Antibacterial activity and antibiotic modulating potential of the essential oil obtained from Eugenia jambolana in association with led lights

Compounds from myrtle flowers as antibacterial agents and SARS-CoV-2 inhibitors: In-vitro and molecular docking studies

Plants and their related phytochemicals play a key role in the treatment of bacterial and viral infections, which inspire scientists to design and develop more efficient drugs starting from the phytochemical active scaffold. This work aims to characterize the chemical compounds of Myrtus communis essential oil (EO) from Algeria and to evaluate its in vitro antibacterial effect, as well as the in silico anti-SARS-CoV-2 activity. The chemical profile of hydrodistilled EO from myrtle flowers was determined using GC/MS analysis. The results showed qualitative and quantitative fluctuations and 54 compounds were identified including the main components: α-pinene (48.94%) and 1,8-cineole (28.3%) whereas other minor compounds were detected. The in vitro antibacterial activity of myrtle EO against Gram-negative bacteria was carried out by using the disc diffusion method. The best inhibition zone values ranged between 11 and 25 mm. The results revealed that Escherichia coli (25 mm), Klebsiella oxytoca (20 mm) and Serratia marcescens (20 mm) are the most susceptible strains to the EO which is endowed with a bactericidal effect. Furthermore, the antibacterial and anti-SARS-CoV-2 activities were investigated by the means of molecular docking (MD) study, in addition to ADME(Tox) analysis. The phytochemicals were docked against four targets: E. coli topoisomerase II DNA gyrase B (PDB: 1KZN), SARS-CoV-2 Main protease (PDB: 6LU7), Spike (PDB: 6ZLG) and angiotensin-converting enzyme II ACE2 (PDB: 1R42). The MD investigation revealed that 1,8-cineole could be the main phytochemical associated with the antibacterial activity of EO; s-cbz-cysteine, mayurone and methylxanthine were found the most promising phytochemicals against SARS-CoV-2; The ADME(Tox) analysis has shown their good druggability with no Lipinski's rule violation.

The resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing the efficacy of this antibiotic

For around three decades, the fluoroquinolone (FQ) antibiotic ciprofloxacin has been used to treat a range of diseases, including chronic otorrhea, endocarditis, lower respiratory tract, gastrointestinal, skin and soft tissue, and urinary tract infections. Ciprofloxacin's main mode of action is to stop DNA replication by blocking the A subunit of DNA gyrase and having an extra impact on the substances in cell walls. Available in intravenous and oral formulations, ciprofloxacin reaches therapeutic concentrations in the majority of tissues and bodily fluids with a low possibility for side effects. Despite the outstanding qualities of this antibiotic, Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa have all shown an increase in ciprofloxacin resistance over time. The rise of infections that are resistant to ciprofloxacin shows that new pharmacological synergisms and derivatives are required. To this end, ciprofloxacin may be more effective against the biofilm community of microorganisms and multi-drug resistant isolates when combined with a variety of antibacterial agents, such as antibiotics from various classes, nanoparticles, natural products, bacteriophages, and photodynamic therapy. This review focuses on the resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing its efficacy.

Essential Oils Encapsulated in Zeolite Structures as Delivery Systems (EODS): An Overview

Essential oils (EO) obtained from plants have proven industrial applications in the manufacturing of perfumes and cosmetics, in the production and flavoring of foods and beverages, as therapeutic agents in aromatherapy, and as the active principles or excipients of medicines and pharmaceutics due to their olfactory, physical-chemical, and biological characteristics. On behalf of the new paradigm of a more natural and sustainable lifestyle, EO are rather appealing due to their physical, chemical, and physiological actions in human beings. However, EO are unstable and susceptible to degradation or loss. To tackle this aspect, the encapsulation of EO in microporous structures as zeolites is an attractive solution, since these host materials are cheap and non-toxic to biological environments. This overview provides basic information regarding essential oils, including their recognized benefits and functional properties. Current progress regarding EO encapsulation in zeolite structures is also discussed, highlighting some representative examples of essential oil delivery systems (EODS) based on zeolites for healthcare applications or aromatherapy.

Breaking down antibiotic resistance in methicillin-resistant Staphylococcus aureus: Combining antimicrobial photodynamic and antibiotic treatments

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant Staphylococcus aureus (MRSA) strains, USA300 and RN4220. Additional resistant S. aureus strain and antibiotic combinations reveal similar results. Taken together, these results suggest that concurrent aPDT consistently decreases S. aureus resistance by improving susceptibility to antibiotic treatment. In turn, this development exhibits an alternative to overcome some of the growing MRSA challenge.

Synergic dual phototherapy: Cationic imidazolyl photosensitizers and ciprofloxacin for eradication of in vitro and in vivo E. coli infections

The emergence of new microorganisms with resistance to current antimicrobials is one of the key issues of modern healthcare that must be urgently addressed with the development of new molecules and therapies. Photodynamic inactivation (PDI) in combination with antibiotics has been recently regarded as a promising wide-spectrum therapy for the treatment of localized topical infections. However, further studies are required regarding the selection of the best photosensitizer structures and protocol optimization, in order to maximize the efficiency of this synergic interaction. In this paper, we present results that demonstrate the influence of the structure of cationic imidazolyl-substituted photosensitizers and light on the enhancement of ciprofloxacin (CIP) activity, for the inactivation of Escherichia coli. Structure-activity studies have highlighted the tetra cationic imidazolyl porphyrin IP-H-Me⁴⁺ at sub-bactericide concentrations (4-16 nM) as the most promising photosensitizer for combination with sub-inhibitory CIP concentration (<0.25 mg/L). An optimized dual phototherapy protocol using this photosensitizer was translated to in vivo studies in mice wounds infected with E. coli. This synergic combination reduced the amount of photosensitizer and ciprofloxacin required for full E. coli inactivation and, in both in vitro and in vivo studies, the combination therapy was clearly superior to each monotherapy (PDI or ciprofloxacin alone). Overall, these findings highlight the potential of cationic imidazolyl porphyrins in boosting the activity of antibiotics and lowering the probability of resistance development, which is essential for a sustainable long-term treatment of infectious diseases.

Silver Trimolybdate (Ag2Mo3O10.2H2O) Nanorods: Synthesis, Characterization, and Photo-Induced Antibacterial Activity under Visible-Light Irradiation

The present study reports the synthesis, characterization, and antibacterial properties of silver trimolybdate (Ag2Mo3O10.2H2O) nanorods. The synthesis was performed using a conventional hydrothermal method. The sample was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Vis-NIR diffuse reflectance, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The direct antibacterial activity was evaluated using the microdilution method to determine the minimum inhibitory concentration (MIC). To assess the ability of Ag2Mo3O10.2H2O nanorods to modulate antibacterial resistance, the MIC of aminoglycosides was established in the presence of a subinhibitory concentration of this substance alone and associated with LED light exposure. The characterization of the sample indicated that the synthesis of silver trimolybdate generated nanometric crystals with rod-like morphology, without secondary phases. The treatment with Ag2Mo3O10.2H2O nanorods alone or combined with visible LED lights exhibited clinically relevant antibacterial activity against both Gram-negative and Gram-positive bacteria. This nanostructure presented a variable antibiotic-modulating action, which was not improved by visible LED light exposure. Nevertheless, LED lights showed promising antibiotic-enhancing activities in the absence of Ag2Mo3O10.2H2O nanorods. In conclusion, silver trimolybdate dihydrate nanorods have antibacterial properties that can be photocatalysed by visible-light exposure. While showing the potential use to combat antibacterial resistance, the simultaneous combination of silver trimolybdate, visible LED lights, and antibacterial drugs should be carefully analysed to avoid antagonist effects that could impair the effectiveness of antibiotic therapy.

Cuminum cyminum L. Essential Oil: A Promising Antibacterial and Antivirulence Agent Against Multidrug-Resistant Staphylococcus aureus

Cuminum cyminum L. (cumin) is valued for its aromatic and medicinal properties. There are several reports of antibacterial activity of C. cyminum essential oil (CcEO). Accordingly, the present study was conducted to investigate the mechanism(s) of action of the CcEO against multidrug-resistant (MDR) Staphylococcus aureus. Therefore, 10 S. aureus MDR isolates, obtained from different sources, were selected based on the antibiotic susceptibility patterns and the Clinical and Laboratory Standards Institute definition and subjected to the examinations. Our results exhibited promising bacteriostatic and bactericidal properties of the CcEO. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration values ranged from 5 to 10 and 10 to 20 μL ⋅ mL^–1, respectively. Scanning electron microscope was used to assess the bacterial cell structure and morphology after the induction with 1/2 MIC concentration of the CcEO. The observed morphological changes appeared to be deformation of the cell membrane and destruction of the cells. In the case of quorum sensing inhibitory potential, treatment of S. aureus isolates with the sub-MIC concentrations (1/2 MIC) of the CcEO significantly reduced the hld expression (3.13-fold downregulation), which considerably controls S. aureus quorum-sensing accessory regulator system. Another virulence factor influenced by the CcEO was the polysaccharide intercellular adhesion production system, as an important component of cell–cell adhesion and biofilm formation. Consequently, the expression level of the intercellular adhesion (ica) locus in the S. aureus cells was examined following treatment with CcEO. The results showed significant decrease (−3.3-fold) in ica expression, indicating that the CcEO could potentially interfere with the process of biofilm formation. Using the ethidium bromide efflux inhibition assay, the S. aureus NorA efflux pump was phenotypically but not genotypically (in quantitative polymerase chain reaction assay) affected by the CcEO treatment. Using gas chromatography–mass spectrometry analysis, cuminic aldehyde (38.26%), α,β-dihydroxyethylbenzene (29.16%), 2-caren-10-al (11.20%), and γ-terpinene (6.49%) were the most detected compounds. The antibacterial and antivirulence action of the CcEO at sub-MIC concentrations means that no microbial resistance will be promoted and developed after the treatment with this agent. These findings revealed that the CcEO is a promising antibacterial agent to control infections caused by the MDR S. aureus strains.

Photodynamic Therapy Combined with Antibiotics or Antifungals against Microorganisms That Cause Skin and Soft Tissue Infections: A Planktonic and Biofilm Approach to Overcome Resistances

The present review covers combination approaches of antimicrobial photodynamic therapy (aPDT) plus antibiotics or antifungals to attack bacteria and fungi in vitro (both planktonic and biofilm forms) focused on those microorganisms that cause infections in skin and soft tissues. The combination can prevent failure in the fight against these microorganisms: antimicrobial drugs can increase the susceptibility of microorganisms to aPDT and prevent the possibility of regrowth of those that were not inactivated during the irradiation; meanwhile, aPDT is effective regardless of the resistance pattern of the strain and their use does not contribute to the selection of antimicrobial resistance. Additive or synergistic antimicrobial effects in vitro are evaluated and the best combinations are presented. The use of combined treatment of aPDT with antimicrobials could help overcome the difficulty of fighting high level of resistance microorganisms and, as it is a multi-target approach, it could make the selection of resistant microorganisms more difficult.

The Galactose-Binding Lectin Isolated from Vatairea macrocarpa Seeds Enhances the Effect of Antibiotics Against Staphylococcus aureus-Resistant Strain

The use of natural products together with standard antimicrobial drugs has recently received more attention as a strategy to combat infectious diseases caused by multidrug-resistant (MDR) microorganisms. This study aimed to evaluate the capacity of a galactose-binding lectin from Vatairea macrocarpa seeds (VML) to modulate antibiotic activity against standard and MDR Staphylococcus aureus and Escherichia coli bacterial strains. The minimum inhibitory concentration (MIC) obtained for VML against all strains was not clinically relevant (MIC ≥ 1024 μg/mL). However, when VML was combined with the antibacterial drugs gentamicin, norfloxacin and penicillin, a significant increase in antibiotic activity was observed against S. aureus, whereas the combination of VML and norfloxacin presented decreased and, hence, antagonistic antibiotic activity against E. coli. By its inhibition of hemagglutinating activity, gentamicin (MIC = 50 mM) revealed its interaction with the carbohydrate-binding site (CBS) of VML. Using molecular docking, it was found that gentamicin interacts with residues that constitute the CBS of VML with a score of - 120.79 MDS. It is this interaction between the antibiotic and the lectin's CBS that may be responsible for the enhanced activity of gentamicin in S. aureus. Thus, our results suggest that the VML can be an effective modulating agent against S. aureus. This is the first study to report the effect of lectins as modulators of bacterial sensitivity, and as such, the outcome of this study could lay the groundwork for future research involving the use of lectins and conventional antibiotics against such infectious diseases such as community-acquired methicillin-resistant S. aureus (MRSA).

Synergistic Antimicrobial Effectiveness of Plant Essential Oil and Its Application in Seafood Preservation: A Review

The synergistic potential of plant essential oils (EOs) with other conventional and non-conventional antimicrobial agents is a promising strategy for increasing antimicrobial efficacy and controlling foodborne pathogens. Spoilage microorganisms are one of main concerns of seafood products, while the prevention of seafood spoilage principally requires exclusion or inactivation of microbial activity. This review provides a comprehensive overview of recent studies on the synergistic antimicrobial effect of EOs combined with other available chemicals (such as antibiotics, organic acids, and plant extracts) or physical methods (such as high hydrostatic pressure, irradiation, and vacuum-packaging) utilized to reduce the growth of foodborne pathogens and/or to extend the shelf-life of seafood products. This review highlights the synergistic ability of EOs when used as a seafood preservative, discovering the possible routes of the combined techniques for the development of a novel seafood preservation strategy.

Essentials Oils from Brazilian Eugenia and Syzygium Species and Their Biological Activities

The Eugenia and Syzygium genera include approximately 1000 and 1800 species, respectively, and both belong to the Myrtaceae. Their species present economic and medicinal importance and pharmacological properties. Due to their chemical diversity and biological activity, we are reporting the essential oils of 48 species of these two genera, which grow in South America and found mainly in Brazil. Chemically, a total of 127 oil samples have been described and displayed a higher intraspecific and interspecific diversity for both Eugenia spp. and Syzygium spp., according to the site of collection or seasonality. The main volatile compounds were sesquiterpene hydrocarbons and oxygenated sesquiterpenes, mainly with caryophyllane and germacrane skeletons and monoterpenes of mostly the pinane type. The oils presented many biological activities, especially antimicrobial (antifungal and antibacterial), anticholinesterase, anticancer (breast, gastric, melanoma, prostate), antiprotozoal (Leishmania spp.), antioxidant, acaricidal, antinociceptive and anti-inflammatory. These studies can contribute to the rational and economic exploration of Eugenia and Syzygium species once they have been identified as potent natural and alternative sources to the production of new herbal medicines.

Rosuvastatin as forthcoming antibiotic or as adjuvant additive agent: In vitro novel antibacterial study

INTRODUCTION:

Rosuvastatin is a lipid-lowering agent that inhibits 3-hydroxy-3-methylglutaryl coenzyme A reductase leading to a reduction of cholesterol biosynthesis. Many studies have shown an association between statins use and the reduction of sepsis. The aim of the present study was to evaluate the in vitro combined antibacterial activity of rosuvastatin and cefixime.

MATERIALS AND METHODS:

Five pathogenic bacteria isolates (Gram positive and Gram negative) were used for testing the antibacterial activity of rosuvastatin alone and in combination with cefixime.

RESULTS:

Rosuvastatin mainly inhibited Klebsiella pneumoniae and Escherichia coli where it caused zones of inhibition of (17.9 ± 0.6 mm) and (16.9 ± 0.3 mm), respectively; however, it moderately inhibited the growth of Staphylococcus epidermidis (12.9 ± 0.2 mm) and Staphylococcus aureus (12.76 ± 0.2) and produced less inhibition for Pseudomonas aeruginosa growth where it led to a zone of inhibition equal to (9.1 ± 0.5 mm). Minimal inhibitory concentration (μg/mL) of rosuvastatin was high compared to cefixime. Fractional inhibitory concentration (FIC) of rosuvastatin was low for E. coli and K. pneumoniae compared to the other types of bacterial strains. Rosuvastatin exhibited additive effects with cefixime against E. coli and K. pneumoniae. ΣFIC index was 0.536 and 0.734 for E. coli and K. pneumoniae, respectively.

CONCLUSION:

Rosuvastatin has a significant antibacterial activity against both Gram-negative and Gram-positive bacteria with a potential additive effect when used in combination with cefixime.

Photoinduced Antibacterial Activity of the Essential Oils from Eugenia brasiliensis Lam and Piper mosenii C. DC. by Blue Led Light

The objective of this work was to evaluate the phytochemical composition and the antibacterial and antibiotic-modulating activities of the essential oils of Eugenia brasiliensis Lam (OEEb) and Piper mosenii C. DC (OEPm) singly or in association with blue LED (Light-emitting diode) light. The antibacterial and antibiotic-modulatory activities of the essential oils on the activity of aminoglycosides were evaluated to determine the minimum inhibitory concentration (MIC, μg/mL) in the presence or absence of exposure to blue LED light. The chemical analysis showed α-pinene and bicyclogermacrene as major constituents of OEPm, whereas α-muurolol was the main compound of OEEb. Both OEEb and OEPm showed MIC ≥ 512 μg/mL against the strains under study. However, the association of these oils with the blue LED light enhanced the action of the aminoglycosides amikacin and gentamicin. In conclusion, the association of aminoglycosides with the blue LED light and essential oils was effective against resistant bacteria.

Effect of the essential oils from Piper sp. and blue led lights in the enhancement of the antibiotic activity of drugs against mdr bacterial strains

The indiscriminate use of antibiotics has made bacterial resistance an important public health problem, since many antibiotics have become ineffective. Phototherapy can be considered an alternative to reduce the abusive use of antimicrobials, thus impacting microbial resistance. The objective of this study was to determine the chemical profile and to evaluate the effect of blue LED lights on the antibacterial activity of essential oils from Piper species, as well as their aminoglycoside antibiotic activity modulation using the microdilution method to determine the Minimum Inhibitory Concentration (MIC). The antibiotic activity modulating effect of these oils was also determined using the broth microdilution method with 96-well plates which were exposed to LED light for 20 min. Chemical components were characterized by gas chromatography coupled to mass spectrometry, revealing β-copaen-4-α-ol, germacrene A and germacrene B as major essential oil constituents for Piper arboreum (OEPar), Piper aduncum (OEPad) and Piper gaudichaudianum (OEPg), respectively. OEPar obtained a MIC of 512 μg/mL against Staphylococcus aureus and a MIC ≥ 1024 μg/mL against Escherichia coli. OEPad and OEPg showed MIC values ≥ 1024 μg/mL against the utilized strains. The essential oils modulated the effect of the antibiotics amikacin and gentamicin, with this effect being potentiated when exposed to blue LED. The blue LED light in the absence of the essential oil also showed an ability to modulate aminoglycoside antibiotic activity in this study, presenting mostly synergistic effects. In conclusion, the results obtained in this study demonstrate that photodynamic therapy using blue LED light interferes with the antibacterial action of P. arboreum, P. aduncum and P. gaudichaudianum essential oils and aminoglycoside antibiotic activity.

LC-MS analysis and cytoprotective effect against the mercurium and aluminium toxicity by bioactive products of Psidium brownianum Mart. ex DC

This study aimed to verify the chelating, antioxidant and cytoprotective activities of Psidium brownianum Mart. Ex DC against mercury and aluminum. The ethanolic extract, as well as the tannic and flavonoid fractions, were prepared and subjected to liquid chromatography-mass spectrometry analysis. Ferric ion reduction and antioxidant activity measurement using the FRAP method were performed with P. brownianum. After determining the sub-allelopathic doses, germination tests using Lactuca sativa (lettuce) seeds were performed. The main compounds identified in the extract and fractions were: quercetin and its derivatives; myricetin and its derivatives; gallic acid; ellagic acid; quinic acid and gallocatechin. The Minimum Inhibitory Concentration (MIC) for all samples were ≥ 1024 μg/mL. The flavonoid fraction in association with mercury chloride demonstrated cytoprotection (p < 0.001). The sub-allelopathic concentration used was 64 μg/mL. The extract and fractions were cytoprotective for radicles and caulicles when assayed in association with mercury and against aluminum for radicles. This suggests that the P. brownianum extract and its fractions present cytoprotective activity, possibly related to the antioxidant effect of secondary metabolites, especially flavonoids.

Combined Antimicrobial Activity of Photodynamic Inactivation and Antimicrobials-State of the Art

Antimicrobial photodynamic inactivation (aPDI) is a promising tool for the eradication of life-threatening pathogens with different profiles of resistance. This study presents the state-of-the-art published studies that have been dedicated to analyzing the bactericidal effects of combining aPDI and routinely applied antibiotics in in vitro (using biofilm and planktonic cultures) and in vivo experiments. Furthermore, the current paper reviews the methodology used to obtain the published data that describes the synergy between these antimicrobial approaches. The authors are convinced that even though the combined efficacy of aPDI and antimicrobials could be investigated with the wide range of methods, the use of a unified experimental methodology that is in agreement with antimicrobial susceptibility testing (AST) is required to investigate possible synergistic cooperation between aPDI and antimicrobials. Conclusions concerning the possible synergistic activity between the two treatments can be drawn only when appropriate assays are employed. It must be noticed that some of the described papers were just aimed at determination if combined treatments exert enhanced antibacterial outcome, without following the standard methodology to evaluate the synergistic effect, but in most of them (18 out of 27) authors indicated the existence of synergy between described antibacterial approaches. In general, the increase in bacterial inactivation was observed when both therapies were used in combination.

Synchronous application of antibiotics and essential oils: dual mechanisms of action as a potential solution to antibiotic resistance

Antibiotic resistance has increased dramatically in recent years, yet the antibiotic pipeline has stalled. New therapies are therefore needed to continue treating antibiotic resistant infections. One potential strategy currently being explored is the use of non-antibiotic compounds to potentiate the activity of currently employed antibiotics. Many natural products including Essential Oils (EOs) possess broad spectrum antibacterial activity and so have been investigated for this purpose. This article aims to review recent literature concerning the antibacterial activity of EOs and their interactions with antibiotics, with consideration of dual mechanisms of action of EOs and antibiotics as a potential solution to antibiotic resistance. Synergistic interactions between EOs and their components with antibiotics have been reported, including several instances of antibiotic resensitization in resistant isolates, in support of this strategy to control antibiotic resistance. However, a lack of consistency in methods and interpretation criteria makes drawing conclusions of efficacy of studied combinations difficult. Synergistic effects are often not explored beyond preliminary identification of antibacterial interactions and mechanism of action is rarely defined, despite many hypotheses and recommendations for future study. Much work is needed to fully understand EO-antibiotic associations before they can be further developed into novel antibacterial formulations.

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

As an innovative non-antibiotic approach, antimicrobial blue light in the spectrum of 400-470nm has demonstrated its intrinsic antimicrobial properties resulting from the presence of endogenous photosensitizing chromophores in pathogenic microbes and, subsequently, its promise as a counteracter of antibiotic resistance. Since we published our last review of antimicrobial blue light in 2012, there have been a substantial number of new studies reported in this area. Here we provide an updated overview of the findings from the new studies over the past 5 years, including the efficacy of antimicrobial blue light inactivation of different microbes, its mechanism of action, synergism of antimicrobial blue light with other angents, its effect on host cells and tissues, the potential development of resistance to antimicrobial blue light by microbes, and a novel interstitial delivery approach of antimicrobial blue light. The potential new applications of antimicrobial blue light are also discussed.