Filomena Silva

Coriander (Coriandrum sativum L.) essential oil: its antibacterial activity and mode of action evaluated by flow cytometry

The aim of this work was to study the antibacterial effect of coriander (Coriandrum sativum) essential oil against Gram-positive and Gram-negative bacteria. Antibacterial susceptibility was evaluated using classical microbiological techniques concomitantly with the use of flow cytometry for the evaluation of cellular physiology. Our results showed that coriander oil has an effective antimicrobial activity against all bacteria tested. Also, coriander oil exhibited bactericidal activity against almost all bacteria tested, with the exception of Bacillus cereus and Enterococcus faecalis. Propidium iodide incorporation and concomitant loss of all other cellular functions such as efflux activity, respiratory activity and membrane potential seem to suggest that the primary mechanism of action of coriander oil is membrane damage, which leads to cell death. The results obtained herein further encourage the use of coriander oil in antibacterial formulations due to the fact that coriander oil effectively kills pathogenic bacteria related to foodborne diseases and hospital infections.

Synergistic activity of coriander oil and conventional antibiotics against Acinetobacter baumannii

In this study we investigated the existence of synergistic antibacterial effect between coriander (Coriandrum sativum L.) essential oil and six different antibacterial drugs (cefoperazone, chloramphenicol, ciprofloxacin, gentamicin, tetracycline and piperacillin). The antibacterial activity of coriander oil was assessed using microdilution susceptibility testing and synergistic interaction by checkerboard assays. The association of coriander essential oil with chloramphenicol, ciprofloxacin, gentamicin and tetracycline against Acinetobacter baumannii showed in vitro effectiveness, which is an indicator of a possible synergistic interaction against two reference strains of A. baumannii (LMG 1025 and LMG 1041) (FIC index from 0.047 to 0.375). However, when tested the involvement between coriander essential oil and piperacillin or cefoperazone, the isobolograms and FIC index showed an additive interaction. The in vitro interaction could improve the antimicrobial effectiveness of ciprofloxacin, gentamicin and tetracycline and may contribute to resensitize A. baumannii to the action of chloramphenicol.

Nanoparticle mediated delivery of pure P53 supercoiled plasmid DNA for gene therapy

The translation of non-viral gene replacement therapies for cancer into clinical application is currently hindered due to known issues associated with the effectiveness of plasmid DNA (pDNA) expression vectors and the production of gene delivery vehicles. Herein we report an integrative approach established on the synthesis of nanoparticulated carriers, in association with the supercoiled (sc) isoform purification of a p53 tumor suppressor encoding plasmid, to improve both delivery and transfection. An arginine-based chromatographic matrix with specific recognition for the different topoisoforms was used to completely isolate the biologically active sc pDNA. Our findings showed that the sc topoisoform is recovered under mild conditions with high purity and structural stability. In addition, to further enhance protection and transfection efficiency, the naked sc pDNA was encapsulated within chitosan nanoparticles by ionotropic gelation. The mild conditions for particle synthesis used in the former technique allowed the attainment of a high encapsulation efficiency for sc pDNA (>75%). Moreover, in vitro transfection experiments confirmed the reinstatement of the p53 protein expression and most importantly, the sc pDNA transfected cells exhibited the highest p53 expression levels when compared to other formulations. Overall, given the fact that sc pDNA topoisoform indeed enhances transgene expression rates this approach might have a profound impact on the development of a sustained nucleic acid-based therapy for cancer.

Antistaphylococcal and biofilm inhibitory activities of gallic, caffeic, and chlorogenic acids

Staphylococcus aureus is a Gram-positive pathogen which is able to form biofilms, exhibiting a more pronounced resistance to antibiotics and disinfectants. The hurdles posed in eradicating biofilms have driven the search for new compounds able to fight these structures. Phenolic compounds constitute one of the most numerous and ubiquitous group of plant secondary metabolites with many biological activities. The aim of the present work was to study the potential antimicrobial and antibiofilm properties of gallic, caffeic, and chlorogenic acids against S. aureus as well to elucidate its mechanism of action. It was concluded that the phenolic acids studied in this work have antistaphylococcal properties. For instance, gallic acid is able to influence the adhesion properties of S. aureus. The phenolic acids tested were also able to inhibit the production of α-hemolysin by this microorganism, with the exception of chlorogenic acid. Regarding its mechanism of action, caffeic acid interferes with the stability of the cell membrane and with the metabolic activity of the cells of S. aureus.

Strategies to improve the solubility and stability of stilbene antioxidants: A comparative study between cyclodextrins and bile acids

Aiming at the development of an active food packaging, the goal of this study was to increase stilbenes (resveratrol (RV), pterostilbene (PT) and pinosylvin (PS)) aqueous solubility and stability using hydropropyl-cyclodextrins (HP-CDs) and bile salts. To evaluate stilbene concentration, an HPLC-DAD method was validated. Stilbene solubility was improved by the formation of inclusion complexes and micellar systems with higher solubility values obtained for the inclusion complexes with cyclodextrins. Inclusion complexes revealed a 1:1 stoichiometry for RV and PT and a 1:2 for PS. Solid state characterisation was carried out using X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry. (1)H NMR studies were also performed to characterise the prepared complexes. Photostability studies revealed that CDs were able to increase stilbene photostability at 4 °C. This work showed that stable stilbene solutions can be achieved using hydroxypropyl-CDs, contributing for their incorporation in several materials for the food and pharmaceutical industries.

Biofunctionalization of cellulosic fibres with l-cysteine: Assessment of antibacterial properties and mechanism of action against Staphylococcus aureus and Klebsiella pneumoniae

The main purpose of this work is to obtain a cotton-based textile material functionalized with L-cysteine (L-cys) to achieve an antimicrobial effect with potential application in biomedical, geriatric or pediatric textiles. The binding capacity of L-cys to cotton fibers was assessed through different functionalization strategies-surface activation and exhaustion processes. A subsequent analysis of the possible antibacterial action against Staphylococcus aureus and Klebsiella pneumoniae was performed according with the Japanese International standard (JISL 1902-2002). To determine the mechanism of action of L-cys on the selected strains, flow cytometry was used. The results revealed that the exhaustion process was performed with success to confer bioactivity to the treated fabric, as assessed by an effective antibacterial effect against both Gram-positive and Gram-negative bacteria, and successfully linkage of L-cys was observed via FTIR with a durable effect demonstrated after the washing tests (fastness to washing). It was also observed that L-cys exerts a bacteriostatic effect against both bacterial strains, since there were alterations in the metabolic activity of the microorganisms after the application of the bioactive textile which was shown by the CTC (cyanoditolyl tetrazolium chloride) staining used in flow cytometry. This study shows a new and successful biotechnological process to develop antibacterial textiles through the functionalization of cotton fibres with L-cys which presents a broad range of applications in healthcare, since L-cys is a natural antibacterial compound, non-toxic and affects pathogenic bacteria related to hospital infections.

Bacteriostatic versus bactericidal activity of ciprofloxacin in Escherichia coli assessed by flow cytometry using a novel far-red dye

As common microbiological methods for the assessment of bacteriostatic or bactericidal activities are very time-consuming, in this work we describe that the use of a novel far-red fluorescent stain, Vybrant DyeCycle Ruby (DCR) for the flow cytometric analysis of fluoroquinolone (ciprofloxacin) bacteriostatic and bactericidal activities in Escherichia coli proved to be specific for bacterial DNA and, after ciprofloxacin exposure, DNA distribution analysis was achieved using a 7.5 μM DCR concentration to stain 5 × 105 ethanol-fixed bacterial cells. The analysis of the bacterial DNA histograms obtained from the ciprofloxacin concentrations tested, enabled the distinction between ciprofloxacin bacteriostatic and bactericidal activities.

Antimicrobial activity of coriander oil and its effectiveness as food preservative

ABTRACT Foodborne illness represents a major economic burden worldwide and a serious public health threat, with around 48 million people affected and 3,000 death each year only in the USA. One of the possible strategies to reduce foodborne infections is the development of effective preservation strategies capable of eradicating microbial contamination of foods. Over the last years, new challenges for the food industry have arisen such as the increase of antimicrobial resistance of foodborne pathogens to common preservatives and consumers demand for naturally based products. In order to overcome this, new approaches using natural or bio-based products as food preservatives need to be investigated. Coriander (Coriandrum sativum L.) is a well-known herb widely used as spice, or in folk medicine, and in the pharmacy and food industries. Coriander seed oil is the worlds second most relevant essential oil, exhibiting antimicrobial activity against Gram-positive and Gram-negative bacteria, some yeasts, dermatophytes and filamentous fungi. This review highlights coriander oil antimicrobial activity and possible mechanisms of action in microbial cells and discusses the ability of coriander oil usage as a food preservative, pointing out possible paths for the successful evolution for these strategies towards a successful development of a food preservation strategy using coriander oil.

Trends in microbial control techniques for poultry products

ABSTRACT Fresh poultry meat and poultry products are highly perishable foods and high potential sources of human infection due to the presence of several foodborne pathogens. Focusing on the microbial control of poultry products, the food industry generally implements numerous preventive measures based on the Hazard Analysis and Critical Control Points (HACCP) food safety management system certification together with technological steps, such as refrigeration coupled to modified atmosphere packaging that are able to control identified potential microbial hazards during food processing. However, in recent years, to meet the demand of consumers for minimally processed, high-quality, and additive-free foods, technologies are emerging associated with nonthermal microbial inactivation, such as high hydrostatic pressure, irradiation, and natural alternatives, such as biopreservation or the incorporation of natural preservatives in packaging materials. These technologies are discussed throughout this article, emphasizing their pros and cons regarding the control of poultry microbiota and their effects on poultry sensory properties. The discussion for each of the preservation techniques mentioned will be provided with as much detail as the data and studies provided in the literature for poultry meat and products allow. These new approaches, on their own, have proved to be effective against a wide range of microorganisms in poultry meat. However, since some of these emergent technologies still do not have full consumers acceptability and, taking into consideration the hurdle technology concept for poultry processing, it is suggested that they will be used as combined treatments or, more frequently, in combination with modified atmosphere packaging.

Resveratrol production in bioreactor: Assessment of cell physiological states and plasmid segregational stability

Highlights • Precursor concentration affected cell viability and resveratrol yields.• Cell viability and culture conditions influenced resveratrol yields.• Results show the relevance of process monitoring for bioprocess optimization.