and Fe(III) complexes with aroylhydrazones.

The in vitro antimicrobial activity of Fe(III) and Ga(III) complexes with N'-(2,3-dihydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (H2L1), N'-(2,4-dihydroxy-phenyl-methylidene)-3-pyridinecarbohydrazide (H2L2), N'-(2,5-dihydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (H2L3), N'-(2-hydroxy-3-methoxyphenyl-methylidene)-3-pyridine-carbohydrazide (H2L4), N'-(2-hydroxy-4-methoxyphenylmethyl-idene)-3-pyridine-carbohydrazide (H2L5), and N'-(2-hydroxy-5-methoxyphenylmethylidene)-3-pyridinecarbo-hydrazide (H2L6) toward several Gram-positive strains of Staphylococcus aureus, a Gram-negative strain of Escherichia coli, and a yeast Candida albicans were investigated. Fe(III)-complexes do not possess antimicrobial activity against all tested strains at concentrations up to 10 mg mL-1. Ga(III) complexes with dihydroxy derivatives showed selective activity, while the broadest range of antibacterial and antifungal activities was observed for complex with 2-hydroxy-3-methoxy-derivative, ligand H2L5. In addition, the coordination properties of ligands H2L1-H2L3 in solution were investigated by UV-Vis spectroscopy. The stability constants (logK) for Ga(III)-H2L 1:1 complexes in MeOH/H2O 1/1 at pH 2.52 were determined, and amounted to 5.8, 5.68, and 4.7, respectively. Detailed characterization of complexes was performed by high-resolution mass spectrometry. The fragmentation pathways for dimer [Fe2(L1)2]2+, [Fe(HL)2]+, [Ga(HL2)2]+ and adduct ions are given. The comparison with analogue Ga(III) and Fe(III) complexes with compounds H2L4-H2L6 was made as well.

Antifungal and Anti-Virulent Activity of Origanum majorana L. Essential Oil on Candida albicans and In Vivo Toxicity in the Galleria mellonella Larval Model.

The aim of this study was to investigate and compare in detail both the antifungal activity in vitro (with planktonic and biofilm-forming cells) and the essential oil composition (EOs) of naturally growing (OMN) and cultivated (OMC) samples of Origanum majorana L. (marjoram). The essential oil composition was analyzed using GC-MS. The major constituent of both EOs was carvacrol: 75.3% and 84%, respectively. Both essential oils showed high antifungal activity against clinically relevant Candida spp. with IC50 and IC90 less than or equal to 0.5 µg mL-1 and inhibition of biofilm with a concentration of 3.5 µg mL-1 or less. Cultivated marjoram oil showed higher anti-biofilm activity against C. albicans. In addition, OMC showed greater inhibition of germ-tube formation (inhibition by 83% in Spider media), the major virulence factor of C. albicans at a concentration of 0.125 µg mL-1. Both EOs modulated cell surface hydrophobicity (CSH), but OMN proved to be more active with a CSH% up to 58.41%. The efficacy of O. majorana EOs was also investigated using Galleria mellonella larvae as a model. It was observed that while the larvae of the control group infected with C. albicans (6.0 × 108 cells) and not receiving treatment died in the controls carried out after 24 h, all larvae in the infected treatment group survived at the end of the 96th hour. When the treatment group and the infected group were evaluated in terms of vital activities, it was found that the difference was statistically significant (p < 0.001). The infection of larvae with C. albicans and the effects of O. majorana EOs on the hemocytes of the model organism and the blastospores of C. albicans were evaluated by light microscopy on slides stained with Giemsa. Cytological examination in the treatment group revealed that C. albicans blastospores were phagocytosed and morphological changes occurred in hemocytes. Our results indicated that the essential oil of both samples showed strong antifungal activities against planktonic and biofilm-forming C. albicans cells and also had an influence on putative virulence factors (germ-tube formation and its length and on CSH).

In Vitro Confirmation of Siramesine as a Novel Antifungal Agent with In Silico Lead Proposals of Structurally Related Antifungals.

The limited number of medicinal products available to treat of fungal infections makes control of fungal pathogens problematic, especially since the number of fungal resistance incidents increases. Given the high costs and slow development of new antifungal treatment options, repurposing of already known compounds is one of the proposed strategies. The objective of this study was to perform in vitro experimental tests of already identified lead compounds in our previous in silico drug repurposing study, which had been conducted on the known Drugbank database using a seven-step procedure which includes machine learning and molecular docking. This study identifies siramesine as a novel antifungal agent. This novel indication was confirmed through in vitro testing using several yeast species and one mold. The results showed susceptibility of Candida species to siramesine with MIC at concentration 12.5 µg/mL, whereas other candidates had no antifungal activity. Siramesine was also effective against in vitro biofilm formation and already formed biofilm was reduced following 24 h treatment with a MBEC range of 50-62.5 µg/mL. Siramesine is involved in modulation of ergosterol biosynthesis in vitro, which indicates it is a potential target for its antifungal activity. This implicates the possibility of siramesine repurposing, especially since there are already published data about nontoxicity. Following our in vitro results, we provide additional in depth in silico analysis of siramesine and compounds structurally similar to siramesine, providing an extended lead set for further preclinical and clinical investigation, which is needed to clearly define molecular targets and to elucidate its in vivo effectiveness as well.

Design and synthesis of novel antimicrobial peptide scaffolds.

Muramic acid (Mur), a sugar amino acid (SAA), is present in the cell walls of bacteria asN-acetyl muramic acid (MurNAc) where together with ofN-acetylglucosamine (GlcNAc) and peptide makes main building block of peptidoglycan (PGN). It was challenging to incorporate muramic acid as SAA characteristic for bacteria into the peptides and investigate the antimicrobial activity of these scaffolds. Four building units were used in designing the desired peptide: muramic acid, tetrapeptide Leu-Ser-Lys-Leu, Nε-Lys, and Asn. Positions of three components were changeable while the position of Asn was always C-terminal (in linear peptides). The glycopeptide libraries of linear and cyclic peptides were synthesized using solid-phase peptide synthesis (SPPS). The antimicrobial effect of linear and cyclic glycopeptides, as well as the LSKL sequence used as a control, was investigated on several standard laboratory microbial strains. Liner glycopeptide with sequences Leu-Ser-Lys-Leu-Nε-Lys-Mur-Asn was active onStaphylococcus aureus(Gram-positive bacteria). Prepared compounds did not show activity towards applied tumor and normal human cell lines.

First Extensive Polyphenolic Profile of Erodium cicutarium with Novel Insights to Elemental Composition and Antioxidant Activity.

Erodium cicutarium is known for its total polyphenolic content, but this work reveals the first highly detailed profile of E. cicutarium, obtained with UHPLC-LTQ OrbiTrap MS4 and UHPLC-QqQ-MS/MS techniques. A total of 85 phenolic compounds were identified and 17 constituents were quantified. Overall, 25 new compounds were found, which have not yet been reported for the Erodium genera, or the family Geraniaceae. Along with methanolic extracts, the so far poorly investigated water extracts exhibited in vitro antioxidant activity according to all performed assays, including the ferric reducing/antioxidant power assay (FRAP), 2,2-diphenyl-1-picrylhydrazyl assay (DPPH), 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) assay (ABTS) and cupric ion reducing antioxidant capacity assay (CUPRAC). Elemental composition analysis performed with inductively coupled plasma atomic emission spectrometry (ICP-AES) and, additionally, hydride generation atomic absorption spectrometry (HydrEA-ETAAS) showed six most abundant elements to be decreasing as follows: Mg>Ca>K>S>P>Na, and gave first data regarding inorganic arsenic content (109.3-248.4 ng g-1 ). These results suggest E. cicutarium to be a valuable source of various phenolic compounds with substantial potential for further bioactivity testing.

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes-7.

Breakthroughs in Medicinal Chemistry [...].

Inhibition of Satellite RNA Associated Cucumber Mosaic Virus Infection by Essential Oil of Micromeria croatica (Pers.) Schott.

The present results dealing with the antiphytoviral activity of essential oil indicate that these plant metabolites can trigger a response to viral infection. The essential oil from Micromeria croatica and the main oil components ß-caryophyllene and caryophyllene oxide were tested for antiphytoviral activity on plants infected with satellite RNA associated cucumber mosaic virus. Simultaneous inoculation of virus with essential oil or with the dominant components of oil, and the treatment of plants prior to virus inoculation, resulted in a reduction of virus infection in the local and systemic host plants. Treatment with essential oil changed the level of alternative oxidase gene expression in infected Arabidopsis plants indicating a connection between the essential oil treatment, aox gene expression and the development of viral infection.

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes-6.

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes is a series of Editorials that is published on a biannual basis by the Editorial Board of the Medicinal Chemistry section of the journal Molecules [...].

Insights into biological activity of ureidoamides with primaquine and amino acid moieties.

Primaquine (PQ) ureidoamides 5a-f were screened for antimicrobial, biofilm eradication and antioxidative activities. Susceptibility of the tested microbial species towards tested compounds showed species- and compound-dependent activity. N-(diphenylmethyl)-2-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]-4-methylpentanamide (5a) and 2-(4-chlorophenyl)-N-(diphenylmethyl)-2-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]acetamide (5d) showed antibacterial activity against S. aureus strains (MIC = 6.5 µg/ml). Further, compounds 5c and 5d had weak antibacterial activity against Escherichia coli and Pseudomonas aeruginosa. None of the tested compounds showed a wide spectrum of antifungal activity. In contrast, most of the compounds exerted strong activity in a biofilm eradication assay against E. coli, P. aeruginosa and Candida albicans, comparable to or even higher than gentamycin, amphotericin B or parent PQ. The most active compounds were 5a and 5b. Tested compounds were inactive against biofilm formation by C. parapsylosis, Enterococcus faecalis, C. tropicalis and C. krusei. Compounds 5b-f significantly inhibited lipid peroxidation (80-99%), whereas compound 5c presented interesting LOX inhibition.

Asymmetric Primaquine and Halogenaniline Fumardiamides as Novel Biologically Active Michael Acceptors.

Novel primaquine (PQ) and halogenaniline asymmetric fumardiamides 4a⁻f, potential Michael acceptors, and their reduced analogues succindiamides 5a⁻f were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (1a) or mono-methyl succinate (1b), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates 2a,b to corresponding acids 3a,b, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig's base. Compounds 4 and 5 were evaluated against a panel of bacteria, several Mycobacterium strains, fungi, a set of viruses, and nine different human tumor cell lines. p-Chlorofumardiamide 4d showed significant activity against Staphylococcus aureus,Streptococcus pneumoniae and Acinetobacter baumannii, but also against Candida albicans (minimum inhibitory concentration (MIC) 6.1⁻12.5 µg/mL). Together with p-fluoro and p-CF3 fumardiamides 4b,f, compound 4d showed activity against Mycobacterium marinum and 4b,f against M. tuberculosis. In biofilm eradication assay, most of the bacteria, particularly S. aureus, showed susceptibility to fumardiamides. m-CF3 and m-chloroaniline fumardiamides 4e and 4c showed significant antiviral activity against reovirus-1, sindbis virus and Punta Toro virus (EC50 = 3.1⁻5.5 µM), while 4e was active against coxsackie virus B4 (EC50 = 3.1 µM). m-Fluoro derivative 4a exerted significant cytostatic activity (IC50 = 5.7⁻31.2 µM). Acute lymphoblastic leukemia cells were highly susceptible towards m-substituted derivatives 4a,c,e (IC50 = 6.7⁻8.9 µM). Biological evaluations revealed that fumardiamides 4 were more active than succindiamides 5 indicating importance of Michael conjugated system.

Membrane of Candida albicans as a target of berberine.

BACKGROUND: We investigated the mechanisms of anti-Candida action of isoquinoline alkaloid berberine, active constituent of medically important plants of Barberry species. METHODS: The effects on membrane, morphological transition, synthesis of ergosterol and the consequent changes in membrane permeability have been studied. Polarization and lipid peroxidation level of the membrane following berberine treatment have been addressed. RESULTS: Minimal inhibitory concentration (MIC) of berberine against C. albicans was 17.75 µg/mL. Cytotoxic effect of berberine was concentration dependent, and in sub-MIC concentrations inhibit morphological transition of C. albicans cells to its filamentous form. Results showed that berberine affects synthesis of membrane ergosterol dose-dependently and induces increased membrane permeability causing loss of intracellular material to the outer space (DNA/protein leakage). Berberine also caused membrane depolarization and lipid peroxidation of membrane constituents indicating its direct effect on the membrane. Moreover, ROS levels were also increased following berberine treatment indicating further the possibility of membrane damage. CONCLUSION: Based on the obtained results it seems that berberine achieves its anti-Candida activity by affecting the cell membrane.

Antifungal Activity of Oleuropein against Candida albicans-The In Vitro Study.

In the present study we investigated activity of oleuropein, a complex phenol present in large quantities in olive tree products, against opportunistic fungal pathogen Candida albicans. Oleuropein was found to have in vitro antifungal activity with a minimal inhibitory concentration (MIC) value of 12.5 mg·mL-1. Morphological changes in the nuclei after staining with fluorescent DNA-binding dyes revealed that apoptosis was a primary mode of cell death in the analyzed samples treated with subinhibitory concentrations of oleuropein. Our results suggest that this antifungal agent targets virulence factors essential for establishment of the fungal infection. We noticed that oleuropein modulates morphogenetic conversion and inhibits filamentation of C. albicans. The hydrophobicity assay showed that oleuropein in sub-MIC values has significantly decreased, in both aerobic and anaerobic conditions, the cellular surface hydrophobicity (CSH) of C. albicans, a factor associated with adhesion to epithelial cells. It was also demonstrated that the tested compound inhibits the activity of SAPs, cellular enzymes secreted by C. albicans, which are reported to be related to the pathogenicity of the fungi. Additionally, we detected that oleuropein causes a reduction in total sterol content in the membrane of C. albicans cells, which might be involved in the mechanism of its antifungal activity.

Virulence Factors and Susceptibility to Ciprofloxacin, Vancomycin, Triclosan, and Chlorhexidine among Enterococci from Clinical Specimens, Food, and Wastewater.

Enterococcus faecalis and E. faecium are opportunistic pathogens commonly found in the microbiota of humans and other animals as well as in the environment. This article presents the results of antimicrobial susceptibility testing using phenotypic methods (broth microdilution and standardized disk diffusion) on selected clinical, food, and wastewater isolates of E. faecalis and E. faecium. The isolates were divided into subgroups based on their sensitivity to the following antibiotics: vancomycin (VAN) and ciprofloxacin (CIP), and biocides triclosan (TCL) and chlorhexidine (CHX). The study also investigated in vitro virulence factors, including biofilm formation ability, cell surface hydrophobicity (CSH) and ß-hemolysis, to explore aspects of pathogenesis. In our study, regardless of the isolation source, VAN-resistant (VAN-R) and CIP-resistant (CIP-R) E. faecalis and E. faecium were detected. The highest proportion of CIP-R strains was found among clinical isolates of E. faecalis and E. faecium, with clinical E. faecium also showing the highest proportion of VAN-R strains. But the highest proportion of VAN-R E. faecalis strains was found in wastewater samples. The highest TCL MIC90 values for E. faecalis were found in wastewater isolates, while for E. faecium, the highest TCL MIC90 values were observed in food isolates. The highest CHX MIC90 values for both E. faecalis and E. faecium were identified in clinical specimens. The results obtained for E. faecalis did not indicate differences in TCL MIC and CHX MIC values with respect to sensitivity to VAN and CIP. Higher CHX MIC50 and CHX MIC90 values were obtained for CIP-R and VAN-R E. faecium. Among the tested isolates, 97.75% of the E. faecalis isolates produced biofilm, while 72.22% of the E. faecium isolates did so as well. In biofilm-forming strength categories III and IV, statistically significantly higher proportions of CIP-susceptible (CIP-S) and VAN-susceptible (VAN-S) E. faecalis were determined. In category III, there is no statistically significant difference in E. faecium CIP sensitivity. In category IV, we had a significantly higher proportion of CIP-R strains. On the other hand, the association between the moderate or strong category of biofilm formation and E. faecium VAN susceptibility was not significant. E. faecalis isolated from wastewater had a CSH index (HI) ≥ 50%, categorizing them as "moderate", while all the other strains were categorized as "low" based on the CSH index. Among the E. faecalis isolates, cell surface hydrophobicity indices differed significantly across isolation sources. In contrast, E. faecium isolates showed similar hydrophobicity indices across isolation sources, with no significant difference found. Moreover, no correlation was found between the enterococcal cell surface hydrophobicity and biofilm formation in vitro. After anaerobic incubation, ß-hemolytic activity was confirmed in 19.10% of the E. faecalis and 3.33% of the E. faecium strains.

Assessment of DNA damage and lipid peroxidation in diabetic mice: effects of propolis and epigallocatechin gallate (EGCG).

There is growing recognition that polyphenolic compounds present in many plants and natural products may have beneficial effects on human health. Propolis - a substance produced by honeybees - and catechins in tea, in particular (-)-epigallocatechin gallate (EGCG), are strong antioxidants that appear to have anti-obesity and anti-diabetic effects. The present study was designed to elucidate the anti-diabetic effect of the water-soluble derivative of propolis (WSDP), which contains phenolic acids as the main compounds, and EGCG in alloxan-induced (75mg/kg, iv) diabetes in mice. Intraperitoneal administration of EGCG or propolis at doses of 50mg/kg body weight (bw) to diabetic mice for a period of 7 days resulted in a significant increase in body weight and in haematological/immunological blood parameters, as well as in 100% survival of the mice. A significant decrease in lipid peroxidation in liver, kidney and brain tissue was also observed in diabetic mice treated with these two agents. Additionally, EGCG and propolis clearly reduced DNA damage in peripheral lymphocytes of diabetic mice. Our studies demonstrate the anti-oxidative and anti-inflammatory potential of WSDP and EGCG, which could exert beneficial effects against diabetes and the associated consequences of free-radical formation in kidney, liver, spleen and brain tissue. The results suggest that dietary supplementation with WSDP or EGCG could potentially contribute to nutritional strategies for the prevention and treatment of diabetes mellitus.

Untying the anchor for the lipopolysaccharide: lipid A structural modification systems offer diagnostic and therapeutic options to tackle polymyxin resistance.

Polymyxin antibiotics are the last resort for treating patients in intensive care units infected with multiple-resistant Gram-negative bacteria. Due to their polycationic structure, their mode of action is based on an ionic interaction with the negatively charged lipid A portion of the lipopolysaccharide (LPS). The most prevalent polymyxin resistance mechanisms involve covalent modifications of lipid A: addition of the cationic sugar 4-amino-L-arabinose (L-Ara4N) and/or phosphoethanolamine (pEtN). The modified structure of lipid A has a lower net negative charge, leading to the repulsion of polymyxins and bacterial resistance to membrane disruption. Genes encoding the enzymatic systems involved in these modifications can be transferred either through chromosomes or mobile genetic elements. Therefore, new approaches to resistance diagnostics have been developed. On another note, interfering with these enzymatic systems might offer new therapeutic targets for drug discovery. This literature review focuses on diagnostic approaches based on structural changes in lipid A and on the therapeutic potential of molecules interfering with these changes.

Cytotoxicity and genotoxicity of versicolorins and 5-methoxysterigmatocystin in A549 cells.

Aspergillus versicolor and A. flavus are primary colonizers in damp dwellings, and they produce sterigmatocystin (ST) and aflatoxin B1 (AFB(1)), respectively. These hepatotoxic and carcinogenic mycotoxins and their precursors and derivates possess a furofuran ring, which has proven responsible for their toxicity. The aim of this study was to investigate the cytotoxicity and genotoxicity of versicolorin A (VER A) and versicolorin B (VER B), as the furofuran precursors of aflatoxins and ST, and of 5-methoxysterigmatocystin (5-MET-ST), a methoxy derivative of ST, in human adenocarcinoma lung cells A549. The IC(50) values of the tested compounds were obtained by the cell proliferation MTT test as follows: 109 ± 3.5 µM (VER A), 172 ± 4 µM (VER B) and 181 ± 2.6 µM (5-MET-ST). The comet assay and micronucleus test were used to assess their genotoxic potential after 24 h of treatment with concentrations corresponding to ½ and » IC(50) in comparison with AFB(1) and ST, applied in concentrations corresponding to ½ IC(50), as previously determined in A549 cells. DNA damage parameters assessed by the comet assay were tail length, tail intensity and tail moment, while the level of DNA damage in the micronucleus test was evaluated by the number of formed micronuclei (MN), nuclear buds (NB) and nucleoplasmic bridges (NPB) in 1,000 binucleated cells. Considering the three comet parameters, all applied toxins exerted significant DNA damage compared to the control, while ST and VER B produced the highest DNA damage. All toxins provoked a statistically significant increase in MN, and a slightly decreased formation of NB and NPB. AFB(1), ST and 20 µM VER A showed a statistically significant increase in all three micronucleus parameters compared to the control, and the highest increase in the number of MN occurred in cells treated with 50 µM VER A. The differences between results obtained by the micronucleus test and comet assay could be explained by the fact that the micronucleus detects irreversible DNA damage, which is usually correlated with the previously determined cytotoxic potential of the AFB(1) precursors.

Micromorphological and chemotaxonomical traits of Micromeria croatica (Pers.) Schott.

A study on the types and distribution of trichomes, pollen morphology, chemical composition of essential oil (analyzed by GC-FID and GC/MS), and the content of macroelements (Na, K, Ca, and Mg) and trace elements (B, Fe, Cu, Mn, Zn, Al, Pb, Cr, Cd, Ni, Hg, and As) analyzed by ICP-AES (=inductively coupled plasma atomic emission spectroscopy) was conducted on Micromeria croatica (Pers.) Schott. Non-glandular trichomes, peltate trichomes (typical hairs of Lamiaceae), small capitate trichomes (composed of one basal epidermal cell and one head cell), and larger capitate trichomes (composed of one basal epidermal cell, two to three stalk cells, and one head cell with subcuticular space) were observed on leaves, stems, the calyx, and corolla. Pollen of M. croatica had six apertures (hexacolpate) which were set in the equatorial pollen belt (zonocolpate) and showed medium reticulate ornamentation (hetrobrochate type). The essential oil contained from 27 to 39 constituents, the most representative of which were caryophyllene oxide and E-caryophyllene. Among the investigated macroelements, the content of K was highest (8730-10080 mg/kg). The content of trace elements ranged from 0.12 mg/kg (Cr) to 78.00 mg/kg (Fe), while the content of Cd, Ni, Hg, and As were lower than the limit of quantification.

Chemotaxonomic and micromorphological traits of Satureja montana L. and S. subspicata Vis. (Lamiaceae).

Satureja montana and S. subspicata are used as spice, pepper substitute, for preparing tea, juice, and as a medicine. Fourteen populations (seven per species) of Satureja montana L. and S. subspicata Vis. growing in Croatia were examined to determine the chemical composition of the essential oil (analyzed by GC-FID and GC/MS), the content of macroelements (Na, K, Ca, Mg) and trace elements (B, Fe, Cu, Mn, Zn, Al, Pb, Cr, Cd, Ni, Hg, As) analyzed by ICP-AES, antioxidant compounds (analyzed by UV/VIS spectrophotometer), and the types and distribution of trichomes (analyzed by scanning electron microscopy). The main constituents of the essential oil were carvacrol and thymol in S. montana (all populations belong to one phenol chemotype), while α-eudesmol, ß-eudesmol, and spathulenol dominated in S. subspicata (three chemotypes could be distinguished). Both species possess considerably higher quantities of Ca and Mg, and moderate concentrations of K and Na, while Hg and As levels were below the limit of quantification. Non-glandular trichomes, peltate trichomes, and three types of capitate trichomes were observed on leaves, stem, calyx, and corolla.

Innovative Insights into In Vitro Activity of Colloidal Platinum Nanoparticles against ESBL-Producing Strains of Escherichia coli and Klebsiella pneumoniae.

Growing morbidity and mortality rates due to increase in the number of infections caused by MDR (multi-drug resistant) microorganisms are becoming some of the foremost global health issues. Thus, the need to search for and find novel approaches to fight AMR (antimicrobial resistance) has become obligatory. This study aimed to determine the antimicrobial properties of commercially purchased colloidal platinum nanoparticles by examining the existence and potency of their antibacterial effects and investigating the mechanisms by means of which they express these activities. Antimicrobial properties were investigated with respect to standard laboratory ATCC (American Type Cell Culture) and clinical extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia (E.) coli and Klebsiella (K.) pneumoniae. Standard microbiological methods of serial microdilution, modulation of microbial cell death kinetics ("time-kill" assays), and biofilm inhibition were used. Bacterial cell wall damage and ROS (reactive oxygen species) levels were assessed in order to explore the mechanisms of platinum nanoparticles' antibacterial activities. Platinum nanoparticles showed strong antibacterial effects against all tested bacterial strains, though their antibacterial effects were found to succumb to time kinetics. Antibiofilm activity was modest overall and significantly effective only against E. coli strains. By measuring extracellular DNA/RNA and protein concentrations, induced bacterial cell wall damage could be assumed. The determination of ROS levels induced by platinum nanoparticles revealed their possible implication in antibacterial activity. We conclude that platinum nanoparticles exhibit potent antibacterial effects against standard laboratory and resistant strains of E. coli and K. pneumoniae. Both, cell wall damage and ROS induction could have important role as mechanisms of antibacterial activity, and, require further investigation.

Antibacterial Fractions from Erodium cicutarium Exposed-Clinical Strains of Staphylococcus aureus in Focus.

Followed by a buildup of its phytochemical profile, Erodium cicutarium is being subjected to antimicrobial investigation guided with its ethnobotanical use. The results of performed in vitro screening on Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans strains, show that E. cicutarium has antimicrobial activity, with a particular emphasis on clinical S. aureus strains-both the methicillin sensitive (MSSA) and the methicillin resistant (MRSA) S. aureus. Experimental design consisted of general methods (the serial microdilution broth assay and the agar well diffusion assay), as well as observing bactericidal/bacteriostatic activity through time (the "time-kill" assay), investigating the effect on cell wall integrity and biofilm formation, and modulation of bacterial hemolysis. Observed antibacterial activity from above-described methods led to further activity-guided fractionation of water and methanol extracts using bioautography coupled with UHPLC-LTQ OrbiTrap MS4. It was determined that active fractions are predominantly formed by gallic acid derivatives and flavonol glycosides. Among the most active phytochemicals, galloyl-shikimic acid was identified as the most abundant compound. These results point to a direct connection between galloyl-shikimic acid and the observed E. cicutarium antibacterial activity, and open several new research approaches for future investigation.