Carla Dias

Antimicrobial activity of phenolics and glucosinolate hydrolysis products and their synergy with streptomycin against pathogenic bacteria.

The purpose of the present study was to evaluate the in vitro antibacterial effects of different classes of important and common dietary phytochemicals (5 simple phenolics - tyrosol, gallic acid, caffeic acid, ferulic acid, and chlorogenic acid; chalcone - phloridzin; flavan-3-ol - (-) epicatechin; seco-iridoid - oleuropein glucoside; 3 glucosinolate hydrolysis products - allylisothiocyanate, benzylisothiocyanate and 2-phenylethylisothiocyanate) against Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes and Staphylococcus aureus. Another objective of this study was to evaluate the effects of dual combinations of streptomycin with the different phytochemicals on antibacterial activity. A disc diffusion assay was used to evaluate the antibacterial activity of the phytochemicals and 3 standard antibiotics (ciprofloxacin, gentamicin and streptomycin) against the four bacteria. The antimicrobial activity of single compounds and dual combinations (streptomycin-phytochemicals) were quantitatively assessed by measuring the inhibitory halos. The results showed that all of the isothiocyanates had significant antimicrobial activities, while the phenolics were much less efficient. No antimicrobial activity was observed with phloridzin. In general P. aeruginosa was the most sensitive microorganism and L. monocytogenes the most resistant. The application of dual combinations demonstrated synergy between streptomycin and gallic acid, ferulic acid, chlorogenic acid, allylisothiocyanate and 2-phenylethylisothiocyanate against the Gram-negative bacteria. In conclusion, phytochemical products and more specifically the isothiocyanates were effective inhibitors of the in vitro growth of the Gram-negative and Gram-positive pathogenic bacteria. Moreover, they can act synergistically with less efficient antibiotics to control bacterial growth.

Prognostic value of neutrophil gelatinase-associated lipocalin in acute heart failure

BACKGROUND The identification of patients at risk for worse outcome is still a challenge. We hypothesized that cystatin C, a marker of renal function, and neutrophil gelatinase-associated lipocalin (NGAL), a marker of acute renal injury, would have a role in the prognostic stratification of these patients. METHODS We prospectively evaluated 121 patients admitted for acute HF. Serum NGAL and cystatin C levels were measured on the first morning after admission. The outcome measures used were the occurrence of death from all causes, and the combined endpoint defined as the first occurrence of either death or hospital admission. Patients were followed for up to 3 months. RESULTS The variables associated with a higher occurrence of death in a univariate approach were older age and higher levels of BNP, cystatin C and NGAL, and those associated with the occurrence of the combined endpoint were older age, Diabetes mellitus, lower GFR, type 1 cardio-renal syndrome, BNP, cystatin C and NGAL. BNP and NGAL remained independent predictors of the occurrence of both all-cause death and the combined endpoint. NGAL levels in the 75th percentile (>167.5 ng/mL) were associated with a 2.7-fold increase in the risk of death and a 2.9-fold increase in the risk of the first occurrence of either death or hospitalization. CONCLUSIONS Serum NGAL, a marker of acute renal injury, is an independent predictor of worse short term prognosis in patients with acute HF. This suggests a role of renal damage, apart from renal function, in the prognosis of these patients.

New Perspectives on the Use of Phytochemicals as an Emergent Strategy to Control Bacterial Infections Including Biofilms

The majority of current infectious diseases are almost untreatable by conventional antibiotic therapy given the advent of multidrug-resistant bacteria. The degree of severity and the persistence of infections are worsened when microorganisms form biofilms. Therefore, efforts are being applied to develop new drugs not as vulnerable as the current ones to bacterial resistance mechanisms, and also able to target bacteria in biofilms. Natural products, especially those obtained from plants, have proven to be outstanding compounds with unique properties, making them perfect candidates for these much-needed therapeutics. This review presents the current knowledge on the potentialities of plant products as antibiotic adjuvants to restore the therapeutic activity of drugs. Further, the difficulties associated with the use of the existing antibiotics in the treatment of biofilm-related infections are described. To counteract the biofilm resistance problems, innovative strategies are suggested based on literature data. Among the proposed strategies, the use of phytochemicals to inhibit or eradicate biofilms is highlighted. An overview on the use of phytochemicals to interfere with bacterial quorum sensing (QS) signaling pathways and underlying phenotypes is provided. The use of phytochemicals as chelating agents and efflux pump inhibitors is also reviewed.

Antimicrobial Activity of Isothiocyanates from Cruciferous Plants against Methicillin-Resistant Staphylococcus aureus (MRSA)

Purified isothiocyanates from cruciferous plants (Brassicacea, Syn. Cruciferae) plants were evaluated against 15 isolates of methicillin-resistant S. aureus isolated from diabetic foot-ulcer patients aiming the study of the potential usage of allyl-isothiocyanate, benzyl-isothiocyanate and 2-phenylethyl-isothiocyanate against this important bacteria. Disc diffusion and minimum inhibitory concentration methods were used to access the antimicrobial activity. The index (Ia) and rate (Ra) of the antibacterial activity for each compound were calculated. The results showed a highly dose-dependent compound and chemical structure antibacterial effectiveness. The results showed a strong relation between the chemical structure of isothiocyanates and its antibacterial effectiveness. The benzyl-isothiocyanate was the most effective with a minimum inhibitory concentration varying between 2.9 and 110 µg· mL−1 with an antibacterial activity rate up to 87%. Moreover, their antibacterial activity was mainly bactericidal. This study provides scientific evidence that isothiocyanates have an interesting biological value and must be considered as an important tool to be used against MRSA.

Antimicrobial Resistance Patterns of Aeromonas spp. Isolated from Ornamental Fish

The potential risk of occurrence of new diseases associated with the trade of live animals is well known. However, little importance is still given to the problematic of the dissemination of resistance genes that pass along with the animal trade. In this study we aimed to isolate Aeromonas spp. strains from water and skin of ornamental fish and test their resistance to antibiotics. The samples were collected from a national ornamental fish importer, with the intent of obtaining a collection of Aeromonas strains. The identification of the strains was made by gyrB and rpoD gene sequencing. A total of 288 strains grouped in seven different species - Aeromonas veronii, Aeromonas media, Aeromonas jandaei, Aeromonas hydrophila, Aeromonas caviae, Aeromonas culicicola, Aeromonas aquariorum, were isolated. The susceptibility profile was determined for 28 antibiotics commonly used. All the strains presented multi-resistance to the tested antibiotics. The antibiotic susceptibility profile to tetracycline, ticarcillin, carbenicillin, ampicillin and erythromycin revealed resistance levels of more than 80%. Few strains resistant to aztreonam and imipenem were identified. On the other hand, all were sensitive to cefotaxime and cefepime. The results show that these Aeromonas spp. strains are potentially reservoirs of antibiotic resistance genes.

First Study on Antimicriobial Activity and Synergy between Isothiocyanates and Antibiotics Against Selected Gram-Negative And Gram-Positive Pathogenic Bacteria From Clinical And Animal Source

The emergence of new diseases and the resurgence of several infections that were controlled in the past, associated with recent increase of bacterial resistance have created the necessity for more studies towards to the development of new antimicrobials and new treatment strategies. The aim of the present study was to evaluate the in vitro synergy between different classes of important glucosinolates hydrolysis products-isothiocyanates with antibiotics (gentamycin and vancomycin), against important pathogenic bacteria: Escherichia coli, Enterococcus faecalis, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus. A disc diffusion method was used to evaluate the antibacterial activity. The antimicrobial activity of phytochemicals and combinations between gentamycin, vancomycin and phytochemicals were quantitatively assessed by measuring the inhibitory halos. The results showed a selective antimicrobial effect of isothiocyanates, and this effect was strictly related with their chemical structure. In general the benzylisothiocyanate was the most effective compound against both Gram-positive and Gram-negative bacteria. The Listeria monocytogenes and Staphylococcus aureus were the bacteria most affected either by the phytochemicals alone or by the combination phytochemical-antibiotic. The bacteria Pseudomonas aeruginosa was the less affected pathogen. The most important synergism detected occurred between the commercial antibiotics with benzylisothiocyanate and 2-phenylethylisothiocyanate. In conclusion, some isothiocyanates are effective inhibitors of in vitro bacterial growth, and they can act synergistically with antibiotics.

Antibacterial Effects of Glucosinolate-Derived Hydrolysis Products Against Enterobacteriaceae and Enterococci Isolated from Pig Ileum Segments

The aim of this study was to evaluate the effects of various glucosinolate-derived hydrolysis products (HP) as antibacterial compounds against Enterobacteriaceae and Enterococcaceae isolated from intestinal segments of healthy pigs collected directly from slaughter-houses in the North of Portugal. Using a previously described disk-diffusion bioassay, all HP were tested at six different doses (0.015, 0.15, 0.75, 1.5, 3.0, and 15.0 μmoles) in dimethyl-sulfoxide (DMSO), with the exception of sulforaphane (SFN), which was not tested at 15.0 μmoles. Positive (antibiotic standard) and negative controls (DMSO) were included in all experiments. All the experiments were conducted in triplicate. In vitro inhibition of the bacterial growth by the HP was proportional to the concentration used and in many cases was even higher than for the gentamycin, the antibiotic control. The results clearly showed that the glucosinolates-derived HPs were very effective in vitro inhibitors of bacterial growth. The natural products, and specifically the isothiocyanates, should be evaluated as potential alternative control agents for potentially pathogenic bacteria (e.g., dietary amendment of pig foods with glucosinolate-containing plants).

Phytochemical Composition and Antibacterial Activity of Hydroalcoholic Extracts of Pterospartum tridentatum and Mentha pulegium against Staphylococcus aureus Isolates

Pterospartum tridentatum and Mentha pulegium are largely used in Portuguese folk medicine to treat several human disorders and inflammatory processes but without any consistent evidence for those beneficial pointed properties. Thus, the aim of the current work is to evaluate its benefits and phytochemicals related to those beneficial properties. A distinct polyphenol profile between P. tridentatum and M. pulegium was found. Taxifolin, myricetin, ginestin, ginestein, and ginestein derivatives, biochanin A-glucoside, and biochanin A were identified in P. tridentatum, whilst in M. pulegium the luteolin-7-rutinoside, diosmin, and apigenin and respective derivatives were most representative polyphenols. These variations had implications in the antiradical and antibacterial activity and the P. tridentatum exhibited the highest antibacterial activity against methicillin-resistant and methicillin-sensitive Staphylococcus aureus MSSA, which was mainly dose-dependent. This antibacterial activity seems to be related to high content of flavonols, flavones, and isoflavones, which can act synergistically with each other against this type of bacteria. Our results showed consistent evidence that Pterospartum tridentatum and Mentha pulegium are an important reservoir of phytochemicals with antiradical activity and antibacterial capacity and thus they might be used in a preventive way or in a combined pharmaceutical and antibiotic therapy against pathogenic bacteria.

Antimicrobial Susceptibility of Aeromonas Spp. Isolated from Pig Ileum Segments to Natural Isothiocyanates

With this study we intend to evaluate the effects of 8 different glucosinolate hydrolysis products including isothiocyanates as antibacterial compounds against Aeromonadaceae, isolated from intestinal segments of pigs collected directly from slaughter-houses in the North of Portugal. Four Aeromonas species, A. allosaccharophila, A. hydrophila, A. media and A. veronii were identified. Using disc-diffusion bioassay all compounds were tested at 6 different doses (0.015, 0.15, 0.75, 1.5 and 3.0 µmoles) in dimethyl-sulfoxide (DMSO). Antibiotic standard (gentamicin) and DMSO (negative control) were included in all experiments. Minimum and maximum dose inhibitions (in µmoles) were assessed. To our knowledge, this is the first study of antimicrobial activity of glucosinolate hydrolysis products against Aeromonas species. The results showed that glucosinolate hydrolysis products and particularly the isothiocyanates have antimicrobial activity, which was proportional to the concentration used. However, not all revealed the same tendency, which means that the chemical structure of each compound is fundamental to understand their effectiveness. Among the different isothiocyanates the benzylisothiocyanate, sulforaphane and 2-phenylethylisothiocyanate were the most effective in vitro inhibitors of bacterial growth. This in vitro study provides enough data to demonstrate the potential use of these natural dietary chemicals for treating infectious diseases caused by Aeromonas spp.

Biofilms and antibiotic susceptibility of multidrug-resistant bacteria from wild animals

Background The “One Health” concept recognizes that human health and animal health are interdependent and bound to the health of the ecosystem in which they (co)exist. This interconnection favors the transmission of bacteria and other infectious agents as well as the flow of genetic elements containing antibiotic resistance genes. This problem is worsened when pathogenic bacteria have the ability to establish as biofilms. Therefore, it is important to understand the characteristics and behaviour of microorganisms in both planktonic and biofilms states from the most diverse environmental niches to mitigate the emergence and dissemination of resistance. Methods The purpose of this work was to assess the antibiotic susceptibility of four bacteria (Acinetobacter spp., Klebsiella pneumoniae, Pseudomonas fluorescens and Shewanella putrefaciens) isolated from wild animals and their ability to form biofilms. The effect of two antibiotics, imipenem (IPM) and ciprofloxacin (CIP), on biofilm removal was also assessed. Screening of resistance genetic determinants was performed by PCR. Biofilm tests were performed by a modified microtiter plate method. Bacterial surface hydrophobicity was determined by sessile drop contact angles. Results The susceptibility profile classified the bacteria as multidrug-resistant. Three genes coding for β-lactamases were detected in K. pneumoniae (TEM, SHV, OXA-aer) and one in P. fluorescens (OXA-aer). K. pneumoniae was the microorganism that carried more β-lactamase genes and it was the most proficient biofilm producer, while P. fluorescens demonstrated the highest adhesion ability. Antibiotics at their MIC, 5 × MIC and 10 × MIC were ineffective in total biofilm removal. The highest biomass reductions were found with IPM (54% at 10 × MIC) against K. pneumoniae biofilms and with CIP (40% at 10 × MIC) against P. fluorescens biofilms. Discussion The results highlight wildlife as important host reservoirs and vectors for the spread of multidrug-resistant bacteria and genetic determinants of resistance. The ability of these bacteria to form biofilms should increase their persistence.