Inhibition of Biofilm Formation by the Synergistic Action of EGCG-S and Antibiotics

Targeting bacterial growth in biofilm conditions: rational design of novel inhibitors to mitigate clinical and food contamination using QSAR

Antimicrobial resistance (AMR) is a pressing global issue exacerbated by the abuse of antibiotics and the formation of bacterial biofilms, which cause up to 80% of human bacterial infections. This study presents a computational strategy to address AMR by developing three novel quantitative structure-activity relationship (QSAR) models based on molecular topology to identify potential anti-biofilm and antibacterial agents. The models aim to determine the chemo-topological pattern of Gram (+) antibacterial, Gram (-) antibacterial, and biofilm formation inhibition activity. The models were applied to the virtual screening of a commercial chemical database, resulting in the selection of 58 compounds. Subsequent in vitro assays showed that three of these compounds exhibited the most promising antibacterial activity, with potential applications in enhancing food and medical device safety.

Green synthesized silver nanoparticles from Phoenix dactylifera synergistically interact with bioactive extract of Punica granatum against bacterial virulence and biofilm development

The global rise of antibiotic resistance poses a substantial risk to mankind, underscoring the necessity for alternative antimicrobial options. Developing novel drugs has become challenging in matching the pace at which microbial resistance is evolving. Recently, nanotechnology, coupled with natural compounds, has emerged as a promising solution to combat multidrug-resistant bacteria. In the present study, silver nanoparticles were green-synthesized using aqueous extract of Phoenix dactylifera (variety Ajwa) fruits and characterized by UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) coupled with Energy dispersive X-ray analysis (EDX), Transmission electron microscopy (TEM) and Thermogravimetric-differential thermal analysis (TGA-DTA). The in-vitro synergy of green synthesized P. dactylifera silver nanoparticle (PD-AgNPs) with selected antibiotics and bioactive extract of Punica granatum, i.e., ethyl acetate fraction (PGEF), was investigated using checkerboard assays. The most effective synergistic combination was evaluated against the QS-regulated virulence factors production and biofilm of Pseudomonas aeruginosa PAO1 by spectroscopic assays and electron microscopy. In-vivo anti-infective efficacy was examined in Caenorhabditis elegans N2 worms. PD-AgNPs were characterized as spherical in shape with an average diameter of 28.9 nm. FTIR analysis revealed the presence of functional groups responsible for the decrease and stabilization of PD-AgNPs. The signals produced by TGA-DTA analysis indicated the generation of thermally stable and pure crystallite AgNPs. Key phytocompounds detected in bioactive fractions include gulonic acid, dihydrocaffeic acid 3-O-glucuronide, and various fatty acids. The MIC of PD-AgNPs and PGEF ranged from 32 to 128 μg/mL and 250-500 μg/mL, respectively, against test bacterial strains. In-vitro, PD-AgNPs showed additive interaction with selected antibiotics (FICI 0.625-0.75) and synergy with PGEF (FICI 0.25-0.375). This combination inhibited virulence factors by up to 75 % and biofilm formation by 84.87 % in P. aeruginosa PAO1. Infected C. elegans worms with P. aeruginosa PAO1 had a 92.55 % survival rate when treated with PD-AgNPs and PGEF. The combination also reduced the reactive oxygen species (ROS) level in C. elegans N2 compared to the untreated control. Overall, these findings highlight that biosynthesized PD-AgNPs and bioactive P. granatum extract may be used as a potential therapeutic formulation against MDR bacteria.

Synthesis and Isolation of Phenol- and Thiol-Derived Epicatechin Adducts Prepared from Avocado Peel Procyanidins Using Centrifugal Partition Chromatography and the Evaluation of Their Antimicrobial and Antioxidant Activity

Polyphenols from agro-food waste represent a valuable source of bioactive molecules that can be recovered to be used for their functional properties. Another option is to use them as starting material to generate molecules with new and better properties through semi-synthesis. A proanthocyanidin-rich (PACs) extract from avocado peels was used to prepare several semi-synthetic derivatives of epicatechin by acid cleavage in the presence of phenol and thiol nucleophiles. The adducts formed by this reaction were successfully purified using one-step centrifugal partition chromatography (CPC) and identified by chromatographic and spectroscopic methods. The nine derivatives showed a concentration-dependent free radical scavenging activity in the DPPH assay. All compounds were also tested against a panel of pathogenic bacterial strains formed by Listeria monocytogenes (ATCC 7644 and 19115), Staphylococcus aureus (ATCC 9144), Escherichia coli (ATCC 11775 and 25922), and Salmonella enterica (ATCC 13076). In addition, adducts were tested against two no-pathogenic strains, Limosilactobacillus fermentum UCO-979C and Lacticaseibacillus rhamnosus UCO-25A. Overall, thiol-derived adducts displayed antimicrobial properties and, in some specific cases, inhibited biofilm formation, particularly in Listeria monocytogenes (ATCC 7644). Interestingly, phenolic adducts were inactive against all the strains and could not inhibit its biofilm formation. Moreover, depending on the structure, in specific cases, biofilm formation was strongly promoted. These findings contribute to demonstrating that CPC is a powerful tool to isolate new semi-synthetic molecules using avocado peels as starting material for PACc extraction. These compounds represent new lead molecules with antioxidant and antimicrobial activity.

In Vitro Antibiofilm Activity of Fosfomycin Alone and in Combination with Other Antibiotics against Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa

BACKGROUND

Due to its rapid resistance development and ability to form biofilms, treatment of Pseudomonas aeruginosa infections is becoming more complicated by the day. Drug combinations may help reduce both resistance and biofilm formation.

METHODS

Using the microtiter plate assay, we investigated the in vitro inhibition of biofilm formation and the disruption of preformed biofilms in multidrug-resistant and extensively drug-resistant clinical isolates of P. aeruginosa in the presence of peak plasma levels of eight antipseudomonal antibiotics alone and in combination with fosfomycin: ceftazidime, piperacillin/tazobactam, cefepime, imipenem, gentamicin, amikacin, ciprofloxacin and colistin.

RESULTS

Combination therapy was significantly superior to monotherapy in its inhibition of biofilm formation. The highest inhibition rates were observed for combinations with colistin, cefepime and ceftazidime.

CONCLUSION

Our results support fosfomycin combination therapy as an enhanced prophylactic option. Moreover, combinations with β-lactam antibiotics and colistin demonstrated a more potent inhibition effect on biofilm formation than protein synthesis inhibitors.

Repression of resistance mechanisms of Pseudomonas aeruginosa: implications of the combination of antibiotics and phytoconstituents

Antimicrobial resistance is a prevalent problem witnessed globally and creating an alarming situation for the treatment of infections caused by resistant pathogens. Available armaments such as antibiotics often fail to exhibit the intended action against resistant pathogens, leading to failure in the treatments that are causing mortality. New antibiotics or a new treatment approach is necessary to combat this situation. P. aeruginosa is an opportunistic drug resistant pathogen and is the sixth most common cause of nosocomial infections. P. aeruginosa due to its genome organization and other factors are exhibiting resistance against drugs. Bacterial biofilm formation, low permeability of outer membrane, the production of the beta-lactamase, and the production of several efflux systems limits the antibacterial potential of several classes of antibiotics. Combination of phytoconstituents with antibiotics is a promising strategy to combat multidrug resistant P. aeruginosa. Phytoconstituents such as flavonoids, terpenoids, alkaloids, polypeptides, phenolics, and essential oils are well known antibacterial agents. In this review, the activity of combination of the phytoconstituents and antibiotics, and their corresponding mechanism of action was discussed elaborately. The combination of antibiotics and plant-derived compounds exhibited better efficacy compared to antibiotics alone against the antibiotic resistance P. aeruginosa infections.

Silver Nanoparticle-Embedded Carbon Nitride: Antifungal Activity on Candida albicans and Toxicity toward Animal Cells

The development of engineered nanomaterials has been considered a promising strategy to control oral infections. In this study, silver-embedded carbon nitrides (Ag@g-CN) were synthesized and tested against Candida albicans, investigating their antifungal action and biocompatibility in animal cells. Ag@g-CN was synthesized by a simple one-pot thermal polymerization technique and characterized by various analytical techniques. X-ray diffraction (XRD) analysis revealed slight alterations in the crystal structure of g-CN upon the incorporation of Ag. Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of Ag-N bonds, indicating successful silver incorporation and potential interactions with g-CN's amino groups. UV-vis spectroscopy demonstrated a red shift in the absorption edge of Ag@g-CN compared with g-CN, attributed to the surface plasmon resonance effect of silver nanoparticles. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) confirmed the 2D layered sheet like morphology of both materials. The Ag 3d peaks found in X-ray photoelectron spectroscopy (XPS) confirmed the presence of metallic Ag0 nanoparticles in Ag@g-CN. The Ag@g-CN materials exhibited high antifungal activity against reference and oral clinical strains of C. albicans, with minimal inhibitory concentration (MIC) ranges between 16-256 μg/mL. The mechanism of Ag@g-CN on C. albicans was attributed to the disruption of the membrane integrity and disturbance of the biofilm. In addition, the Ag@g-CN material showed good biocompatibility in the fibroblastic cell line and in Galleria mellonella, with no apparent cytotoxicity observed at a concentration up to 1000 μg/mL. These findings demonstrate the potential of the Ag@g-CN material as an effective and safe antifungal agent for the treatment of oral fungal infections.

In vitro antibiofilm, antibacterial, antioxidant, and antitumor activities of the brown alga Padina pavonica biomass extract

The antibiofilm, antibacterial, antioxidant, and anticancer activities of the methanolic extract of Padina pavonica L. were determined. Results deduced that the algal extract had a high biofilm formation inhibitory action done via crystal violet (CV) assay, to 88-99%. The results showed a strong antibacterial against the identified bacteria species. Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella pneumonia, Bacillus subtilis, and the extract had moderate antibacterial activity against Escherichia coli, Pseudomonas fluorescens and Streptococcus agalactiae. The algal extract has a concentration-dependent DPPH radical scavenging activity (84.59%, with IC50 = 170.31 µg/ml). The inhibitory percent of P. pavonica methanolic extract in vitro antiproliferative activity was 1.79-98.25% with IC50 = 15.14 µg/ml against lung carcinoma. Phenols, terpenes, amino acids, alkaloids, flavones, alcohols, and fatty acids were among the metabolites whose biological actions were evaluated. In conclusion, for the first time, P. pavonica methanolic extract exhibited effective antibiofilm, antibacterial, antioxidant, and anticancer activities.      .

Selenium Nanoparticle Activity against S. mutans Biofilms as a Potential Treatment Alternative for Periodontitis

The disruption of periodontal biofilms and prevailing antimicrobial resistance issues continue to pose a great challenge to the treatment of periodontitis. Here, we report on selenium nanoparticles (SeNPs) as a treatment alternative for periodontitis by determining their antibiofilm activity against S. mutans biofilms and the potential role of particle size in disrupting biofilms. SeNPs were synthesised via a reduction reaction. Various physicochemical characterisations were conducted on the NPs, including size and shape. The microbroth dilution method was used to conduct the biofilm and antibiofilm assay against S. mutans, which was analysed by absorbance. SeNPs displayed hydrodynamic sizes as low as 46 ± 4 nm at a volume ratio of 1:5 (sodium selenite/ascorbic acid) with good monodispersity and stability. Hydrodynamic sizes of SeNPs after resuspension in tryptic soy broth supplemented with 2.5% sucrose (TSB + 2.5% suc.) and incubated at 37 °C for 24 h, ranged from 112 to 263 nm, while the zeta potential values increased to greater than -11 mV. The biofilm assay indicated that S. mutans are weakly adherent, bordering on moderately adherent biofilm producers. The minimum biofilm inhibitory concentration (MBIC) was identified at 500 µg/mL. At a 1000 µg/mL concentration, SeNPs were able to inhibit S. mutan biofilms up to 99.87 ± 2.41% at a volume ratio of 1:1. No correlation was found between antibiofilm activity and particle size; however, antibiofilm activity was proven to be concentration-dependant. SeNPs demonstrate antibiofilm activity and may be useful for further development in treating periodontitis.

P-type ATPase zinc transporter Rv3270 of Mycobacterium tuberculosis enhances multi-drug efflux activity

Metal homeostasis is maintained by the uptake, storage and efflux of metal ions that are necessary for the survival of the bacterium. Homeostasis is mostly regulated by a group of transporters categorized as ABC transporters and P-type ATPases. On the other hand, efflux pumps often play a role in drug-metal cross-resistance. Here, with the help of antibiotic sensitivity, antibiotic/dye accumulation and semi-quantitative biofilm formation assessments we report the ability of Rv3270, a P-type ATPase known for its role in combating Mn2+ and Zn2+ metal ion toxicity in Mycobacterium tuberculosis, in influencing the extrusion of multiple structurally unrelated drugs and enhancing the biofilm formation of Escherichia coli and Mycobacterium smegmatis. Overexpression of Rv3270 increased the tolerance of host cells to norfloxacin, ofloxacin, sparfloxacin, ampicillin, oxacillin, amikacin and isoniazid. A significantly lower accumulation of norfloxacin, ethidium bromide, bocillin FL and levofloxacin in cells harbouring Rv3270 as compared to host cells indicated its role in enhancing efflux activity. Although over-expression of Rv3270 did not alter the susceptibility levels of levofloxacin, rifampicin and apramycin, the presence of a sub-inhibitory concentration of Zn2+ resulted in low-level tolerance towards these drugs. Of note, the expression of Rv3270 enhanced the biofilm-forming ability of the host cells strengthening its role in antimicrobial resistance. Therefore, the study indicated that the over-expression of Rv3270 enhances the drug efflux activity of the micro-organism where zinc might facilitate drug-metal cross-resistance for some antibiotics.

Synergistic Effect of Plant Compounds in Combination with Conventional Antimicrobials against Biofilm of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida spp

Bacterial and fungal biofilm has increased antibiotic resistance and plays an essential role in many persistent diseases. Biofilm-associated chronic infections are difficult to treat and reduce the efficacy of medical devices. This global problem has prompted extensive research to find alternative strategies to fight microbial chronic infections. Plant bioactive metabolites with antibiofilm activity are known to be potential resources to alleviate this problem. The phytochemical screening of some medicinal plants showed different active groups, such as stilbenes, tannins, alkaloids, terpenes, polyphenolics, flavonoids, lignans, quinones, and coumarins. Synergistic effects can be observed in the interaction between plant compounds and conventional drugs. This review analyses and summarises the current knowledge on the synergistic effects of plant metabolites in combination with conventional antimicrobials against biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. The synergism of conventional antimicrobials with plant compounds can modify and inhibit the mechanisms of acquired resistance, reduce undesirable effects, and obtain an appropriate therapeutic effect at lower doses. A deeper knowledge of these combinations and of their possible antibiofilm targets is needed to develop next-generation novel antimicrobials and/or improve current antimicrobials to fight drug-resistant infections attributed to biofilm.

Isolation, characterization, and application of a novel, lytic phage vB_SalA_KFSST3 with depolymerase for the control of Salmonella and its biofilm on cantaloupe under cold temperature

This study investigated the efficacy of a novel Salmonella phage with depolymerase activity to control S. Typhimurium (ST) and its biofilm on cantaloupes, for the first time, under simulated cold temperature. vB_SalA_KFSST3 forming a halo zone was isolated and purified from a slaughterhouse with a final concentration of 12.1 ± 0.1 log PFU/mL. Based on the morphological and bioinformatics analyses, vB_SalA_KFSST3 was identified as a novel phage belonging to the family Ackermannviridae. Before employing the phage on cantaloupe, its genetic characteristics, specificity, stability, and bactericidal effect were investigated. Genetic analyses confirmed its safety and identified endolysin and two depolymerase domains possessing antibiofilm potential. In addition, the phage exhibited a broad specificity with great efficiencies toward five Salmonella strains at 4 °C, 22 °C, and 37 °C, as well as stable lytic activity over a wide range of pHs (3 to 11) and temperatures (-20 °C to 60 °C). The optimal multiplicity of infection (MOI) and exposure time of phage were determined to be 100 and 2 h, respectively, based on the highest bacterial reduction of ∼2.7 log CFU/mL. Following the formation of ST biofilm on cantaloupe at 4 °C and 22 °C, the cantaloupe was treated with phage at an MOI of 100 for 2 h. The antibiofilm efficacy of phage was evaluated via the plate count method, confocal laser scanning microscopy, and scanning electron microscopy (SEM). The initial biofilm population at 22 °C was significantly greater and more condensed than that at 4 °C. After phage treatment, biofilm population and the percentage of viable ST in biofilm were reduced by ∼4.6 log CFU/cm2 and ∼90% within 2 h, respectively, which were significantly greater than those at 22 °C (∼2.0 log CFU/cm2 and ∼45%) (P < 0.05). SEM images also confirmed more drastic destruction of the cohesive biofilm architecture at 4 °C than at 22 °C. As a result of its cold temperature-robust lytic activity and the contribution of endolysin and two depolymerases, vB_SalA_KFSST3 demonstrated excellent antibiofilm efficacy at cold temperature, highlighting its potential as a promising practical biocontrol agent for the control of ST and its biofilm.

Investigation of the effects of antimicrobial and anti-biofilm peptide IDR1018 and chitosan nanoparticles on ciprofloxacin-resistant Escherichia coli

Peptide IDR1018 and chitosan nanoparticles (CNs) showed antimicrobial and anti-biofilm activity against bacteria. In this study, the antimicrobial effects of peptide IDR1018 and CNs were evaluated on 50 clinical isolates of uropathogenic Escherichia coli (UPEC) resistant to ciprofloxacin. Ion gelation method was applied for CNs synthesis. Scanning electron microscope (SEM) and dynamic light scattering (DLS) were utilized to evaluate the nanoparticles. Antimicrobial and synergistic activity of peptide IDR1018 and CNs with ciprofloxacin were evaluated by microtiter broth dilution method. The checkerboard test was used to investigate the antimicrobial effects of IDR1018 and CNS in combination with ciprofloxacin. Anti-biofilm effect of ciprofloxacin, peptide IDR1018, and CNs was evaluated using crystal violet method. Fourteen (28%), 21 (42%), and 15 (30%) of clinical isolates produced strong, moderate, and weak biofilm, respectively. The CNs were spherical and uniform under electron microscopy with an average diameter of 246 nm. The minimum inhibitory concentration (MIC) values were 16-128, 20-40, and 375-750 (µg/ml) for ciprofloxacin, peptide IDR1018, and CNs, respectively. Fractional inhibitory concentration (FIC) analysis indicated a synergistic effect of ciprofloxacin in combination with peptide IDR1018, but in combination with CNs, this antibiotic showed an additive effect. Our results revealed that peptide IDR1018 and CNs have antimicrobial properties on UPEC isolates. Biofilm inhibition and biofilm eradication of clinical isolate were shown by peptide IDR1018 and CNs in a concentration-dependent manner. The antimicrobial agents alone and in combination decreased the number of viable bacteria in the biofilms. Therefore, these components seem to be a treating approach against biofilm-forming UPEC isolates.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

Beneficial Effects of Green Tea EGCG on Skin Wound Healing: A Comprehensive Review

Epigallocatechin gallate (EGCG) is associated with various health benefits. In this review, we searched current work about the effects of EGCG and its wound dressings on skin for wound healing. Hydrogels, nanoparticles, micro/nanofiber networks and microneedles are the major types of EGCG-containing wound dressings. The beneficial effects of EGCG and its wound dressings at different stages of skin wound healing (hemostasis, inflammation, proliferation and tissue remodeling) were summarized based on the underlying mechanisms of antioxidant, anti-inflammatory, antimicrobial, angiogenesis and antifibrotic properties. This review expatiates on the rationale of using EGCG to promote skin wound healing and prevent scar formation, which provides a future clinical application direction of EGCG.

Chemical Derivatization of Commercially Available Condensed and Hydrolyzable Tannins

Novel valorization routes for tannins were opened by the development of a simple, straightforward, robust, and flexible approach to the selective functionalization of condensed and hydrolyzable tannins. Irrespective of the different degrees of polymerization, different commercial tannins were efficiently functionalized by the generation of an ether linkage bound to a short linker carrying the desired functional group. Functionalizations could be realized at varying degrees of technical loadings, i.e., amounts of introduced tannin-alien functionalities per number of phenolic hydroxyl groups. The same strategy was found suitable for the synthesis of polyethylene glycol-functionalized tannin copolymers. Condensed tannins functionalized with carboxylic acid moieties could be converted into a tannin-oligopeptide hybrid.