In vitro synergistic effect of curcumin in combination with third generation cephalosporins against bacteria associated with infectious diarrhea

Harnessing bioactive nanocurcumin and curcumin nanocomposites to combat microbial pathogens: a comprehensive review

The alarming rise in bacterial infections including those caused by multidrug-resistant pathogens has garnered the attention of the scientific community, compelling them to explore as novel and effective alternatives to combat these infections. Moreover, the emerging viruses such as Influenza A virus subtype H1N1 (A/H1N1), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), Ebolavirus, recent coronavirus (SARS-CoV-2), etc. also has a significant impact all over the world. Therefore, the management of all such infections without any side effects is one of the most important challenges for the scientific community. Hence, the development of novel and effective antimicrobial agents is a need of the hour. In this context, Curcuma longa, commonly known as turmeric, has been used as traditional medicine for centuries to manage and treat such infections. Its bioactive constituent, curcumin has garnered significant attention in medicine due to its multifunctional bioactivities. Apart from antimicrobial properties, it also possesses potent antioxidant and anti-inflammatory activities. However, available reports suggest that its low solubility, stability, and biocompatibility limit its use. Moreover, on the other hand, it has been reported that these limitations associated with the use of curcumin can be resolved by transforming it into its nano-form, specifically curcumin nanoparticles. Recent advancements have brought curcumin nanoparticles into the spotlight, showcasing superior properties and a broad spectrum of antimicrobial applications. In this review, we have mainly focused on antimicrobial potential of curcumin and nanocurcumin, mechanisms underpinning their antimicrobial actions. Moreover, other aspects of toxicity and safety guidelines for nano-based products have been also discussed.

Comprehensive Overview of Antibacterial Drugs and Natural Antibacterial Compounds Found in Food Plants

The aim of this review is to list the various natural sources of antimicrobials that are readily available. Indeed, many plant sources are known to have antibiotic properties, although it is not always clear which molecule is responsible for this activity. Many food supplements also have this therapeutic indication. We propose here to take stock of the scientific knowledge attesting or not to these indications for some food sources. An overview of the various antibiotic drugs commercially available will be provided. A structural indication of the natural molecules present in various plants and reported to contribute to their antibiotic power will be given. The plants mentioned in this review, which does not claim to be exhaustive, are referenced for fighting Gram-positive and/or Gram-negative bacteria. It is difficult to attribute activity to just one of these natural molecules, as it is likely to result from synergy within the plant. Similarly, chitosan is mentioned for its fungistatic and bacteriostatic properties. In this case, this polymeric compound derived from the chitin of marine organisms is referenced for its antibiofilm activity. It seems that, in the face of growing antibiotic resistance, it makes sense to keep high-performance synthetic antibiotics on hand to treat the difficult pathologies that require them. On the other hand, for minor infections, the use of better-tolerated natural sources is certainly sufficient. To achieve this, we need to take stock of common plant sources, available as food products or dietary supplements, which are known to be active in this field.

Development of Curcumin Encapsulated Liposomes in Chlorhexidine-Loaded Organogel Using Ternary Phase Systems for Treatment of Omphalitis in Infants

Infections in infants, after childbirth, remain a leading cause of neonatal morbidity and mortality, globally. A soaring percentage of these infections arise from bacterial colonization of the umbilicus. Current therapy for omphalitis includes the topical application of chlorhexidine on the umbilicus. Bacteria such as Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, which are the key causative organisms of omphalitis, are resistant to chlorhexidine. In this study, curcumin-loaded liposomes were prepared using the "thin film hydration" method. Liposomes were characterized by particle size analysis, light microscopy, encapsulation efficiency, and flux. Stable organogels were formed via a high-speed homogenization method and stabilized by an emulsifier mix. They were evaluated for stability over a period by observing for phase separation. Four gels F1 (curcumin-loaded liposomes in chlorhexidine organogel), F2 (curcumin-loaded liposomes in organogel), F3 (chlorhexidine in organogel), and control (plain organogel) were prepared. Physicochemical properties of all gels were evaluated such as organoleptic tests, gel-to-sol transition, rheological studies, pH, skin irritancy, spreadability, accelerated stability, and antibacterial activity studies. Liposomes were spherical with an average size of 7 μm and an encapsulation efficiency of 97%. The in vitro release profile best fits the Higuchi mathematical model implying that curcumin release was by diffusion and dissolution mechanism. In vitro release was also higher at pH 5.5. F1 had the highest spreadability of 63 mm2g-1 and the lowest viscosity of 184,400 MPas at a shear rate of 10 rotations per minute with a pH of 6.5. Formulation F1 also displayed the highest antibacterial activity against all three bacteria. It can be concluded that the synergistic interaction between curcumin and chlorhexidine may be responsible for the significant antibacterial potency exhibited in formulation F1. Curcumin-loaded liposomes in chlorhexidine organogel (F1) can serve as a prototype for the development of an antibacterial topical formulation having intrinsic activity and enhanced potency to combat omphalitis.

Combination Effect of Phenylalanine-Arginine-Beta-Naphthylamide and Curcumin on the Expression of the mexY Gene in Aminoglycoside-Resistant Clinical Isolates of Pseudomonas aeruginosa

Background and Aims

Overexpression of MexXY-OprM efflux pump causes resistance to aminoglycosides in Pseudomonas aeruginosa. We aimed to investigate the relationship between resistance to aminoglycosides and the MexXY-OprM expression level in P. aeruginosa clinical isolates without and after treatment with curcumin and/or phenylalanine-arginine-beta-naphthylamide (PAβN) as the efflux pump inhibitors.

Methods

We collected 100 clinical isolates from hospitalized patients. The minimum inhibitory concentrations of aminoglycosides were determined by the micro-broth dilution method in the presence and absence of PAβN and/or curcumin. Then, real-time PCR was used to determine the expression level of the MexXY-OprM efflux pump.

Results

In this study, 34%, 35%, 10%, 38%, 43%, 42%, and 39% of the clinical isolates were resistant to gentamicin, tobramycin, amikacin, netilmicin, spectinomycin, kanamycin, and streptomycin, respectively. Also, 45% of the isolates showed an overexpression of the mexY gene, while 31 (68.88%) isolates exhibited a 2-3-fold overexpression, and 14 (31.11%) isolates had a more than threefold overexpression of the mexY gene. However, 4 (8.88%) isolates showed a ≥ 10-fold overexpression of this gene. The combination of PAβN with spectinomycin, netilmicin, streptomycin, and kanamycin exhibited a reduced MIC range of these aminoglycosides in 93.02%, 86.8%, 76.9%, and 71.4% of resistant isolates, respectively. Additionally, all gentamicin-, tobramycin-, kanamycin-, streptomycin-, and netilmicin-resistant isolates showed a decreased MIC range in combination with curcumin. The most synergistic effect of curcumin and PAβN was observed in combination with spectinomycin, while the least synergistic effect was detected with kanamycin.

Conclusion

Curcumin can be a significant efflux inhibitor as an adjuvant in combination with aminoglycosides for successful treatment of patients infected by P. aeruginosa overexpressing the MexXY-OprM efflux pump.

Assessment of antibacterial activity, modes of action, and synergistic effects of Origanum vulgare hydroethanolic extract with antibiotics against avian pathogenic Escherichia coli

This study evaluates the antibacterial effectiveness of Origanum vulgare hydroethanolic extract, both independently and in combination with antibiotics, against Escherichia coli strains associated with avian colibacillosis-a significant concern for the poultry industry due to the rise of antibiotic-resistant E. coli. The urgent demand for new treatments is addressed by analyzing the extract's phytochemical makeup via High-Performance Liquid Chromatography (HPLC), which identified sixteen phenolic compounds. Antibacterial activity was determined through agar diffusion and the measurement of minimum inhibitory and bactericidal concentrations (MIC and MBC), showing moderate efficacy (MIC: 3.9 to 7.8 mg/mL, MBC: 31.2 to 62.4 mg/mL). Combining the extract with antibiotics like ampicillin and tetracycline amplified antibacterial activity, indicating a synergistic effect and highlighting the importance of combinatory treatments against resistant strains. Further analysis revealed the extract's mechanisms of action include disrupting bacterial cell membrane integrity and inhibiting ATPase/H+ proton pumps, essential for bacterial survival. Moreover, the extract effectively inhibited and eradicated biofilms, crucial for preventing bacterial colonization. Regarding cytotoxicity, the extract showed no hemolytic effect at 1 to 9 mg/mL concentrations. These results suggest Origanum vulgare extract, particularly when used with antibiotics, offers a promising strategy for managing avian colibacillosis, providing both direct antibacterial benefits and moderating antibiotic resistance, thus potentially reducing the economic impact of the disease on the poultry industry.

Mechanism of antibacterial phytoconstituents: an updated review

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

Recovering the susceptibility of antibiotic-resistant bacteria using photooxidative damage

Multidrug-resistant bacteria are one of the most serious threats to infection control. Few new antibiotics have been developed; however, the lack of an effective new mechanism of their action has worsened the situation. Photodynamic inactivation (PDI) can break antimicrobial resistance, since it potentiates the effect of antibiotics, and induces oxidative stress in microorganisms through the interaction of light with a photosensitizer. This paper addresses the application of PDI for increasing bacterial susceptibility to antibiotics and helping in bacterial persistence and virulence. The effect of photodynamic action on resistant bacteria collected from patients and bacteria cells with induced resistance in the laboratory was investigated. Staphylococcus aureus resistance breakdown levels for each antibiotic (amoxicillin, erythromycin, and gentamicin) from the photodynamic effect (10 µM curcumin, 10 J/cm2) and its maintenance in descendant microorganisms were demonstrated within five cycles after PDI application. PDI showed an innovative feature for modifying the degree of bacterial sensitivity to antibiotics according to dosages, thus reducing resistance and persistence of microorganisms from standard and clinical strains. We hypothesize a reduction in the degree of antimicrobial resistance through photooxidative action combats antibiotic failures.

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.

A review on curcumin colon-targeted oral drug delivery systems for the treatment of inflammatory bowel disease

Synthetic drugs and monoclonal antibodies are the typical treatments to combat inflammatory bowel disease (IBD). However, side effects are present when these treatments are used, and their continued application could be restricted by the high relapse rate of the disease. One potential alternative to these treatments is the use of plant-derived products. The use curcumin is one such treatment option that has seen an increase in usage in treating IBD. Curcumin is derived from a rhizome of turmeric (Curcuma longa), and the results of studies on the use of curcumin to treat IBD are promising. These studies suggest that curcumin interacts with cellular targets such as NF-κB, JAKs/STATs, MAPKs, TNF-α, IL-6, PPAR, and TRPV1 and may reduce the progression of IBD. Potentially, curcumin can be used as a therapeutic agent for patients with IBD when it reduces the incidence of clinical relapse. This review discusses the strategies utilized in designing and developing an oral colonic delivery dosage form of curcumin.

Enhancement of hypericin nanoparticle-mediated sonoinduced disruption of biofilm and persister cells of Streptococcus mutans by dermcidin-derived peptide DCD-1L

BACKGROUND

Streptococcus mutans is considered a major significant contributor to dental caries and its effective removal is difficult due to the formation of biofilm. Therefore, the development of adjuvant therapeutic strategies with anti-biofilm properties is a promising approach. In the present study, we examined the effect of dermcidin-derived peptide DCD-1 L on the antibacterial activity of hypericin nanoparticle (HypNP)-mediated antimicrobial sonodynamic therapy (aSDT) against persister cells growing- and biofilm cultures of S. mutans.

MATERIALS AND METHODS

Following synthesis and confirmation of HypNP, the fractional inhibitory concentration (FIC) index of HypNP and DCD-1 L was determined by checkerboard assay. Cellular uptake of HypNP-DCD-1 L and generation of endogenous reactive oxygen species (ROS) were assessed and followed by the determination of antimicrobial sonoactivity of HypNP-DCD-1 L against persister cells growing- and biofilm cultures of S. mutans. The water-insoluble extracellular polysaccharide (EPS) and expression of the gtfD, comDE, and smuT genes were then evaluated in persister cells growing- and biofilm cultures of S. mutans.

RESULTS

There was a synergistic activity in the combination of HypNP and DCD-1 L against S. mutans with an FIC index value of 0.37. The HypNP-DCD-1L-mediated aSDT also displayed the highest cellular uptake and endogenous ROS generation by bacterial cells. When biofilm and persister cells of S. mutans were treated with HypNP-DCD-1 L and subsequently exposed to ultrasound waves, 5.1 log and 3.8 log reductions, respectively, in bacterial numbers were observed (P<0.05). According to the data, EPS in both persister cells growing- and biofilm cultures of S. mutans were significantly decreased after exposure to the HypNP-DCD-1L-mediated aSDT (P<0.05). In addition, the quantitative real-time PCR data illustrated the high level of similarities in very low-expression profiles of the gtfD before and after all treated groups for persister cells. While, following HypNP-DCD-1L-mediated aSDT treatment, the expression levels of gtfD, comDE, and smuT were significantly lower in treated persister cells growing- and biofilm cultures of S. mutans in comparison with control groups (P<0.05).

CONCLUSIONS

Combined, the results of this study indicate that ultrasound waves-activated HypNP-DCD-1 L can sonoinactivate S. mutans biofilms and persister cells, as well as reduce effectively pathogenicity potency of S. mutans. Hence, HypNP-DCD-1L-mediated aSDT may be proposed as a promising adjunctive therapeutic approach for dental caries.

Assessment of synergistic activity of rhamnolipid and linezolid against methicillin-resistant Staphylococcus aureus in-vitro and in-vivo with Galleria mellonella larvae model

Antibiotic resistance, one of the most crucial public health problems, has increased the interest in synergy studies of antibiotics with existing antibiotics and natural compounds to make current treatment more effective in addition to new drug development. In this study, the effectiveness of rhamnolipid and linezolid on the Galleria mellonella larvae model in-vitro and in-vivo against Methicillin-resistant Staphylococcus aureus isolates, which are problematic in treatment, were investigated. Four S.aureus (One ATCC 29213 strain and three methicillin-resistant strains) were used in the study. Two MRSA isolates were resistant to linezolid, and one was susceptible. Partial synergy was observed in one resistant strain, and although no synergy was observed in the other resistant strain, the minimum inhibitory concentration of the resistant strain decreased from 16 to 4 μg/mL with a four-fold decrease and reached the susceptibility limit. No change was observed in the MIC of linezolid-susceptible strains. The G.mellonella larval model demonstrated that combined therapy was more effective than monotherapy by survival function tests and CFU determination. RML/LNZ combination improved survival compared to monotherapy and decreased the bacterial burden from 10⁸ to 10³.

Cocktail of isobavachalcone and curcumin enhance eradication of Staphylococcus aureus biofilm from orthopedic implants by gentamicin and alleviate inflammatory osteolysis

Orthopedic device-related infection (ODRI) caused by Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) biofilm may lead to persist infection and severe inflammatory osteolysis. Previous studies have demonstrated that both isobavachalcone and curcumin possess antimicrobial activity, recent studies also reveal their antiosteoporosis, anti-inflammation, and immunoregulatory effect. Thus, this study aims to investigate whether the combination of isobavachalcone and curcumin can enhance the anti-S. aureus biofilm activity of gentamicin and alleviate inflammatory osteolysis in vivo. EUCAST and a standardized MBEC assay were used to verify the synergy between isobavachalcone and curcumin with gentamicin against planktonic S. aureus and its biofilm in vitro, then the antimicrobial and immunoregulatory effect of cocktail therapy was demonstrated in a femoral ODRI mouse model in vivo by μCT analysis, histopathology, quantification of bacteria in bone and myeloid-derived suppressor cell (MDSC) in bone marrow. We tested on standard MSSA ATCC25923 and MRSA USA300, 5 clinical isolated MSSA, and 2 clinical isolated MRSA strains and found that gentamicin with curcumin (62.5–250 μg/ml) and gentamicin with isobavachalcone (1.56 μg/ml) are synergistic against planktonic MSSA, while gentamicin (128 μg/ml) with curcumin (31.25–62.5, 250–500 μg/ml) and gentamicin (64–128 μg/ml) with isobavachalcone (1.56–12.5 μg/ml) exhibit synergistic effect against MSSA biofilm. Results of further study revealed that cocktail of 128 μg/ml gentamicin together with 125 μg/ml curcumin +6.25 μg/ml isobavachalcone showed promising biofilm eradication effect with synergy against USA300 biofilm in vitro. Daily intraperitoneal administration of 20 mg/kg/day isobavachalcone, 20 mg/kg/day curcumin, and 20 mg/kg/day gentamicin, can reduce inflammatory osteolysis and maintain microarchitecture of trabecular bone during orthopedic device-related MRSA infection in mice. Cocktail therapy also enhanced reduction of MDSC M1 polarization in peri-implant tissue, suppression of MDSC amplification in bone marrow, and Eradication of USA300 biofilm in vivo. Together, these results suggest that the combination of isobavachalcone and curcumin as adjuvants administrated together with gentamicin significantly enhances its antimicrobial effect against S. aureus biofilm, and can also modify topical inflammation in ODRI and protect bone microstructure in vivo, which may serve as a potential treatment strategy, especially for S. aureus induced ODRI.

Curcumin Stimulates the Overexpression of Virulence Factors in Salmonella enterica Serovar Typhimurium: In Vitro and Animal Model Studies

Salmonella spp. is one of the most common food poisoning pathogens and the main cause of diarrheal diseases in humans in developing countries. The increased Salmonella resistance to antimicrobials has led to the search for new alternatives, including natural compounds such as curcumin, which has already demonstrated a bactericidal effect; however, in Gram-negatives, there is much controversy about this effect, as it is highly variable. In this study, we aimed to verify the antibacterial activity of curcumin against the Salmonella enterica serovar Typhimurium growth rate, virulence, and pathogenicity. The strain was exposed to 110, 220 or 330 µg/mL curcumin, and by complementary methods (spectrophotometric, pour plate and MTT assays), we determined its antibacterial activity. To elucidate whether curcumin regulates the expression of virulence genes, Salmonella invA, fliC and siiE genes were investigated by quantitative real-time reverse transcription (qRT-PCR). Furthermore, to explore the effect of curcumin on the pathogenesis process in vivo, a Caenorhabditis elegans infection model was employed. No antibacterial activity was observed, even at higher concentrations of curcumin. All concentrations of curcumin caused overgrowth (35−69%) and increased the pathogenicity of the bacterial strain through the overexpression of virulence factors. The latter coincided with a significant reduction in both the lifespan and survival time of C. elegans when fed with curcumin-treated bacteria. Our data provide relevant information that may support the selective antibacterial effects of curcumin to reconsider the indiscriminate use of this phytochemical, especially in outbreaks of pathogenic Gram-negative bacteria.

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.

The Natural Product Curcumin as an Antibacterial Agent: Current Achievements and Problems

The rapid spread of antibiotic resistance and lack of effective drugs for treating infections caused by multi-drug resistant bacteria in animal and human medicine have forced us to find new antibacterial strategies. Natural products have served as powerful therapeutics against bacterial infection and are still an important source for the discovery of novel antibacterial drugs. Curcumin, an important constituent of turmeric, is considered safe for oral consumption to treat bacterial infections. Many studies showed that curcumin exhibited antibacterial activities against Gram-negative and Gram-positive bacteria. The antibacterial action of curcumin involves the disruption of the bacterial membrane, inhibition of the production of bacterial virulence factors and biofilm formation, and the induction of oxidative stress. These characteristics also contribute to explain how curcumin acts a broad-spectrum antibacterial adjuvant, which was evidenced by the markedly additive or synergistical effects with various types of conventional antibiotics or non-antibiotic compounds. In this review, we summarize the antibacterial properties, underlying molecular mechanism of curcumin, and discuss its combination use, nano-formulations, safety, and current challenges towards development as an antibacterial agent. We hope that this review provides valuable insight, stimulates broader discussions, and spurs further developments around this promising natural product.

Synergistic Effect of Polyalthia longifolia Leaf and Antibiotics against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus (MRSA) by Microscopic Technique

BACKGROUND

Polyalthia longifolia is a popular medicinal plant and has been widely used as a traditional remedy for centuries in curing of various ailments. The purpose of this study was conducted to determine the in situ antimicrobial synergistic effects between Polyalthia longifolia leaf ethyl acetate fraction (PLEAF) and ampicillin against MRSA local isolate by using modern microscopy technique.

METHODS

Hence, the evaluation of the synergistic activity of PLEAF and ampicillin against MRSA local isolate was conducted with scanning electron microscopy (SEM).

RESULTS

The combinational effect of PLEAF fraction and ampicillin exhibited significant antibacterial activity against MRSA. Bacterial cells observations showed invagination, impaired cell division, extensive wrinkles, cell shrinkage, the appearance of a rougher cell with fibrous matrix and clustered cells which confirmed the synergistic effect of PLEAF and ampicillin against MRSA local isolate by SEM.

CONCLUSION

Conclusively, the in situ SEM observation proved the synergistic antimicrobial activity between PLEAF fraction and ampicillin to destroy the MRSA resistance bacteria which is an important aspect of PLEAF fraction to be used in the future combinational therapy.

Strategic approach of multifaceted antibacterial mechanism of limonene traced in Escherichia coli

Antibacterial potential of Limonene against Multi Drug Resistant (MDR) pathogens was studied and mechanism explored. Microscopic techniques viz. Fluorescent Microscopy (FM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) indicated membrane disruption, cellular leakage and cell death of Escherichia coli (E. coli) cells when treated with limonene. Leakage of intracellular proteins, lipids and nucleic acid confirmed membrane damage and disruption of cell permeability barrier. Further, release of intracellular ATP, also suggested disruption of membrane barrier. Interaction of limonene with DNA revealed its capability in unwinding of plasmid, which could eventually inhibit DNA transcription and translation. Differential expression of various proteins and enzymes involved in transport, respiration, metabolism, chemotaxis, protein synthesis confirmed the mechanistic role of limonene on their functions. Limonene thus can be a potential candidate in drug development.

Cytotoxicity and effects of curcumin and cinnamaldehyde hybrids on biofilms of oral pathogens

The objective of the study was to evaluate the cytotoxicity and effect of curcumin-cinnamaldehyde hybrids (CCHs) on the biofilm of oral pathogens. Of the 18 hybrids tested, nine had an inhibitory effect on at least one of the bacterial species tested, with minimal inhibitory and bactericidal concentrations ranging from 9 to 625 μg ml^-1. CCH 7 promoted a potent inhibitory effect against all the bacterial species tested and better compatibility than chlorhexidine (CHX). CCH 7 also presented a similar or improved effect over that of CHX, causing a reduction in bacterial metabolism and viability in single and dual-species biofilms. CCH 7 reduced by 86% and 34% the viability of multispecies biofilms formed by collection and clinical strains. It can be concluded that CCH 7 was cytocompatible at the minimal inhibitory concentration, presented anti-biofilm action against oral pathogens, and could act as an antimicrobial agent for application in endodontics.

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.

Curcumin, a Natural Antimicrobial Agent with Strain-Specific Activity

Curcumin, a principal bioactive substance of turmeric (Curcuma longa L.), is reported as a strong antioxidant, anti-inflammatory, antibacterial, antifungal, and antiviral agent. However, its antimicrobial properties require further detailed investigations into clinical and multidrug-resistant (MDR) isolates. In this work, we tested curcumin's efficacy against over 100 strains of pathogens belonging to 19 species. This activity was determined by the broth microdilution method and by calculating the minimum inhibitory concentration (MIC). Our findings confirmed a much greater sensitivity of Gram-positive than Gram-negative bacteria. This study exhibited a significantly larger variation in the curcumin activity than previous works and suggested that numerous clinical strains of widespread pathogens have a poor sensitivity to curcumin. Similarly, the MICs of the MDR types of Staphylococcus aureus, S. haemolyticus, Escherichia coli, and Proteus mirabilis were high (≥2000 µg/mL). However, curcumin was effective against some species and strains: Streptococcus pyogenes (median MIC = 31.25 µg/mL), methicillin-sensitive S. aureus (250 µg/mL), Acinetobacter lwoffii (250 µg/mL), and individual strains of Enterococcus faecalis and Pseudomonas aeruginosa (62.5 µg/mL). The sensitivity of species was not associated with its affiliation to the genus, and it could differ a lot (e.g., S. pyogenes, S. agalactiae and A. lwoffii, A. baumannii). Hence, curcumin can be considered as a promising antibacterial agent, but with a very selective activity.

Conjugation of micro/nanocurcumin particles to ZnO nanoparticles changes the surface charge and hydrodynamic size thereby enhancing its antibacterial activity against Escherichia coli and Staphylococcus aureus

Nanobiotechnology-mediated synthesis of ZnO nanoparticles, micro/nanocurcumin, and curcumin-ZnO nanocomposites and their characterization followed by comparative study of their antibacterial, antioxidant, and iron-chelating efficiency at various dosages are discussed. Micro/nanocurcumin and ZnO nanoparticles were synthesized using curcumin and zinc nitrate as precursor and then conjugated by sonication to synthesize curcumin-ZnO nanocomposites. The synthesized nanoparticles were then characterized by using ultraviolet-visible spectroscopy, X-ray diffraction, Scanning electron microscopy, Fourier-transform infrared spectroscopy, and dynamic light scattering analysis. After that, the antibacterial activity of the synthesized nanoparticles was evaluated by the optical density (OD₆₀₀ ) method against Escherichia coli and Staphylococcus aureus cells. The DPPH (2,2-diphenyl-1-picrylhydrazyl ), hydroxyl radical scavenging activity, and ferrous ion-chelating efficiency of synthesized nanoparticles were evaluated by spectrophotometry analysis. Nanocurcumin (mean zeta potential = -25 mV; average hydrodynamic diameter = 410 nm) based coating of ZnO nanoparticles (mean zeta potential = -15.9 mV; average hydrodynamic diameter = 274 nm) to synthesize curcumin-ZnO nanocomposites (mean zeta potential = -18.8 mV; average hydrodynamic diameter = 224 nm) exhibited enhanced zeta potential, which resulted in reduced agglomeration, smaller hydrodynamic size in water, improved aqueous solubility, and dispersion. All the aforesaid factors including the synergistic antibacterial effect of ZnO nanoparticle and micro/nanocurcumin contributed to increased antibacterial efficiency of curcumin-ZnO nanocomposites. Micro/nanocurcumin due to its better water solubility and small hydrodynamic diameter exhibited enhanced antioxidant and ferrous ion-chelating efficiency than curcumin.

Drug Susceptibility Testing and Synergistic Antibacterial Activity of Curcumin with Antibiotics against Enterotoxigenic Escherichia coli

Aim: This study investigated the susceptibility of Enterotoxigenic Escherichia coli to curcumin, as well as its synergistic effect with 12 antimicrobial drugs. Methods and Results: Our study shows that curcumin did not affect bacterial growth. The antimicrobial susceptibility of curcumin and antibiotic synergy were identified using disc diffusion on Mueller-Hinton agar. The strain of Enterotoxigenic Escherichia coli used was resistant to Ampicillin, Amoxicillin/Clavulanic acid, Ampicillin/Sulbactam, Ciprofloxacin, and Cefazolin. There was synergy between curcumin and the majority of antibiotics tested. Maximum synergy was observed with combinations of 330 µg/mL curcumin and Ceftazidime, followed by Cefotaxime, Amoxicillin/Clavulanic acid, Ampicillin, Aztreonam, Trimethoprim, Ciprofloxacin, Ceftriaxone, Cefazolin, Tetracycline, and Imipenem. Conclusion: Our findings indicated that curcumin might be useful as a combinatorial strategy to combat the antibiotic resistance of Enterotoxigenic Escherichia coli.

Antibacterial effects of curcumin encapsulated in nanoparticles on clinical isolates of Pseudomonas aeruginosa through downregulation of efflux pumps

Curcumin as a flavonoid from the rhizome of Curcuma longa has antibacterial, antiviral and antifungal activity. Multidrug resistance in pathogenic bacteria is continuously increasing in hospitals. The aim of this study was to investigate the effect of curcumin encapsulated in micellar/polymersome nanoparticles as an efflux pump inhibitor (EPI) on the expression of mexX and oprM genes in curcumin-treated and -untreated isolates of Pseudomonas aeruginosa. Clinical isolates of Pseudomonas aeruginosa were treated with ciprofloxacin (sub-MICs) alone and/or in combination with curcumin-encapsulated in micellar/polymersome nanoparticles. The expression of mexX and oprM genes was quantitatively evaluated by qRT-PCR in curcumin-treated and -untreated bacteria after 24 h. Curcumin-encapsulated in nanoparticles (400 µg/mL) induced cell death up to 50% in ciprofloxacin-treated (1/2MIC) resistant isolates during 24 h, while the bacteria treated with ciprofloxacin (without curcumin) were not inhibited. Also, curcumin in different concentrations increased effect of ciprofloxacin (sub-MICs). Downregulation of mexX and oprM genes was observed in cells treated with curcumin and ciprofloxacin compared to cells treated with ciprofloxacin alone. It seems that curcumin can be used as complementary drug in ciprofloxacin-resistant isolates through downregulating genes involved in efflux pumps and trapping ciprofloxacin on bacterial cells and increasing the effects of drug.

Antimicrobial effect of Licochalcone A and Epigallocatechin-3-gallate against Salmonella Typhimurium isolated from poultry flocks

BACKGROUND AND OBJECTIVES

Salmonellosis due to multi-drug resistant Salmonella Typhimurium with biofilm formation ability is a serious public health threat worldwide. Studies have shown that medicinal plants inhibit the growth of bacterial species. The present study aimed at determining antibiotic resistance pattern and biofilm formation ability of S. Typhimurium isolated from poultry flocks. Moreover, the antibacterial activity of Licochalcone A (LAA) and Epigallocatechin-3-gallate (EGCG) against the studied isolates were investigated in this study.

MATERIALS AND METHODS

Antibiotic susceptibility testing of S. Typhimurium RITCC1730 and 23 clinical isolates of S. Typhimurium against 8 antibiotics was performed using standard Kirby-Bauer disc diffusion method. The extent of biofilm formation was measured by Microtiter dish biofilm formation assay. Antimicrobials activities of LAA and EGCG were determined by MIC and MBC assays using microdilution method.

RESULTS

The highest antimicrobial resistance was detected against chloramphenicol (52.17%), followed by furazolidone (26.08%), and trimethoprim/sulfamethoxazole (21.73%). All isolates were sensitive to ciprofloxacin (100%), followed by gentamicin, imipenem (95.65%), and cefixime (91.30%). Most of the isolates (78.26%) were able to produce weak biofilm. LAA and EGCG inhibited the growth of S. Typhimurium at the MIC levels of 62.5∼1000 and 1.56∼400 μg/mL, respectively. The MBC value of LAA was >1000 μg/mL, while the corresponding value of EGCG varied from 100 to 800 μg/mL.

CONCLUSION

S. Typhimurium isolates revealed a multiple antibiotic resistance with biofilm production ability. As a result, EGCG, and to a lesser extent, LAA displayed potential antibacterial activity against S. Typhimurium and could be considered as useful compounds for the development of antibacterial agents against salmonellosis.

Application of chemometrics in quality control of Turmeric (Curcuma longa) based on Ultra-violet, Fourier transform-infrared and 1H NMR spectroscopy

Turmeric (Curcuma longa L.) belongs to the family Zingiberaceae that is widely used as a spice in food preparations in addition to its biological activities. UV, FT-IR, ¹H NMR in addition to HPLC were applied to construct a metabolic fingerprint for Turmeric in an attempt to assess its quality. 30 samples were analyzed, and then principal component analysis (PCA) and hierarchical clustering analysis (HCA) were utilized to assess the differences and similarities between collected samples. PCA score plot based on both HPLC and UV spectroscopy showed the same discriminatory pattern, where the samples were segregated into four main groups depending on their total curcuminoids content. The results revealed that UV could be utilized as a simple and rapid alternative for HPLC. However, FT-IR failed to discriminate between the same species. By applying ¹H NMR, the metabolic variability between samples was more evident in the essential oils/fatty acid region.

Inhibition of Pseudomonas aeruginosa quorum sensing by subinhibitory concentrations of curcumin with gentamicin and azithromycin

OBJECTIVES

Pseudomonas aeruginosa quorum sensing (QS) circuits regulate virulence factors and co-ordinate bacterial pathogenicity. This study aimed to investigate the inhibitory activity of subinhibitory concentrations of curcumin with azithromycin and gentamicin against P. aeruginosa QS-related genes and virulence factors.

METHODS

The minimum inhibitory concentrations (MICs) and synergistic activity of curcumin with azithromycin and gentamicin against P. aeruginosa PAO1 were determined using broth microdilution and checkerboard titration methods, respectively. The activity of sub-MICs (1/4× and 1/16× MIC) of curcumin on the QS signal molecules was assessed using a reporter strain assay. The influence of sub-MICs of curcumin, azithromycin and gentamicin alone and in combination on motility and biofilm formation was also determined and was confirmed by RT-PCR to test the expression of the QS regulatory genes lasI, lasR, rhlI and rhlR.

RESULTS

Addition of curcumin drastically decreased the MIC of azithromycin and gentamicin. Curcumin showed synergistic effects with azithromycin and gentamicin. Treated PAO1 cultures in the presence of curcumin showed a significant reduction of signals C12-HSL and C4-HSL (P<0.05). Sub-MICs (1/4× and 1/16× MIC) of curcumin, azithromycin and gentamicin alone and in combination significantly reduced swarming and twitching motilities as well as biofilm formation. Expression of QS regulatory genes lasI, lasR, rhlI and rhlR using 1/4× MIC of curcumin, azithromycin and gentamicin alone and in combination was decreased significantly compared with untreated PAO1.

CONCLUSIONS

These results indicate that a combination of sub-MIC of curcumin with azithromycin and gentamicin exhibited synergism against P. aeruginosa QS systems.

Antibacterial Action of Curcumin against Staphylococcus aureus: A Brief Review

Curcumin, the major constituent of Curcuma longa L. (Zingiberaceae family) or turmeric, commonly used for cooking in Asian cuisine, is known to possess a broad range of pharmacological properties at relatively nontoxic doses. Curcumin is found to be effective against Staphylococcus aureus (S. aureus). As demonstrated by in vitro experiment, curcumin exerts even more potent effects when used in combination with various other antibacterial agents. Hence, curcumin which is a natural product derived from plant is believed to have profound medicinal benefits and could be potentially developed into a naturally derived antibiotic in the future. However, there are several noteworthy challenges in the development of curcumin as a medicine. S. aureus infections, particularly those caused by the multidrug-resistant strains, have emerged as a global health issue and urgent action is needed. This review focuses on the antibacterial activities of curcumin against both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). We also attempt to highlight the potential challenges in the effort of developing curcumin into a therapeutic antibacterial agent.

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

INTRODUCTION

The role of natural bioactive substances in treating infections has been rediscovered as bacterial resistance become common to most of the antibiotics. Curcumin is a bioactive substance from turmeric. Owing to antimicrobial properties, its prospect as an antibacterial agent is currently under focus.

MATERIALS AND METHODS

We have evaluated the in vitro synergy of curcumin with antibiotics against sixty biofilm producing bacterial isolates. Congo red agar method was used to identify the biofilm producing isolates. Curcumin minimum inhibitory concentration (MIC) was determined by agar dilution method. Its antibiotic synergy was identified by the increase in disc diffusion zone size on Mueller-Hinton agar with 32 mg/L curcumin.

RESULTS

The mean MICs of curcumin against Gram-positive and Gram-negative isolates were 126.9 mg/L and 117.4 mg/L, respectively. Maximum synergy was observed with ciprofloxacin among Gram-positive and amikacin, gentamicin, and cefepime among Gram-negative isolates.

CONCLUSIONS

Curcumin per se as well as in combination with other antibiotics has a demonstrable antibacterial action against biofilm producing bacterial isolates. It may have a beneficial role in supplementing antibiotic therapy.

Antibacterial non-woven nanofibers of curcumin acrylate oligomers

Oligomers of curcumin acrylates were blended with polylactide and electrospun to nanofiber mats, which were antibacterial and highly porous.