Antibacterial synergy of curcumin with antibiotics against biofilm producing clinical bacterial isolates

Synergistic berberine chloride and Curcumin-Loaded nanofiber therapies against Methicillin-Resistant Staphylococcus aureus Infection: Augmented immune and inflammatory responses in zebrafish wound healing

BACKGROUND

Wound healing pivots on a finely orchestrated inflammatory cascade, critical for tissue repair. Chronic wounds, compounded by persistent inflammation and susceptibility to infection, pose formidable clinical challenges. Nanofiber dressings offer promising avenues for wound care, yet their interaction with inflammation and infection remains elusive. We aim to delineate the inflammatory cascade preceding wound closure and assess Cu@Bbc nanofibers' therapeutic efficacy in mitigating inflammation and combating infection. Their unique attributes suggest promise in modulating inflammation, fostering tissue regeneration, and preventing microbial colonization. Investigating the intricate interplay between nanofiber scaffolds, inflammation, and infection may unveil mechanisms of enhanced wound healing. Our findings could stimulate the development of tailored dressings, urgently needed for effective wound management amidst immune dysregulation, infection, and inflammation.

METHODS

In this investigation, we synthesized Cu@Bbc nanofibers, incorporating curcumin and berberine chloride, for wound healing applications. We evaluated their individual and combined antibacterial, anti-biofilm, and antioxidant activities, alongside binding affinity with pro-inflammatory cytokines through molecular docking. Morphological characterization was conducted via SEM, FTIR assessed functional groups, and wettability contact angle measured hydrophobic properties. The physical properties, including tensile strength, swelling behavior, and thermal stability, were evaluated using tensile testing, saline immersion method and thermogravimetric analysis. Biodegradability of the nanofibers was assessed through a soil burial test. Biocompatibility was determined via MTT assay, while wound healing efficacy was assessed with in vitro scratch assays. Controlled drug release and antibacterial activity against MRSA were examined, with in vivo assessment in a zebrafish model elucidating inflammatory responses and tissue remodeling.

RESULTS

In this study, the synergistic action of curcumin and berberine chloride exhibited potent antibacterial efficacy against MRSA, with significant anti-mature biofilm disruption. Additionally, the combination demonstrated heightened antioxidant potential. Molecular docking studies revealed strong binding affinity with pro-inflammatory cytokines, suggesting a role in expediting the inflammatory response crucial for wound healing. Morphological analysis confirmed nanofiber quality, with drug presence verified via FTIR spectroscopy. Cu@Bbc demonstrated higher tensile strength, optimal swelling behavior, and robust thermal stability as evaluated through tensile testing and thermogravimetric analysis. Additionally, the Cu@Bbc nanofiber showed enhanced biodegradability, as confirmed by the soil burial test. Biocompatibility assessments showed favorable compatibility, while in vitro studies demonstrated potent antibacterial activity. In vivo zebrafish experiments revealed accelerated wound closure, re-epithelialization, and heightened immune response, indicative of enhanced wound healing.

CONCLUSION

In summary, our investigation highlights the efficacy of Cu@Bbc nanofibers, laden with curcumin and berberine chloride, in displaying robust antibacterial and antioxidant attributes while also modulating immune responses and inflammatory cascades essential for wound healing. These results signify their potential as multifaceted wound dressings for clinical implementation.

Combating bacterial biofilms and related drug resistance: Role of phyto-derived adjuvant and nanomaterials

The emergence of antimicrobial resistance (AMR) in clinical microbes has led to a search for novel antibiotics for combating bacterial infections. The treatment of bacterial infections becomes more challenging with the onset of biofilm formation. AMR is further accelerated by biofilm physiology and differential gene expression in bacteria with an inherent resistance to conventional antibiotics. In the search for innovative strategies to control the spread of AMR in clinical isolates, plant-derived therapeutic metabolites can be repurposed to control biofilm-associated drug resistance. Unlike antibiotics, designed to act on a single cellular process, phytochemicals can simultaneously target multiple cellular components. Furthermore, they can disrupt biofilm formation and inhibit quorum sensing, offering a comprehensive approach to combat bacterial infections. In bacterial biofilms, the first line of AMR is due to biofilms associated with the extracellular matrix, diffusion barriers, quorum sensing, and persister cells. These extracellular barriers can be overcome using phytochemical-based antibiotic adjuvants to increase the efficacy of antibiotic treatment and restrict the spread of AMR. Furthermore, phytochemicals can be used to target bacterial intracellular machinery such as DNA replication, protein synthesis, efflux pumps, and degrading enzymes. In parallel with pristine phytochemicals, phyto-derived nanomaterials have emerged as an effective means of fighting bacterial biofilms. These nanomaterials can be formulated to cross the biofilm barriers and function on cellular targets. This review focuses on the synergistic effects of phytochemicals and phyto-derived nanomaterials in controlling the progression of biofilm-related AMR. IT provides comprehensive insights into recent advancements and the underlying mechanisms of the use of phyto-derived adjuvants and nanomaterials.

Antivirulence Effects of Trans-Resveratrol and Curcumin on Methicillin-Resistant Staphylococcus aureus (MRSA) from Saudi Arabia

Methicillin-resistant Staphylococcus aureus (MRSA) is a common resistant bacterium, whose resistance has expanded to commonly used antibiotics. It is crucial to create novel treatments to tackle bacterial resistance. Trans-resveratrol and curcumin are naturally occurring phenolic compounds, whose effects on MRSA virulence are the subject of this investigation. Sub-MICs of trans-resveratrol and curcumin were tested on the virulence factors of 50 MRSA clinical isolates (CIs), including biofilm, hemolysin, hemagglutination, protease, and lecithinase. The distribution of the virulence factors of the CIs was as follows: hemolysin: 98%, hemagglutination: 70%, protease: 62%, biofilm: 56%, and lecithinase: 52%. The sub-MIC that could reduce the effect of the tested virulence factors by 50% or more (IC50) was observed in the strains that showed susceptibility to the individual administration of trans-resveratrol at 50 µg/mL and curcumin at 20 µg/mL. Hemagglutination and hemolysin activity were inhibited by at least 50% in the majority of CIs (57-94%). Meanwhile, the IC50 for protease and biofilm was observed in 6.5-17.8% of the CIs. A few of the CIs were susceptible to lecithinase inhibition, but all showed a full inhibition. This research supports the possibility of the use of these compounds to reduce the bacterial virulence that can reduce antibiotic utilization, and eventually, they can become a potential alternative treatment in combating bacterial resistance.

Staphopain mediated virulence and antibiotic resistance alteration in co-infection of Staphylococcus aureus and Pseudomonas aeruginosa: an animal model

Polymicrobial communities lead to worsen the wound infections, due to mixed biofilms, increased antibiotic resistance, and altered virulence production. Promising approaches, including enzymes, may overcome the complicated condition of polymicrobial infections. Therefore, this study aimed to investigate Staphopain A-mediated virulence and resistance alteration in an animal model of Staphylococcus aureus and Pseudomonas aeruginosa co-infection. S. aureus and P. aeruginosa were co-cultured on the L-929 cell line and wound infection in an animal model. Then, recombinant staphopain A was purified and used to treat mono- and co-infections. Following the treatment, changes in virulence factors and resistance were investigated through phenotypic methods and RT-PCR. Staphopain A resulted in a notable reduction in the viability of S. aureus and P. aeruginosa. The biofilm formed in the wound infection in both animal model and cell culture was disrupted remarkably. Moreover, the biofilm-encoding genes, quorum sensing regulating genes, and virulence factors (hemolysin and pyocyanin) controlled by QS were down-regulated in both microorganisms. Furthermore, the resistance to vancomycin and doripenem decreased following treatment with staphopain A. According to this study, staphopain A might promote wound healing and cure co-infection. It seems to be a promising agent to combine with antibiotics to overcome hard-to-cure infections.

Molecular Aspects of the Functioning of Pathogenic Bacteria Biofilm Based on Quorum Sensing (QS) Signal-Response System and Innovative Non-Antibiotic Strategies for Their Elimination

One of the key mechanisms enabling bacterial cells to create biofilms and regulate crucial life functions in a global and highly synchronized way is a bacterial communication system called quorum sensing (QS). QS is a bacterial cell-to-cell communication process that depends on the bacterial population density and is mediated by small signalling molecules called autoinducers (AIs). In bacteria, QS controls the biofilm formation through the global regulation of gene expression involved in the extracellular polymeric matrix (EPS) synthesis, virulence factor production, stress tolerance and metabolic adaptation. Forming biofilm is one of the crucial mechanisms of bacterial antimicrobial resistance (AMR). A common feature of human pathogens is the ability to form biofilm, which poses a serious medical issue due to their high susceptibility to traditional antibiotics. Because QS is associated with virulence and biofilm formation, there is a belief that inhibition of QS activity called quorum quenching (QQ) may provide alternative therapeutic methods for treating microbial infections. This review summarises recent progress in biofilm research, focusing on the mechanisms by which biofilms, especially those formed by pathogenic bacteria, become resistant to antibiotic treatment. Subsequently, a potential alternative approach to QS inhibition highlighting innovative non-antibiotic strategies to control AMR and biofilm formation of pathogenic bacteria has been discussed.

Inhibition of pathogenic microbes in oral infectious diseases by natural products: Sources, mechanisms, and challenges

The maintenance of oral health is of utmost importance for an individual's holistic well-being and standard of living. Within the oral cavity, symbiotic microorganisms actively safeguard themselves against potential foreign diseases by upholding a multifaceted equilibrium. Nevertheless, the occurrence of an imbalance can give rise to a range of oral infectious ailments, such as dental caries, periodontitis, and oral candidiasis. Presently, clinical interventions encompass the physical elimination of pathogens and the administration of antibiotics to regulate bacterial and fungal infections. Given the limitations of various antimicrobial drugs frequently employed in dental practice, the rising incidence of oral inflammation, and the escalating bacterial resistance to antibiotics, it is imperative to explore alternative remedies that are dependable, efficacious, and affordable for the prevention and management of oral infectious ailments. There is an increasing interest in the creation of novel antimicrobial agents derived from natural sources, which possess attributes such as safety, cost-effectiveness, and minimal adverse effects. This review provides a comprehensive overview of the impact of natural products on the development and progression of oral infectious diseases. Specifically, these products exert their influences by mitigating dental biofilm formation, impeding the proliferation of oral pathogens, and hindering bacterial adhesion to tooth surfaces. The review also encompasses an examination of the various classes of natural products, their antimicrobial mechanisms, and their potential therapeutic applications and limitations in the context of oral infections. The insights garnered from this review can support the promising application of natural products as viable therapeutic options for managing oral infectious diseases.

Effect of Resveratrol and Curcumin on Gene Expression of Methicillin-Resistant Staphylococcus aureus (MRSA) Toxins

Staphylococcus aureus is an opportunistic pathogen that can lead to a number of potentially terrible community- and hospital-acquired illnesses. Among the diverse set of virulence factors that S. aureus possesses, secreted toxins play a particularly preeminent role in defining its virulence. In this work, we aimed to facilitate the development of novel strategies utilizing natural compounds to lower S. aureus's toxin production and consequently enhance therapeutic approaches. Two natural polyphenols, resveratrol (RSV) and curcumin (CUR), were tested for their effect on reducing toxin gene production of MRSA isolates. Fifty clinical MRSA isolates were gathered from Riyadh and Jeddah. Molecular screening of toxin genes (sea, seb, sec, sed, seh, lukF, and lukS) harbored by MRSA was performed. Sub-inhibitory concentrations of RSV (50 μg/ml) and CUR (20 μg/ml) were determined to study their effect on the gene expression MRSA's toxin genes. Our findings revealed the presence of the tested genes in MRSA isolates, with lukF being the most prevalent gene and seh the least detected gene. We found that RSV reduced the relative expression of toxin genes, sea, seb, lukF, and lukS, respectively, while CUR decreased the relative expression of sea and seb genes in the examined isolates. Regarding lukF and lukS, CUR downregulated the expression of both genes in some isolates and upregulated the expression in other isolates. From these results, we concluded that RSV and CUR could be used as alternative therapeutic approaches to treat MRSA infections through reducing toxin production.

Susceptibility of periodontal pathogens to a novel target-specific drug delivery system containing self-nanoemulsifying curcumin: An in vitro study

Background

Long-term use of many classic chemotherapeutic agents as adjuncts in the management of periodontitis has adverse complications, leading to seeking out naturopathic remedies. Although curcumin has been investigated in managing periodontitis, its therapeutic benefits have not been fully explored due to its limited solubility in an aqueous medium. This study aimed to develop a novel target-specific drug delivery system containing 1% self-nanoemulsifying curcumin (SNEC) in a hydroxypropylmethylcellulose (HPMC) matrix and evaluate the susceptibility of periodontal pathogens to this system in vitro.

Methods

Its antibacterial activity against Tannerella forsythia, Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans was evaluated and compared to pure nano-curcumin and SNEC alone by estimating their minimum inhibitory concentrations (MIC).

Results

The antibacterial activity of pure nano-curcumin, SNEC, and SNEC in HPMC against the four periodontal pathogens evaluated in terms of MIC was recorded in the range of 0.2‒0.4, 0.4‒0.8, and 0.2‒0.8 µg/mL, respectively. However, the MIC of all three curcumin formulations against the periodontal pathogens tested was higher than that of the standard moxifloxacin. While both pure nano-curcumin and SNEC showed increasing values of inhibition zones with increasing concentrations on disk diffusion assay, lower concentrations of SNEC in HPMC did not show a zone of inhibition against the tested pathogens.

Conclusion

The novel delivery system containing SNEC in HPMC may be a potential adjunct in managing periodontitis due to its probable sustained antimicrobial activity against the tested periodontal pathogens.

Review: The Chemistry, Toxicity and Antibacterial Activity of Curcumin and Its Analogues

Antimicrobial resistance is a global challenge that is already exacting a heavy price both in terms of human health and financial cost. Novel ways of approaching this crisis include the investigation of natural products. Curcumin is the major constituent in turmeric, and it is commonly used in the preparation of Asian cuisine. In addition, it possesses a wide range of pharmacological properties. This review provides a detailed account of curcumin and its analogues' antibacterial activity against both gram-positive and gram-negative isolates, including its potential mechanism(s) of action and the safety and toxicity in human and animal models. We also highlight the key challenges in terms of solubility/bioavailability associated with the use of curcumin and include research on how these challenges have been overcome.

In vitro study of nanoliposomes containing curcumin and doxycycline for enhanced antimicrobial photodynamic therapy against Aggregatibacter actinomycetemcomitans

The excessive inappropriate use of systemic antibiotics has contributed to the emergence of antibiotic-resistant pathogens, which pose a significant risk to the success of treatment. This study has approached this problem by developing doxycycline-loaded liposome doped with curcumin (NL-Cur^+Dox) for combination antibacterial therapy against Aggregatibacter actinomycetemcomitans. The characterization of formulation revealed encapsulation of both drugs in NL-Cur^+Dox with an average size of 239 nm and sustained release behavior. Transmission electron microscopy analysis confirmed the vesicular-shaped nanocarriers without any aggregation or crystallization. The cytotoxic and hemolytic activities of NL-Cur^+Dox were evaluated. The anti-biofilm and anti-metabolic effects of NL-Cur^+Dox -mediated antimicrobial photodynamic therapy (aPDT) were examined. The data indicated that NL-Cur^+Dox -mediated aPDT led to a significant reduction of biofilm (82.7%, p = 0.003) and metabolic activity (75%, p < 0.001) of A. actinomycetemcomitans compared to the control. NL-Cur^+Dox had no significant cytotoxicity to human gingival fibroblast cells under selected conditions (p = 0.074). In addition, the hemolytic activity of NL-Cur^+Dox were negligible (< 5%). These findings demonstrate the potential application of such potent formulations in reducing one of the main bacteria causing periodontitis where the NL-Cur^+Dox could be exploited to achieve an improved phototherapeutic efficiency.

Mikania micrantha extract enhances cutaneous wound healing activity through the activation of FAK/Akt/mTOR cell signaling pathway

Mikania micrantha (MM) has been traditionally used for various health benefits, including mental health, anti-inflammatory, wound dressing, and healing of sores. However, the molecular mechanisms and dose required for the wound healing activity of MM have yet to be reported. Therefore, a study was conducted to evaluate the wound healing potential of a cold methanolic extract of MM through in vitro and in vivo studies. Human dermal fibroblast adult (HDFa) cells were treated with 0 (control), 75 ng/ml, 125 ng/ml, 250 ng/ml, and 500 ng/ml of MMmethanolic extract (MME) for 24 h. MME at 75 ng/ml has significantly (p˂0.05) promoted HDFa cell proliferation and migration. Further, MME has also been shown to enhance the invasiveness of human umbilical vascular endothelial cells (HUVECs), indicating the neovasculature for wound healing. The tube formation assay demonstrated a significant (p<0.05) increase in the angiogenic effect of the MME starting at a concentration of 75 ng/ml as compared to the control. Treatment of excision wounds in Wistar rats with 5% and 10% MME ointment significantly enhanced wound contraction compared to control animals. Incision wounds in rats treated with 5% and 10% MME showed a significant (p<0.01) increase in tensile strength compared to control. HDFa cells, and granulation tissue collected on day 14 post-wounding, revealed the modulation of the FAK/Akt/mTOR cell signaling pathway during the enhancement of wound healing. The results of gel zymography showed increased activity of MMP-2 and MMP-9 in the HDFa cells after treatment with the extract.  It is concluded that MMEcan potentially accelerate cutaneous wound healing.

Therapeutic potential and limitations of curcumin as antimetastatic agent

Treatment of metastatic cancer is one of the biggest challenges in anticancer therapy. Curcumin is interesting nature polyphenolic compound with unique biological and medicinal effects, including repression of metastases. High impact studies imply that curcumin can modulate the immune system, independently target various metastatic signalling pathways, and repress migration and invasiveness of cancer cells. This review discusses the potential of curcumin as an antimetastatic agent and describes potential mechanisms of its antimetastatic activity. In addition, possible strategies (curcumin formulation, optimization of the method of administration and modification of its structure motif) to overcome its limitation such as low solubility and bioactivity are also presented. These strategies are discussed in the context of clinical trials and relevant biological studies.

Therapeutic potential of curcumin in ARDS and COVID-19

Curcumin is a safe, non-toxic, readily available and naturally occurring compound, an active constituent of Curcuma longa (turmeric). Curcumin could potentially treat diseases, but faces poor physicochemical and pharmacological characteristics. To overcome these limitations, we developed a stable, water-soluble formulation of curcumin called cyclodextrin-complexed curcumin (CDC). We have previously shown that direct delivery of CDC to the lung following lipopolysaccharides exposure reduces acute lung injury (ALI) and effectively reduces lung injury, inflammation and mortality in mice following Klebsiella pneumoniae. Recently, we found that administration of CDC led to a significant reduction in angiotensin-converting enzyme 2 and signal transducer and activator of transcription 3 expression in gene and protein levels following pneumonia, indicating its potential in treating coronavirus disease 2019 (COVID-19). In this review, we consider the clinical features of ALI and acute respiratory distress syndrome (ARDS) and the role of curcumin in modulating the pathogenesis of bacterial/viral-induced ARDS and COVID-19.

Functional liposome loaded curcumin for the treatment of Streptococcus mutans biofilm

Introduction: Plaque biofilms, mainly formed by Streptococcus mutans (S. mutans), play an important role in the occurrence and development of dental caries. Antibiotic treatment is the traditional way to control plaque. However, problems such as poor drug penetration and antibiotic resistance have encouraged the search for alternative strategies. In this paper, we hope to avoid antibiotic resistance through the antibacterial effect of curcumin, a natural plant extract with photodynamic effects, on S. mutans. However, the clinical application of curcumin is limited due to its low water solubility, poor stability, high metabolic rate, fast clearance rate, and limited bioavailability. In recent years, liposomes have become a widely used drug carrier due to their numerous advantages, such as high drug loading efficiency, high stability in the biological environment, controlled release, biocompatibility, non-toxic, and biodegradability. So, we constructed a curcumin-loaded liposome (Cur@LP) to avoid the defect of curcumin.

Methods: Cur@LP functioned with NHS can adhere to the surface of the S. mutans biofilm by condensation reaction. Liposome (LP) and Cur@LP was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The cytotoxicity of Cur@LP was evaluated by CCK-8 assay and LDH assay. The adhesion of Cur@LP to S. mutans biofilm was observed by confocal laser scanning microscope (CLSM). The antibiofilm efficiency of Cur@LP were evaluated by crystal violet staining, CLSM, and scanning electron microscope (SEM).

Results: The mean diameter of LP and Cur@LP were 206.67 ± 8.38 nm and 312 ± 18.78 nm respectively. The ζ-potential of LP and Cur@LP were ∼−19.3 mV and ∼−20.8 mV respectively. The encapsulation efficiency of Cur@LP was (42.61 ± 2.19) %, and curcumin was rapidly released up to ±21% at 2 h. Cur@LP has negligible cytotoxicity, and can effectively adhered to the S. mutans biofilm and inhibited its growth.

Discussion: Curcumin has been widely studied in many fields such as cancer, which can be attributed to its antioxidant and anti-inflammatory effects. At present, there are few studies on the delivery of curcumin to S. mutans biofilm. In this study, we verified the adhesion and antibiofilm of Cur@LP to S. mutans biofilm. This biofilm removal strategy has the potential to be translated into the clinic.

Combination drug strategies for biofilm eradication using synthetic and natural agents in KAPE pathogens

Antibiotic resistance is a global threat caused by factors such as overuse of antibiotics, lack of awareness, development of biofilms etc. World Health Organization released a list of global priority pathogens which consisted of 12 species of bacteria categorized as expressing critical, high and medium resistance. Several Gram-negative and Gram-positive species are known to cause wide varieties of infections and have become multidrug or extremely drug resistant. Pathogens causing infections associated with invasive medical devices are biofilm producers and hence their treatment becomes difficult due to a structurally stable matrix which prevents antibiotics from penetrating the biofilm and thereby showing its effects. Factors contributing to tolerance are inhibition of penetration, restricted growth and activation of biofilm genes. Combination drug therapies has also shown potential to eradicate biofilm infections. A combination of inhaled Fosfomycin/tobramycin antibiotic strategy has been effective against Gram-negative as well as Gram positive organisms. Along with antibiotics, use of natural or synthetic adjuvants shows promising effects to treat biofilm infections. Fluroquinolone activity on biofilms is disrupted by low oxygen tension in the matrix, a strategy known as hyperbaric oxygen treatment that can enhance efficacy of antibiotics if well optimized. Adjuvants such as Ethylenediaminetetraacetic acid (EDTA), Sodium Dodecyl Sulphate (SDS) and chlorhexidine act by killing non-growing microbial cells aggregated on the inner layer of the biofilm. This review aims to list down current combination therapies used against Gram-negative and Gram-positive biofilm forming pathogens and brief about comparison of combination drugs and their efficacies.

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Multidrug-resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top 10 global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad-spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection, and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin, and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe, and sustainable antibacterial molecule against clinically important bacterial species that uses multitarget mechanism such as inactivation of antioxidant enzyme, reactive oxygen species-mediated cellular damage, and inhibition of acyl-homoserine-lactone synthase necessary for quorum sensing and biofilm formation, thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance.

Demonstration of the efficacy of curcumin on carbapenem-resistant Pseudomonas aeruginosa with Galleria mellonella larvae model

Due to increasing antimicrobial resistance, studies where new treatment options are investigated along with the synergistic effects of natural products with antibiotics have arisen. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen and infection with multi-drug resistant (MDR) P. aeruginosa poses a critical problem during treatment. Curcumin (CUR) is listed in the literature as one of the promising natural ingredients with its strong antimicrobial activity. In our study, our aim was to investigate the in vitro synergistic effect of CUR with imipenem (IMP) and Colistin (CST) in MDR P. aeruginosa isolates and in vivo activity on Galleria mellonella (G. mellonella) larvae. Three clinical isolates of MDR P. aeruginosa, which were determined to be phenotypically resistant to carbapenems, were used, and KPC and OXA48 resistance genes were determined by PCR method. The synergistic effect of CUR with antibiotics were investigated by the checkerboard method. Larval survival and bacterial load were compared with the in vivo study. In this study, IMP MIC values were significantly reduced (two to eight-fold decrease) in the presence of CUR, and partial synergy was observed. For CST, this value decreased two-fold. Bacterial load was evaluated to investigate the effect of antimicrobials during infection. While the CFUs increased over time in non-treated larvae as compared to the initial inoculum, bacterial load was significantly decreased for the groups treated with CUR, IMP and CST compared to the untreated group (p < 0.05). It was concluded CUR-antibiotic combinations can provide an alternative approach in the treatment of infections with MDR bacteria.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

Azithromycin possesses biofilm–inhibitory activity and potentiates non-bactericidal colistin methanesulfonate (CMS) and polymyxin B against Klebsiella pneumonia

Novel antibiotic combinations may act synergistically to inhibit the growth of multidrug-resistant bacterial pathogens but predicting which combination will be successful is difficult, and standard antimicrobial susceptibility testing may not identify important physiological differences between planktonic free-swimming and biofilm-protected surface-attached sessile cells. Using a nominally macrolide-resistant model Klebsiella pneumoniae strain (ATCC 10031) we demonstrate the effectiveness of several macrolides in inhibiting biofilm growth in multi-well plates, and the ability of azithromycin (AZM) to improve the effectiveness of the antibacterial last-agent-of-choice for K. pneumoniae infections, colistin methanesulfonate (CMS), against biofilms. This synergistic action was also seen in biofilm tests of several K. pneumoniae hospital isolates and could also be identified in polymyxin B disc-diffusion assays on azithromycin plates. Our work highlights the complexity of antimicrobial-resistance in bacterial pathogens and the need to test antibiotics with biofilm models where potential synergies might provide new therapeutic opportunities not seen in liquid culture or colony-based assays.

Using Caenorhabditis elegans to Model Therapeutic Interventions of Neurodegenerative Diseases Targeting Microbe-Host Interactions

Emerging evidence from both clinical studies and animal models indicates the importance of the interaction between the gut microbiome and the brain in the pathogenesis of neurodegenerative diseases (NDs). Although how microbes modulate neurodegeneration is still mostly unclear, recent studies have started to probe into the mechanisms for the communication between microbes and hosts in NDs. In this review, we highlight the advantages of using Caenorhabditis elegans (C. elegans) to disentangle the microbe-host interaction that regulates neurodegeneration. We summarize the microbial pro- and anti-neurodegenerative factors identified using the C. elegans ND models and the effects of many are confirmed in mouse models. Specifically, we focused on the role of bacterial amyloid proteins, such as curli, in promoting proteotoxicity and neurodegeneration by cross-seeding the aggregation of endogenous ND-related proteins, such as α-synuclein. Targeting bacterial amyloid production may serve as a novel therapeutic strategy for treating NDs, and several compounds, such as epigallocatechin-3-gallate (EGCG), were shown to suppress neurodegeneration at least partly by inhibiting curli production. Because bacterial amyloid fibrils contribute to biofilm formation, inhibition of amyloid production often leads to the disruption of biofilms. Interestingly, from a list of 59 compounds that showed neuroprotective effects in C. elegans and mouse ND models, we found that about half of them are known to inhibit bacterial growth or biofilm formation, suggesting a strong correlation between the neuroprotective and antibiofilm activities. Whether these potential therapeutics indeed protect neurons from proteotoxicity by inhibiting the cross-seeding between bacterial and human amyloid proteins awaits further investigations. Finally, we propose to screen the long list of antibiofilm agents, both FDA-approved drugs and novel compounds, for their neuroprotective effects and develop new pharmaceuticals that target the gut microbiome for the treatment of NDs. To this end, the C. elegans ND models can serve as a platform for fast, high-throughput, and low-cost drug screens that target the microbe-host interaction in NDs.

Synergy based extracts of medicinal plants: Future antimicrobials to combat multidrug resistance

The use of herbal medicines and supplements in the last thirty years has increased enormously. Herbal medication has demonstrated promising and effective potential against various diseases. Herbal and phytoconstituent medications are gaining popularity globally and many people are adopting herbal remedies to deal with different health issues. The indiscriminate use of antibiotics, due to the development of antimicrobial resistance, poses an unprecedented problem for human civilization. Bacterial infections are difficult to cure because of the propensity of microbes to acquire resistance to a wide range of antimicrobial drugs. New compounds are being explored and quantified for possible antibacterial activity with little or no side effects. Researchers are investigating the range of therapeutic plants mentioned in Unani, Ayurveda, and Siddha around the globe. Known and commonly acclaimed global databases such as PubMed, Research Gate, Science Direct, Google Scholar, were searched using different search strings such as Indian medicinal plants, multidrug resistance (MDR), thin layer chromatography (TLC), antimicrobials, and Synergism were used in diverse combinations to reclaim numerous citations associated with this area. Thus, the current review aims to shed a light on the information of medicinal plants as a potential foundation of herbal drugs and elucidate how synergism and TLC bioautography plays a crucial role in finding antimicrobial compounds.

Antibiotic resistance modifying ability of phytoextracts in anthrax biological agent Bacillus anthracis and emerging superbugs: a review of synergistic mechanisms

Background and objectives

The chemotherapeutic management of infections has become challenging due to the global emergence of antibiotic resistant pathogenic bacteria. The recent expansion of studies on plant-derived natural products has lead to the discovery of a plethora of phytochemicals with the potential to combat bacterial drug resistance via various mechanisms of action. This review paper summarizes the primary antibiotic resistance mechanisms of bacteria and also discusses the antibiotic-potentiating ability of phytoextracts and various classes of isolated phytochemicals in reversing antibiotic resistance in anthrax agent Bacillus anthracis and emerging superbug bacteria.

Methods

Growth inhibitory indices and fractional inhibitory concentration index were applied to evaluate the in vitro synergistic activity of phytoextract-antibiotic combinations in general.

Findings

A number of studies have indicated that plant-derived natural compounds are capable of significantly reducing the minimum inhibitory concentration of standard antibiotics by altering drug-resistance mechanisms of B. anthracis and other superbug infection causing bacteria. Phytochemical compounds allicin, oleanolic acid, epigallocatechin gallate and curcumin and Jatropha curcas extracts were exceptional synergistic potentiators of various standard antibiotics.

Conclusion

Considering these facts, phytochemicals represents a valuable and novel source of bioactive compounds with potent antibiotic synergism to modulate bacterial drug-resistance.

Curcumin activation of a bacterial mechanosensitive channel underlies its membrane permeability and adjuvant properties

Curcumin, a natural compound isolated from the rhizome of turmeric, has been shown to have antibacterial properties. It has several physiological effects on bacteria including an apoptosis-like response involving RecA, membrane permeabilization, inhibiting septation, and it can also work synergistically with other antibiotics. The mechanism by which curcumin permeabilizes the bacterial membrane has been unclear. Most bacterial species contain a Mechanosensitive channel of large conductance, MscL, which serves the function of a biological emergency release valve; these large-pore channels open in response to membrane tension from osmotic shifts and, to avoid cell lysis, allow the release of solutes from the cytoplasm. Here we show that the MscL channel underlies the membrane permeabilization by curcumin as well as its synergistic properties with other antibiotics, by allowing access of antibiotics to the cytoplasm; MscL also appears to have an inhibitory role in septation, which is enhanced when activated by curcumin.

Curcumin-meropenem synergy in carbapenem resistant Klebsiella pneumoniae curcumin-meropenem synergy

Background and Objectives:

The frequency of multiple resistant bacterial infections, including carbapenems, is increasing worldwide. As the decrease in treatment options causes difficulties in treatment, interest in new antimicrobials is increasing. One of the promising natural ingredients is curcumin. It is known to be effective in bacteria such as Pseudomonas aeruginosa, Escherichia coli, Burkholderia pseudomallei through efflux pump inhibition, toxin inhibition and enzymes. However, because its bioavailability is poor, it seffectiveness occurs in combination with antibiotics. In the study, the interaction of meropenem and curcumin in carbapenemase producing strains of Klebsiella pneumoniae was tested.

Materials and Methods:

Thirty-nine Klebsiella pneumoniae isolates, resistant to meropenem, were used in this study. From those 15 MBL, 6 KPC, 17 OXA-48 and 1 AmpC resistance pattern were detected by combination disk method. Meropenem and Curcumin MIC values were determined by liquid microdilution. Checkerboard liquid microdilution was used to determine the synergy between meropenem and curcumin.

Results:

Synergistic effects were observed in 4 isolates producing MBL, 3 isolates producing KPC, 4 isolates producing OXA-48, and 1 isolates producing AmpC (totally 12 isolates) according to the calculated FICI. No antagonistic effects were observed in any isolates.

Conclusion:

Curcumin was thought to be an alternative antimicrobial in combination therapies that would positively contribute to the treatment of bacterial infection. The effectiveness of this combination should be confirmed by other in vitro and clinical studies.

Exploring Phenolic Compounds as Quorum Sensing Inhibitors in Foodborne Bacteria

The emergence of multidrug-resistant bacteria stimulates the search for new substitutes to traditional antimicrobial agents, especially molecules with antivirulence properties, such as those that interfere with quorum sensing (QS). This study aimed to evaluate the potential of phenolic compounds for QS inhibition in a QS biosensor strain (Chromobacterium violaceum) and three foodborne bacterial species (Aeromonas hydrophila, Salmonella enterica serovar Montevideo, and Serratia marcescens). Initially, an in silico molecular docking study was performed to select the compounds with the greatest potential for QS inhibition, using structural variants of the CviR QS regulator of C. violaceum as target. Curcumin, capsaicin, resveratrol, gallic acid, and phloridizin presented good affinity to at least four CviR structural variants. These phenolic compounds were tested for antimicrobial activity, inhibition of biofilm formation, and anti-QS activity. The antimicrobial activity when combined with kanamycin was also assessed. Curcumin, capsaicin, and resveratrol inhibited up to 50% of violacein production by C. violaceum. Biofilm formation was inhibited by resveratrol up to 80% in A. hydrophila, by capsaicin and curcumin up to 40% in S. Montevideo and by resveratrol and capsaicin up to 60% in S. marcescens. Curcumin completely inhibited swarming motility in S. marcescens. Additionally, curcumin and resveratrol increased the sensitivity of the tested bacteria to kanamycin. These results indicate that curcumin and resveratrol at concentrations as low as 6μM are potential quorum sensing inhibitors besides having antimicrobial properties at higher concentrations, encouraging applications in the food and pharmaceutical industries.

Enzyme-based sensing on nanohybrid film coated over FTO electrode for highly sensitive detection of antibiotics

Cefepime and Meropenem are the new class of antibiotics, which are particularly used as last potent defender or the antibiotics of the last resort against multi-resistant bacterial species. In this paper, an impedance-based electrochemical biosensor was fabricated for identifying antibiotics of last resort in the forensic samples including gastric lavage and other body fluids. The sensor was developed using platinum nanoparticles (PtNPs) and electrodeposited zinc oxide- zinc hexacyanoferrate hybrid film (ZnO/ZnHCF) on the surface of a fluorine-doped glass electrode (FTO). Further, penicillinase was immobilized onto the modified electrode using penicillinase enzyme. The developed biosensor exhibits a good analytical response for the detection of antibiotics evaluated using electrochemistry studies. The linear response of the fabricated electrode was observed from 0.1 to 750 µM and the electrode limit of detection (LOD) was observed as 0.1 µM. The sensor confirms good accuracy, is highly selective, and sensitive for the target. While storing the modified electrode at 4 °C, the stability of biosensor was evaluated for 45 days, and activity loss of 30-40% was observed. The highly sensitive interface of Penicillinase@CHIT/PtNP-ZnO/ZnHCF/FTO electrode shows a promising future in forensic studies.

Metal-Curcumin Complexes in Therapeutics: An Approach to Enhance Pharmacological Effects of Curcumin

Curcumin, an active component of the rhizome turmeric, has gained much attention as a plant-based compound with pleiotropic pharmacological properties. It possesses anti-inflammatory, antioxidant, hypoglycemic, antimicrobial, neuroprotective, and immunomodulatory activities. However, the health-promoting utility of curcumin is constrained due to its hydrophobic nature, water insolubility, poor bioavailability, rapid metabolism, and systemic elimination. Therefore, an innovative stride was taken, and complexes of metals with curcumin have been synthesized. Curcumin usually reacts with metals through the β-diketone moiety to generate metal–curcumin complexes. It is well established that curcumin strongly chelates several metal ions, including boron, cobalt, copper, gallium, gadolinium, gold, lanthanum, manganese, nickel, iron, palladium, platinum, ruthenium, silver, vanadium, and zinc. In this review, the pharmacological, chemopreventive, and therapeutic activities of metal–curcumin complexes are discussed. Metal–curcumin complexes increase the solubility, cellular uptake, and bioavailability and improve the antioxidant, anti-inflammatory, antimicrobial, and antiviral effects of curcumin. Metal–curcumin complexes have also demonstrated efficacy against various chronic diseases, including cancer, arthritis, osteoporosis, and neurological disorders such as Alzheimer’s disease. These biological activities of metal–curcumin complexes were associated with the modulation of inflammatory mediators, transcription factors, protein kinases, antiapoptotic proteins, lipid peroxidation, and antioxidant enzymes. In addition, metal–curcumin complexes have shown usefulness in biological imaging and radioimaging. The future use of metal–curcumin complexes may represent a new approach in the prevention and treatment of chronic diseases.

Ag-Based Synergistic Antimicrobial Composites. A Critical Review

The emerging problem of the antibiotic resistance development and the consequences that the health, food and other sectors face stimulate researchers to find safe and effective alternative methods to fight antimicrobial resistance (AMR) and biofilm formation. One of the most promising and efficient groups of materials known for robust antimicrobial performance is noble metal nanoparticles. Notably, silver nanoparticles (AgNPs) have been already widely investigated and applied as antimicrobial agents. However, it has been proposed to create synergistic composites, because pathogens can find their way to develop resistance against metal nanophases; therefore, it could be important to strengthen and secure their antipathogen potency. These complex materials are comprised of individual components with intrinsic antimicrobial action against a wide range of pathogens. One part consists of inorganic AgNPs, and the other, of active organic molecules with pronounced germicidal effects: both phases complement each other, and the effect might just be the sum of the individual effects, or it can be reinforced by the simultaneous application. Many organic molecules have been proposed as potential candidates and successfully united with inorganic counterparts: polysaccharides, with chitosan being the most used component; phenols and organic acids; and peptides and other agents of animal and synthetic origin. In this review, we overview the available literature and critically discuss the findings, including the mechanisms of action, efficacy and application of the silver-based synergistic antimicrobial composites. Hence, we provide a structured summary of the current state of the research direction and give an opinion on perspectives on the development of hybrid Ag-based nanoantimicrobials (NAMs).

In situ functionalizing calcium phosphate biomaterials with curcumin for the prevention of bacterial biofilm infections

This study developed a novel bioactive bone substitute (hydroxyapatite, HA) with improved anti-biofilm activity by functionalizing with curcumin (anti-biofilm compound) which provide sufficient flux of curcumin concentration for 14 days. The released curcumin acts to inhibit biofilm formation and control the number of viable planktonic cells simultaneously. To prepare curcumin-functionalized HA, different concentrations of curcumin (up to 3% w/v) were added simultaneously during the precipitation process of HA. The highest loading (50 mg/g HA) of curcumin onto HA was achieved with 2% w/v of curcumin. Physicochemical characterizations of curcumin-functionalized HA composites revealed that curcumin was successfully incorporated onto HA. Curcumin was sustainably released over 14 days, while higher curcumin release was observed in acidic condition (pH 4.4) compared to physiological (pH 7.4). The cytotoxicity assays revealed that no significant difference on bone cells growth on curcumin-functionalized HA and non-functionalized HA. Curcumin-functionalized HA was effective to inhibit bacterial cell attachment and subsequent biofilm maturation stages. The anti-biofilm effect was stronger against Staphylococcus aureus compared to Pseudomonas aeruginosa. The curcumin-functionalized HA composite significantly delayed the maturation of S. aureus compared to non-functionalized HA in which microcolonies of cells only begin to appear at 96 h. Up to 3.0 log reduction in colony forming unit (CFU)/mL of planktonic cells was noted at 24 h of incubation for both microorganisms. Thus, in this study we have suggested that curcumin loaded HA could be an alternative antimicrobial agent to control the risk of infections in post-surgical implants.

Activation of kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element pathway by curcumin enhances the anti-oxidative capacity of corneal endothelial cells

Fuchs endothelial corneal dystrophy is one of the most common indications for corneal transplantation, and impaired anti-oxidative function is observed in corneal endothelial cells (CECs). Curcumin is well-known for its anti-oxidative property; but, no study has examined the effect of curcumin on anti-oxidative therapeutic roles in corneal endothelial disease. In our experiments, oxidative stress 0.25 mM tert-butyl hydroperoxide for 2 h was induced in immortalized human CECs pretreated with curcumin. Cell behavior and viability, reactive oxygen species production, and the protein expression of the kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2(Nrf2)/antioxidant response element (ARE) pathway were examined; the Keap1/Nrf2/ARE pathway is crucial anti-oxidative pathway of curcumin. The results showed that pretreatment with 12.5 μM curcumin significantly reduced the ROS production and improved the survival of CECs under oxidative stress. In addition, curcumin pretreatment significantly increased the expression of nuclear Nrf2, and the productions of superoxide dismutase 1 and heme oxygenase-1, which were the target anti-oxidative enzymes of the Keap1/Nrf2/ARE pathway. Our findings showed that curcumin enhanced the growth and differentiation of CECs under oxidative stress. The activation of Keap1/Nrf2/ARE pathway by curcumin was crucial for CECs to improve their anti-oxidative capacity.

Incorporation of Antibiotics into Solid Lipid Nanoparticles: A Promising Approach to Reduce Antibiotic Resistance Emergence

Antimicrobial resistance is one of the biggest threats to global health as current antibiotics are becoming useless against resistant infectious pathogens. Consequently, new antimicrobial strategies are urgently required. Drug delivery systems represent a potential solution to improve current antibiotic properties and reverse resistance mechanisms. Among different drug delivery systems, solid lipid nanoparticles represent a highly interesting option as they offer many advantages for nontoxic targeted drug delivery. Several publications have demonstrated the capacity of SLNs to significantly improve antibiotic characteristics increasing treatment efficiency. In this review article, antibiotic-loaded solid lipid nanoparticle-related works are analyzed to summarize all information associated with applying these new formulations to tackle the antibiotic resistance problem. The main antimicrobial resistance mechanisms and relevant solid lipid nanoparticle characteristics are presented to later discuss the potential of these nanoparticles to improve current antibiotic treatment characteristics and overcome antimicrobial resistance mechanisms. Moreover, solid lipid nanoparticles also offer new possibilities for other antimicrobial agents that cannot be administrated as free drugs. The advantages and disadvantages of these new formulations are also discussed in this review. Finally, given the progress of the studies carried out to date, future directions are discussed.

Determination of efficacy of curcumin and Tulsi extracts as local drugs in periodontal pocket reduction: A clinical and microbiological study

Background:

The aim of our study is to assess the effectiveness of Curcumin and Tulsi in the control of periodontal parameters when delivered in the form of local drug delivery (LDD) agents.

Methods:

Curenext gel^® and Tulsi gel were used as the two LDD agent. A split mouth randomized clinical trial was carried out in 15 patients. Three sites in different quadrants were assigned treatment modality of scaling and root planing (SRP) alone, SRP with LDD of curcumin and SRP with LDD of Tulsi extract, respectively. Clinical parameters Probing Pocket Depth, Clinical Attachment Level, Plaque Index, Gingival Index, and modified Sulcus Bleeding Index were recorded and subgingival plaque sample collected for N-benzoyl-L-arginine-p-nitroanilide (BAPNA) assay on baseline followed by LDD with extracts in the assigned group. The parameters were recorded at baseline and on 30^th day postoperatively. Unpaired and Paired-'t' test were used for intergroup and intragroup comparison of recorded clinical and microbiological parameters.

Results:

All the treatment modalities showed statistically significant reduction in clinical and microbiological parameters on intragroup comparison. Intergroup comparison showed statistically significant reduction in Plaque Index in curcumin group and BAPNA assay in Tulsi group when compared to SRP.

Conclusion:

Both the herbs were effective in improving periodontal parameters and may develop as an alternative to currently used LDD agents in near future.

Curcumin: Modern Applications for a Versatile Additive

The recent development of several methods for extracting curcumin from the root of the plant Curcuma longa has led to intensified research on the properties of curcumin and its fields of application. Following the studies and the accreditation of curcumin as a natural compound with antifungal, antiviral, and antibacterial properties, new fields of application have been developed in two main directions—food and medical, respectively. This review paper aims to synthesize the fields of application of curcumin as an additive for the prevention of spoilage, safety, and quality of food. Simultaneously, it aims to present curcumin as an additive in products for the prevention of bacterial infections and health care. In both cases, the types of curcumin formulations in the form of (nano)emulsions, (nano)particles, or (nano)composites are presented, depending on the field and conditions of exploitation or their properties to be used. The diversity of composite materials that can be designed, depending on the purpose of use, leaves open the field of research on the conditioning of curcumin. Various biomaterials active from the antibacterial and antibiofilm point of view can be intuited in which curcumin acts as an additive that potentiates the activities of other compounds or has a synergistic activity with them.

Polyphenols against infectious diseases: Controlled release nano-formulations

The emergence of multi-drug resistant (MDR) pathogens has become a global threat and a cause of significant morbidity and mortality around the world. Natural products have been used as a promising approach to counter the infectious diseases associated with these pathogens. The application of natural products and their derivatives especially polyphenolic compounds as antibacterial agents is an active area of research, and prior studies have successfully treated a variety of bacterial infections using these polyphenolic compounds. However, delivery of polyphenolic compounds has been challenging due to their physicochemical properties and often poor aqueous solubility. In this regard, nanotechnology-based novel drug delivery systems offer many advantages, including improving bioavailability and the controlled release of polyphenolic compounds. This review summarizes the pharmacological mechanism and use of nano-formulations in developing controlled release delivery systems of naturally occurring polyphenols in infectious diseases.

Antibacterial Activity of Curcumin Against Periodontal Pathogens: A Systematic Review

Periodontitis is a chronic inflammatory disease characterized by destruction of the supporting structures of teeth caused by development of dental plaques and accumulation of microorganism around the gingival tissue. Curcumin has been shown to improve clinical parameters in periodontal diseases. However, the efficacy of curcumin in the elimination of periodontal pathogens is not clearly defined. The purpose of this study was to carry out a systematic review of the antibacterial activity of curcumin against periodontal pathogens. An electronic literature search in Medline, Scopus, Science Direct, Web of Science, Cochrane library, and Google scholar was performed up to February 29, 2020, to identify studies assessing the antibacterial activity of curcumin against periodontal pathogens. From 1238 publications, three clinical trials and five in vitro studies met the eligibility criteria. All three clinical studies reported improvement in restoring gingival health in clinical and microbiological parameters, following adjunctive use of curcumin for treatment of periodontitis. All five in vitro studies showed that curcumin could inhibit the growth of bacterial strains. Three of the five in vitro studies evaluated the effect of curcumin on mixed biofilm of periopathogens, which showed a significant inhibitory effect of curcumin on periodontal biofilms. This systematic review found that curcumin has antibacterial activity against periopathogens. The anti-biofilm activity of curcumin is reported as one of the mechanisms for this phenomenon. Curcumin could improve the clinical parameters of periodontal tissue not only by inhibition of the pathogens but also by modulating the host response.

Biofilms as Promoters of Bacterial Antibiotic Resistance and Tolerance

Multidrug resistant bacteria are a global threat for human and animal health. However, they are only part of the problem of antibiotic failure. Another bacterial strategy that contributes to their capacity to withstand antimicrobials is the formation of biofilms. Biofilms are associations of microorganisms embedded a self-produced extracellular matrix. They create particular environments that confer bacterial tolerance and resistance to antibiotics by different mechanisms that depend upon factors such as biofilm composition, architecture, the stage of biofilm development, and growth conditions. The biofilm structure hinders the penetration of antibiotics and may prevent the accumulation of bactericidal concentrations throughout the entire biofilm. In addition, gradients of dispersion of nutrients and oxygen within the biofilm generate different metabolic states of individual cells and favor the development of antibiotic tolerance and bacterial persistence. Furthermore, antimicrobial resistance may develop within biofilms through a variety of mechanisms. The expression of efflux pumps may be induced in various parts of the biofilm and the mutation frequency is induced, while the presence of extracellular DNA and the close contact between cells favor horizontal gene transfer. A deep understanding of the mechanisms by which biofilms cause tolerance/resistance to antibiotics helps to develop novel strategies to fight these infections.

Bidirectional alterations in antibiotics susceptibility in Staphylococcus aureus-Pseudomonas aeruginosa dual-species biofilm

In mixed infections, the bacterial susceptibility differs significantly compared to monocultures of bacteria, and generally the concentrations of antibiotics required for the treatment increases drastically. For S. aureus and P. aeruginosa dual species biofilms, it has been numerously reported that P. aeruginosa decreases S. aureus susceptibility to a broad range of antibiotics, including beta-lactams, glycopeptides, aminoglycosides, macrolides, while sensitizes to quinolones via secretion of various metabolites. Here we show that S. aureus also modulates the susceptibility of P. aeruginosa to antibiotics in mixed cultures. Thus, S. aureus-P. aeruginosa consortium was characterized by tenfold increase in susceptibility to ciprofloxacin and aminoglycosides compared to monocultures. The same effect could be also achieved by the addition of cell-free culture of S. aureus to P. aeruginosa biofilm. Moreover, similar increase in antibiotics efficacy could be observed following addition of S. aureus suspension to the P. aeruginosa mature biofilm, compared to P. aeruginosa monoculture, and vice versa. These findings open promising perspectives to increase the antimicrobial treatment efficacy of the wounds infected with nosocomial pathogens by the transplantation of the skin residential microflora.

Investigating the Effect of Nano-Curcumin on the Expression of Biofilm Regulatory Genes of Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen that causes serious nosocomial infections, especially in immunodeficient patients and cystic fibrosis, cancer, and burned individuals. The biofilm that plays an important role in the virulence of P. aeruginosa is under the regulation of quorum sensing and two-component regulatory systems of bacteria. Curcumin, an active phenolic extract of turmeric has shown an inhibitory effect on the biofilm formation of some pathogenic bacteria. Thus, the present study aims to evaluate the effect of Nano-Curcumin on the expression of major regulatory genes involved in biofilm formation of P. aeruginosa.

MATERIALS AND METHODS

The biofilm formation of P. aeruginosa ATCC 10145 was assessed in the presence of 15, 20, and 25 µg/mL concentrations of Nano-Curcumin using the microplate titer method. The effect of Nano-Curcumin on the expression level of regulatory genes were determined by relative reverse transcriptase-realtime PCR.

RESULTS

In the absence of Nano-Curcumin, P. aeruginosa strain ATCC 10145 strongly produced biofilm (3+) and in the presence of 15 and 20 µg/mL, biofilm formation was reduced to moderate (2+) and weak biofilm producer (1+), respectively. Nano-Curcumin at a concentration of 25µg/mL inhibited biofilm formation in P. aeruginosa. The expression of regulatory genes was not affected by biofilm inhibitory concentrations of Nano-Curcumin.

CONCLUSION

The antibiofilm mechanism of Curcumin is not related to the downregulation of regulatory systems of P. aeruginosa and probably it prevents the formation of a complete biofilm structure.

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.

Enhancing curcumin's solubility and antibiofilm activity via silica surface modification

Bacterial biofilms are microbial communities in which bacterial cells in sessile state are mechanically and chemically protected against foreign agents, thus enhancing antibiotic resistance. The delivery of active compounds to the inside of biofilms is often hindered due to the existence of the biofilm extracellular polymeric substances (EPS) and to the poor solubility of drugs and antibiotics. A possible strategy to overcome the EPS barrier is the incorporation of antimicrobial agents into a nanocarrier, able to penetrate the matrix and deliver the active substance to the cells. Here, we report the synthesis of antimicrobial curcumin-conjugated silica nanoparticles (curc-NPs) as a possibility for dealing with these issues. Curcumin is a known antimicrobial agent and to overcome its low solubility in water it was grafted onto the surface of silica nanoparticles, the latter functioning as nanocarrier for curcumin into the biofilm. Curc-NPs were able to impede the formation of model P. putida biofilms up to 50% and disrupt mature biofilms up to 54% at 2.5 mg mL^-1. Cell viability of sessile cells in both cases was also considerably affected, which is not observed for curcumin delivered as a free compound at the same concentration. Furthermore, proteomics of extracted EPS matrix of biofilms grown in the presence of free curcumin and curc-NPs revealed differences in the expression of key proteins related to cell detoxification and energy production. Therefore, curc-NPs are presented here as an alternative for curcumin delivery that can be exploited not only to other bacterial strains but also to further biological applications.

Bacterial biopolymers: from pathogenesis to advanced materials

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications.

Anti-microbial activity of curcumin nanoformulations: New trends and future perspectives

Curcumin has been used in numerous anti-microbial research because of its low side effects and extensive traditional applications. Despite having a wide range of effects, the intrinsic physicochemical characteristics such as low bioavailability, poor water solubility, photodegradation, chemical instability, short half-life and fast metabolism of curcumin derivatives limit their pharmaceutical importance. To overcome these drawbacks and improve the therapeutic ability of curcuminoids, novel approaches have been attempted recently. Nanoparticulate drug delivery systems can increase the efficiency of curcumin in several diseases, especially infectious diseases. These innovative strategies include polymeric nanoparticles, hydrogels, nanoemulsion, nanocomposite, nanofibers, liposome, nanostructured lipid carriers (NLCs), polymeric micelles, quantum dots, polymeric blend films and nanomaterial-based combination of curcumin with other anti-bacterial agents. Integration of curcumin in these delivery systems has displayed to improve their solubility, bioavailability, transmembrane permeability, prolong plasma half-life, long-term stability, target-specific delivery and upgraded the therapeutic effects. In this review paper, a range of in vitro and in vivo studies have been critically discussed to explore the therapeutic viability and pharmaceutical significance of the nano-formulated delivery systems to elevate the anti-bacterial activities of curcumin and its derivatives.

Nutraceuticals as modulators of gut microbiota: Role in therapy

As our knowledge of the various roles of the gut microbiota in the maintenance of homeostasis grows and as we learn how a disrupted microbiota may contribute to disease, therapeutic strategies that target our microbial fellow-travellers become ever more attractive. Most appealing are those interventions that seek to modify or supplement our diet through the addition of nutraceuticals. We now know that our diet, whether in the short or long term, is a major modifier of microbiota composition and function. Of the various nutraceuticals, two categories, prebiotics and probiotics, have received the greatest attention in basic research and product development. While our understanding of the impacts of prebiotics and probiotics on the indigenous microbiota and host biology have been described in great detail in vitro and in animal models, the clinical literature leaves much to be desired. While many claims have been made, few are supported by high quality clinical trials. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Single components of botanicals and nature-identical compounds as a non-antibiotic strategy to ameliorate health status and improve performance in poultry and pigs

In the current post-antibiotic era, botanicals represent one of the most employed nutritional strategies to sustain antibiotic-free and no-antibiotic-ever production. Botanicals can be classified either as plant extracts, meaning the direct products derived by extraction from the raw plant materials (essential oils (EO) and oleoresins (OR)), or as nature-identical compounds (NIC), such as the chemically synthesised counterparts of the pure bioactive compounds of EO/OR. In the literature, differences between the use of EO/OR or NIC are often unclear, so it is difficult to attribute certain effects to specific bioactive compounds. The aim of the present review was to provide an overview of the effects exerted by botanicals on the health status and growth performance of poultry and pigs, focusing attention on those studies where only NIC were employed or those where the composition of the EO/OR was defined. In particular, phenolic compounds (apigenin, quercetin, curcumin and resveratrol), organosulfur compounds (allicin), terpenes (eugenol, thymol, carvacrol, capsaicin and artemisinin) and aldehydes (cinnamaldehyde and vanillin) were considered. These molecules have different properties such as antimicrobial (including antibacterial, antifungal, antiviral and antiprotozoal), anti-inflammatory, antioxidant, immunomodulatory, as well as the improvement of intestinal morphology and integrity of the intestinal mucosa. The use of NIC allows us to properly combine pure compounds, according to the target to achieve. Thus, they represent a promising non-antibiotic tool to allow better intestinal health and a general health status, thereby leading to improved growth performance.

A pH-sensitive delivery system based on N-succinyl chitosan-ZnO nanoparticles for improving antibacterial and anticancer activities of curcumin

Inherent selective cytotoxicity, antibacterial activity and unique physicochemical properties of ZnO nanostructures and chitosan (CS) make them promising candidates for drug delivery. In this study, ZnO nanoparticles functionalized by N-succinyl chitosan as a pH-sensitive delivery system were synthesized to enhance the therapeutic potential of curcumin (CUR). CS coated-ZnO nanoparticles were synthesized by a co-precipitation method in the presence of CS. Chemical modification of CS-ZnO particles was performed by succinic anhydride for introducing -COOH functional groups which were then activated using 1,1'‑carbonyldiimidazole for CUR conjugation. The spherical-like CUR-conjugated system (CUR-CS-ZnO) with the average particle size of 40 nm presented significantly enhanced water dispersibility versus free CUR. The experimental study of CUR release from the system showed a pH-sensitive release profile, which enabled drug delivery to tumors and infection sites. MTT and Annexin-V FITC/PI assays revealed the superior anticancer activity of CUR-CS-ZnO compared to free CUR against breast cancer cells (MDA-MB-231) by inducing the apoptotic response with no cytotoxic effects on HEK293 normal cells. Moreover, CUR conjugation to the system notably dropped the MIC (25 to 50-fold) and MBC values (10 to 40-fold) against S. aureus and E. coli. The features qualify the formulation for anticancer and antimicrobial applications in the future.