Quorum quenching activity of Syzygium cumini (L.) Skeels and its anthocyanin malvidin against Klebsiella pneumoniae

Mechanism of antibacterial phytoconstituents: an updated review

The increase of multiple drug resistance bacteria significantly diminishes the effectiveness of antibiotic armory and subsequently exaggerates the level of therapeutic failure. Phytoconstituents are exceptional substitutes for resistance-modifying vehicles. The plants appear to be a deep well for the discovery of novel antibacterial compounds. This is owing to the numerous enticing characteristics of plants, they are easily accessible and inexpensive, extracts or chemicals derived from plants typically have significant levels of action against infections, and they rarely cause serious adverse effects. The enormous selection of phytochemicals offers very distinct chemical structures that may provide both novel mechanisms of antimicrobial activity and deliver us with different targets in the interior of the bacterial cell. They can directly affect bacteria or act together with the crucial events of pathogenicity, in this manner decreasing the aptitude of bacteria to create resistance. Abundant phytoconstituents demonstrate various mechanisms of action toward multi drug resistance bacteria. Overall, this comprehensive review will provide insights into the potential of phytoconstituents as alternative treatments for bacterial infections, particularly those caused by multi drug resistance strains. By examining the current state of research in this area, the review will shed light on potential future directions for the development of new antimicrobial therapies.

Thymoquinone is a natural antibiofilm and pathogenicity attenuating agent in Pseudomonas aeruginosa

Pseudomonas aeruginosa belongs to the critical pathogens that represent a global public health problem due to their high rate of resistance as listed by WHO. P. aeruginosa can result in many nosocomial infections especially in individuals with compromised immune systems. Attenuating virulence factors by interference with quorum sensing (QS) systems is a promising approach to treat P. aeruginosa-resistant infections. Thymoquinone is a natural compound isolated from Nigella sativa (black seed) essential oil. In this study, the minimum inhibitory concentration of thymoquinone was detected followed by investigating the antibiofilm and antivirulence activities of the subinhibitory concentration of thymoquinone against P. aeruginosa PAO1. The effect of thymoquinone on the expression of QS genes was assessed by quantitative real-time PCR, and the protective effect of thymoquinone against the pathogenesis of PAO1 in mice was detected by the mouse survival test. Thymoquinone significantly inhibited biofilm, pyocyanin, protease activity, and swarming motility. At the molecular level, thymoquinone markedly downregulated QS genes lasI, lasR, rhlI, and rhlR. Moreover, thymoquinone could protect mice from the pathologic effects of P. aeruginosa increasing mouse survival from 20% to 100%. In conclusion, thymoquinone is a promising natural agent that can be used as an adjunct therapeutic agent with antibiotics to attenuate the pathogenicity of P. aeruginosa.

Carbazole and Quinazolinone Derivatives from a Fluoride-Tolerant Streptomyces Strain OUCMDZ-5511

Six new 9H-carbazole derivatives (1-6) and nine previously reported compounds (7-15) were isolated from a fermented solid medium of the Thailand mangrove-derived Streptomyces strain, OUCMDZ-5511, under fluoride stress. Compounds 2-5, 12, and 15 were exclusively present in the fluoride-supplemented fermentation medium, while compounds 7-9, 13, and 14 were newly discovered natural products. The molecular structures of the compounds were identified by a spectroscopic analysis. The new compound 2 displayed antiquorum sensing activity against Chromobacterium violaceum ATCC 12472 by reducing the violacein production and inhibiting the biofilm formation in a concentration-dependent manner. The study revealed that compound 2 could be a novel potential inhibitor of quorum sensing.

Perspectives on antimicrobial properties of Paulownia tomentosa Steud. fruit products in the control of Staphylococcus aureus infections

ETHNOPHARMACOLOGICAL RELEVANCE

Paulownia tomentosa Steud. (P. tomentosa) is a medium-sized tree traditionally used in Chinese folk medicine for the treatment of infectious diseases. It is a rich source of prenylated phenolic compounds that have been extensively studied for their promising biological activities.

AIM OF THE STUDY

Due to the increasing development of antibiotic resistance, our study investigated plant-derived natural products from the fruits of P. tomentosa that could control Staphylococcus aureus infections with novel targets/modes of action and reduce antimicrobial resistance.

MATERIALS AND METHODS

The ethanolic extract was fractionated and detected by liquid chromatography. The antistaphylococcal effects of the plant formulations were studied in detail in vitro by various biological methods, including microdilution methods for minimum inhibitory concentration (MIC), the checkerboard titration technique for synergy assay, fluorescence measurements for membrane disruption experiments, autoinducer-2-mediated bioassay for quorum sensing inhibition, and counting of colony-forming units for relative adhesion. Morphology was examined by transmission electron microscopy.

RESULTS

Total ethanolic extract and chloroform fraction showed MICs of 128 and 32 μg/mL, respectively. Diplacol, diplacone, and 3'-O-methyl-5'-hydroxydiplacone inhibited S. aureus growth in the range of 8-16 μg/mL. Synergistic potential was shown in combination with mupirocin and fusidic acid. The ethanolic extract and the chloroform fraction destroyed the cell membranes by 91.61% and 79.46%, respectively, while the pure compounds were less active. The ethanolic extract and the pure compounds reduced the number of adhered cells to 47.33-10.26% compared to the untreated control. All tested plant formulations, except diplacone, inhibited quorum sensing of S. aureus. Transmission electron microscopy showed deformation of S. aureus cells.

CONCLUSIONS

The products from the fruit of P. tomentosa showed antimicrobial properties against S. aureus alone and in combination with antibiotics. By affecting intracellular targets, geranylated flavonoids proposed novel approaches in the control of staphylococcal infections.

Revealing active constituents within traditional Chinese Medicine used for treating bacterial pneumonia, with emphasis on the mechanism of baicalein against multi-drug resistant Klebsiella pneumoniae

ETHNOPHARMACOLOGICAL RELEVANCE

The emergence of antibiotic-resistant bacteria has rendered it more challenging to treat bacterial pneumonia. Traditional Chinese medicine (TCM) has superior efficacy in the treatment of pneumonia, and it has the unique advantage of antibacterial resistance against multi-drug resistant (MDR) bacteria, but the medication rule and pharmacological mechanism of its antibacterial activity are not clear.

AIM OF THE STUDY

This study aims to reveal Chinese medication patterns in treating bacterial pneumonia to select bioactive constituents in core herbs, predict their pharmacological mechanisms and further explore their antibacterial ability against clinically isolated MDR Klebsiella pneumoniae (KP) and their antibacterial mechanisms.

MATERIALS AND METHODS

The high-frequency medicinal herbs to treat lung diseases were first screened from Pharmacopoeia of the People's Republic of China (ChP.), and then bioactive compounds in core herbs and targets for compounds and disease were collected. Potential targets, signaling pathways, and drugs' core components were determined by constructing protein-protein interaction network, enrichment analysis and "component-target-pathway-disease" network were mapped by Cytoscape 3.8.2, and the potential therapeutic value of selected core components was verified by comparing the disease targets in the GEO database with the herbal component targets in the ITCM database. The clinically isolated KP were screened by drug sensitivity tests with meropenem (MEM), polymyxin E (PE), and tigecycline and biofilm-forming assay; broth microdilution, chessboard methods and biofilm morphology and permeability experiments were employed to determine the antibacterial, bactericidal and biofilm inhibition ability of selected bioactive constituents alone and in combination with antibiotics; The mechanism of bioactive components on quorum sensing (QS) genes LuxS and LuxR was predicted by molecular docking and tested by RT-PCR.

RESULTS

The 13 core Chinese medicines were obtained by mining ChP., and 615 potential targets of core herbal medicine were screened, and the PI3K-Akt signaling pathway might play crucial roles in the therapeutic process. In-vitro experiments revealed that the selected core compounds, including forsythoside B, baicalin, baicalein, and forsythin, all have antibacterial activity, in which baicalein had the strongest ability and a synergistic effect in combination with MEM or PE. Their synergy exhibited a stronger effect on biofilms of MDR KP, inhibiting biofilm formation, disrupting formed biofilms, and removing the residual structures of dead bacteria. Baicalein was predicted to have stable binding capacity to LuxS and LuxR genes by molecular docking, and RT-PCR results verified that the combination of baicalein with MEM or PE was effective in inhibiting the expression of QS genes (LuxS and LuxR) and consequently suppressing biofilm formation.

CONCLUSION

The core Chinese herbal medicine in the ChP. to treat lung diseases has a multi-component, multi-target, and multi-pathway synergy to improve bacterial pneumonia. Experimental studies have confirmed that the bioactive compound baicalein was able to combat MDR KP alone and synergistic with MEM or PE, inhibited and disrupted biofilms via regulating LuxS and LuxR genes, and further disturbed quorum sensing system to promote the therapeutic efficacy, which provides a new pathway and rationale for treating MDR KP-induced bacterial pneumonia.

Plant-Origin Components: New Players to Combat Antibiotic Resistance in Klebsiella pneumoniae

Klebsiella pneumoniae (Kpn) is an opportunistic pathogen that causes intrahospital complications such as pneumonia, liver abscesses, soft tissue infections, urinary infections, bacteraemia, and, in some cases, death. Since this bacterium has a higher frequency than other Gram-negative pathogens, it has become an important pathogen to the health sector. The adaptative genome of Kpn likely facilitates increased survival of the pathogen in diverse situations. Therefore, several studies have been focused on developing new molecules, synergistic formulations, and biomaterials that make it possible to combat and control infections with and dispersion of this pathogen. Note that the uncontrolled antibiotic administration that occurred during the pandemic led to the emergence of new multidrug-resistant strains, and scientists were challenged to overcome them. This review aims to compile the latest information on Kpn that generates intrahospital infections, specifically their pathogenicity-associated factors. Furthermore, it explains the natural-product-based treatments (extracts and essential oils) developed for Kpn infection and dispersion control.

Polyphenols and their nanoformulations as potential antibiofilm agents against multidrug-resistant pathogens

The emergence of multidrug-resistant (MDR) pathogens is a major problem in the therapeutic management of infectious diseases. Among the bacterial resistance mechanisms is the development of an enveloped protein and polysaccharide-hydrated matrix called a biofilm. Polyphenolics have demonstrated beneficial antibacterial effects. Phenolic compounds mediate their antibiofilm effects via disruption of the bacterial membrane, deprivation of substrate, protein binding, binding to adhesion complex, viral fusion blockage and interactions with eukaryotic DNA. However, these compounds have limitations of chemical instability, low bioavailability, poor water solubility and short half-lives. Nanoformulations offer a promising solution to overcome these challenges by enhancing their antibacterial potential. This review summarizes the antibiofilm role of polyphenolics, their underlying mechanisms and their potential role as resistance-modifying agents.

Physicochemical and bioactive constituents, microbial counts, and color components of spray-dried Syzygium cumini L. pulp powder stored in different packaging materials under two controlled environmental conditions

Currently, the demand for functional food items that impart health benefits has been rising. Blackberry (Syzygium cumini L.) fruit has high anthocyanin content and other functional attributes. However, this seasonal fruit is highly perishable, and a large proportion of it goes unharvested and wasted worldwide. Spray drying of the fruit pulp can impart improved shelf life, ensuring long-term availability for consumers to exploit its health benefits. The storage quality varies according to the type of packaging material and the storage environment. Therefore, in this study, the shelf life span of the spray-dried Syzygium cumini L. pulp powder (SSCPP) was investigated during 6 months of storage under three types of packaging materials (i.e., polystyrene, metalized polyester, and 4-ply laminates) in a low-temperature environmental (LTE) and at ambient environmental conditions. The physicochemical stability of bioactive principles (TPC and TAC), microbial counts, and color components were analyzed at 0, 2, 4, and 6 months of storage. There was a significant gradual loss of dispersibility and solubility with an increase in flowability, bulk density, and wettability during the entire storage period for all three packaging materials. The TSS, pH, TPC, TAC, and microbial counts decreased in the SSCPP both at ambient and LTE conditions during the study. Among all the packaging materials, the 4-ply laminate was found to be the most appropriate and safe for storage of spray-dried SCPP at LTE conditions.

Evolving biofilm inhibition and eradication in clinical settings through plant-based antibiofilm agents

BACKGROUND

After almost 100 years since evidence of biofilm mode of growth and decades of intensive investigation about their formation, regulatory pathways and mechanisms of antimicrobial tolerance, nowadays there are still no therapeutic solutions to eradicate bacterial biofilms and their biomedical related issues.

PURPOSE

This review intends to provide a comprehensive summary of the recent and most relevant published studies on plant-based products, or their isolated compounds with antibiofilm activity mechanisms of action or identified molecular targets against bacterial biofilms. The objective is to offer a new perspective of most recent data for clinical researchers aiming to prevent or eliminate biofilm-associated infections caused by bacterial pathogens.

METHODS

The search was performed considering original research articles published on PubMed, Web of Science and Scopus from 2015 to April 2023, using keywords such as "antibiofilm", "antivirulence", "phytochemicals" and "plant extracts".

RESULTS

Over 180 articles were considered for this review with a focus on the priority human pathogens listed by World Health Organization, including Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. Inhibition and detachment or dismantling of biofilms formed by these pathogens were found using plant-based extract/products or derivative compounds. Although combination of plant-based products and antibiotics were recorded and discussed, this topic is currently poorly explored and only for a reduced number of bacterial species.

CONCLUSIONS

This review clearly demonstrates that plant-based products or derivative compounds may be a promising therapeutic strategy to eliminate bacterial biofilms and their associated infections. After thoroughly reviewing the vast amount of research carried out over years, it was concluded that plant-based products are mostly able to prevent biofilm formation through inhibition of quorum sensing signals, but also to disrupt mature biofilms developed by multidrug resistant bacteria targeting the biofilm extracellular polymeric substance. Flavonoids and phenolic compounds seemed the most effective against bacterial biofilms.

A review on biofilms and the currently available antibiofilm approaches: Matrix-destabilizing hydrolases and anti-bacterial peptides as promising candidates for the food industries

Biofilms are communities of microorganisms that can be harmful and/or beneficial, depending on location and cell content. Since in most cases (such as the formation of biofilms in laboratory/medicinal equipment, water pipes, high humidity-placed structures, and the food packaging machinery) these bacterial and fungal communities are troublesome, researchers in various fields are trying to find a promising strategy to destroy or slow down their formation. In general, anti-biofilm strategies are divided into the plant-based and non-plant categories, with the latter including nanoparticles, bacteriophages, enzymes, surfactants, active peptides and free fatty acids. In most cases, using a single strategy will not be sufficient to eliminate biofilm, and consequently, two or more strategies will inevitably be used to deal with this unwanted phenomenon. According to the analysis of potential biofilm inhibition strategies, the best option for the food industry would be the use of hydrolase enzymes and peptides extracted from natural sources. This article represents a systematic review of the previous efforts made in these directions.

Phytocompound Mediated Blockage of Quorum Sensing Cascade in ESKAPE Pathogens

Increased resistance of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp. (ESKAPE) pathogens against various drugs has enhanced the urge for the development of alternate therapeutics. Quorum sensing (QS) is a density dependent cell-to-cell communication mechanism responsible for controlling pathogenicity with the regulation of gene expression. Thus, QS is considered a potential target for the development of newer anti-biofilm agents that do not depend on the utilization of antibiotics. Compounds with anti-QS effects are known as QS inhibitors (QSIs), and they can inhibit the QS mechanism that forms the major form in the development of bacterial pathogenesis. A diverse array of natural compounds provides a plethora of anti-QS effects. Over recent years, these natural compounds have gained importance as new strategies for combating the ESKAPE pathogens and inhibiting the genes involved in QS. Different pharmacognostical and pharmacological studies have been carried out so far for identification of novel drugs or for the discovery of their unique structures that may help in developing more effective anti-biofilm therapies. The main objective of this review is to discuss the various natural compounds, so far identified and their employed mechanisms in hindering the genes responsible for QS leading to bacterial pathogenesis.

Antimicrobial Effect of Phytochemicals from Edible Plants

Current strategies of combating bacterial infections are limited and involve the use of antibiotics and preservatives. Each of these agents has generally inadequate efficacy and a number of serious adverse effects. Thus, there is an urgent need for new antimicrobial drugs and food preservatives with higher efficacy and lower toxicity. Edible plants have been used in medicine since ancient times and are well known for their successful antimicrobial activity. Often photosensitizers are present in many edible plants; they could be a promising source for a new generation of drugs and food preservatives. The use of photodynamic therapy allows enhancement of antimicrobial properties in plant photosensitizers. The purpose of this review is to present the verified data on the antimicrobial activities of photodynamic phytochemicals in edible species of the world’s flora, including the various mechanisms of their actions.

Design of novel hybrid secondary metabolite targets to diguanylate cyclase of Acinetobacter baumannii

Biofilm formation in bacteria is a resistance determinant and is positively regulated by cyclic diguanylate signaling. This signaling is a near universal signaling, and c-di-GMP produced by diguanylate cyclase (DGC) in this signaling is involved in different bacterial behaviors. The present study aims to find a plant-based novel hybrid therapeutic agent that can target the DGC of Acinetobacter baumannii. In this study, we have tried to design a hybrid molecule from the anti-biofilm plant secondary metabolites and screened its binding with the DGC of A. baumannii. The modeled and validated DGC was used to identify the active site and docking grid. Designed hybrid compounds were analysed for their interaction with the active site residues of DGC of A. baumannii. Further, the binding free energies of the docked complexes obtained from the Generalized Born model and Solvent Accessibility (MMGBSA) were analysed. The results indicated that VR-QEg-180 has a predicted high binding affinity with enzyme DGC as compared to other hybrids, parent secondary metabolites and positive control. Molecular dynamics simulation (MDS) analysis confirmed the interaction of VR-QEg-180 with DGC of the A. baumannii. The designed lead has favorable ADMET properties, has no human off-targets and has no predicted cytotoxicity in cell lines. Therefore, the designed hybrid molecule (VR-QEg-180) targeting the DGC of A. baumannii may play a very significant role in controlling this pathogen.

Mutual effects of free and nanoencapsulated phenolic compounds on human microbiota

Phenolic compounds (PC) have many health benefits such as antioxidant, anticarcinogenic, neuroprotective, and anti-inflammatory activities. All of these activities depend on their chemical structures and their interaction with biological targets in the body. PC occur naturally in polymerized form, linked to glycosides and requires metabolic transformation from their ingestion to their absorption. The gut microbiota can transform PC into more easily absorbed metabolites. The PC, in turn, have prebiotic and antimicrobial actions on the microbiota. Despite this, their low oral bioavailability still compromises biological performance. Therefore, the use of nanocarriers has been demonstrated to be a useful strategy to improve PC absorption and, consequently, their health effects. Nanotechnology is an excellent alternative able to overcome the limits of oral bioavailability of PC, since it offers protection from degradation during their passage through the gastrointestinal tract. Moreover, nanotechnology is also capable of promoting controlled PC release and modulating the interaction between PC and the microbiota. However, little is known about the impact of the nanotechnology on PC effects on the gut microbiota. This review highlights the use of nanotechnology for PC delivery on gut microbiota, focusing on the ability of such formulations to enhance oral bioavailability by applying nanocarriers (polymeric nanoparticles, nanostructured lipid carriers, solid lipid nanoparticles). In addition, the effects of free and nanocarried PC or nanocarriers per se on gut microbiota are also described.

Physicochemical Composition and Characterization of Bioactive Compounds of Mulberry (Morus indica L.) Fruit During Ontogeny

Mulberry fruit is well recognized as one of the richest sources of bioactive compounds. We investigated the physicochemical composition and characterized the bioactive compounds during different ripening stages of mulberry (Morus indica) fruit and evaluated their anti-quorum sensing activity on Chromobacterium violaceum. The proximate components such as carbohydrates, proteins and lipids were found to be high in the ripe fruit compared to unripe and mid-ripe fruit. The ripe fruit contained higher content of total phenolics and flavonoids (336.05 and 282.55 mg/100 g fresh weight (FW), respectively). Epicatechin and resveratrol were the major polyphenols detected in the fruit with the range 5.13-19.46 and 4.07-14.45 mg/100 g FW, respectively. Chlorogenic acid and myricetin were predominant in the unripe and mid-ripe fruit (7.14 and 1.84 mg/100 g FW, respectively). The fruit was found to be an excellent source of anti-diabetic compound 1-deoxynojirimycin. The highest content of 1-deoxynojirimycin was present in the mid-ripe fruit, with a content of 2.91 mg/100 g FW. Furthermore, fruit extracts exhibited anti-quorum sensing activity against Chromobacterium violaceum by effectively inhibiting violacein production. Ripe fruit extracts showed the highest activity of 76.30% at 1 mg/mL and thus, could be used as a potent anti-quorum sensing agent. The results could be promising in the selection of appropriate developmental stages for M. indica fruit commercial exploitation in the food formulations rich in potential health components.

Strategies to combat antimicrobial resistance in Indian scenario

Antimicrobial resistance (AMR) is one of the major public health crisis recognised globally. Microbial infections cause significant productivity losses in animals and humans. In livestock, these microbial infections reduce the growth rates and fertility, diminish production of meat and milk, and occasionally lead to mortality, and are therefore, a major concern for animal welfare. In the dearth of alternative prophylactic measures, antibiotics remain the principal tool for their management. Once an antibiotic is used rampantly, resistance against it is inevidently seen in the microbe population and the hunt for a new drug grows. Discovery and development of a new antimicrobial drug is a time taking and expensive procedure with limited assurance of success. As a result, the past few decades have witnessed only a very few new classes of antibiotics. If the AMR can be restricted or reverted, the success rate of antimicrobial therapy can be boosted and many public health issues be avoided. All these ask for a comprehensive plan to prevent or reduce the antimicrobial resistance and economic losses to the animal husbandry sector. The present review provides an overview of AMR in India, mechanism of its occurrence and the possible roadmap to combat the emerging threat of AMR in Indian scenario.

Pyranoanthocyanins Interfering with the Quorum Sensing of Pseudomonas aeruginosa and Staphylococcus aureus

Bacterial quorum sensing (QS) is a cell-cell communication system that regulates several bacterial mechanisms, including the production of virulence factors and biofilm formation. Thus, targeting microbial QS is seen as a plausible alternative strategy to antibiotics, with potentiality to combat multidrug-resistant pathogens. Many phytochemicals with QS interference activity are currently being explored. Herein, an extract and a compound of bioinspired origin were tested for their ability to inhibit biofilm formation and interfere with the expression of QS-related genes in Pseudomonas aeruginosa and Staphylococcus aureus. The extract, a carboxypyranoanthocyanins red wine extract (carboxypyrano-ant extract), and the pure compound, carboxypyranocyanidin-3-O-glucoside (carboxypyCy-3-glc), did not cause a visible effect on the biofilm formation of the P. aeruginosa biofilms; however, both significantly affected the formation of biofilms by the S. aureus strains, as attested by the crystal violet assay and fluorescence microscopy. Both the extract and the pure compound significantly interfered with the expression of several QS-related genes in the P. aeruginosa and S. aureus biofilms, as per reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results. Indeed, it was possible to conclude that these molecules interfere with QS at distinct stages and in a strain-specific manner. An extract with anti-QS properties could be advantageous because it is easily obtained and could have broad, antimicrobial therapeutic applications if included in topical formulations.

Anthocyanins: Promising Natural Products with Diverse Pharmacological Activities

Anthocyanins are natural products that give color to plants. As natural plant pigments, anthocyanins also have a series of health-promoting benefits. Many researchers have proved that anthocyanins have therapeutic effects on diseases, such as circulatory, nervous, endocrine, digestive, sensory, urinary and immune systems. Additionally, a large number of studies have reported that anthocyanins have an anticancer effect through a wide range of anti-inflammatory and antioxidant effects. The anti-disease impact and mechanism of anthocyanins are diverse, so they have high research value. This review summarizes the research progress of anthocyanins on the pharmacological agents of different diseases to provide references for subsequent research.

Micro and nanoemulsions of Carissa spinarum fruit polyphenols, enhances anthocyanin stability and anti-quorum sensing activity: Comparison of degradation kinetics

The low stability of anthocyanins is a constraint in the food industry. The present work has been carried out to overcome this low stability by encapsulating fruit concentrate of underutilized plant Carissa spinarum (CS) with polyphenols in microemulsions (CSME) and nanoemulsions (CSNE). Increasing the amount of CS reduced the particle size from 1154 to 70-300 nm whereas addition of Tween 80 reduced it optimally to 5-25 nm. Degradation of anthocyanins in control and ME/NE proceeded with zero- and first-order reaction rates, respectively, at 28 °C (half-life 6, 25 and 40 days, respectively). The degradation kinetics of phenolics-flavonoids were also studied. CSNE exhibited higher anti-quorum sensing (QS) activity than CSME against Chromobacterium violaceum (73.7%); it inhibited biofilm formation by 70.1 and 64.4% in Pseudomonas aeruginosa, and Yersinia enterocolitica, respectively. This is the first report of using the more stable ME/NE to study anti-QS activity, an alternative to conventional antibiotics.

Phenolic extract of Eugenia uniflora L. and furanone reduce biofilm formation by Serratia liquefaciens and increase its susceptibility to antimicrobials

Serratia liquefaciens is a spoilage microorganism of relevance in the dairy industry because it is psychrotrophic, able to form biofilm, and produces thermoresistant proteases and lipases. Phenolic compounds and furanones have been studied as inhibitors of biofilm formation. In this study, the potential of the pulp phenolic extract of Eugenia uniflora L. orange fruits, also called pitanga, and furanone C30 on the inhibition of biofilm formation by S. liquefaciens L53 and the susceptibility to different antimicrobials were evaluated. The pulp phenolic extract of pitanga had a high total phenolic content, being mainly composed of glycosylated quercetins and ellagitannins. Sub-inhibitory concentrations of this extract and furanone reduced biofilm formation by S. liquefaciens on polystyrene and the amount of polysaccharides, proteins and extracellular DNA in the biofilms. These biofilms were also more susceptible to kanamycin. The combinations of furanone with phenolic extract of pitanga or kanamycin showed a synergistic effect with total growth inhibition of S. liquefaciens.

Cranberry extract-based formulations for preventing bacterial biofilms

Generating formulations for the delivery of a mixture of natural compounds extracted from natural sources is a challenge because of unknown active and inactive ingredients and possible interactions between them. As one example, natural cranberry extracts have been proposed for the prevention of biofilm formation on dental pellicle or teeth. However, such extracts may contain phenolic acids, flavonol glycosides along with other constituents like coumaroyl iridoid glycosides, flavonoids, alpha-linolenic acid, n-6 (or n-3) fatty acids, and crude fiber. Due to the presence of a variety of compounds, determining which molecules (and how many molecules) are essential for preventing biofilm growth is nontrivial to ascertain. Therefore, a formulation that could contain natural, unrefined, cranberry extract (with all its constituent compounds) at high loading would be ideal. Accordingly, we have generated several candidate formulations including poly(lactic-co-glycolic) acid (PLGA)-based microencapsulation of cranberry extract (CE15) as well as formulations including stearic acid along with polyvinylpyrrolidone (PVP) or Ethyl lauroyl arginate (LAE) complexed with cranberry extracts (CE15). We found that stearic acid in combination with PVP or LAE as excipients led to higher loading of the active and inactive compounds in CE15 as compared with a PLGA microencapsulation and also sustained release of CE15 in a tunable manner. Using this method, we have been able to generate two successful formulations (one preventative based, one treatment based) that effectively inhibit biofilm growth when incubated with saliva. In addition to cranberry extract, this technique could also be a promising candidate for other natural extracts to form controlled release systems.Graphical abstract.

Functional Diversity of Quorum Sensing Receptors in Pathogenic Bacteria: Interspecies, Intraspecies and Interkingdom Level

The formation of biofilm by pathogenic bacteria is considered as one of the most powerful mechanisms/modes of resistance against the action of several antibiotics. Biofilm is formed as a structural adherent over the surfaces of host, food and equipments etc. and is further functionally coordinated by certain chemicals produced itself. These chemicals are known as quorum sensing (QS) signaling molecules and are involved in the cross talk at interspecies, intraspecies and interkingdom levels thus resulting in the production of virulence factors leading to pathogenesis. Bacteria possess receptors to sense these chemicals, which interact with the incoming QS molecules. It is followed by the secretion of virulence molecules, regulation of bioluminescence, biofilm formation, antibiotic resistance development and motility behavioral responses. In the natural environment, different bacterial species (Gram-positive and Gram-negative) produce QS signaling molecules that are structurally and functionally different. Recent and past research shows that various antagonistic molecules (naturally and chemically synthesized) are characterized to inhibit the formation of biofilm and attenuation of bacterial virulence by blocking the QS receptors. This review article describes about the diverse QS receptors at their structural, functional and production levels. Thus, by blocking these receptors with inhibitory molecules can be a potential therapeutic approach to control pathogenesis. Furthermore, these receptors can also be used as a structural platform to screen the most potent inhibitors with the help of bioinformatics approaches.

Synergistic effects of pomegranate and rosemary extracts in combination with antibiotics against antibiotic resistance and biofilm formation of Pseudomonas aeruginosa

The combination of plant extract and antibiotic represents a template for developing of antibiofilm drugs. This study investigated the synergistic effects of pomegranate/rosemary/antibiotic combinations against antibiotic resistance and biofilm formation of Pseudomonas aeruginosa. The results showed that 17 (85%) of total P. aeruginosa isolates were biofilm producers; however, 5 (25%) isolates were demonstrated as a strong biofilm producer. The highest MIC level (1024 μg/ml) of tested antibiotics against strong biofilm producer isolates was observed with piperacillin, however the MIC ranges of ceftazidime, gentamycin, imipenem, and levofloxacin against these isolates were reached to (256-1024 μg/ml), (32-1024 μg/ml), (8-1024 μg/ml), and (8-512 μg/ml), respectively. PS-1 was the representative isolate for strong biofilm formation and high antibiotic resistance. 16S rRNA gene analysis suggested that PS-1 (accession No. MN619678) was identified as a strain of P. aeruginosa POA1. Pomegranate and rosemary extracts were the most effective extracts in biofilm inhibition, which significantly inhibited 91.93 and 90.83% of PS-1 biofilm, respectively. Notably, the synergism between both plant extracts and antibiotics has significantly reduced the MICs of used antibiotics at the level lower than the susceptibility breakpoints. Pomegranate/rosemary/antibiotic combinations achieved the highest biofilm eradication, which ranging from 90.0 to 99.6%, followed by the eradication ranges of pomegranate/rosemary combination, rosemary, and pomegranate extracts, which reached to (76.5-85.4%), (53.1-73.7%), and (41.2-71.5%), respectively. The findings suggest that pomegranate/rosemary/antibiotic combinations may be an effective therapeutic agent for antibiotic resistance and biofilm formation of P. aeruginosa.

The Search for Natural Inhibitors of Biofilm Formation and the Activity of the Autoinductor C6-AHL in Klebsiella pneumoniae ATCC 13884

Human nosocomial infections are common around the world. One of the main causes is the bacteria Klebsiella pneumoniae, which shows high rates of resistance to antibiotics. Thus, drugs with novel mechanisms of action are needed. In this work, we report the effects of various natural substances on the formation of biofilm in Klebsiella pneumoniae, as well as its stability. The effect of the molecules on the growth of K. pneumoniae was initially determined by measuring the optical density. The modification of the biofilm, the changes relating to its resistance, the effects on the bacterial adhesion to the urethral catheter and its antagonist role the hexanoyl-homoserinelactone were assessed by crystal violet, as well as by microscopy. The best effects were obtained with 3-methyl-2(5H)-furanone and 2´-hydroxycinnamic acid, which inhibited the formation of biofilm by 67.38% and 65.06%, respectively. Additionally, the remaining biofilm formed was more susceptible to gentamicin. Through microscopy examination, there were evident changes in the biofilm and adherence on the polyvinyl chloride (PVC) urethral catheter. Besides, 3-methyl-2(5H)-furanone inhibited the biofilm-forming effect of the autoinducer hexanoyl-homoserinelactone. Thus, these molecules could be developed as supplemental of antibiotics.

Quorum quenching: role of nanoparticles as signal jammers in Gram-negative bacteria

Quorum sensing (QS) is a cell density dependent regulatory process that uses signaling molecules to manage the expression of virulence genes and biofilm formation. The study of QS inhibitors has emerged as one of the most fascinating areas of research to discover novel antimicrobial agents. Compounds that block QS have become candidates as unusual antimicrobial agents, as they are leading players in the regulation of virulence of drug-resistant pathogens. Metal and metal oxide nanoparticles offer novel alternatives to combat antibiotic resistance in Gram-negative bacteria aiming their capacity as QS inhibitors. This review provides an insight into the quorum quenching potential of metal and metal oxide nanoparticles by targeting QS regulated virulence of Gram-negative bacteria.

Inhibition of Staphylococcus aureus and Pseudomonas aeruginosa Biofilm and Virulence by Active Fraction of Syzygium cumini (L.) Skeels Leaf Extract: In-Vitro and In Silico Studies

Syzygium cumini L. Skeels (Myretacae family) is a native plant of the Indian subcontinent which has wide socio-economical importance and is well known for its ant diabetic activity. The present study aimed to investigate the antibiofilm activity of purified fraction (EA) from S. cumini leaf extract against P. aeruginosa and S. aureus. The EA did not show any effect on growth of P. aeruginosa and S. aureus at the concentration of 900 µg/ml. At this concentration EA showed biofilm inhibition up to 86 ± 1.19% (***P < 0.0001) and 86.40 ± 1.19% (***P < 0.0001) in P. aeruginosa and S. aureus respectively. SEM examination also confirmed the reduction in biofilm formation. Further EA also disrupted some virulence phenotypes in P. aeruginosa and S. aureus. Bioactive compounds detected by GC-MS showed their possible molecular interaction with RhlG/NADP active-site complex (PDB ID: 2B4Q), LasR-TP4 complex (PDB ID: 3JPU) and Pseudaminidase (PDB ID: 2W38) from P. aeruginosa. The in vitro biofilm inhibition, virulence factor inhibition and the mode of interaction of bioactive components in Syzygium cumini with QS proteins of bacteria reported in this study might be an affordable and effective alternative method of controlling quorum sensing/biofilm-associated infections.

Synergistic Effect of Quinic Acid Derived From Syzygium cumini and Undecanoic Acid Against Candida spp. Biofilm and Virulence

In recent decades, fungal infections have incredibly increased with Candida genus as the major cause of morbidity and mortality in hospitalized and immunocompromised patients. Most of the Candida species are proficient in biofilm formation on implanted medical devices as well as human tissues. Biofilm related Candida infections are very difficult to treat using common antifungal agents owing to their increased drug resistance. To address these issues, the present study investigated the antibiofilm and antivirulent properties of Syzygium cumini derived quinic acid in combination with known antifungal compound undecanoic acid. Initially, antibiofilm potential of S. cumini leaf extract was assessed and the active principles were identified through gas chromatography and mass spectrometry analysis. Among the compounds identified, quinic acid was one of the major compounds. The interaction between quinic acid and undecanoic acid was found to be synergistic in the Fractional inhibitory concentration index (≤0.5). Results of in vitro assays and gene expression analysis suggested that the synergistic combinations of quinic acid and undecanoic acid significantly inhibited virulence traits of Candida spp. such as the biofilm formation, yeast-to-hyphal transition, extracellular polymeric substances production, filamentation, secreted hydrolases production and ergosterol biosynthesis. In addition, result of in vivo studies using Caenorhabditis elegans demonstrated the non-toxic nature of QA-UDA combination and antivirulence effect against Candida spp. For the first time, synergistic antivirulence ability of quinic acid and undecanoic acid was explored against Candida spp. Thus, results obtained from the present study suggest that combination of phytochemicals might be used an alternate therapeutic strategy for the prevention and treatment of biofilm associated Candida infection.

Exploring the anti-quorum sensing activity of a d-limonene nanoemulsion for Escherichia coli O157:H7

In this study, a d-limonene nanoemulsion was developed by using a spontaneous emulsification method and its potential to inhibit the quorum sensing (QS)-regulated properties of Escherichia coli O157:H7 (E. coli) were revealed. The results in this study showed that d-limonene nanoemulsion inhibited E. coli biofilm formation through the suppression of curli and extracellular polymeric substance (EPS) production without inhibiting cell growth, and decreased swimming and swarming ability. Further analyses showed that d-limonene nanoemulsion interfered with auto-inducer 2 (AI-2) communication and repressed the expression of curli related genes and AI-2 importer genes in E. coli. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1979-1986, 2018.

Anti-Quorum Sensing Natural Compounds

Increasing extent of pathogenic resistance to drugs has encouraged the seeking for new anti-virulence drugs. Many pharmacological and pharmacognostical researches are performed to identify new drugs or discover new structures for the development of novel therapeutic agents in the antibiotic treatments. Although many phytochemicals show prominent antimicrobial activity, their power lies in their anti-virulence properties. Quorum sensing (QS) is a bacterial intercellular communication mechanism, which depends on bacterial cell population density and controls the pathogenesis of many organisms by regulating gene expression, including virulence determinants. QS has become an attractive target for the development of novel anti-infective agents that do not rely on the use of antibiotics. Anti-QS compounds are known to have the ability to prohibit bacterial pathogenicity. Medicinal plants offer an attractive repertoire of phytochemicals with novel microbial disease-controlling potential, due to the spectrum of secondary metabolites present in extracts, which include phenolics, quinones, flavonoids, alkaloids, terpenoids, and polyacetylenes. They have recently received considerable attention as a new source of safe and effective QS inhibitory substances. The objective of this review is to give a brief account of the research reports on the plants and natural compounds with anti-QS potential.

Metabolite profiling of red and blue potatoes revealed cultivar and tissue specific patterns for anthocyanins and other polyphenols

Metabolite profiling of tuber flesh and peel for selected colored potato varieties revealed cultivar and tissue specific profiles of anthocyanins and other polyphenols with variations in composition and concentration. Starchy tubers of Solanum tuberosum are a staple crop and food in many countries. Among cultivated potato varieties a huge biodiversity exists, including an increasing number of red and purple colored cultivars. This coloration relates to the accumulation of anthocyanins and is supposed to offer nutritional benefits possibly associated with the antioxidative capacity of anthocyanins. However, the anthocyanin composition and its relation to the overall polyphenol constitution in colored potato tubers have not been investigated closely. This study focuses on the phytochemical characterization of the phenolic composition of a variety of colored potato tubers, both for peel and flesh tissues. First, liquid chromatography (LC) separation coupled to UV and mass spectrometry (MS) detection of polyphenolic compounds of potato tubers from 57 cultivars was used to assign groups of potato cultivars differing in their anthocyanin and polyphenol profiles. Tissues from 19 selected cultivars were then analyzed by LC separation coupled to multiple reaction monitoring (MRM) to detect quantitative differences in anthocyanin and polyphenol composition. The measured intensities of 21 anthocyanins present in the analyzed potato cultivars and tissues could be correlated with the specific tuber coloration. Besides secondary metabolites well-known for potato tubers, the metabolic profiling led to the detection of two anthocyanins not described for potato tuber previously, which we tentatively annotated as pelargonidin feruloyl-xylosyl-glucosyl-galactoside and cyanidin 3-p-coumaroylrutinoside-5-glucoside. We detected significant correlations between some of the measured metabolites, as for example the negative correlation between the main anthocyanins of red and blue potato cultivars. Mainly hydroxylation and methylation patterns of the B-ring of dihydroflavonols, leading to the formation of specific anthocyanidin backbones, can be assigned to a distinct coloring of the potato cultivars and tuber tissues. However, basically the same glycosylation and acylation reactions occur regardless of the main anthocyanidin precursor present in the respective red and blue/purple tissue. Thus, the different anthocyanin profiles in red and blue potato cultivars likely relate to superior regulation of the expression and activities of hydroxylases and methyltransferases rather than to differences for downstream glycosyl- and acyltransferases. In this regard, the characterized potato cultivars represent a valuable resource for the molecular analysis of the genetic background and the regulation of anthocyanin side chain modification.

Phytochemicals for human disease: An update on plant-derived compounds antibacterial activity

In recent years, many studies have shown that phytochemicals exert their antibacterial activity through different mechanisms of action, such as damage to the bacterial membrane and suppression of virulence factors, including inhibition of the activity of enzymes and toxins, and bacterial biofilm formation. In this review, we summarise data from the available literature regarding the antibacterial effects of the main phytochemicals belonging to different chemical classes, alkaloids, sulfur-containing phytochemicals, terpenoids, and polyphenols. Some phytochemicals, besides having direct antimicrobial activity, showed an in vitro synergistic effect when tested in combination with conventional antibiotics, modifying antibiotic resistance. Review of the literature showed that phytochemicals represent a possible source of effective, cheap and safe antimicrobial agents, though much work must still be carried out, especially in in vivo conditions to ensure the selection of effective antimicrobial substances with low side and adverse effects.

Antibiofilm Activity of Plant Polyphenols

In the history of human medicine, antibiotics represent epochal examples of medical progress. However, with an approaching antibiotic crisis due to the emergence and extensive spread of antimicrobial resistance among bacterial agents, as well as to increasing number of patients with chronic and recalcitrant bacterial biofilm-associated infections, the naturally occurring molecules may become new sources of antibacterial and antibiofilm drugs for clinical usage. Polyphenols represent a class of plant natural products which are important in plant defense against microbial pathogens. The main focus of the review is on the antibiofilm activities of phenolic compounds against bacteria which play an essential role in medical device biofilm-associated infections. The other, not negligible part of the review is devoted to polyphenols’ activity against bacterial agents that cause dental caries and periodontal disease.

Plant Natural Products Targeting Bacterial Virulence Factors

Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.

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

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

Regulation of acylated homoserine lactones (AHLs) in beef by spice marination

Quorum sensing (QS) is a signaling mechanism used by bacteria to communicate each other through the release of auto-inducing signaling molecules. Despite the fact that bacteria regulate its phenotypes by QS mechanism, their potential role in meat spoilage is not yet elucidated. In the current study, beef samples were analyzed for its microbial association and for the presence of N-acyl-homoserine-lactone (AHLs) throughout the storage experiments. Isolates were screened for AHLs production and selected spices were screened for their quorum sensing inhibitory (QSI) activity. In addition, effect of spices on AHLs production of Y. enterocolitica was quantified through high performance thin layer chromatography (HP-TLC). Outcome showed that microbial association of beef mainly consists of lactic acid bacteria (LAB) and Enterobacteriaceae. Samples stored at both aerobic and modified atmospheric packaging (MAP) exhibited higher counts whereas; marinated samples stored at MAP exhibited the lowest. It was found that out of 35 isolates Y. enterocolitica induced reporter strain CV026 and its cell-free supernatant contained 26.36 nM/100 ml of AHLs when compared to standard. Among the tested spices, C. cyminum exhibited pronounced results by significantly reducing the AHLs concentration up to 47.75 %. Findings revealed the presence of quorum molecules (AHLs) in beef meat throughout the spoilage process and spices can acts as quorum quenchers to influence the spoilage rate by reducing AHLs production.

Effect of Blueberry Anthocyanins Malvidin and Glycosides on the Antioxidant Properties in Endothelial Cells

The objective of this research was to survey the antioxidant functional role of the main anthocyanins of blueberries in endothelial cells. Changes on the reactive oxygen species (ROS), xanthine oxidase-1 (XO-1), superoxide dismutase (SOD), and heme oxygenase-1 (HO-1) in cells of malvidin and the two glycosides were investigated. The results showed that these anthocyanins decreased the levels of ROS and XO-1 but increased the levels of SOD and HO-1. Glycosides improved the antioxidant capacity of malvidin to a great extent. The changes in the antioxidant properties of malvidin-3-glucoside were more pronounced than malvidin-3-galactoside. Variation in levels of malvidin-3-glucoside and malvidin-3-galactoside had a significant impact on antioxidant properties to different extents. It indicates that blueberries are a good resource of anthocyanins, which can protect cells from oxidative deterioration and use blueberry as a potential functional food to prevent diseases related to oxidative stress.

Cyanidin inhibits quorum signalling pathway of a food borne opportunistic pathogen

Quorum sensing (QS) is the process of population dependent cell to cell communication used by bacteria to regulate their phenotypic characteristics. Key virulence factors that determine the bacterial pathogenicity and food spoilage were found to be regulated by QS mechanism. Hence, disrupting the QS signaling pathway could be an attractive strategy to manage food borne pathogens. In the current study, QS inhibitory activity of a naturally occurring anthocyanin-cyanidin and its anti-biofilm property were assessed against an opportunistic pathogen Klebsiella pneumoniae, using a bio-sensor strain. Further, QS inhibitory property of a naturally occurring anthocyanin cyanidin was further confirmed using in-silico techniques like molecular docking and molecular dynamics simulation studies. Cyanidin at sub-lethal dose significantly inhibited QS-dependent phenotypes like violacein production (73.96 %), biofilm formation (72.43 %), and exopolysaccharide production (68.65) in a concentration-dependent manner. Cyanidin enhanced the sensitivity of test pathogen to conventional antibiotics in a synergistic manner. Molecular docking analysis revealed that cyanidin binds more rigidly with LasR receptor protein than the signaling compound with a docking score of -9.13 Kcal/mol. Molecular dynamics simulation predicted that QS inhibitory activity occurs through the conformational changes between the receptor and cyanidin complex. Our results indicate that cyanidin, can be a potential QS based antibiofilm and antibacterial agent for food borne pathogens.

Petunidin as a competitive inhibitor of acylated homoserine lactones in Klebsiella pneumoniae

Most of the bacterial species communicate with each other through a mechanism called Quorum Sensing (QS) to regulate their phenotypic characteristics.

Quercetin Influences Quorum Sensing in Food Borne Bacteria: In-Vitro and In-Silico Evidence

Quorum sensing (QS) plays a vital role in regulating the virulence factor of many food borne pathogens, which causes severe public health risk. Therefore, interrupting the QS signaling pathway may be an attractive strategy to combat microbial infections. In the current study QS inhibitory activity of quercetin and its anti-biofilm property was assessed against food-borne pathogens using a bio-sensor strain. In addition in-silico techniques like molecular docking and molecular dynamics simulation studies were applied to screen the quercetin's potentiality as QS inhibitor. Quercetin (80 μg/ml) showed the significant reduction in QS-dependent phenotypes like violacein production, biofilm formation, exopolysaccharide (EPS) production, motility and alginate production in a concentration-dependent manner. Synergistic activity of conventional antibiotics with quercetin enhanced the susceptibility of all tested pathogens. Furthermore, Molecular docking analysis revealed that quercetin binds more rigidly with LasR receptor protein than the signaling compound with docking score of -9.17 Kcal/mol. Molecular dynamics simulation predicted that QS inhibitory activity of quercetin occurs through the conformational changes between the receptor and quercetin complex. Above findings suggest that quercetin can act as a competitive inhibitor for signaling compound towards LasR receptor pathway and can serve as a novel QS-based antibacterial/anti-biofilm drug to manage food-borne pathogens.