Antimicrobial effect and mode of action of terpeneless cold-pressed Valencia orange essential oil on methicillin-resistant Staphylococcus aureus

Insights into the antibacterial effectiveness of linalool against Shigella flexneri on pork surface: Changes in bacterial growth and pork quality

Shigella flexneri has the ability to contaminate pork and cause foodborne diseases. This study aimed to examine the effectiveness of linalool (a natural preservative) against S. flexneri and explore its potential application in contaminated pork. The results showed that linalool was capable of damaging the cell membrane and binding to the DNA of S. flexneri, and inhibiting biofilm formation and disrupting mature biofilms. The antibacterial effectiveness of linalool on the surface of pork was further demonstrated by analyzing the physicochemical properties of the pork (i.e., weight loss rate, pH value, color index, and TVB-N value) and its protein profiles. Linalool did not completely kill S. flexneri in pork at minimum bactericidal concentration (MBC) concentration and its antibacterial effect of linalool was stronger during the initial stage of storage. During storage, linalool influenced the abundance of specific proteins in the pork, particularly those involved in pathways related to fat metabolism. These findings offer novel insights into the antibacterial efficacy of linalool and its underlying mechanism in pork.

Gelatin based preservation technologies on the quality of food: a comprehensive review

Gelatin has played a great potential in food preservation because of its low price and superior film forming characteristics. This review provides a comprehensive overview of the latest research progress and application of gelatin preservation technologies (film, coating, antifreeze peptide, etc.), discussing their preservation mechanisms and efficiency through the viewpoints of quality and shelf life of animal and aquatic products as well as fruits and vegetables. It showed that bioactive and intelligent gelatin-based films exhibit antibacterial, antioxidant, water resistance and pH responsive properties, making them excellent for food preservation. In addition, pH responsive properties of films also intuitively reflect the freshness of food by color. Similarly, gelatin and its hydrolysate can be widely used in antifreeze peptides to reduce the mass loss of food during freezing and extend the shelf life of frozen food. However, extensive works are still required to extend their commercial application values.

Mesoporous silica nanoparticles: A versatile platform for encapsulation and delivery of essential oils for food applications

Essential oils (EOs) are biologically active and volatile substances that have found widespread applications in the food, cosmetics, and pharmaceutical industries. However, there are some challenges to their commercial utilization due to their high volatility, susceptibility to degradation, and hydrophobicity. In their free form, EOs can quickly evaporate, as well as undergo degradation reactions like oxidation, isomerization, dehydrogenation, or polymerization when exposed to light, heat, or air. Encapsulating EOs within mesoporous silica nanoparticles (MSNPs) could overcome these limitations and thereby broaden their usage. MSNPs may endow protection and slow-release properties to EOs, thereby extending their stability, enhancing their efficacy, and improving their dispersion in aqueous environments. This review explores and compares the design and development of different MSNP-based nanoplatforms to encapsulate, protect, and release EOs. Initially, a brief overview of the various types of available MSNPs, their properties, and their synthesis methods is given to better understand their roles as carriers for EOs. Several encapsulation technologies are then examined, including solvent-based and solvent-free methods. The suitability of each technology for EO encapsulation, as well as its impact on their stability and release, is discussed in detail. Opportunities and challenges for using EO-loaded MSNPs as preservatives, flavor enhancers, and antimicrobial agents in the food industry are then highlighted. Overall, this review aims to bridge a knowledge gap by providing a thorough understanding of EO encapsulation within MSNPs, which should facilitate the application of this technology in the food industry.

Unveiling the Potential Ways to Apply Citrus Oil to Control Causative Agents of Pullorum Disease and Fowl Typhoid in Floor Materials

This study investigates the potential role of Cold-pressed Valencia Terpeneless citrus oil (CO), as a natural antimicrobial, in controlling causative agents of pullorum disease and fowl typhoid in floor materials for poultry farming, specifically wooden chips. The study addresses the issues that have arisen as a result of the reduction in antibiotic use in poultry farming, which has resulted in the re-emergence of bacterial diseases including salmonellosis. CO efficiently inhibits the growth of pathogens including various serovars of Salmonella enterica (SE), including SE serovar Gallinarum (S. Gallinarum) and SE serovar Pullorum (S. Pullorum), in a dose-dependent manner. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of CO showed potential for controlling diverse S. Gallinarum and S. Pullorum isolates. Growth inhibition assays demonstrated that 0.4% (v/w) CO eliminated S. Pullorum and S. Gallinarum from 24 h onwards, also impacting poultry gut microbiota and probiotic strains. Floor material simulation, specifically wooden chips treated with 0.4% CO, confirmed CO's effectiveness in preventing S. Gallinarum and S. Pullorum growth on poultry house floors. This study also investigated the effect of CO on the expression of virulence genes in S. Gallinarum and S. Pullorum. Specifically, the study revealed that the application of CO resulted in a downregulation trend in virulence genes, including spiA, invA, spaN, sitC, and sifA, in both S. Pullorum and S. Gallinarum, implying that CO may alter the pathogenicity of these bacterial pathogens. Overall, this study reveals that CO has the potential to be used as a natural antimicrobial in the prevention and management of Salmonella-related infections in chicken production, offering a viable alternative to control these re-emerging diseases.

Alternative approaches to therapeutics and subtherapeutics for sustainable poultry production

The world population is growing rapidly and thus its demand for food is growing as well. To meet the demand of the ever-increasing number of consumers, the poultry industry and both of its main sectors-conventional and organic/cage-free farming-are expanding in parallel. Due to increasing demand of poultry products and higher mortality rate of chicks (an average 0.3% increase of mortality over last 5 yr), both conventional and organic poultry farming systems struggle with various issues; animal welfare, environmental sustainability, and antibiotic resistance of the prevailing zoonotic/enteric pathogens are common issues for conventional farming whereas slow growth rate, higher costs, inefficient land use, different diseases of the chicken, and cross-contamination with bacterial pathogens into the final products are the major issues for organic poultry farming. On top of these issues, the use of subtherapeutic antibiotics was recently banned in conventional farming systems and by definition the organic farming system cannot use the antibiotics/synthetic chemicals even for therapeutic use. In conventional farming system, use of therapeutic antibiotics may result in residuals antibiotics in the final products. As a result, sustainable alternatives are in demand to mitigate the prevailing issues for both conventional and organic farming. Potential alternatives may include bacteriophages, vaccination, probiotics, plant-derived prebiotics, and synbiotics. These alternatives have beneficial attributes and shortcomings of their use in both conventional and organic poultry production system. In this review, we'll discuss the scope of these potential alternatives as therapeutics and subtherapeutics in sustainable poultry production and ways to improve their efficacy.

Application of essential oils as slow-release antimicrobial agents in food preservation: Preparation strategies, release mechanisms and application cases

Food spoilage caused by foodborne microorganisms will not only cause significant economic losses, but also the toxins produced by some microorganisms will also pose a serious threat to human health. Essential oil (EOs) has significant antimicrobial activity, but its application in the field of food preservation is limited because of its volatile, insoluble in water and sensitive to light and heat. Therefore, in order to solve these problems effectively, this paper first analyzed the antibacterial effect of EOs as an antimicrobial agent on foodborne bacteria and its mechanism. Then, the application strategies of EOs as a sustained-release antimicrobial agent in food preservation were reviewed. On this basis, the release mechanism and application cases of EOs in different antibacterial composites were analyzed. The purpose of this paper is to provide technical support and solutions for the preparation of new antibacterial packaging materials based on plant active components to ensure food safety and reduce food waste.

Newly discovered Staphylococcus aureus serine hydrolase probe and drug targets

There is an urgent need for new diagnosis and treatment options for the bacterial pathogen Staphylococcus aureus. This review will summarize data on ten recently discovered biofilm-associated serine hydrolases called fluorophosphonate-binding hydrolases (FphA-J). Based on the summarized findings, many of these proteins represent intriguing new targets for probe and drug development.

Antibacterial Activities and Synergistic Interaction of Citrus Essential Oils and Limonene with Gentamicin against Clinically Isolated Methicillin-Resistant Staphylococcus aureus

Citrus reticulata Blanco and Citrus aurantifolia are the edible plants which contain several biological properties including antibacterial activity. The aims of the present study were to determine the chemical compositions and evaluate antibacterial activities of citrus essential oils extracted from the fruit peels of C. reticulata (CREO) and C. aurantifolia (CAEO), alone and in combination with gentamicin, against a panel of clinically isolated methicillin-resistant S. aureus (MRSA) (n = 40) and methicillin-susceptible S. aureus (MSSA) (n = 45). Gas chromatography-mass spectrometry analysis revealed that 12 and 25 compounds were identified in CREO and CAEO with the most predominant compound of limonene (62.9-72.5%). The antibacterial activities were determined by agar disk diffusion and resazurin-based microdilution methods. The results found that almost all MRSA isolates were resistant to ciprofloxacin, erythromycin, and clindamycin, and some isolates were resistant to gentamicin. CREO and CAEO exhibited inhibitory effects toward clinical isolates (MIC: 1.0-32.0 and 8.0-32.0 mg/mL, respectively), with a similar trend to limonene (MIC: 1.0-32.0 mg/mL). However, the higher antibacterial effects were found in CREO and limonene when compared to CAEO (p < 0.01). In combination effect, the results showed the synergistic interaction of gentamicin with CREO and limonene on the MRSA and MSSA isolates (FIC indexes: 0.012-0.258 and 0.012-0.375), but that interaction of gentamicin with CAEO was observed only on MRSA (FIC index: 0.012-0.016). These findings demonstrated the potential of these citrus essential oils as natural antibacterial agents that may contribute to reduce the emerging of antimicrobial-resistant bacteria.

New treatment options for acute rhinosinusitis according to EPOS 2020

Acute rhinosinusitis (ARS) is a very common condition and mostly of viral origin. About 0.5–2% of the viral ARS are complicated by a bacterial infection. Due to viral etiology and inflammatory mechanisms of rhinitis and rhinosinusitis, symptomatic treatment including phytotherapy have been used for their treatment for decades. Scientific societies and expert groups recommend the use of herbal medicines in acute viral and acute post-viral rhinosinusitis. In 2021, Polish patients gained access to a new therapeutic option for acute sinusitis in the form of a drug containing a distillate of a mixture of rectified essential oils of eucalyptus, sweet orange, myrtle and lemon common.

Rapid Screening of Essential Oils as Substances Which Enhance Antibiotic Activity Using a Modified Well Diffusion Method

Antimicrobial resistance is recognized as one of the major global health challenges of the 21st century. Synergistic combinations for antimicrobial therapies can be a good strategy for the treatment of multidrug resistant infections. We examined the ability of a group of 29 plant essential oils as substances which enhance the antibiotic activity. We used a modified well diffusion method to establish a high-throughput screening method for easy and rapid identification of high-level enhancement combinations against bacteria. We found that 25 essential oils possessed antibacterial activity against Escherichia Coli ATCC 25922 and methicillin-resistant Staphylococcus aureus (MRSA) 43300 with MICs that ranged from 0.01% to 2.5% v/v. We examined 319 (11 × 29) combinations in a checkerboard assay with E. Coli ATCC 25922 and MRSA 43300, and the result showed that high-level enhancement combinations were 48 and 44, low-level enhancement combinations were 214 and 211, and no effects combinations were 57 and 64, respectively. For further verification we randomly chose six combinations that included orange and Petitgrain essential oils in a standard time-killing assay. The results are in great agreement with those of the well diffusion assays. Therefore, the modified diffusion method was a rapid and effective method to screen high-level enhancement combinations of antibiotics and essential oils.

Nanoencapsulation of Plant Volatile Organic Compounds to Improve Their Biological Activities

Plant volatile organic compounds (volatiles) are secondary plant metabolites that play crucial roles in the reproduction, defence, and interactions with other vegetation. They have been shown to exhibit a broad range of biological properties and have been investigated for antimicrobial and anticancer activities. In addition, they are thought be more environmentally friendly than many other synthetic chemicals 1. Despite these facts, their applications in the medical, food, and agricultural fields are considerably restricted due to their volatilities, instabilities, and aqueous insolubilities. Nanoparticle encapsulation of plant volatile organic compounds is regarded as one of the best strategies that could lead to the enhancement of the bioavailability and biological activity of the volatile compounds by overcoming their physical limitations and promoting their controlled release and cellular absorption. In this review, we will discuss the biosynthesis and analysis of plant volatile organic compounds, their biological activities, and limitations. Furthermore, different types of nanoparticle platforms used to encapsulate the volatiles and the biological efficacies of nanoencapsulated volatile organic compounds will be covered.

Isopropoxy Benzene Guanidine Kills Staphylococcus aureus Without Detectable Resistance

Serious infections caused by multidrug-resistant Staphylococcus aureus clearly urge the development of new antimicrobial agents. Drug repositioning has emerged as an alternative approach that enables us to rapidly identify effective drugs. We first reported a guanidine compound, isopropoxy benzene guanidine, had potent antibacterial activity against S. aureus. Unlike conventional antibiotics, repeated use of isopropoxy benzene guanidine had a lower probability of resistance section. We found that isopropoxy benzene guanidine triggered membrane damage by disrupting the cell membrane potential and cytoplasmic membrane integrity. Furthermore, we demonstrated that isopropoxy benzene guanidine is capable of treating invasive MRSA infections in vivo studies. These findings provided strong evidence that isopropoxy benzene guanidine represents a new chemical lead for novel antibacterial agent against multidrug-resistant S. aureus infections.

Antibacterial Activity and Mechanism of Ginger Essential Oil against Escherichia coli and Staphylococcus aureus

Though essential oils exhibit antibacterial activity against food pathogens, their underlying mechanism is understudied. We extracted ginger essential oil (GEO) using supercritical CO2 and steam distillation. A chemical composition comparison by GC-MS showed that the main components of the extracted GEOs were zingiberene and α-curcumene. Their antibacterial activity and associated mechanism against Staphylococcus aureus and Escherichia coli were investigated. The diameter of inhibition zone (DIZ) of GEO against S. aureus was 17.1 mm, with a minimum inhibition concentration (MIC) of 1.0 mg/mL, and minimum bactericide concentration (MBC) of 2.0 mg/mL. For E. coli, the DIZ was 12.3 mm with MIC and MBC values of 2.0 mg/mL and 4.0 mg/mL, respectively. The SDS-PAGE analysis revealed that some of the electrophoretic bacterial cell proteins bands disappeared with the increase in GEO concentration. Consequently, the nucleic acids content of bacterial suspension was raised significantly and the metabolic activity of bacteria was markedly decreased. GEO could thus inhibit the expression of some genes linked to bacterial energy metabolism, tricarboxylic acid cycle, cell membrane-related proteins, and DNA metabolism. Our findings speculate the bactericidal effects of GEO primarily through disruption of the bacterial cell membrane indicating its suitability in food perseveration.

Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments - A review

Bovine mastitis, an inflammation of the mammary gland, is the most common disease of dairy cattle causing economic losses due to reduced yield and poor quality of milk. The etiological agents include a variety of gram-positive and gram-negative bacteria, and can be either contagious (e.g., Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma spp.) or environmental (e.g., Escherichia coli, Enterococcus spp., coagulase-negative Staphylococcus, Streptococcus uberis). Improving sanitation such as enhanced milking hygiene, implementation of post-milking teat disinfection, maintenance of milking machines are general measures to prevent new cases of mastitis, but treatment of active mastitis infection is dependant mainly on antibiotics. However, the extensive use of antibiotics increased concerns about emergence of antibiotic-resistant pathogens and that led the dairy industries to reduce the use of antibiotics. Therefore, alternative therapies for prevention and treatment of bovine mastitis, particularly natural products from plants and animals, have been sought. This review provides an overview of bovine mastitis in the aspects of risk factors, control and treatments, and emerging therapeutic alternatives in the control of bovine mastitis.

Chemical Composition, Antioxidant and Antibacterial Activity of Bunium persicum, Eucalyptus globulus, and Rose Water on Multidrug-Resistant Listeria Species

This research was aimed at investigating the antioxidant and antibacterial activity of Bunium persicum, Eucalyptus globulus, and rose water on multidrug-resistant Listeria species. The antibiotic resistance of Listeria spp obtained from seafood samples were determined by the Kirby-Bauer method. The antioxidant and antibacterial activity of the essential oils and extracts were evaluated using ferric reducing antioxidant power and microdilution methods, respectively. A total 2 samples (1.88%) were positive for Listeria spp. L monocytogenes was found to be resistant to ampicillin, amoxicillin/clavulanic acid, penicillin, vancomycin, and kanamycin. B persicum essential oil showed the greatest antioxidant activity (248.56 ± 1.09 µM Fe²⁺/g). The E globulus essential oil showed consistently strong antimicrobial activity against L monocytogenes and L grayi, while rose water showed no antimicrobial activity against any of the tested bacterial strains. The results showed that after adding the B persicum and E globulus essential oils to bacteria, the cell components’ release increased significantly.

Identification of a S. aureus virulence factor by activity-based protein profiling (ABPP)

Serine hydrolases play diverse roles in regulating host-pathogen interactions in a number of organisms, yet few have been characterized in the human pathogen Staphylococcus aureus. Here we describe a chemical proteomic screen that identified ten previously uncharacterized S. aureus serine hydrolases that mostly lack human homologs. We termed these enzymes fluorophosphonate-binding hydrolases (FphA-J). One hydrolase, FphB, can process short fatty acid esters, exhibits increased activity in response to host cell factors, is located predominantly on the bacterial cell surface in a subset of cells, and is concentrated in the division septum. Genetic disruption of fphB confirmed that the enzyme is dispensable for bacterial growth in culture but crucial for establishing infection in distinct sites in vivo. A selective small molecule inhibitor of FphB effectively reduced infectivity in vivo, suggesting that it may be a viable therapeutic target for the treatment or management of Staphylococcus infections.

Essential Oil of Cymbopogon citratus on the Control of the Curvularia Leaf Spot Disease on Maize

The Curvularia Leaf Spot is becoming more common due to the culture expansion and the low resistance of the cultivated genotypes in tropical regions. Thus, the objective was to evaluate the fungitoxicity of the essential oil of Cymbopogon citratus upon the phytopathogen Curvularia lunata, causative agent of the Curvularia Leaf Spot. There was realized pathogenicity tests of C. lunata in maize plants, phytotoxicity of the essential oil of C. citratus and gas chromatography attached, germination tests of the conidia, and of in vitro inhibition of C. lunata. Also, there were realized tests aiming at verifying the phytopathogen control in vivo. In the pathogenicity tests, there were verified symptoms of the disease in all of the suspensions tested on plants. It was observed that the essential oil concentrations of 7.5 µL mL⁻¹ to 50 µL mL⁻¹ were phytotoxic. The majoritarian chemical components of the essential oil of C. citratus were Geranial (41.46%) and Neral (32.43%). The concentrations of 5 and 7.5 µL mL⁻¹ inhibited 100% of conidia germination. None of the concentrations evaluated effectively inhibited C. lunata mycelial growth in in vitro tests. In the preventive control, the concentration of 7.5 µL mL⁻¹ was sufficient for the reduction of the progress of the disease, however the curative control was not efficient on the tested dosages.

Effect of limonene on the heterotrophic growth and polyhydroxybutyrate production by Cupriavidus necator H16

The inhibitory effect of limonene on polyhydroxybutyrate (PHB) production in Cupriavidus necator H16 was studied. Firstly, results demonstrate the feasibility of using orange juicing waste (OJW) as a substrate for PHB production. An intracellular PHB content of 81.4% (w/w) was attained for a total dry matter concentration of 9.58gL^-1, when the OJW medium was used. Later, a mineral medium designed to mimic the nutrient levels found in the complex medium derived from OJW was used to study the effect of limonene on the production of PHB. Results showed a drop in specific growth rate (μ) of more than 50% when the initial limonene concentration was 2% (v/v) compared to the limonene free medium. This work highlights the importance of a limonene recovery stage prior to fermentation, to maintain levels below 1% (v/v) in the medium, adding value to the OJW and enhancing the fermentation process productivity.

Application of Omics Technologies for Evaluation of Antibacterial Mechanisms of Action of Plant-Derived Products

In the face of increasing bacterial resistance to antibiotics currently in use, the search for new antimicrobial agents has received a boost in recent years, with natural products playing an important role in this field. In fact, several methods have been proposed to investigate the antibacterial activities of natural products. However, given that the ultimate aim is future therapeutic use as novel drugs, it is extremely necessary to elucidate their modes of action, stating the molecular effects in detail, and identifying their targets in the bacterial cell. This review analyzes the application of “omics technologies” to understand the antibacterial mechanisms of bioactive natural products, to stimulate research interest in this area and promote scientific collaborations. Some studies have been specifically highlighted herein by examining their procedures and results (targeted proteins and metabolic pathways). These approaches have the potential to provide new insights into our comprehension of antimicrobial resistance/susceptibility, creating new perspectives for the struggle against bacteria, and leading to the development of novel products in the future.

Antibacterial activity of oxyresveratrol against methicillin-resistant Staphylococcus aureus and its mechanism

Oxyresveratrol (ORV) is a naturally occurring compound found in mulberries that exhibits a wide spectrum of biological activities. However, the underlying mechanism of the action of ORV against the methicillin-resistant S. aureus (MRSA) pathogen has not yet been reported. MRSA is multidrug-resistant, causing skin and other types of infections. The aim of the present study was to examine the antimicrobial activity of ORV and the underlying mechanism of its action on MRSA. The antibacterial activity of ORV was evaluated using a minimum inhibitory concentration (MIC) assay, and the mechanism of its antibacterial action on S. aureus was investigated using a combination of ORV with detergent, ATPase inhibitors and peptidoglycan (PGN). In addition, the survival characteristics and changes in MRSA morphology were monitored using transmission electron microscopy (TEM). The MIC value of ORV against all S. aureus strains was found to be 125 µg/ml. The optical density at 600 nm of each suspension treated using a combination of ORV with Triton X-100, N,N'-dicyclohexylcarbodiimide or sodium azide was reduced by 68.9-89.8% compared with the value upon treatment with ORV alone. In the ORV and PGN combination assay, direct binding of ORV with PGN from S. aureus was evident. Furthermore, TEM examination of MRSA treated with ORV showed alterations in septa formation. In conclusion, these results showed that ORV has a strong antibacterial effect against S. aureus, mainly by increasing membrane permeability and inhibiting ATPase when combined with other drugs.

Comparison of the Composition and Antimicrobial Activities of the Essential Oils of Green Branches and Leaves of Egyptian Navel Orange (Citrus sinensis (L.) Osbeck var. malesy)

The essential oils isolated from the leaves and green branches of the Egyptian navel orange trees were analyzed by GC and GC/MS. A total of 33 and 24 compounds were identified from the oils of the leaves and branches accounting for 96.0% and 97.9%, respectively, of the total detected constituents. The major ones were sabinene (36.5; 33.0%), terpinen-4-ol (8.2; 6.2%), δ-3-carene (7.0; 9.4%), limonene (6.8; 18.7%), trans-ocimene (6.7; 6.1%), and β-myrcene (4.5; 4.4%). The antimicrobial activities of both oils were evaluated using the agar-well diffusion method toward three representatives for each of Gram-positive bacteria, Gram-negative bacteria, and fungi. The oil of leaves was more effective as antimicrobial agent than that of the branches. Streptococcus pyogenes, Staphylococcus aureus, Salmonella typhimurium, and Aspergillus fumigatus were the most sensitive bacteria and fungi by the leaves oil.

Antibacterial Activity of Carum copticum Essential Oil Against Escherichia Coli O157:H7 in Meat: Stx Genes Expression

This work were aimed to (a) determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Carum copticum essential oil (EO) against Escherichia. coli O157:H7 in vitro Trypticase Soy Broth, (TSB) and in ground beef; (b) evaluation of the effect of sub-inhibitory concentrations (sub-MICs) of EO on the growth of bacterium in TSB over 72 h (at 35 °C) and ground beef over 9 days (at 4 °C); and (c) investigation of gene expression involved in Shiga toxins production using relative quantitative real-time PCR method. The MIC in broth and ground beef medium were determined as 0.05 (v/v) and 1.75 % (v/w), respectively. In comparison with control cultures, the EO concentration of 0.03 % in broth caused reduction of colony counting as 1.93, 1.79, and 2.62 log10 CFU ml(-1) after 24, 48, and 72 h at 35 °C, and similarly EO (0.75 %) in ground beef resulted to reduction of colony counting as 1.03, 0.92, 1.48, and 2.12 log10 CFU g (-1) after 2, 5, 7, and 9 days at 4 °C, respectively. An increase and decrease in gene expression were observed as result of EO addition (0.03 %) to broth and (0.5 %) to ground beef was noticed, respectively.

Chemistry and Pharmacology of Citrus sinensis

Presently the search for new drugs from natural resources is of growing interest to the pharmaceutical industry. Natural products have been the source of new drugs since ancient times. Plants are a good source of secondary metabolites which have been found to have beneficial properties. The present study is a review of the chemistry and pharmacology of Citrus sinensis. This review reveals the therapeutic potential of C. sinensis as a source of natural compounds with important activities that are beneficial for human health that could be used to develop new drugs.

Potent Inhibition of Pseudogymnoascus destructans, the Causative Agent of White-Nose Syndrome in Bats, by Cold-Pressed, Terpeneless, Valencia Orange Oil

The causative agent of White-nose Syndrome (WNS), Pseudogymnoascus destructans, has been shown to be fatal to several species of bats in North America. To date, no compounds or chemical control measures have been developed which eliminates the growth of the fungus in the environment or in affected animals. In the current study, we evaluated the activity of cold-pressed, terpeneless orange oil (CPT) against multiple isolates of P. destructans in vitro. For all assays, a modified Kirby-Bauer disk diffusion assay was used. Standardized spore suspensions were prepared, adjusted to a specific optical density, and used to plate fungal lawns. Plates were incubated at either 15°C or 4°C for up to 6 months and checked at regular intervals for growth. Once controls had grown, zones of inhibition were measured (mm) on test plates and compared to those obtained using current antifungal drugs. All P. destructans isolates were completely inhibited by 100% CPT (10 μL) at 1 month of incubation regardless of temperature (4°C and 15°C). Complete inhibition persisted up to 6 months following a single exposure at this concentration. Of the standard antifungals, only amphotericin B demonstrated any activity, resulting in zone diameters ranging from 58 mm to 74 mm. CPT, at the highest concentration tested (100%), had no significant effect against a variety of other environmental organisms including various filamentous fungi, bacteria and aerobic actinomycetes. Given that CPT is relatively non-toxic, the possibility exists that the all-natural, mixture could be used as an environmental pre-treatment to eradicate P. destructans from bat habitats. Additional studies are needed to assess any undesirable effects of CPT on bat behavior and health and overall impacts on other members of the interconnected ecosystem(s).

Potentiating activity of luteolin on membrane permeabilizing agent and ATPase inhibitor against methicillin-resistant Staphylococcus aureus

OBJECTIVE

To investigate the mechanism of antibacterial activity of luteolin (LUT) against methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

The mechanism of anti-MRSA activity of LUT was analyzed by the viability assay in membrane permeabilizing agent, ATPase inhibitors, and peptidoglycan (PGN) derived from Staphylococcus aureus (S. aureus). Also, transmission electron microscopy was used to monitor survival characteristics and changes in S. aureus morphology.

RESULTS

Compared to the LUT alone, the optical density of suspensions treated with the combination of 125 μg/mL Tris and 250 μg/mL N,N'-dicyclohexylcarbodiimide were reduced to 60% and 46% of the control, respectively. PGN (15.6 μg/mL) gradually impeded the activity of LUT, and PGN (62.5 μg/mL) completely blocked the activity of LUT on S. aureus.

CONCLUSIONS

Increased susceptibility to LUT with the Tris-dicyclohexylcarbodiimide combinations is evident in all tested MRSA isolates. The results indicate LUT synergy in increasing cytoplasmic membrane permeability and inhibiting ATPase. S. aureus PGN directly blocks the antibacterial activity of LUT, suggesting the direct binding of LUT with PGN. These findings may be validated for the development of antibacterial agent for low MRSA resistance.

Essential oils in the treatment of respiratory tract diseases highlighting their role in bacterial infections and their anti-inflammatory action: a review

The appearance of multidrug resistant bacteria and growing antibiotic resistance is leading to a continuous need for discovering new drugs and alternative treatments against infections. The investigation of the antibacterial effect of essential oils (EOs), which are commonly used nowadays in cosmetics, health care, traditional medicine and food industry, could be one of the promising solutions for this worldwide problem. EOs have a complex mode of action due to their multiple composition. Respiratory tract diseases (RTDs) associated with bacterial infection and inflammation affect a large number of people from every age group worldwide. Because of volatility, EOs can easily reach the upper and lower parts of the respiratory tract via inhalation. Moreover, due to their antimicrobial and anti-inflammatory potency, they offer an effective treatment in respiratory tract infections (RTIs). The purpose of this review is to describe the most frequently developing infections of the upper and lower respiratory tract and to show methods used for the determination of the antibacterial activity of EOs by gaseous contact. The mode of action of EOs on bacterial cells and their anti-inflammatory action are also discussed. Results coming from recently performed in vivo animal studies as well as human trials are also reported. Patents deal with the role of EOs and their volatile constituents in the treatment of RTIs are also introduced. On the whole, this review aimed at showing EOs as potential antimicrobials and as anti-inflammatory agents to alleviate symptoms and signs of RTDs including RTIs. Copyright © 2015 John Wiley & Sons, Ltd.

The effect of citrus-derived oil on bovine blood neutrophil function and gene expression in vitro

Research on the use of natural products to treat or prevent microbial invasion as alternatives to antibiotic use is growing. Polymorphonuclear leukocytes (PMNL) play a vital role with regard to the innate immune response that affects severity or duration of mastitis. To our knowledge, effect of cold-pressed terpeneless Valencia orange oil (TCO) on bovine PMNL function has not been elucidated. Therefore, the objective of this study was to investigate the effect of TCO on bovine blood PMNL chemotaxis and phagocytosis capabilities and the expression of genes involved in inflammatory response in vitro. Polymorphonuclear leukocytes were isolated from jugular blood of 12 Holstein cows in mid-lactation and were incubated with 0.0 or 0.01% TCO for 120min at 37°C and 5% CO2, and phagocytosis (2×10(6) PMNL) and chemotaxis (6×10(6) PMNL) assays were then performed in vitro. For gene expression, RNA was extracted from incubated PMNL (6×10(6) PMNL), and gene expression was analyzed using quantitative PCR. The supernatant was stored at -80°C for analysis of tumor necrosis factor-α. Data were analyzed using a general linear mixed model with cow and treatment (i.e., control or TCO) in the model statement. In vitro supplementation of 0.01% of TCO increased the chemotactic ability to IL-8 by 47%; however, migration of PMNL to complement 5a was not altered. Treatment did not affect the production of tumor necrosis factor-α by PMNL. Expression of proinflammatory genes (i.e., SELL, TLR4, IRAK1, TRAF6, and LYZ) coding for proteins was not altered by incubation of PMNL with TCO. However, downregulation of TLR2 [fold change (FC=treatment/control)=-2.14], NFKBIA (FC=1.82), IL1B (FC=-2.16), TNFA (FC=-9.43), and SOD2 (FC=-1.57) was observed for PMNL incubated with TCO when compared with controls. Interestingly, expression of IL10, a well-known antiinflammatory cytokine, was also downregulated (FC=-3.78), whereas expression of IL8 (FC=1.93), a gene coding for the cytokine IL-8 known for its chemotactic function, tended to be upregulated in PMNL incubated with TCO. Incubation of PMNL with TCO enhanced PMNL chemotaxis in vitro. The expression of genes involved in the inflammatory response was primarily downregulated. Results showed that 0.01% TCO did not impair the function of PMNL in vitro. Future studies investigating the use of TCO as an alternative therapy for treatment of mastitis, including dose and duration, for cows during lactation are warranted.

The mechanism of antimicrobial activity of sophoraflavanone B against methicillin-resistant Staphylococcus aureus

Sophoraflavanone B (SPF-B), a prenylated flavonoid, can be isolated from the roots of Desmodium caudatum. The aim of this study was to determine the mechanism of SPF-B's antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a multidrug-resistant pathogen and the main cause of hospital- and community-acquired infections. The minimum inhibitory concentration (MIC) of SPF-B was assessed using the broth microdilution method. The mechanism of action of SPF-B on S. aureus was analyzed in combination assays incorporating detergents, ATPase inhibitors, and peptidoglycan (PGN) derived from S. aureus. Furthermore, morphological changes in the SPF-B-treated MRSA strains were investigated using transmission electron microscopy. The MIC of SPF-B for MRSA was in the range of 15.6-31.25 μg/mL. The mechanism of action of SPF-B on MRSA was investigated using combination assays with detergent and ATPase inhibitors. The optical density at 600 nm of MRSA suspensions treated with a combination of detergent and SPF-B reduced the MRSA by 63%-73%. In the SPF-B and PGN combination assay, direct binding of SPF-B with PGN from S. aureus was evident. These data may be validated for the development of new antibacterial drugs for low MRSA resistance.

Purification and characterization of the Staphylococcus aureus bacillithiol transferase BstA

BACKGROUND

Gram-positive bacteria in the phylum Firmicutes synthesize the low molecular weight thiol bacillithiol rather than glutathione or mycothiol. The bacillithiol transferase YfiT from Bacillus subtilis was identified as a new member of the recently discovered DinB/YfiT-like Superfamily. Based on structural similarity using the Superfamily program, we have determined 30 of 31 Staphylococcus aureus strains encode a single bacillithiol transferase from the DinB/YfiT-like Superfamily, while the remaining strain encodes two proteins.

METHODS

We have cloned, purified, and confirmed the activity of a recombinant bacillithiol transferase (henceforth called BstA) encoded by the S. aureus Newman ORF NWMN_2591. Moreover, we have studied the saturation kinetics and substrate specificity of this enzyme using in vitro biochemical assays.

RESULTS

BstA was found to be active with the co-substrate bacillithiol, but not with other low molecular weight thiols tested. BstA catalyzed bacillithiol conjugation to the model substrates monochlorobimane, 1-chloro-2,4-dinitrobenzene, and the antibiotic cerulenin. Several other molecules, including the antibiotic rifamycin S, were found to react directly with bacillithiol, but the addition of BstA did not enhance the rate of reaction. Furthermore, cells growing in nutrient rich medium exhibited low BstA activity.

CONCLUSIONS

BstA is a bacillithiol transferase from S. aureus that catalyzes the detoxification of cerulenin. Additionally, we have determined that bacillithiol itself might be capable of directly detoxifying electrophilic molecules.

GENERAL SIGNIFICANCE

BstA is an active bacillithiol transferase from S. aureus Newman and is the first DinB/YfiT-like Superfamily member identified from this organism. Interestingly, BstA is highly divergent from B. subtilis YfiT.

Physicochemical, mechanical, and molecular properties of nonlysogenic and p22-lysogenic Salmonella typhimurium treated with citrus oil

The aim of this study was to evaluate the phenotypic and genotypic properties of nonlysogenic Salmonella Typhimurium (ST(P22-)) and lysogenic Salmonella Typhimurium (ST(P22+)) in the presence of sublethal concentrations (SLC2D) of citrus essential oils (CEOs), which were used to evaluate antimicrobial susceptibility, cell surface hydrophobicity, autoaggregation ability, bacterial motility, lysogenic conversion, gene expression patterns, and antibiofilm formation. The SLC2D values of non-heat-treated (N-CEO) and heat-treated (H-CEO) CEO in an autoclave at 121°C for 20 min were 2.0 to 2.1 mg/ml against ST(P22-) and 1.7 to 1.9 mg/ml against STP(22+). The rates of injured ST(P22-) and ST(P22+) cells treated with SLC2D of N-CEO and H-CEO ranged from 67 to 83%. The hydrophobicity and autoaggregation were decreased to 2.5 and 19.5% for ST(P22-) and 4.7 and 21.7% for ST(P22+), respectively, in the presence of N-CEO. A noticeable reduction in the swarming motility was observed in ST(P22-) with N-CEO (14.5%) and H-CEO (13.3%). The numbers of CEO-induced P22 were 5.40 log PFU/ml for N-CEO and 5.65 log PFU/ml for H-CEO. The relative expression of hilA, hilC, hilD, invA, invC, invE, invF, sirA, and sirB was down-regulated in ST(P22-) and ST(P22+) with N-CEO and H-CEO. The numbers of adherent ST(P22-) and ST(P22+) were effectively reduced by more than 1 log in the presence of CEO. These results suggest that CEO has potential to be used to control bacterial attachment, colonization, and invasion.

Application of orange essential oil as an antistaphylococcal agent in a dressing model

Background

Staphylococcus aureus is the pathogen most often and prevalently involved in skin and soft tissue infections. In recent decades outbreaks of methicillin-resistant S. aureus (MRSA) have created major problems for skin therapy, and burn and wound care units. Topical antimicrobials are most important component of wound infection therapy. Alternative therapies are being sought for treatment of MRSA and one area of interest is the use of essential oils. With the increasing interest in the use and application of natural products, we screened the potential application of terpeneless cold pressed Valencia orange oil (CPV) for topical therapy against MRSA using an in vitro dressing model and skin keratinocyte cell culture model.

Methods

The inhibitory effect of CPV was determined by disc diffusion vapor assay for MRSA and vancomycin intermediate-resistant S. aureus (VISA) strains. Antistaphylococcal effect of CPV in an in vitro dressing model was tested on S. aureus inoculated tryptic soya agar plate. Bactericidal effect of CPV on MRSA and VISA infected keratinocyte cells was examined by enumeration of extra- and intra-cellular bacterial cells at different treatment time points. Cytotoxic effects on human skin cells was tested by adding CPV to the keratinocyte (HEK001) cells grown in serum free KSFM media, and observed by phase-contrast microscope.

Results

CPV vapour effectively inhibited the MRSA and VISA strains in both disc diffusion vapour assay and in vitro dressing model. Compared to untreated control addition of 0.1% CPV to MRSA infected keratinocyte decreased the viable MRSA cells by 2 log CFU/mL in 1 h and in VISA strain 3 log CFU/mL reduction was observed in 1 h. After 3 h viable S. aureus cells were not detected in the 0.2% CPV treatment. Bactericidal concentration of CPV did not show any cytotoxic effect on the human skin keratinocyte cells in vitro.

Conclusions

At lower concentration addition of CPV to keratinocytes infected with MRSA and VISA rapidly killed the bacterial cells without causing any toxic effect to the keratinocytes. Therefore, the results of this study warrant further in vivo study to evaluate the potential of CPV as a topical antistaphylococcal agent.