Inhibitory effects of grape seed extract on growth, quorum sensing, and virulence factors of CDC “top-six” non-O157 Shiga toxin producing E. coli

Dietary Effects on the Gut Phageome

As knowledge of the gut microbiome has expanded our understanding of the symbiotic and dysbiotic relationships between the human host and its microbial constituents, the influence of gastrointestinal (GI) microbes both locally and beyond the intestine has become evident. Shifts in bacterial populations have now been associated with several conditions including Crohn's disease (CD), Ulcerative Colitis (UC), irritable bowel syndrome (IBS), Alzheimer's disease, Parkinson's Disease, liver diseases, obesity, metabolic syndrome, anxiety, depression, and cancers. As the bacteria in our gut thrive on the food we eat, diet plays a critical role in the functional aspects of our gut microbiome, influencing not only health but also the development of disease. While the bacterial microbiome in the context of disease is well studied, the associated gut phageome-bacteriophages living amongst and within our bacterial microbiome-is less well understood. With growing evidence that fluctuations in the phageome also correlate with dysbiosis, how diet influences this population needs to be better understood. This review surveys the current understanding of the effects of diet on the gut phageome.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Direct microwave treatment enhances antioxidant and antibacterial properties of the seed extracts of Kékfrankos grapes

The Kékfrankos is the most frequently cultivated wine grape in Hungary, with a significant national and regional impact, resulting in considerable amounts of byproducts (e.g. pomace, seeds). To the best of our knowledge no research has been conducted on the antioxidant and antibacterial properties of its seed extracts (GSE). A novel apporach of applying direct microwave treatment on grape seeds was implemented for the first time to enhance antioxidant and antimicrobial properties of GSE. Antioxidant properties were assayed using the DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power) and TPC (Folin-Ciocâlteu's Total Polyphenol Content) methods. Profile and content of polyphenols was studied using high-performance liquid chromatography/tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. Antibacterial properties were evaluated using Gram-positive Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (ST239) (MRSA) and Gram-negative Escherichia coli (EC) bacteria strains. Results proved that the mild direct microwave treatment of grape seeds significantly increased total polyphenol, (+)-catechin, (-)-epicatechin as well as antioxidant capacity levels by 20-30 % compared to untreated samples and resulted the best antibacterial properties based on bacterial growth curves (SA and MRSA: 0.015625 mg/mL, EC: 0.25 mg/mL). Results justify the importance of further pharmacological investigations on Kékfrankos grape seed extracts and that the direct microwave treatment of grape seeds is an innovative approach for the fast and cost efficient improvement of the antibacterial properties of grape seed extracts.

Metabolome shifts triggered by chlorine sanitisation induce Escherichia coli on fresh produce into the viable but nonculturable state

Facing the increasing occurrence of "big six" Escherichia coli outbreaks linked to fresh produce, chlorine-based sanitisers are widely used for fresh produce decontamination in recent years. However, latest finding that chlorine may induce E. coli cells into a viable not nonculturable (VBNC) state is bringing a new challenge to the fresh produce industry. VBNC cells are undetectable by the plate count test, and yet they retain pathogenicity and are more antibiotic-resistant than culturable cells. As a result, their eradication is critical to ensure the safety of fresh produce. Understanding VBNC cells at the metabolic level may provide a breakthrough for their eradication. Therefore, this study was carried out to collect the VBNC pathogenic E. coli (O26:H11, O121:H19, and O157:H7) cells from chlorine-treated pea sprouts and characterise them using NMR-based metabolomics. From the globally increased metabolite contents detected in the VBNC E. coli cells as compared to the culturable cells, mechanisms underlying E. coli's VBNC induction were elucidated. These include rendering the energy generation scheme to become more compatible with the lowered energy needs, disaggregating protein aggregates to release amino acids for osmoprotection and later resuscitation, as well as increasing cAMP content to downregulate RpoS. These identified metabolic characteristics can inspire future development of targeted measures for VBNC E. coli cell inhibition. Our methods can also be applied to other pathogens to help lower the risk of overall foodborne diseases.

A Systematic Quantitative Determination of the Antimicrobial Efficacy of Grape Seed Extract against Foodborne Bacterial Pathogens

Concerns regarding the role of antimicrobial resistance (AMR) in disease outbreaks are growing due to the excessive use of antibiotics. Moreover, consumers are demanding food products that are minimally processed and produced in a sustainable way, without the use of chemical preservatives or antibiotics. Grape seed extract (GSE) is isolated from wine industry waste and is an interesting source of natural antimicrobials, especially when aiming to increase sustainable processing. The aim of this study was to obtain a systematic understanding of the microbial inactivation efficacy/potential of GSE against Listeria monocytogenes (Gram-positive), Escherichia coli and Salmonella Typhimurium (Gram-negative) in an in vitro model system. More specifically, for L. monocytogenes, the effects of the initial inoculum concentration, bacterial growth phase and absence of the environmental stress response regulon (SigB) on the GSE microbial inactivation potential were investigated. In general, GSE was found to be highly effective at inactivating L. monocytogenes, with higher inactivation achieved for higher GSE concentrations and lower initial inoculum levels. Generally, stationary phase cells were more resistant/tolerant to GSE as compared to exponential phase cells (for the same inoculum level). Additionally, SigB appears to play an important role in the resistance of L. monocytogenes to GSE. The Gram-negative bacteria under study (E. coli and S. Typhimurium) were less susceptible to GSE as compared to L. monocytogenes. Our findings provide a quantitative and mechanistic understanding of the impact of GSE on the microbial dynamics of foodborne pathogens, assisting in the more systematic design of natural antimicrobial-based strategies for sustainable food safety.

Antimicrobial Resistance and Recent Alternatives to Antibiotics for the Control of Bacterial Pathogens with an Emphasis on Foodborne Pathogens

Antimicrobial resistance (AMR) is one of the most important global public health problems. The imprudent use of antibiotics in humans and animals has resulted in the emergence of antibiotic-resistant bacteria. The dissemination of these strains and their resistant determinants could endanger antibiotic efficacy. Therefore, there is an urgent need to identify and develop novel strategies to combat antibiotic resistance. This review provides insights into the evolution and the mechanisms of AMR. Additionally, it discusses alternative approaches that might be used to control AMR, including probiotics, prebiotics, antimicrobial peptides, small molecules, organic acids, essential oils, bacteriophage, fecal transplants, and nanoparticles.

Botanicals as a zinc oxide alternative to protect intestinal cells from an Escherichia coli F4 infection in vitro by modulation of enterocyte inflammatory response and bacterial virulence

Pharmacological doses of zinc oxide (ZnO) have been widely used in pig industry to control post-weaning diarrhea (PWD) symptoms exacerbated by enterotoxigenic Escherichia coli F4 infections. Because of environmental issues and regulatory restrictions, ZnO is no longer sustainable, and novel nutritional alternatives to manage PWD are urgently required. Botanicals represent a wide class of compounds employed in animal nutrition because of their diverse beneficial functions. The aim of this study was to investigate the in vitro protective action of a panel of essential oils and natural extracts on intestinal Caco-2 cells against an E. coli F4 infection. Moreover, we explored the potential mechanisms of action of all the botanicals compared to ZnO. Amongst the others, thyme essential oil, grape seed extract, and Capsicum oleoresin were the most effective in maintaining epithelial integrity and reducing bacterial translocation. Their mechanism of action was related to the modulation of cellular inflammatory response, the protection of tight junctions' expression and function, and the control of bacterial virulence, thus resembling the positive functions of ZnO. Moreover, despite their mild effects on the host side, ginger and tea tree essential oils provided promising results in the control of pathogen adhesion when employed during the challenge. These outcomes support the advantages of employing selected botanicals to manage E. coli F4 infections in vitro, therefore offering novel environmentally-friendly alternatives to pharmacological doses of ZnO capable to modulate host-pathogen interaction at different levels during PWD in pigs.

Chemical aspects of polyphenol-protein interactions and their antibacterial activity

The hunt for novel antibiotics has become a global public health imperative due to the rise in multidrug-resistant microorganisms, untreatable infection cases, overuse, and inefficacy of modern antibiotics. Polyphenols are getting much attention in research due to their multiple biological effects; their use as antimicrobial agents is attributed to their activity and that microbes have a hard time developing resistance to these natural compounds. Polyphenols are secondary metabolites produced in higher plants. They are known to possess various functional properties in the human body. Polyphenols also exhibit antibacterial activities against foodborne pathogens. Their antibacterial mechanism is based on inhibiting bacterial biofilm formation or inactivating enzymes. This review focused on polyphenol-protein interactions and the creation of this complex as a possible antibacterial agent. Also, different phenolic interactions on bacterial proteins, efflux pump, cell membrane, bacterial adhesion, toxins, and other bacterial proteins will be explored; these interactions can work in a synergic combination with antibiotics or act alone to assure bacterial inhibition. Additionally, our review will focus on polyphenol-protein interaction as a possible strategy to eradicate bacteria because polyphenols have shown a robust enzyme-inhibitory characteristic and a high tendency to complex with proteins, a response that neutralizes any bactericidal potential.

Mechanisms of Inhibition of Quorum Sensing as an Alternative for the Control of E. coli and Salmonella

Quorum sensing (QS) is a process of cell-cell communication for bacteria such as E. coli and Salmonella that cause foodborne diseases, with the production, release, and detection of autoinducer (AI) molecules that participate in the regulation of virulence genes. All of these proteins are useful in coordinating collective behavior, the expression of virulence factors, and the pathogenicity of Gram-negative bacteria. In this work, we review the natural or synthetic inhibitor molecules of QS that inactivate the autoinducer and block QS regulatory proteins in E. coli and Salmonella. Furthermore, we describe mechanisms of QS inhibitors (QSIs) that act as competitive inhibitors, being a useful tool for preventing virulence gene expression through the downregulation of AI-2 production pathways and the disruption of signal uptake. In addition, we showed that QSIs have negative regulatory activity of genes related to bacterial biofilm formation on clinical artifacts, which confirms the therapeutic potential of QSIs in the control of infectious pathogens. Finally, we discuss resistance to QSIs, the design of next-generation QSIs, and how these molecules can be leveraged to provide a new antivirulence therapy to combat diseases caused by E. coli or Salmonella.

Antioxidants of Fruit Extracts as Antimicrobial Agents against Pathogenic Bacteria

Fruit is an essential part of the human diet and is of great interest because of its richness in phytochemicals. Various fruit extracts from citrus, berries and pomegranates have been shown to possess a broad spectrum of medicinal properties. Fruit phytochemicals are of considerable interest because of their antioxidant properties involving different mechanisms of action, which can act against different pathogenic bacteria. The antioxidant capacity of fruit phytochemicals involves different kinds of reactions, such as radical scavenging and chelation or complexation of metal ions. The interaction between fruit phytochemicals and bacteria has different repercussions: it disrupts the cell envelope, disturbs cell-cell communication and gene regulation, and suppresses metabolic and enzymatic activities. Consequently, fruit phytochemicals can directly inhibit bacterial growth or act indirectly by modulating the expression of virulence factors, both of which reduce microbial pathogenicity. The aim of this review was to report our current knowledge on various fruit extracts and their major bioactive compounds, and determine the effectiveness of organic acids, terpenes, polyphenols, and other types of phenolic compounds with antioxidant properties as a source of antimicrobial agents.

AB5 Enterotoxin-Mediated Pathogenesis: Perspectives Gleaned from Shiga Toxins

Foodborne diseases affect an estimated 600 million people worldwide annually, with the majority of these illnesses caused by Norovirus, Vibrio, Listeria, Campylobacter, Salmonella, and Escherichia coli. To elicit infections in humans, bacterial pathogens express a combination of virulence factors and toxins. AB₅ toxins are an example of such toxins that can cause various clinical manifestations, including dehydration, diarrhea, kidney damage, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Treatment of most bacterial foodborne illnesses consists of fluid replacement and antibiotics. However, antibiotics are not recommended for infections caused by Shiga toxin-producing E. coli (STEC) because of the increased risk of HUS development, although there are conflicting views and results in this regard. Lack of effective treatment strategies for STEC infections pose a public health threat during outbreaks; therefore, the debate on antibiotic use for STEC infections could be further explored, along with investigations into antibiotic alternatives. The overall goal of this review is to provide a succinct summary on the mechanisms of action and the pathogenesis of AB₅ and related toxins, as expressed by bacterial foodborne pathogens, with a primary focus on Shiga toxins (Stx). The role of Stx in human STEC disease, detection methodologies, and available treatment options are also briefly discussed.

Use of Tannin-Containing Plants as Antimicrobials Influencing the Animal Health

The antimicrobial effects of diverse tannin-containing plants, particularly condensed tannins (CTs) produced from various plants, are the subject of this study. CT components can be determined using CT-specific procedures such the HCl-Butanol Acetone assay, Thiolysis reaction, and HPLC/MS analysis. These methods indicate CT contents, including mean degree of polymerization, the procyanidins and prodelphinidins ratio (PC/PD%), the isomers of trans- and cis-, and CT concentration. Tannin-containing plants possess antibacterial action, which can be attributed to their protein linkage technique, and tannin-type variations, particularly CTs extract and their PC/PD%. The effects of CT components on the development of Gram-positive and Gram-negative bacteria have been documented for their relative PC/PD%; this is regarded to be a key predictor of tannin characteristics in terms of antimicrobials. In conclusion, tannins, more specific CT compositions, have significant impacts on in vivo trials of animal productions and utilization of metabolites and fermentation in vitro experiments. These findings need further investigations to fully understand how CT-types act on animal feeding in terms of enhanced nutritional quality of animal diets, which may have implications for human and animal health.

Synergic interactions between polyphenols and gut microbiota in mitigating inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are a group of chronic and recurring inflammatory conditions in the colon and intestine. Their etiology is not fully understood but involves the combination of gut dysbiosis, genetics, immune functions, and environmental factors including diet. Polyphenols from plant-based food synergistically interact with gut microbiota to suppress inflammation and alleviate symptoms of IBD. Polyphenols increase the diversity of gut microbiota, improve the relative abundance of beneficial bacteria, and inhibit the pathogenic species. Polyphenols not absorbed in the small intestine are catabolized in the colon by microbiota into microbial metabolites, many of which have higher anti-inflammatory activity and bioavailability than their precursors. The polyphenols and their microbial metabolites alleviate IBD through reduction of oxidative stress, inhibition of inflammatory cytokines secretion (TNF-α, IL-6, IL-8, and IL-1β), suppression of NF-κB, upregulation of Nrf2, gut barrier protection, and modulation of immune function. Future studies are needed to discover unknown microbial metabolites of polyphenols and correlate specific gut microbes with microbial metabolites and IBD mitigating activity. A better knowledge of the synergistic interactions between polyphenols and gut microbiota will help to devise more effective prevention strategies for IBD. This review focuses on the role of polyphenols, gut microbiota and their synergistic interactions on the alleviation of IBD as well as current trends and future directions of IBD management.

Dietary Modulation of Bacteriophages as an Additional Player in Inflammation and Cancer

Natural compounds such as essential oils and tea have been used successfully in naturopathy and folk medicine for hundreds of years. Current research is unveiling the molecular role of their antibacterial, anti-inflammatory, and anticancer properties. Nevertheless, the effect of these compounds on bacteriophages is still poorly understood. The application of bacteriophages against bacteria has gained a particular interest in recent years due to, e.g., the constant rise of antimicrobial resistance to antibiotics, or an increasing awareness of different types of microbiota and their potential contribution to gastrointestinal diseases, including inflammatory and malignant conditions. Thus, a better knowledge of how dietary products can affect bacteriophages and, in turn, the whole gut microbiome can help maintain healthy homeostasis, reducing the risk of developing diseases such as diverse types of gastroenteritis, inflammatory bowel disease, or even cancer. The present review summarizes the effect of dietary compounds on the physiology of bacteriophages. In a majority of works, the substance class of polyphenols showed a particular activity against bacteriophages, and the primary mechanism of action involved structural damage of the capsid, inhibiting bacteriophage activity and infectivity. Some further dietary compounds such as caffeine, salt or oregano have been shown to induce or suppress prophages, whereas others, such as the natural sweeter stevia, promoted species-specific phage responses. A better understanding of how dietary compounds could selectively, and specifically, modulate the activity of individual phages opens the possibility to reorganize the microbial network as an additional strategy to support in the combat, or in prevention, of gastrointestinal diseases, including inflammation and cancer.

Anti-biofilm Potential of Elletaria cardamomum Essential Oil Against Escherichia coli O157:H7 and Salmonella Typhimurium JSG 1748

Foodborne pathogens, microbial recurrent infections, and antibiotic resistance have driven researchers to explore natural compounds as safe alternative antimicrobials. In this study, the chemical profile, antimicrobial, and mutagenic activities of the Elletaria cardamomum essential oil were investigated. GC-MS analysis identified the major bioactive components as α-terpinyl acetate, 1,8-cineole, linalool acetate, and sabinene, at concentrations of 34.95, 25.30, 8.13, and 5.48% respectively, of the essential oil's content. Regarding antimicrobial activity, the minimum inhibitory concentration of green cardamom essential oil was 1% against Escherichia coli O157:H7 and Pseudomonas aeruginosa ATCC 14213. Green cardamom essential oil, when used at concentrations of 0.015, 0.031, 0.062, and 0.125% (v/v) prevented biofilm formation of Escherichia coli O157:H7 by 64.29, 65.98, 70.41, and 85.59%, respectively. Furthermore, these concentrations inhibited 6.13, 45.50, 49.45, and 100%, respectively, of the Salmonella Typhimurium JSG 1748 biofilm. A mutagenicity assay confirmed that green cardamom essential oil has no demonstrable mutagenic activity against the tested strains. The study's findings suggest that green cardamom derived bioactive compounds are safe organic antimicrobials, effective in controlling biofilm formation by Gram-negative pathogens. Moreover, such compounds could possibly be used in the food industry (e.g., bakery, dairy, meat, and other food products) as a safe alternative to chemical preservatives (antimicrobials) to enhance shelf life by improving the antimicrobial status while at the same time imparting a pleasant and appealing aroma for consumers.

The effect of grape seed protein hydrolysate on the properties of stirred yogurt and viability of Lactobacillus casei in it

In this study, the effect of grape seed protein hydrolysate (GPH) on the physicochemical and sensory properties of stirred yogurt was evaluated. At first, the antioxidant properties and degree of hydrolysis (DH) of GPH were determined using the microbial protease enzymes (alcalase and flavourzyme), the results showed that alcalase enzyme can produce GPH with higher DH and antioxidant properties (p < .05). Also, increasing the hydrolysis time had a positive effect on these properties (p < .05). The DH, free radical scavenging DPPH, and ferric reducing power for GPH by alcalase at 30 min was 21.51%, 88.68%, and 0.33 μmol ferrous/ g, respectively. Therefore, this treatment was used for further experiments. In the next part, the mentioned GPH was added to the stirred yogurt with three concentrations (0.5, 1.5, and 1.5%) and physicochemical properties and viability of Lactobacillus casei and sensory properties were measured during 15 days of storage. The results showed that the GPH treatment had higher pH, viscosity, and texture firmness and less acidity and syneresis compared with the control sample (p < .05). Also, in these samples, the decreasing trend of L. casei viability was slower than the control treatment during the storage period (p < .05). In most parameters, better results were observed with increasing the concentration GPH and all the treatments were acceptable in terms of sensory properties. Therefore, by producing yogurt containing GPH, a new functional food can be provided for consumers of dairy products, which in addition to the desired taste, good nutritional properties can be also achieved from its consumption.

Assessment of the anti-pathogenic effects of condensed tannin extracts using scanning electron microscopy

Two different types of condensed tannins (CTs), which were extracted and purified from tilia (Tilia L.) and black locust (Robinia pseudoacacia), were studied and tested against two kinds of bacteria, including Gram-negative and Gram-positive, avian pathogenic E. coli (APEC) and Staphylococcus epidermidis (S. epidermidis) respectively, by minimal bactericidal concentrations (MBCs) and scanning electron microscopy (SEM). Both CT extracts were significantly effective (p ≤ 0.05) at MBCs of 5-10 mg CT/ml against APEC (Gram-negative), and at 1.25-5 mg CT/ml on S. epidermidis (Gram-positive). This indicated that the CTs were more potent against the Gram-positive than the Gram-negative bacteria. Further, SEM revealed that CTs caused mainly morphological deformations of the bacterial cells and some conjoined cell growth.

Grapevine as a Rich Source of Polyphenolic Compounds

Grapes are rich in primary and secondary metabolites. Among the secondary metabolites, polyphenolic compounds are the most abundant in grape berries. Besides their important impacts on grape and wine quality, this class of compounds has beneficial effects on human health. Due to their antioxidant activity, polyphenols and phenolic acids can act as anti-inflammatory and anticancerogenic agents, and can modulate the immune system. In grape berries, polyphenols and phenolic acids can be located in the pericarp and seeds, but distribution differs considerably among these tissues. Although some classes of polyphenols and phenolic acids are under strict genetic control, the final content is highly influenced by environmental factors, such as climate, soil, vineyard, and management. This review aims to present the main classes of polyphenolic compounds and phenolic acids in different berry tissues and grape varieties and special emphasis on their beneficial effect on human health.

Value-added switchgrass extractives for reduction of Escherichia coli O157:H7 and Salmonella Typhimurium populations on Formica coupons

Recurring outbreaks linked to Escherichia coli O157:H7-contaminated lettuce and Salmonella enterica-contaminated sprouts highlight the need for improved food safety measures. The aim of this study was to determine the ability of a bio-based antimicrobial extract prepared from switchgrass, a dedicated energy crop, to reduce E. coli O157:H7 and S. Typhimurium populations on Formica coupons, a model food-contact surface. Overnight cultures of ~7 log CFU/mL E. coli O157:H7 and S. Typhimurium, air-dried on Formica coupons were treated with 0.625% NaClO, 70% ethanol, sterile water or different batches of switchgrass extractives (SE1, SE2, and SE3) for up to 30 min. E. coli O157:H7 was reduced by 4.43 log CFU/mL after 1 min by SE3, and to non-detectable levels after 1 min by all other treatments. Populations of S. Typhimurium LT2 (15-min drying) were reduced by 3.30 log CFU/mL with 70% ethanol, 5.38 log CFU/mL with SE1, and to non-detectable levels with 0.625% NaClO after 1 min, while S. Typhimurium ATCC 23564 (1-h drying) was non-detectable after 1 min by all treatments. Under soiled conditions, 10-min treatment with SE1 and 70% ethanol reduced both bacteria to non-detectable levels. Studies with concentrated switchgrass extractives combined with various other natural disinfectants or in hurdle approaches warrant further investigation.

Procyanidin-Rich Extract from Grape Seeds as a Putative Tool against Helicobacter pylori

Strains of Helicobacter pylori (H. pylori) resistant to various antibiotics have increased in recent years. In this context, the search for new therapeutic approaches is crucial. The aim of the present study was to demonstrate the antibacterial activity of a procyanidin-rich extract obtained from food-grade winery grape seeds against 14 H. pylori strains and elucidate its phenolic composition. Ten strains (71.4%) showed resistance to at least some of the tested antibiotics, while four isolates (28.6%) were susceptible to all antibiotics. Resistance to more than one class of antibiotics was observed in six strains (42.9%). The extract was able to inhibit the growth of all H. pylori strains in a range of a minimum inhibitory concentration (MIC) from 0.015 mg/mL to 0.125 mg/mL, confirming also the existence of a strain-dependent effect. The phenolic composition determined by reverse phase high pressure liquid chromatography, photodiode array, and mass spectrometry detection (RP-HPLC-PAD-MS) analysis revealed the presence of 43 individual compounds and allowed the quantification of 41 of them, including seven procyanidin tetramers, seven procyanidin pentamers, and six galloylated procyanidin dimers, trimers, and tetramers. The extract was composed mainly by catechin and procyanidin oligomers with a total amount of 5801 mg/100 g, which represent 92% of the total individual phenolic content. Among them, the most abundant were catechins (2047 mg/100 g), followed by procyanidin dimers (1550 mg/100 g), trimers (1176 mg/100 g), tetramers (436 mg/100 g), and pentamers (296 mg/100 g) that represent 35, 27, 20, 8, and 5%, respectively of the total flavanol constituents. The composition profile information may help to improve the production process of useful antibacterial extracts against H. pylori.

Treatment Strategies for Infections With Shiga Toxin-Producing Escherichia coli

Infections with Shiga toxin-producing Escherichia coli (STEC) cause outbreaks of severe diarrheal disease in children and the elderly around the world. The severe complications associated with toxin production and release range from bloody diarrhea and hemorrhagic colitis to hemolytic-uremic syndrome, kidney failure, and neurological issues. As the use of antibiotics for treatment of the infection has long been controversial due to reports that antibiotics may increase the production of Shiga toxin, the recommended therapy today is mainly supportive. In recent years, a variety of alternative treatment approaches such as monoclonal antibodies or antisera directed against Shiga toxin, toxin receptor analogs, and several vaccination strategies have been developed and evaluated in vitro and in animal models. A few strategies have progressed to the clinical trial phase. Here, we review the current understanding of and the progress made in the development of treatment options against STEC infections and discuss their potential.

Plant Phenolics and Phenolic-Enriched Extracts as Antimicrobial Agents against Food-Contaminating Microorganisms

Phenolic compounds and extracts with bioactive properties can be obtained from many kinds of plant materials. These natural substances have gained attention in the food research as possible growth inhibitors of foodborne pathogenic and spoilage bacteria. Many phenolic-enriched plant extracts and individual phenolics have promising anti-quorum sensing potential as well and can suppress the biofilm formation and toxin production of food-related pathogens. Various studies have shown that plant phenolics can substitute or support the activity of synthetic food preservatives and disinfectants, which, by the way, can provoke serious concerns in consumers. In this review, we will provide a brief insight into the bioactive properties, i.e., the antimicrobial, anti-quorum sensing, anti-biofilm and anti-enterotoxin activities, of plant phenolic extracts and compounds, with special attention to pathogen microorganisms that have food relation. Carbohydrase aided applications to improve the antimicrobial properties of phenolic extracts are also discussed.

Fruit extracts to control pathogenic Escherichia coli: A sweet solution

Escherichia coli is a major cause of diarrhea and is as well responsible for extraintestinal infections in humans and animals. Many pathotypes have been defined for this ubiquitous microorganism on the basis of the virulence attributes. For the last 70 years, antibiotics have been used to control infections caused by E. coli. However, with the resistance observed with many strains these drugs are less recommended. Plant extracts, in particular fruit, represent a source of bioactive compounds that could be beneficial in the control of infectious diseases caused by E. coli. These could have bacteriostatic or bactericidal potential or could be used as synergic agents to amplify the activity of antibiotics for which the germs present some level of resistance. Certain studies also revealed that fruit extracts could act directly on virulence characters to attenuate the pathogenic capacity of microorganisms. This review intent to expose the scant but rapidly growing information available that shows that fruit, used as crude extracts or purified molecules, should be considered to manage diverse types of infections caused by E. coli.

Antimicrobial in vitro activities of condensed tannin extracts on avian pathogenic Escherichia coli

Condensed tannins (CTs), which extracted from yew leaves, tilia flower and black locust leaves, were examined for their antimicrobial in vitro activity against avian pathogenic Escherichia coli (APEC). Past research demonstrated that CTs which contain procyanidins and prodelphinidins that could inhibit the growth of a wide range of bacteria. However, there is no information on how these affect pathogenic bacteria from chickens such as APEC. The high concentration of extracts, 10, 5, 2·5 mg ml^-1 , affected the growth curves of APEC, which gave different inhibition values for the three CT extracts. Furthermore, these CTs had significant effects (P ≤ 0·05) on APEC biofilm and motility depending on each CT concentration and composition. However, at low concentration (0·6 mg ml^-1 ), the tilia flowers, a high molar percentage of procyanidins, enhanced bacterial cell attachment and improved the swimming motility of APEC. In contrast, yew, an equal molar percentage of procyanidins/prodelphinidins, and black locust, a high molar percentage of prodelphinidins, interrupted and blocked swarming and swimming motility. The data suggested that the antimicrobial activity of the CT extracts was elicited by a positive relationship between anti-biofilm formation and anti-motility capacities. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that condensed tannins (CTs), which were a group of secondary metabolites of many plants and rich in prodelphinidins (PD), had greater antibacterial activity against avian pathogenic Escherichia coli (APEC) than CTs that were rich in procyanidins (PC). The mode of action of the CTs was to inhibit the swimming and swarming motility of APEC, and its ability to form biofilms. The significance of this finding is that the use of PD-rich CTs to control APEC should not encourage the development of antibiotic resistance by APEC because a different mechanism is used. If confirmed in vivo, this could provide the poultry industry with a valuable and novel means of controlling the antibiotic resistance.

Elucidating antimicrobial mechanism of nisin and grape seed extract against Listeria monocytogenes in broth and on shrimp through NMR-based metabolomics approach

Nisin and grape seed extract (GSE) have been widely used as food preservatives; however, the mechanism against pathogens at molecular level has not been well elucidated. This work aimed to investigate their antimicrobial effect against Listeria monocytogenes and to elucidate the mechanism by NMR-based metabolomics. Nisin exhibited enhanced in vitro antilisterial effect when combined with GSE (4.49 log CFU/mL reduction). Marked change in cell membrane permeability was observed in the combination group using confocal laser scanning microscopy; this was verified by increased leakage of protein and nucleic acid. The underlying antimicrobial mechanism was revealed by NMR coupled with multivariate analysis. Significant decreases in threonine, cysteine, ATP, NADP, adenine were observed, whereas a few of metabolites such as lactic acid and γ-aminobutyric acid (GABA) increased after nisin-GSE treatment (P < 0.05). Pathway analysis further manifested that the nisin-GSE inhibited the survival of L. monocytogenes by blocking the TCA cycle, amino acid biosynthesis and energy-producing pathway. Lastly, nisin and GSE were applied to shrimp and binary combination showed remarkably antilisterial activity (1.79 log CFU/g reduction). GABA shunt and protein degradation from shrimp compensated the unbalanced glycolysis and amino acid metabolism by providing energy and carbon source for L. monocytogenes inoculated on shrimp. Thus, they were more tolerant to nisin and GSE stresses as compared to the broth-grown culture.