Cranberry-derived proanthocyanidins impair virulence and inhibit quorum sensing of Pseudomonas aeruginosa

Trans-cinnamaldehyde nanoemulsion reduces Salmonella Enteritidis biofilm on steel and plastic surfaces and downregulates expression of biofilm associated genes

Salmonella Enteritidis is a major poultry-associated foodborne pathogen that can form sanitizer-tolerant biofilms on various surfaces. The biofilm-forming capability of S. Enteritidis facilitates its survival on farm and food processing equipment. Conventional sanitization methods are not completely effective in killing S. Enteritidis biofilms. This study investigated the efficacy of a Generally Recognized as Safe phytochemical Trans-cinnamaldehyde (TC), and in its nanoemulsion form (TCNE), for inhibiting S. Enteritidis biofilm formation and inactivating mature biofilms developed on polystyrene and stainless-steel surfaces. Moreover, the effect of TC on Salmonella genes critical for biofilm formation was studied. TCNE was prepared using a high energy sonication method with Tween 80. For biofilm inhibition assay, S. Enteritidis was allowed to form biofilms either in the presence or absence of sub-inhibitory concentration (SIC; 0.01 %) of TCNE at 25°C and the biofilm formed was quantified at 24-h intervals for 48 h. For the inactivation assay, S. Enteritidis biofilms developed at 25°C for 48 h were exposed to TCNE (0.5, 1 %) for 1, 5, and 15 min, and surviving S. Enteritidis in the biofilm were enumerated. SIC of TCNE inhibited S. Enteritidis biofilm by 45 % on polystyrene and 75 % on steel surface after 48 h at 25°C compared to control (P < 0.05). All TCNE treatments rapidly inactivated S. Enteritidis mature biofilm on polystyrene and steel surfaces (P < 0.05). The lower concentration of TCNE (0.5 %) reduced S. Enteritidis counts by 1.5 log CFU/ml as early as 1 min of exposure on both polystyrene and stainless-steel surfaces. After 15 min of exposure, TCNE at concentration of 0.5 or 1 % reduced S. Enteritidis count significantly by 4.5 log CFU or 6 log CFU/ml on polystyrene or stainless-steel surfaces. TC downregulated the expression of S. Enteritidis genes (hilA, hilC, flhD, csgA, csgD, sdiA) responsible for biofilm formation (P < 0.05). Results suggest that TCNE has potential as a natural disinfectant for controlling S. Enteritidis biofilms on common farm and food processing surfaces, such as plastic and steel.

Probiotics and Plant-Based Foods as Preventive Agents of Urinary Tract Infection: A Narrative Review of Possible Mechanisms Related to Health

Urinary tract infections (UTIs) are a prevalent global health issue, often requiring antibiotic treatment, which contributes to antimicrobial resistance. This narrative review explores the potential of probiotics and plant-based foods as alternative or complementary preventive strategies against UTIs. Fermented foods, such as yogurt, kefir, and kombucha, contain probiotic strains that can modulate the gut and urogenital microbiota, enhancing resistance to uropathogens. Likewise, plant-based foods, including cranberry, garlic, bearberry, juniper, and nettle, possess bioactive compounds with antimicrobial, anti-inflammatory, and diuretic properties. Laboratory and clinical studies suggest that these natural interventions may reduce the incidence of UTIs by inhibiting pathogen adhesion, modulating immune responses, and promoting urinary tract health. However, despite promising findings, inconsistencies in study methodologies, dosage standardization, and long-term efficacy warrant further investigation. Future research should focus on optimizing probiotic formulations, standardizing plant-based supplement dosages, and assessing potential food-drug interactions to establish evidence-based guidelines for UTI prevention.

Cranberry: A Promising Natural Product for Animal Health and Performance

Cranberries are a distinctive source of bioactive compounds, containing polyphenols such as flavonoids, anthocyanins, phenolic acids, and triterpenoids. Cranberries are often associated with potential health benefits for the urinary tract and digestive system due to their high antioxidant, anti-inflammatory, antimicrobial, and immunomodulatory properties. Cranberry induces the production of antioxidant enzymes, suppresses lipid peroxidation, reduces inflammatory cytokines, modulates immune cells, maintains gut microbiota, and inhibits bacterial adhesion and growth. Cranberry polyphenols also have metal-binding motifs that bind with metals, particularly zinc and iron. The combination of cranberry polyphenols and metals displays increased biological activity. In this review, an attempt is made to describe the physiological properties and health benefits of cranberries for livestock, including poultry, swine, canine, feline, and ruminant animals, as either feed/food or as supplements. Cranberry, and/or its components, has the capability to potentially control infectious diseases like diarrhea, urinary tract infection, gut integrity, and intestinal probiotic health. Moreover, cranberries show efficacy in suppressing the growth of pathogenic microorganisms such as Salmonella species, Campylobacter species, Streptococcus species, and Enterococcus species bacteria. Thus, cranberry could be considered as a potential natural feed additive or food supplement for animal health improvement.

Understanding the pathophysiology of Pseudomonas aeruginosa colonization as a guide for future treatment for chronic leg ulcers

Chronic leg wounds represent a major burden of disease worldwide, costing health care systems billions of dollars each year. Aside from the financial implications, they also impose a significant physical and psychosocial burden on the patient, their relatives and/or carers, and the community. Whilst measures such as maintenance of wound hygiene, debridement, dressings and compression are the current standard of care, complete healing is not always achievable and ulcer recurrence is common. Thus, there is still a gap to breach in terms of understanding the intricate pathophysiology of chronic wounds and the role this plays on treatment and management. Pseudomonas aeruginosa has been linked to poor wound healing, with the pathogen being frequently isolated from chronic leg ulcers. Characterized by its multi-drug resistance, targeting P. aeruginosa requires the development of novel therapeutic options. Thus, the aim of this literature review is to describe the pathophysiology of P. aeruginosa in chronic leg ulcers and discuss novel treatment strategies. Here, we describe the key molecular mechanisms driving the observed clinical effect of P. aeruginosa on wounds and discuss novel strategies of molecular targeting of this common bacteria, establishing new approaches that could benefit patients with chronic hard to heal wounds.

Critical review on plant-derived quorum sensing signaling inhibitors in pseudomonas aeruginosa

Pseudomonas aeruginosa, a biofilm-forming organism with complex quorum mechanisms (Las, Rhl, PQS, and IQS), poses an imminent danger to the healthcare sector and renders current treatment options for chemotherapy ineffectual. The pathogen's diverse pathogenicity, antibiotic resistance, and biofilms make it difficult to eradicate it effectively. Quorum sensing, a complex system reliant on cell density, controls P. aeruginosa's pathogenesis. Quorum-sensing genes are key components of P. aeruginosa's pathogenic arsenal, and their expression determines how severe the spread of infection becomes. Over the past ten years, there has been a noticeable increase in the quest for and development of new antimicrobial medications. Quorum sensing may be an effective treatment for infections triggered by bacteria. Introducing quorum-sensing inhibitors as an anti-virulent strategy might be an intriguing therapeutic method that can be effectively employed along with current medications. Amongst the several speculated processes, a unique anti-virulence strategy using anti-quorum sensing and antibiofilm medications for targeting pseudomonal infestations seems to be at the forefront. Due to their noteworthy quorum quenching capabilities, biologically active phytochemicals have become more well-known in the realm of science in this context. Recent research showed how different phytochemical quorum quenching actions affect P. aeruginosa's QS-dependent pathogenicity. This review focuses on the most current data supporting the implementation of plant bio-actives to treat P.aeruginosa-associated diseases, as well as the benefits and future recommendationsof employing them in anti-virulence therapies as a supplementary drug development approach towards conventional antibiotic approaches.

Antimicrobial and antibiofilm properties of procyanidins: potential for clinical and biotechnological applications

Procyanidins (PCs) have emerged as agents with potential antimicrobial and antibiofilm activities, although their mechanisms of action and structure-activity relationships remain poorly understood. This review assessed the potential mechanisms of action and applications of these compounds to explore these aspects. Studies on the antimicrobial properties of PCs suggest that they are involved in osmotic imbalance, DNA interactions and metabolic disruption. Although less studied, their antibiofilm activities include antiadhesive effects and the modulation of mobility and quorum sensing. However, most research has used uncharacterized plant extracts for in vitro assays, limiting the understanding of the structure-activity relationships of PCs and their in vivo mechanisms. Clinical trials on the antimicrobial and antibiofilm properties of PCs have not clarified these issues due to nonstandardized methodologies, inadequate chemical characterization, and the limited number of studies, preventing a consensus and evaluation of the in vivo effects. Additionally, patent analysis revealed that technological developments in the antimicrobial and antibiofilm uses of PCs are concentrated in health care and dental care, but new biotechnological uses are emerging. Therefore, while PCs are promising antimicrobial and antibiofilm compounds, further research into their chemical structures and mechanisms of action is crucial for evidence-based applications in biotechnology and health care.

Unveiling the hidden language of bacteria: anti-quorum sensing strategies for gram-negative bacteria infection control

Quorum sensing (QS) is a communication mechanism employed by many bacteria to regulate gene expression in a population density-dependent manner. It plays a crucial role in coordinating various bacterial behaviors, including biofilm formation, virulence factor production, and antibiotic resistance. However, the dysregulation of QS can lead to detrimental effects, making it an attractive target for developing novel therapeutic strategies. Anti-QS approaches aim to interfere with QS signaling pathways, inhibiting the communication between bacteria, and disrupting their coordinated activities. Various strategies have been explored to achieve this goal. Advances in understanding QS mechanisms and the discovery of new targets have paved the way for the development of innovative anti-QS approaches. Combining multiple anti-QS strategies or utilizing them in combination with traditional antibiotics holds great promise for combating bacterial infections and addressing the challenges posed by antibiotic resistance. Anti-QS approaches offer a diverse range of strategies including natural compounds, antibody-mediated quorum quenching (QQ), computer-aided drug design for QQ, repurposing of Drugs approved by FDA as anti-QS agents and modulating quorum-sensing molecules which were discussed in detail in this review. This review, comprehensively and for the first time, sheds light on the significance of diverse anti-QS strategies in solving antimicrobial resistance problem in Gram-negative microbial infection.

Unveiling the potential of marine compounds as quorum sensing inhibitors targeting Pseudomonas aeruginosa's LasI: A computational study using molecular docking and molecular dynamics

Antimicrobial resistance (AMR) poses a significant threat to global public health, with multidrug-resistant Pseudomonas aeruginosa being a leading cause of mortality, accounting for 18%-61% of deaths annually. The quorum sensing (QS) systems of P. aeruginosa, particularly the LasI-LasR system, play a crucial role in promoting biofilm formation and expression of virulent genes, which contribute to the development of AMR. This study focuses on LasI, the mediator of biofilm formation for identifying its inhibitors from a marine compound database comprising of 32 000 compounds using molecular docking and molecular simulation techniques. The virtual screening and docking experiments demonstrated that the top 10 compounds exhibited favorable docking scores of <-7.19 kcal/mol compared to the reported inhibitor 3,5,7-Trihydroxyflavone with a docking score of -3.098 kcal/mol. Additionally, molecular mechanics/Poisson-Boltzmann generalized born surface area (MM-GBSA) analyses were conducted to assess these compounds' suitability for further investigation. Out of 10 compounds, five compounds demonstrated high MM-GBSA binding energy (<-35.33 kcal/mol) and were taken up for molecular dynamics simulations to evaluate the stability of the protein-ligand complex over a 100 ns period. Based on root mean square deviation, root mean square fluctuation, radius of gyration, and hydrogen bond interactions analysis, three marine compounds, namely MC-2 (CMNPD13419) and MC-3 (CMNPD1068), exhibited consistent stability throughout the simulation. Therefore, these compounds show potential as promising LasI inhibitors and warrant further validation through in vitro and in vivo experiments. By exploring the inhibitory effects of these marine compounds on P. aeruginosa's QS system, this research aims to contribute to the development of novel strategies to combat AMR.

Understanding resistance acquisition by Pseudomonas aeruginosa and possible pharmacological approaches in palliating its pathogenesis

Pseudomonas aeruginosa can utilize various virulence factors necessary for host infection and persistence. These virulence factors include pyocyanin, proteases, exotoxins, 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), phospholipases, and siderophores that enable the bacteria to cause severe infections in immunocompromised individuals. P. aeruginosa falls into the category of nosocomial pathogens that are typically resistant to available antibiotics and therapeutic approaches. P. aeruginosa bio-film formation is a major concern in hospitals because it can cause chronic infection and increase the risk of mortality. Therefore, the development of new strategies to disrupt biofilm formation and improve antibiotic efficacy for the treatment of P. aeruginosa infections is crucial. Anti-biofilm and anti-quorum sensing (QS) activity can be viewed as an anti-virulence approach to control the infectious nature of P. aeruginosa. Inhibition of QS and biofilm formation can be achieved through pharmacological approaches such as phytochemicals and essential oils, which have shown promising results in laboratory studies. A regulatory protein called LasR plays a key role in QS signaling to coordinate gene expression. Designing an antagonist molecule that mimics the natural autoinducer might be the best approach for LasR inhibition. Here we reviewed the mechanism behind antibiotic resistance and alternative approaches to combat the pathogenicity of P. aeruginosa.

Anti-quorum sensing potential of selenium nanoparticles against LasI/R, RhlI/R, and PQS/MvfR in Pseudomonas aeruginosa: a molecular docking approach

Pseudomonas aeruginosa is an infectious pathogen which has the ability to cause primary and secondary contagions in the blood, lungs, and other body parts of immunosuppressed individuals, as well as community-acquired diseases, such as folliculitis, osteomyelitis, pneumonia, and others. This opportunistic bacterium displays drug resistance and regulates its pathogenicity via the quorum sensing (QS) mechanism, which includes the LasI/R, RhlI/R, and PQS/MvfR systems. Targeting the QS systems might be an excellent way to treat P. aeruginosa infections. Although a wide array of antibiotics, namely, newer penicillins, cephalosporins, and combination drugs are being used, the use of selenium nanoparticles (SeNPs) to cure P. aeruginosa infections is extremely rare as their mechanistic interactions are weakly understood, which results in carrying out this study. The present study demonstrates a computational approach of binding the interaction pattern between SeNPs and the QS signaling proteins in P. aeruginosa, utilizing multiple bioinformatics approaches. The computational investigation revealed that SeNPs were acutely 'locked' into the active region of the relevant proteins by the abundant residues in their surroundings. The PatchDock-based molecular docking analysis evidently indicated the strong and significant interaction between SeNPs and the catalytic cleft of LasI synthase (Phe105-Se = 2.7 Å and Thr121-Se = 3.8 Å), RhlI synthase (Leu102-Se = 3.7 Å and Val138-Se = 3.2 Å), transcriptional receptor protein LasR (Lys42-Se = 3.9 Å, Arg122-Se = 3.2 Å, and Glu124-Se = 3.9 Å), RhlR (Tyr43-Se = 2.9 Å, Tyr45-Se = 3.4 Å, and His61-Se = 3.5 Å), and MvfR (Leu208-Se = 3.2 Å and Arg209-Se = 4.0 Å). The production of acyl homoserine lactones (AHLs) was inhibited by the use of SeNPs, thereby preventing QS as well. Obstructing the binding affinity of transcriptional regulatory proteins may cause the suppression of LasR, RhlR, and MvfR systems to become inactive, thereby blocking the activation of QS-regulated virulence factors along with their associated gene expression. Our findings clearly showed that SeNPs have anti-QS properties against the established QS systems of P. aeruginosa, which strongly advocated that SeNPs might be a potent solution to tackle drug resistance and a viable alternative to conventional antibiotics along with being helpful in therapeutic development to cure P. aeruginosa infections.

Microbiome of Ceca from Broiler Chicken Vaccinated or Not against Coccidiosis and Fed Berry Pomaces

American cranberry (Vaccinium macrocarpon) and lowbush/wild blueberry (V. angustifolium) pomace are polyphenol-rich products having potentially beneficial effects in broiler chickens. This study investigated the cecal microbiome of broiler-vaccinated or non-vaccinated birds against coccidiosis. Birds in each of the two groups (vaccinated or non-vaccinated) were fed a basal non-supplemented diet (NC), a basal diet supplemented with bacitracin (BAC), American cranberry (CP), and lowbush blueberry (BP) pomace alone or in combination (CP + BP). At 21 days of age, cecal DNA samples were extracted and analyzed using both whole-metagenome shotgun sequencing and targeted-resistome sequencing approaches. Ceca from vaccinated birds showed a lower abundance of Lactobacillus and a higher abundance of Escherichia coli than non-vaccinated birds (p < 0.05). The highest and lowest abundance of L. crispatus and E. coli, respectively, were observed in birds fed CP, BP, and CP + BP compared to those from NC or BAC treatments (p < 0.05). Coccidiosis vaccination affected the abundance of virulence genes (VGs) related to adherence, flagella, iron utilization, and secretion system. Toxin-related genes were observed in vaccinated birds (p < 0.05) in general, with less prevalence in birds fed CP, BP, and CP + BP than NC and BAC (p < 0.05). More than 75 antimicrobial resistance genes (ARGs) detected by the shotgun metagenomics sequencing were impacted by vaccination. Ceca from birds fed CP, BP, and CP + BP showed the lowest (p < 0.05) abundances of ARGs related to multi-drug efflux pumps, modifying/hydrolyzing enzyme and target-mediated mutation, when compared to ceca from birds fed BAC. Targeted metagenomics showed that resistome from BP treatment was distant to other groups for antimicrobials, such as aminoglycosides (p < 0.05). Significant differences in the richness were observed between the vaccinated and non-vaccinated groups for aminoglycosides, β-lactams, lincosamides, and trimethoprim resistance genes (p < 0.05). Overall, this study demonstrated that dietary berry pomaces and coccidiosis vaccination significantly impacted cecal microbiota, virulome, resistome, and metabolic pathways in broiler chickens.

Bioaccessibility and Bioavailability of Diet Polyphenols and Their Modulation of Gut Microbiota

It is generally accepted that diet-derived polyphenols are bioactive compounds with several potentially beneficial effects on human health. In general, polyphenols have several chemical structures, and the most representative are flavonoids, phenolic acids, and stilbenes. It should be noted that the beneficial effects of polyphenols are closely related to their bioavailability and bioaccessibility, as many of them are rapidly metabolized after administration. Polyphenols-with a protective effect on the gastrointestinal tract-promote the maintenance of the eubiosis of the intestinal microbiota with protective effects against gastric and colon cancers. Thus, the benefits obtained from dietary supplementation of polyphenols would seem to be mediated by the gut microbiota. Taken at certain concentrations, polyphenols have been shown to positively modulate the bacterial component, increasing Lactiplantibacillus spp. and Bifidobacterium spp. involved in the protection of the intestinal barrier and decreasing Clostridium and Fusobacterium, which are negatively associated with human well-being. Based on the diet-microbiota-health axis, this review aims to describe the latest knowledge on the action of dietary polyphenols on human health through the activity of the gut microbiota and discusses micro-encapsulation of polyphenols as a strategy to improve the microbiota.

Transcriptional profiling of extraintestinal Escherichia coli exposed to cranberry pomace extracts alone or in combination with ceftriaxone

Extraintestinal pathogenic Escherichia coli (ExPEC) includes several serotypes that have been associated with colibacillosis in poultry, as well as urinary tract infections and newborn meningitis in humans. This study investigated the antimicrobial activities of ceftriaxone (AXO) and cranberry pomace extracts (CRAN) alone or in combination (CC) against multidrug-resistant (MDR) ExPEC from broiler. The growth-inhibitory activity of CRAN and synergy tests by a checkerboard method were determined in cation-adjusted Mueller–Hinton broth (CAMHB). The transcriptomic profile of the MDR E. coli O7:H18 (ST38) grown in CAMHB supplemented with sub-inhibitory concertation of CRAN and AXO alone or in combination was obtained by RNA-seq. The MIC of CRAN for all isolates was 16 mg/mL. An additive activity was observed between 4 mg/mL of CRAN and 4 μg/mL of AXO. Compared to the control, the transcriptomic analysis revealed that 4 mg/ml of (1/4MIC) CRAN and its combination with 4 μg/mL of (1/8MIC) AXO (CC) exposures resulted in 727 and 712 differentially expressed genes, respectively (false discovery rate &lt; 0.001 and log2-fold change &gt; 2), in the studied E. coli. Major virulence genes including adhesins (fim, flg, csg, and yad), protectins (omp, tra, waa, and hly), secretion systems (hof, pho, and vir), and quorum sensing (lsr), which are energetically expensive for bacteria, were downregulated. Most importantly, 1/4MIC of CRAN or CC downregulated the β-lactamase blaCMY-2 and efflux pump including tolC, mdtEIJ, gadEW, and their regulator gene evgS, while upregulating the cysteine biosynthesis and oxidative stress-related regulatory genes including cys, dmlA, sbp, nrdGHI, soxSR, and rpoH. Downregulation of multiple enzymes involved in TCA cycles and upregulation of Fe–S cluster coordinated by Cys and Isc proteins reflect the regulation of energy metabolism of the studied E. coli upon CRAN or CC exposure. The downregulation of outer membrane protein genes that control permeability barriers, along with different antimicrobial resistance genes, demonstrates that CRAN may have the unique potential to enhance the antimicrobial activities of third-generation cephalosporins such as AXO against MDR E. coli.

Metabolic Fate of Orally Ingested Proanthocyanidins through the Digestive Tract

Proanthocyanidins (PACs), which are oligomers or polymers of flavan-3ols with potent antioxidative activity, are well known to exert a variety of beneficial health effects. Nonetheless, their bioaccessibility and bioavailability have been poorly assessed. In this review, we focused on the metabolic fate of PACs through the digestive tract. When oligomeric and polymeric PACs are orally ingested, a large portion of the PACs reach the colon, where a small portion is subjected to microbial degradation to phenolic acids and valerolactones, despite the possibility that slight depolymerization of PACs occurs in the stomach and small intestine. Valerolactones, as microbiota-generated catabolites of PACs, may contribute to some of the health benefits of orally ingested PACs. The remaining portion interacts with gut microbiota, resulting in improved microbial diversity and, thereby, contributing to improved health. For instance, an increased amount of beneficial gut bacteria (e.g., Akkermansia muciniphila and butyrate-producing bacteria) could ameliorate host metabolic functions, and a lowered ratio of Firmicutes/Bacteroidetes at the phylum level could mitigate obesity-related metabolic disorders.

A review on the gastrointestinal protective effects of tropical fruit polyphenols

Tropical fruits are popular because of their unique, delicious flavors and good nutritional value. Polyphenols are considered to be the main bioactive ingredients in tropical fruits, and these exert a series of beneficial effects on the human gastrointestinal tract that can enhance intestinal health and prevent intestinal diseases. Moreover, they are distinct from the polyphenols in fruits grown in other geographical zones. Thus, the comprehensive effects of polyphenols in tropical fruits on gut health warrant in-depth review. This article reviews, first, the biological characteristics of several representative tropical fruits, including mango, avocado, noni, cashew apple, passion fruit and lychee; second, the types and content of the main polyphenols in these tropical fruits; third, the effects of each of these fruit polyphenols on gastrointestinal health; and, fourth, the protective mechanism of polyphenols. Polyphenols and their metabolites play a crucial role in the regulation of the gut microbiota, increasing intestinal barrier function, reducing oxidative stress, inhibiting the secretion of inflammatory factors and regulating immune function. Thus, review highlights the value of tropical fruits, highlighting their significance for future research on their applications as functional foods that are oriented to gastrointestinal protection.

Molecular Mechanisms and Applications of N-Acyl Homoserine Lactone-Mediated Quorum Sensing in Bacteria

Microbial biodiversity includes biotic and abiotic components that support all life forms by adapting to environmental conditions. Climate change, pollution, human activity, and natural calamities affect microbial biodiversity. Microbes have diverse growth conditions, physiology, and metabolism. Bacteria use signaling systems such as quorum sensing (QS) to regulate cellular interactions via small chemical signaling molecules which also help with adaptation under undesirable survival conditions. Proteobacteria use acyl-homoserine lactone (AHL) molecules as autoinducers to sense population density and modulate gene expression. The LuxI-type enzymes synthesize AHL molecules, while the LuxR-type proteins (AHL transcriptional regulators) bind to AHLs to regulate QS-dependent gene expression. Diverse AHLs have been identified, and the diversity extends to AHL synthases and AHL receptors. This review comprehensively explains the molecular diversity of AHL signaling components of Pseudomonas aeruginosa, Chromobacterium violaceum, Agrobacterium tumefaciens, and Escherichia coli. The regulatory mechanism of AHL signaling is also highlighted in this review, which adds to the current understanding of AHL signaling in Gram-negative bacteria. We summarize molecular diversity among well-studied QS systems and recent advances in the role of QS proteins in bacterial cellular signaling pathways. This review describes AHL-dependent QS details in bacteria that can be employed to understand their features, improve environmental adaptation, and develop broad biomolecule-based biotechnological applications.

Pseudomonas aeruginosa reference strains PAO1 and PA14: A genomic, phenotypic, and therapeutic review

Pseudomonas aeruginosa is a ubiquitous, motile, gram-negative bacterium that has been recently identified as a multi-drug resistant pathogen in critical need of novel therapeutics. Of the approximately 5,000 strains, PAO1 and PA14 are common laboratory reference strains, modeling moderately and hyper-virulent phenotypes, respectively. PAO1 and PA14 have been instrumental in facilitating the discovery of novel drug targets, testing novel therapeutics, and supplying critical genomic information on the bacterium. While the two strains have contributed to a wide breadth of knowledge on the natural behaviors and therapeutic susceptibilities of P. aeruginosa, they have demonstrated significant deviations from observations in human infections. Many of these deviations are related to experimental inconsistencies in laboratory strain environment that complicate and, at times, terminate translation from laboratory results to clinical applications. This review aims to provide a comparative analysis of the two strains and potential methods to improve their clinical relevance.

Quorum Quenching: A Drug Discovery Approach Against Pseudomonas aeruginosa

Pseudomonas aeruginosa, a ubiquitous opportunistic and nosocomial biofilm-forming pathogen with complex, interconnected and hierarchical nature of QS systems (Las, Rhl, PQS, and IQS), is posing the biggest challenge to the healthcare sector and have made current chemotherapies incapable. Conventional antibiotics designed to intercept the biochemical or physiological processes precisely of planktonic microorganisms exert extreme selective pressure and develop resistance against them thereby emphasizing the development of alternative therapeutic approaches. Additionally, quorum sensing induced pathogenic microbial biofilms and production of virulence factors have intensified the pathogenicity, drug resistance, recurrence of infections, hospital visits, morbidity, and mortality many-folds. In this regard, QS could be a potential druggable target and the discovery of QS inhibiting agents as an anti-virulent measure could serve as an alternative therapeutic approach to conventional antibiotics. Quorum quenching (QQ) is a preferred strategy to combat microbial infections since it attenuates the pathogenicity of microbes and enhances the microbial biofilm susceptibility to antibiotics, thus qualifying as a suitable target for drug discovery. This review discusses the QS-induced pathogenicity of P. aeruginosa, the hierarchical QS systems, and QS inhibition as a drug discovery approach to complement classical antibiotic strategy.

The Molecular Architecture of Pseudomonas aeruginosa Quorum-Sensing Inhibitors

The survival selection pressure caused by antibiotic-mediated bactericidal and bacteriostatic activity is one of the important inducements for bacteria to develop drug resistance. Bacteria gain drug resistance through spontaneous mutation so as to achieve the goals of survival and reproduction. Quorum sensing (QS) is an intercellular communication system based on cell density that can regulate bacterial virulence and biofilm formation. The secretion of more than 30 virulence factors of P. aeruginosa is controlled by QS, and the formation and diffusion of biofilm is an important mechanism causing the multidrug resistance of P. aeruginosa, which is also closely related to the QS system. There are three main QS systems in P. aeruginosa: las system, rhl system, and pqs system. Quorum-sensing inhibitors (QSIs) can reduce the toxicity of bacteria without affecting the growth and enhance the sensitivity of bacterial biofilms to antibiotic treatment. These characteristics make QSIs a popular topic for research and development in the field of anti-infection. This paper reviews the research progress of the P. aeruginosa quorum-sensing system and QSIs, targeting three QS systems, which will provide help for the future research and development of novel quorum-sensing inhibitors.

Therapeutic Potential of Polyphenol and Nanoparticles Mediated Delivery in Periodontal Inflammation: A Review of Current Trends and Future Perspectives

Periodontitis is an oral inflammatory process involving the periodontium, which is mainly caused by the invasion of periodontopathogenic microorganisms that results in gingival connective tissue and alveolar bone destruction. Metabolic products of the oral pathogens and the associated host immune and inflammatory responses triggered are responsible for the local tissue destruction. Numerous studies in the past decades have demonstrated that natural polyphenols are capable of modulating the host inflammatory responses by targeting multiple inflammatory components. The proposed mechanism by which polyphenolic compounds exert their great potential is by regulating the immune cell, proinflammatory cytokines synthesis and gene expression. However, due to its low absorption and bioavailability, the beneficial effects of these substances are very limited and it hampers their use as a therapeutic agent. To address these limitations, targeted delivery systems by nanoencapsulation techniques have been explored in recent years. Nanoencapsulation of polyphenolic compounds with different carriers is an efficient and promising approach to boost their bioavailability, increase the efficiency and reduce the degradability of natural polyphenols. In this review, we focus on the effects of different polyphenolic substances in periodontal inflammation and to explore the pharmaceutical significance of polyphenol-loaded nanoparticles in controlling periodontitis, which may be useful for further enhancement of their efficacy as therapeutic agents for periodontal disease.

A Freeze-Dried Cranberry Powder Consistently Enhances SCFA Production and Lowers Abundance of Opportunistic Pathogens In Vitro

The American cranberry, Vaccinium macrocarpon, contains fibers and (poly)phenols that could exert health-promoting effects through modulation of gut microbiota. This study aimed to investigate how a freeze-dried whole cranberry powder (FCP) modulated metabolite production and microbial composition using both a 48-h incubation strategy and a long-term human gut simulator study with the M-SHIME (Mucosal Simulator of the Human Intestinal Microbial Ecosystem). FCP was repeatedly administered over three weeks. The studies included five and three study subjects, respectively. In both models, FCP significantly increased levels of health-related short-chain fatty acids (SCFA: acetate, propionate and butyrate), while decreased levels of branched-chain fatty acids (markers of proteolytic fermentation). Interestingly, FCP consistently increased luminal Bacteroidetes abundances in the proximal colon of the M-SHIME (+17.5 ± 9.3%) at the expense of Proteobacteria (−10.2 ± 1.5%). At family level, this was due to the stimulation of Bacteroidaceae and Prevotellaceae and a decrease of Pseudomonodaceae and Enterobacteriaceae. Despite of interpersonal differences, FCP also increased the abundance of families of known butyrate producers. Overall, FCP displayed an interesting prebiotic potential in vitro given its selective utilization by host microorganisms and potential health-related effects on inhibition of pathogens and selective stimulation of beneficial metabolites.

Paeoniflorin reduce luxS/AI-2 system-controlled biofilm formation and virulence in Streptococcus suis

Streptococcus suis (S. suis), more specifically serotype 2, is a bacterial pathogen that threatens the lives of pigs and humans. Like many other pathogens, S. suis exhibits quorum sensing (QS) system-controlled virulence factors, such as biofilm formation that complicates treatment. Therefore, impairing the QS involving LuxS/AI-2 cycle in S. suis, may be a promising alternative strategy for overcoming S. suis infections. In this study, we investigated paeoniflorin (PF), a monoterpenoid glycoside compound extracted from peony, as an inhibitor of S. suis LuxS/AI-2 system. At a sub-minimal inhibitory concentration (MIC) (1/16 MIC; 25 μg/ml), PF significantly reduced biofilm formation by S. suis through inhibition of extracellular polysaccharide (EPS) production, without affecting bacterial growth. Moreover, evidence was brought that PF reduces AI-2 activity in S. suis biofilm. Molecular docking indicated that LuxS may be the target of PF. Monitoring LuxS enzymatic activity confirmed that PF had a partial inhibitory effect. Finally, we showed that the use of PF in a mouse model can relieve S. suis infections. This study highlighted the anti-biofilm potential of PF against S. suis, and brought evidence that it may as an inhibitor of the LuxS/AI-2 system to prevent S. suis biofilm-related infections. PF can thus be used as a new type of natural biofilm inhibitor for clinical application.

Preparation and Characterization of Chitosan Films Containing Lychee (Litchi chinensis Sonn.) Pericarp Powder and Their Application as Active Food Packaging

In this study, lychee (Litchi chinensis Sonn.) pericarp powder was added to chitosan (CHS) matrix to develop active packaging films, and their structure, physicochemical, antibacterial, antioxidant, and functional properties were investigated. FT-IR results showed that intermolecular hydrogen bonds were formed between CHS and polyphenols in lychee pericarp powder (LPP), and the intermolecular interaction interfered with the assembly of CHS into semi-crystal structure, which reduced the crystallinity of CHS film. Incorporation of LPP significantly reduced water vapor permeability, water solubility, swelling degree, and elongation at break of CHS film (p < 0.05). However, UV-visible light barrier, tensile strength, and antibacterial and antioxidant properties of CHS films were increased by LPP incorporation. CHS-LPP film remarkably lowered the weight loss, firmness, titratable acidity, and total soluble solids of fresh-cut apple after five days storage. CHS-LPP film packaging effectively inhibited the browning of fresh-cut apple and the reduction of polyphenol content in apple juice caused by polyphenol oxidase (PPO)-mediated oxidation during storage. Therefore, CHS-LPP films have great potential as food packaging material to ensure the quality and extend the shelf life of food products.

Anti-Virulence Properties of Coridothymus capitatus Essential Oil against Pseudomonas aeruginosa Clinical Isolates from Cystic Fibrosis Patients

Pseudomonas aeruginosa is an opportunistic pathogen responsible for nosocomial infections, and is often involved in airway infections of cystic fibrosis (CF) patients. P. aeruginosa virulence is related to its ability to form biofilm, trigger different types of motilities, and produce toxins (for example, bacterial pigments). In this scenario, essential oils (EOs) have gained notoriety for their role in phenotype modulation, including virulence modulation. Among different EOs previously analyzed, herein we investigated the activity of Coridothymus capitatus EO (CCEO) against specific virulence factors produced by P. aeruginosa isolated from CF patients. CCEO showed inhibition of new biofilm formation and reduction in mature biofilm in about half of the tested strains. On selected strains, SEM analysis provided interesting information regarding CCEO action in a pre-adhesion assay. CCEO treatment showed a dramatic modification of the extracellular matrix (ECM) structure. Our results clearly showed a drastic reduction in pyocyanin production (between 84% and 100%) for all tested strains in the presence of CCEO. Finally, CCEO was also able to strongly affect P. aeruginosa swarming and swimming motility for almost all tested strains. In consideration of the novel results obtained on clinical strains isolated from CF patients, CCEO may be a potential candidate to limit P. aeruginosa virulence.

Anti-quorum sensing potential of ketoprofen and its derivatives against Pseudomonas aeruginosa: insights to in silico and in vitro studies

Antibiotics are usually used for the treatment of bacterial infections, but multidrug-resistant strains are a phenomenon that has been growing at an increasing rate worldwide. Thus, there is an increasing need for novel strategies for combatting infectious diseases. Many pathogenic bacteria apply quorum sensing (QS) to regulate their pathogenicity and virulence factors production. This circuit makes the QS system an attractive target for antibacterial therapy. In the present study, an important member of non-steroidal anti-inflammatory drugs (NSAIDs), by reducing the biofilm and producing QS-regulated virulence factors, ketoprofen and its synthetic derivatives were screened against the Pseudomonas aeruginosa PAO1. All compounds showed anti-biofilm activity (16-79%) and most of them presented anti-virulence activity. In the co-treatment of ketoprofen, G20, G21, or G77 with tobramycin, biofilm is significantly reduced (potentiated to > 50%) in the number of cells protected inside the impermeable matrix. The in silico studies in addition to the similarities between the chemical structures of PqsR natural ligands and ketoprofen derivatives reinforce the possibility that the mechanism of action is through PqsR inhibition. Based on the results, the anti-pathogenic effect was more appreciable in ketoprofen, G77, and G20.

A deep insight into the suppression mechanism of Sedum alfredii root exudates on Pseudomonas aeruginosa based on quorum sensing

Quorum sensing (QS) plays an important role in the intensive communication between plants and microbes in the rhizosphere during the phytoremediation. This study explored the influence of the root exudates of hyperaccumulator Sedum alfredii on Pseudomonas aeruginosa based on QS. The effects of the components of root exudates, genes expression and transcription regulation of QS system (especially the las system) in Pseudomonas aeruginosa wild-type strain (WT) and rhl system mutant strain (ΔrhlI) were systematically analyzed and discussed. The WT and ΔrhlI exposed to gradient root exudates (0×, 1×, 2×, 5× and 10×) showed a concentration-corrective inhibition on protease production, with the inhibition rates of 51.4-74.5% and 31.2-50.0%, respectively. Among the components of the root exudates of Sedum alfredii, only thymol had an inhibition effects to the root exudates on the activity of protease and elastase. The inhibition rates of 50 μmol/L thymol on protease and elastase in WT were 44.7% and 24.3%, respectively, which was consistent with the variation in ΔrhlI. The gene expression of lasB declined 36.0% under the 1× root exudate treatment and 73.0% under the 50 μmol/L thymol treatment. Meanwhile, there was no significant impact on N-3-oxo-dodecanoyl-L-homoserine lactone signal production and the gene expression of lasI and lasR. Therefore, thymol from Sedum alfredii root exudates could inhibit the formation of protease and elastase in Pseudomonas aeruginosa by suppressing the expression of lasB, without any significant influence on the main las system as a potential natural QS inhibitor.

Polyphenol-Mediated Gut Microbiota Modulation: Toward Prebiotics and Further

The genome of gut microbes encodes a collection of enzymes whose metabolic functions contribute to the bioavailability and bioactivity of unabsorbed (poly)phenols. Datasets from high throughput sequencing, metabolome measurements, and other omics have expanded the understanding of the different modes of actions by which (poly)phenols modulate the microbiome conferring health benefits to the host. Progress have been made to identify direct prebiotic effects of (poly)phenols; albeit up to date, these compounds are not recognized as prebiotics sensu stricto. Interestingly, certain probiotics strains have an enzymatic repertoire, such as tannase, α-L-rhamnosidase, and phenolic acid reductase, involved in the transformation of different (poly)phenols into bioactive phenolic metabolites. In vivo studies have demonstrated that these (poly)phenol-transforming bacteria thrive when provided with phenolic substrates. However, other taxonomically distinct gut symbionts of which a phenolic-metabolizing activity has not been demonstrated are still significantly promoted by (poly)phenols. This is the case of Akkermansia muciniphila, a so-called antiobesity bacterium, which responds positively to (poly)phenols and may be partially responsible for the health benefits formerly attributed to these molecules. We surmise that (poly)phenols broad antimicrobial action free ecological niches occupied by competing bacteria, thereby allowing the bloom of beneficial gut bacteria. This review explores the capacity of (poly)phenols to promote beneficial gut bacteria through their direct and collaborative bacterial utilization and their inhibitory action on potential pathogenic species. We propose the term duplibiotic, to describe an unabsorbed substrate modulating the gut microbiota by both antimicrobial and prebiotic modes of action. (Poly)phenol duplibiotic effect could participate in blunting metabolic disturbance and gut dysbiosis, positioning these compounds as dietary strategies with therapeutic potential.

The Pseudomonas aeruginosa product pyochelin interferes with Trypanosoma cruzi infection and multiplication in vitro

BACKGROUND

Bacteria are sources of numerous molecules used in treatment of infectious diseases. We investigated effects of molecules produced by 26 Pseudomonas aeruginosa strains against infection of mammalian cell cultures with Trypanosoma cruzi, the aetiological agent of Chagas disease.

METHODS

Vero cells were infected with T. cruzi in the presence of wild-type P. aeruginosa supernatants or supernatants of mutants with defects in the production of various virulence, quorum sensing and iron acquisition factors. Quantification of T. cruzi infection (percentage of infected cells) and multiplication (number of amastigotes per infected cell) was performed and cell viability was determined.

RESULTS

Wild-type P. aeruginosa products negatively affected T. cruzi infection and multiplication in a dose-dependent manner, without evident toxicity for mammalian cells. PvdD/pchE mutation (loss of the P. aeruginosa siderophores pyoverdine and pyochelin) had the greatest impact on anti-T. cruzi activity. Negative effects on T. cruzi infection by pure pyochelin, but not pyoverdine, or other P. aeruginosa exoproducts studied, were quantitatively similar to the effects of benznidazole, the current standard therapy against T. cruzi.

CONCLUSIONS

The P. aeruginosa product pyochelin showed promising activity against T. cruzi and might become a new lead molecule for therapy development.

Cranberry-Derived Proanthocyanidins Potentiate β-Lactam Antibiotics against Resistant Bacteria

The emergence and spread of extended-spectrum β-lactamases (ESBLs), metallo-β-lactamases (MBLs), or variant low-affinity penicillin-binding proteins (PBPs) pose a major threat to our ability to treat bacterial infection using β-lactam antibiotics. Although combinations of β-lactamase inhibitors with β-lactam agents have been clinically successful, there are no MBL inhibitors in current therapeutic use. Furthermore, recent clinical use of new-generation cephalosporins targeting PBP2a, an altered PBP, has led to the emergence of resistance to these antimicrobial agents. Previous work shows that natural polyphenols such as cranberry-extracted proanthocyanidins (cPAC) can potentiate non-β-lactam antibiotics against Gram-negative bacteria. This study extends beyond previous work by investigating the in vitro effect of cPAC in overcoming ESBL-, MBL-, and PBP2a-mediated β-lactam resistance. The results show that cPAC exhibit variable potentiation of different β-lactams against β-lactam-resistant Enterobacteriaceae clinical isolates as well as ESBL- and MBL-producing E. coli We also discovered that cPAC have broad-spectrum inhibitory properties in vitro on the activity of different classes of β-lactamases, including CTX-M3 ESBL and IMP-1 MBL. Furthermore, we observe that cPAC selectively potentiate oxacillin and carbenicillin against methicillin-resistant but not methicillin-sensitive staphylococci, suggesting that cPAC also interfere with PBP2a-mediated resistance. This study motivates the need for future work to identify the most bioactive compounds in cPAC and to evaluate their antibiotic-potentiating efficacy in vivoIMPORTANCE The emergence of β-lactam-resistant Enterobacteriaceae and staphylococci compromises the effectiveness of β-lactam-based therapy. By acquisition of ESBLs, MBLs, or PBPs, it is highly likely that bacteria may become completely resistant to the most effective β-lactam agents in the near future. In this study, we described a natural extract rich in proanthocyanidins which exerts adjuvant properties by interfering with two different resistance mechanisms. By their broad-spectrum inhibitory ability, cranberry-extracted proanthocyanidins could have the potential to enhance the effectiveness of existing β-lactam agents.

Plant-Derivatives Small Molecules with Antibacterial Activity

The vegetal world constitutes the main factory of chemical products, in particular secondary metabolites like phenols, phenolic acids, terpenoids, and alkaloids. Many of these compounds are small molecules with antibacterial activity, although very few are actually in the market as antibiotics for clinical practice or as food preservers. The path from the detection of antibacterial activity in a plant extract to the practical application of the active(s) compound(s) is long, and goes through their identification, purification, in vitro and in vivo analysis of their biological and pharmacological properties, and validation in clinical trials. This review presents an update of the main contributions published on the subject, focusing on the compounds that showed activity against multidrug-resistant relevant bacterial human pathogens, paying attention to their mechanisms of action and synergism with classical antibiotics.

Effects of cranberry beverages on oxidative stress and gut microbiota in subjects with Helicobacter pylori infection: a randomized, double-blind, placebo-controlled trial

Helicobacter pylori-induced oxidative stress plays an important role in gastric diseases. H. pylori disturbs gut microbiota. The objective is to investigate the effects of cranberry beverages on oxidative stress biomarkers and gut microbiota in H. pylori positive subjects. 171 H. pylori positive participants were randomly assigned to one of the three groups: high-dose (HCb; 480 mL cranberry beverage), low-dose (LCb; 240 mL cranberry beverage plus 240 mL placebo) and placebo (480 mL). Subjects consumed the beverages daily for 4 weeks. Fasting blood samples were analyzed for oxidative stress biomarkers. The intestinal microbiome was analyzed by 16S rRNA sequencing. Compared with the placebo, HCb resulted in a significantly higher increase of total antioxidant capacity (mean ± SD: 1.39 ± 1.69 IU mL-1vs. 0.34 ± 1.73 IU mL-1; p < 0.001) and a higher decrease of the lipid peroxidation product malondialdehyde (-7.29 ± 10.83 nmol mg-1vs. -0.84 ± 15.66 nmol mg-1; p = 0.025). A significant dose-dependent effect on the elevation of superoxide dismutase was observed (p < 0.001). Microbiome data showed that consuming HCb and LCb led to a significant reduction of Pseudomonas (p < 0.05). In conclusion, the current research showed that consuming cranberry beverages significantly improved the antioxidant status in H. pylori positive subjects, which may be related to the reshaping of gut microbiota.

Chitosan and procyanidin composite films with high antioxidant activity and pH responsivity for cheese packaging

Chitosan-procyanidin composite films (CS-PC films) with different mass ratios were prepared by solution casting method. Their structural, thermal, physical, and antioxidant properties, antibacterial activity and pH responsivity were determined. Compared with CS-control film, CS-PC films exhibited lower solubility and higher tensile strength. The antimicrobial properties against Escherichia coli and Aspergillus niger were improved by 20.0% and 30.4%, respectively. CS-PC films indicated good antioxidant activity through their DPPH and ABTS⁺ scavenging rates, which were 2.45 times higher than CS-control film. pH responsivity was represented by the outstanding changes in color, which were visible to the naked eye. Food packaging film with high antioxidant activity, bacteriostatic properties and pH responsivity was prepared by CS and PC. Compared with the initial properties of cheese, the characteristics of cheese packaged with CS-PC films were obviously better than those of the control groups.

Novel therapeutic strategies for treating Pseudomonas aeruginosa infection

INTRODUCTION

Persistent infections caused by the superbug Pseudomonas aeruginosa and its resistance to multiple antimicrobial agents are huge threats to patients with cystic fibrosis as well as those with compromised immune systems. Multidrug-resistant P. aeruginosa has posed a major challenge to conventional antibiotics and therapeutic approaches, which show limited efficacy and cause serious side effects. The public demand for new antibiotics is enormous; yet, drug development pipelines have started to run dry with limited targets available for inventing new antibacterial drugs. Consequently, it is important to uncover potential therapeutic targets.

AREAS COVERED

The authors review the current state of drug development strategies that are promising in terms of the development of novel and potent drugs to treat P. aeruginosa infection.

EXPERT OPINION

The prevention of P. aeruginosa infection is increasingly challenging. Furthermore, targeting key virulence regulators has great potential for developing novel anti-P. aeruginosa drugs. Additional promising strategies include bacteriophage therapy, immunotherapies, and antimicrobial peptides. Additionally, the authors believe that in the coming years, the overall network of molecular regulatory mechanism of P. aeruginosa virulence will be fully elucidated, which will provide more novel and promising drug targets for treating P. aeruginosa infections.

Quercetin inhibits Pseudomonas aeruginosa biofilm formation via the vfr-mediated lasIR system

Pseudomonas aeruginosa is one of the most common opportunistic pathogens that cause biofilm-associated infections. Biofilm formation is partially regulated by the quorum sensing (QS) system, and quercetin can inhibit QS, biofilm formation and virulence factors. We therefore speculated that quercetin would inhibit the formation of P. aeruginosa biofilm via the QS system. In this study, we successfully constructed lasI, rhlI and lasI/rhlI gene-knockout strains. The knockout of the lasI and lasI/rhlI genes resulted in decreases in adhesion, biofilm formation, swarming motility and the expression of biofilm-associated genes, whereas deletion of the rhlI gene had no obvious influence on these biofilm-related indicators with the exception of the swarming motility. After treatment with quercetin, the lasI- and lasI/rhlI-mutant strains exhibited increased adhesion, biofilm formation, swarming motility and biofilm-associated gene expression compared with the control group. However, quercetin still exerted an inhibitory effect on these physiological factors and the biofilm-associated gene expression in the rhlI-mutant strain. The knockout of QS genes reduced the production of pyocyanin and protease activity, but after the virulence factors of the QS-mutant strains treated with quercetin showed almost no differences compared with those of the control group. In addition, quercetin could significantly inhibit vfr gene expression regardless of the presence of QS genes. The results indicated that quercetin might inhibit the lasIR system through the vfr gene and ultimately the formation of P. aeruginosa biofilms.

Inhibition of quorum sensing-associated virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1 by Mycoleptodiscus indicus PUTY1

Pseudomonas aeruginosa is the second most emerging multidrug-resistant, opportunistic pathogen after Acinetobacter baumannii that poses a threat in nursing homes, hospitals, and patients who need devices such as ventilators and blood catheters. Its ability to form quorum sensing-regulated virulence factors and biofilm makes it more resistant to top most therapeutic agents such as carbapenems and next-generation antibiotics. In the current study, we studied the quorum quenching potential of secondary metabolites of Mycoleptodiscus indicus PUTY1 strain. In vitro observation showed a mitigation in virulence factors such as rhamnolipids, protease, elastase pyocyanin, exopolysaccharides, and hydrogen cyanide gas. Furthermore, a significant reduction in the motility such as swimming, swarming, twitching, and inhibition in biofilm formation by Pseudomonas aeruginosa PAO1 was observed. Results of in vitro studies were further confirmed by in silico studies through docking and molecular dynamic simulation of GC-MS-detected compounds of Mycoleptodiscus indicus employing LasR and RhlR proteins. Both in vitro and in silico observations indicate a new alternative approach for combating virulence of Pseudomonas aeruginosa by targeting its protein receptors LasR and RhlR. Graphical abstract.

Polyphenols from Salix tetrasperma Impair Virulence and Inhibit Quorum Sensing of Pseudomonas aeruginosa

Bacterial resistance represents one of the emerging obstacles in plants, animals, and humans that impairs treatment with antibacterial agents. Targeting of the bacterial quorum sensing system is one of the strategies to overcome this problem. Recently, research has been focused on natural and food components which can function as quorum sensing inhibitors. In this study, a methanol extract from Salix tetrasperma stem bark was phytochemically profiled by LC-MS analysis. This resulted in the identification of 38 secondary metabolites with (epi)catechin-(epi)catechin, epicatechin, tremulacin, salicortin, and trichocarposide as the major constituents. The extracts of both stem bark and the previously profiled flower of S. tetrasperma were tested for anti-quorum sensing activity in a common and widely distributed pathogen Pseudomonas aeruginosa. The natural products inhibited swimming and swarming motilities, as well as proteolytic and hemolytic activities in a dose-dependent manner. Molecular docking of the constituents from both extracts against the quorum sensing controlling systems Lasl/LasR, rhll/rhlR, and PQS/MvfR showed that epicatechin, (epi)catechin-(epi)catechin, p-hydroxy benzoyl galloyl glucose, p-hydroxy benzoyl protocatechuic acid glucose, and caffeoylmalic acid could be the main active components. This study supports the importance of secondary metabolites, especially polyphenols, as quorum sensing inhibitors.

New Evidences of Antibacterial Effects of Cranberry Against Periodontal Pathogens

The worrying rise in antibiotic resistances emphasizes the need to seek new approaches for treating and preventing periodontal diseases. The purpose of this study was to evaluate the antibacterial and anti-biofilm activity of cranberry in a validated in vitro biofilm model. After chemical characterization of a selected phenolic-rich cranberry extract, its values for minimum inhibitory concentration and minimum bactericidal concentration were calculated for the six bacteria forming the biofilm (Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans). Antibacterial activity of the cranberry extract in the formed biofilm was evaluated by assessing the reduction in bacteria viability, using quantitative polymerase chain reaction (qPCR) combined with propidium monoazide (PMA), and by confocal laser scanning microscopy (CLSM), and anti-biofilm activity by studying the inhibition of the incorporation of different bacteria species in biofilms formed in the presence of the cranberry extract, using qPCR and CLSM. In planktonic state, bacteria viability was significantly reduced by cranberry (p < 0.05). When growing in biofilms, a significant effect was observed against initial and early colonizers (S. oralis (p ≤ 0.017), A. naeslundii (p = 0.006) and V. parvula (p = 0.010)) after 30 or 60 s of exposure, while no significant effects were detected against periodontal pathogens (F. nucleatum, P. gingivalis or A. actinomycetemcomitans (p > 0.05)). Conversely, cranberry significantly (p < 0.001 in all cases) interfered with the incorporation of five of the six bacteria species during the development of 6 h-biofilms, including P. gingivalis, A. actinomycetemcomitans, and F. nucleatum. It was concluded that cranberry had a moderate antibacterial effect against periodontal pathogens in biofilms, but relevant anti-biofilm properties, by affecting bacteria adhesion in the first 6 h of development of biofilms.

Pectic Oligosaccharides from Cranberry Prevent Quiescence and Persistence in the Uropathogenic Escherichia coli CFT073

Urinary tract infections (UTIs) caused by Escherichia coli create a large burden on healthcare and frequently lead to recurrent infections. Part of the success of E. coli as an uropathogenic bacterium can be attributed to its ability to form quiescent intracellular reservoirs in bladder cells and its persistence after antibiotic treatment. Cranberry juice and related products have been used for the prevention of UTIs with varying degrees of success. In this study, a group of cranberry pectic oligosaccharides (cPOS) were found to both inhibit quiescence and reduce the population of persister cells formed by the uropathogenic strain, CFT073. This is the first report detailing constituents of cranberry with the ability to modulate these important physiological aspects of uropathogenic E. coli. Further studies investigating cranberry should be keen to include oligosaccharides as part of the ‘active’ cocktail of chemical compounds.

Tart cherry (Prunus cerasus L.) fractions inhibit biofilm formation and adherence properties of oral pathogens and enhance oral epithelial barrier function

Dental caries, candidiasis, and periodontal disease are the most common oral infections affecting a wide range of the population worldwide. The present study investigated the effects of two tart cherry (Prunus cerasus L.) fractions on important oral pathogens, including Candida albicans, Streptococcus mutans, and Fusobacterium nucleatum, as well as on the barrier function of oral epithelial cells. Procyanidins and quercetin and its derivatives were the most important constituents found in the tart cherry fractions. Although the fractions showed poor antimicrobial activity, they inhibited biofilm formation by the three oral pathogens in a dose-dependent manner. The tart cherry fractions also attenuated the adherence of C. albicans and S. mutans to a hydroxylapatite surface as well as the adherence of F. nucleatum to oral epithelial cells. Treating oral epithelial cells with the tart cherry fractions significantly enhanced the barrier function as determined by monitoring the transepithelial electrical resistance. In conclusion, this study showed that the tart cherry fractions and their bioactive constituents could be promising antiplaque compounds by targeting biofilm formation and adherence properties of oral pathogens. Furthermore, its property of increasing the epithelial barrier function may protect against microbial invasion of the underlying connective tissue.

Endolichenic fungus, Aspergillus quandricinctus of Usnea longissima inhibits quorum sensing and biofilm formation of Pseudomonas aeruginosa PAO1

Lichens are composite organisms, comprising of a fungus (mycobiont) and a blue-green alga (photobiont). Along with the mycobiont, numerous non-obligate microfungi live in lichen thalli. These microfungi are called endolichenic fungi (ELF). In recent years, the ELF are emerging as promising natural sources because of their capability to exert unique drug molecules. The current study aimed to isolate the ELF from the lichen, Usnea longissima Ach., to control of biofilm formation and quorum sensing phenomenon in Pseudomonas aeruginosa PAO1, an opportunistic multidrug resistance pathogen that uses quorum sensing network to produce an array of pathogenic agents. Therefore, inhibiting quorum sensing to manage the infection caused by PAO1 could be the paramount alternative approach to conventional antibiotics. The isolated ELF was identified by amplifying the long subunit region of the fungal genome. The extracted metabolites of ELF (MELE) using the acetone solvent was further investigated for anti-quorum sensing activity using the biomarker strain Chromobacterium violaceum 12472 which exerts violacein pigment via the AHL mediated quorum sensing signalling. Moreover, the effect of MELE was also evaluated on the production of virulence factors and biofilm formation of P. aeruginosa PAO1. The molecular identification revealed that ELF (accession number MN171299) exhibited 100% similarity with Aspergillus quandricinctus strain CBS 135.52. The MELE showed significant anti-quorum sensing activity at the concentration of 4 mg/mL without affecting the bacterial cell viability of P. aeruginosa PAO1. The MELE diminished the production of virulence factors, including pyocyanin, protease, elastase, rhamnolipids, and extracellular polysaccharides of P. aeruginosa PAO1 in a concentration-dependent manner. The MELE also disturbed biofilm formation of P. aeruginosa PAO1. The 3-D analysis of biofilm architecture showed that the thickness and surface area covered by microcolonies was decreased as the concentration of MELE was increased. The GC-MS analysis of MELE exhibited that organic acids and fatty acids are major constituents of the MELE. The present study reports first time that the ELF, A. quandricinctus possesses potential to inhibit quorum sensing and biofilm formation of P. aeruginosa and can be further exploited for hospital and healthcare facilities.

Investigation of Antibacterial and Antiinflammatory Activities of Proanthocyanidins from Pelargonium sidoides DC Root Extract

The study explores antibacterial, antiinflammatory and cytoprotective capacity of Pelargonium sidoides DC root extract (PSRE) and proanthocyanidin fraction from PSRE (PACN) under conditions characteristic for periodontal disease. Following previous finding that PACN exerts stronger suppression of Porphyromonas gingivalis compared to the effect on commensal Streptococcus salivarius, the current work continues antibacterial investigation on Staphylococcus aureus, Staphylococcus epidermidis, Aggregatibacter actinomycetemcomitans and Escherichia coli. PSRE and PACN are also studied for their ability to prevent gingival fibroblast cell death in the presence of bacteria or bacterial lipopolysaccharide (LPS), to block LPS- or LPS + IFNγ-induced release of inflammatory mediators, gene expression and surface antigen presentation. Both PSRE and PACN were more efficient in suppressing Staphylococcus and Aggregatibacter compared to Escherichia, prevented A. actinomycetemcomitans- and LPS-induced death of fibroblasts, decreased LPS-induced release of interleukin-8 and prostaglandin E2 from fibroblasts and IL-6 from leukocytes, blocked expression of IL-1β, iNOS, and surface presentation of CD80 and CD86 in LPS + IFNγ-treated macrophages, and IL-1β and COX-2 expression in LPS-treated leukocytes. None of the investigated substances affected either the level of secretion or expression of TNFα. In conclusion, PSRE, and especially PACN, possess strong antibacterial, antiinflammatory and gingival tissue protecting properties under periodontitis-mimicking conditions and are suggestable candidates for treatment of the disease.

Plant-Derived Inhibitors of AHL-Mediated Quorum Sensing in Bacteria: Modes of Action

Numerous gram-negative phytopathogenic and zoopathogenic bacteria utilise acylated homoserine lactone (AHL) in communication systems, referred to as quorum sensing (QS), for induction of virulence factors and biofilm development. This phenomenon positions AHL-mediated QS as an attractive target for anti-infective therapy. This review focused on the most significant groups of plant-derived QS inhibitors and well-studied individual compounds for which in silico, in vitro and in vivo studies provide substantial knowledge about their modes of anti-QS activity. The current data about sulfur-containing compounds, monoterpenes and monoterpenoids, phenylpropanoids, benzoic acid derivatives, diarylheptanoids, coumarins, flavonoids and tannins were summarized; their plant sources, anti-QS effects and bioactivity mechanisms have also been summarized and discussed. Three variants of plant-derived molecules anti-QS strategies are proposed: (i) specific, via binding with LuxI-type AHL synthases and/or LuxR-type AHL receptor proteins, which have been shown for terpenes (carvacrol and l-carvone), phenylpropanoids (cinnamaldehyde and eugenol), flavonoid quercetin and ellagitannins; (ii) non-specific, by affecting the QS-related intracellular regulatory pathways by lowering regulatory small RNA expression (sulphur-containing compounds ajoene and iberin) or c-di-GMP metabolism reduction (coumarin); and (iii) indirect, via alteration of metabolic pathways involved in QS-dependent processes (vanillic acid and curcumin).

Proanthocyanidin Interferes with Intrinsic Antibiotic Resistance Mechanisms of Gram-Negative Bacteria

Antibiotic resistance is spreading at an alarming rate among pathogenic bacteria in both medicine and agriculture. Interfering with the intrinsic resistance mechanisms displayed by pathogenic bacteria has the potential to make antibiotics more effective and decrease the spread of acquired antibiotic resistance. Here, it is demonstrated that cranberry proanthocyanidin (cPAC) prevents the evolution of resistance to tetracycline in Escherichia coli and Pseudomonas aeruginosa, rescues antibiotic efficacy against antibiotic-exposed cells, and represses biofilm formation. It is shown that cPAC has a potentiating effect, both in vitro and in vivo, on a broad range of antibiotic classes against pathogenic E. coli, Proteus mirabilis, and P. aeruginosa. Evidence that cPAC acts by repressing two antibiotic resistance mechanisms, selective membrane permeability and multidrug efflux pumps, is presented. Failure of cPAC to potentiate antibiotics against efflux pump-defective mutants demonstrates that efflux interference is essential for potentiation. The use of cPAC to potentiate antibiotics and mitigate the development of resistance could improve treatment outcomes and help combat the growing threat of antibiotic resistance.

Trans-Cinnamaldehyde, Eugenol and Carvacrol Reduce Campylobacter jejuni Biofilms and Modulate Expression of Select Genes and Proteins

Campylobacter jejuni is the leading cause of human foodborne illness globally, and is strongly linked with the consumption of contaminated poultry products. Several studies have shown that C. jejuni can form sanitizer tolerant biofilm leading to product contamination, however, limited research has been conducted to develop effective control strategies against C. jejuni biofilms. This study investigated the efficacy of three generally recognized as safe status phytochemicals namely, trans-cinnamaldehyde (TC), eugenol (EG), or carvacrol (CR) in inhibiting C. jejuni biofilm formation and inactivating mature biofilm on common food contact surfaces at 20 and 37°C. In addition, the effect of phytochemicals on biofilm architecture and expression of genes and proteins essential for biofilm formation was evaluated. For the inhibition study, C. jejuni was allowed to form biofilms either in the presence or absence of sub-inhibitory concentrations of TC (0.75 mM), EG (0.61 mM), or CR (0.13 mM) for 48 h and the biofilm formation was quantified at 24-h interval. For the inactivation study, C. jejuni biofilms developed at 20 or 37°C for 48 h were exposed to the phytochemicals for 1, 5, or 10 min and surviving C. jejuni in the biofilm were enumerated. All phytochemicals reduced C. jejuni biofilm formation as well as inactivated mature biofilm on polystyrene and steel surface at both temperatures (P < 0.05). The highest dose of TC (75.64 mM), EG (60.9 mM) and CR (66.56 mM) inactivated (>7 log reduction) biofilm developed on steel (20°C) within 5 min. The genes encoding for motility systems (flaA, flaB, and flgA) were downregulated by all phytochemicals (P < 0.05). The expression of stress response (cosR, ahpC) and cell surface modifying genes (waaF) was reduced by EG. LC-MS/MS based proteomic analysis revealed that TC, EG, and CR significantly downregulated the expression of NapA protein required for oxidative stress response. The expression of chaperone protein DnaK and bacterioferritin required for biofilm formation was reduced by TC and CR. Scanning electron microscopy revealed disruption of biofilm architecture and loss of extracellular polymeric substances after treatment. Results suggest that TC, EG, and CR could be used as a natural disinfectant for controlling C. jejuni biofilms in processing areas.