Young astringent persimmon tannin inhibits methicillin-resistant Staphylococcus aureus isolated from pork

Unlocking the potential of persimmons: A comprehensive review on emerging technologies for post-harvest challenges, processing innovations, and prospective applications

Persimmons are widely acknowledged as a valuable source of both medicinal and nutritional components, providing a diverse spectrum of nutrients and phytochemicals. Despite these benefits, biases against persimmons persists due to their characteristic astringent flavor that sets them apart from other fruits. Although several studies have explored various aspects of persimmons, a comprehensive review that addresses post-harvest challenges, processing innovations, and potential applications is notably absent in the literature. This review aims to fill this gap by discussing a range of topics, including emerging preservation technologies, methods for detecting and eliminating astringency, identification of functional elements, health-promoting prospects, and advancements in processed persimmon products. The primary objective is to enhance the utilization of persimmons and promote the development of diverse, customized products, thereby fostering the emergence of functional and futuristic foods.

Transcriptome analysis reveals important regulatory factors for condensed tannins synthesis in acorn

Condensed tannins are widely present in the fruits and seeds of plants and effectively prevent them from being eaten by animals before maturity due to their astringent taste. In addition, condensed tannins are a natural compound with strong antioxidant properties and significant antibacterial effects. Four samples of mature and near-mature Quercus fabri acorns, with the highest and lowest condensed tannin content, were used for genome-based transcriptome sequencing. The KEGG enrichment analysis revealed that the differentially expressed genes (DEGs) were highly enriched in phenylpropanoid biosynthesis and starch and sucrose metabolism. Given that the phenylpropanoid biosynthesis pathway is a crucial step in the synthesis of condensed tannins, we screened for significantly differentially expressed transcription factors and structural genes from the transcriptome data of this pathway and found that the expression levels of four MADS-box, PAL, and 4CL genes were significantly increased in acorns with high condensed tannin content. The quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) experiment further validated this result. In addition, yeast one-hybrid assay confirmed that three MADS-box transcription factors could bind the promoter of the 4CL gene, thereby regulating gene expression levels. This study utilized transcriptome sequencing to discover new important regulatory factors that can regulate the synthesis of acorn condensed tannins, providing new evidence for MADS-box transcription factors to regulate the synthesis of secondary metabolites in fruits.

Condensed tannins-Their content in plant foods, changes during processing, antioxidant and biological activities

Condensed tannins are considered nutritionally undesirable, because they precipitate proteins, inhibit digestive enzymes, and can affect the absorption of vitamins and minerals. From the consumer's point of view, they impart astringency to foods. Yet, they are viewed as a double-edged sword, since they possess antioxidant and anti-inflammatory activities. Intake of a small quantity of the right kind of tannins may in fact be beneficial to human health. This chapter reports on the chemical structure of condensed tannins, their content in plants and food of plant origin, how they are extracted, and methods for their determination. A description of the effects of processing on condensed tannins is discussed and includes soaking, dehulling, thermal processing (i.e., cooking, boiling, autoclaving, extrusion), and germination. The astringency of condensed tannins is described in relation to their interactions with proteins. Finally, details about the biological properties of condensed tannins, including their antimicrobial, anti-inflammatory, anticancer, anti-diabetic, and anti-obesity activities, are reviewed.

Contribution of amino acids to Alicyclobacillus acidoterrestris DSM 3922T resistance towards acid stress

Spoilage of juice and beverages by a thermo-acidophilic bacterium, Alicyclobacillus acidoterrestris, has been considered to be a major and widespread concern for juice industry. Acid-resistant property of A. acidoterrestris supports its survival and multiplication in acidic juice and challenges the development of corresponding control measures. In this study, intracellular amino acid differences caused by acid stress (pH 3.0, 1 h) were determined by targeted metabolomics. The effect of exogenous amino acids on acid resistance of A. acidoterrestris and the related mechanisms were also investigated. The results showed that acid stress affected the amino acid metabolism of A. acidoterrestris, and the selected glutamate, arginine, and lysine contributed to its survival under acid stress. Exogenous glutamate, arginine, and lysine significantly increased the intracellular pH and ATP level, alleviated cell membrane damage, reduced surface roughness, and suppressed deformation caused by acid stress. Additionally, the up-regulated gadA and speA genes and the enhanced enzymatic activity confirmed that glutamate and arginine decarboxylase systems played a crucial role in maintaining pH homeostasis of A. acidoterrestris under acid stress. Our research reveals an important factor contributing to acid resistance of A. acidoterrestris, which provides an alternative target for effectively controlling this contaminant in fruit juices.

The Genus Diospyros: A Review of Novel Insights into the Biological Activity and Species of Mozambican Flora

Species of the Diospyros L. genus (Ebenaceae family) have been largely used in traditional medicine for the treatment of several diseases, especially infectious ones. To date, active major compounds such as naphthoquinones, triterpenoids, and tannins have been isolated and pharmacologically validated from Diospyros species. The present study summarizes the information available in the literature on the species described in the Flora of Mozambique. To do so, scientific databases (e.g., PubMed, Scopus, Web of Science, and Google Scholar) were searched using various keywords and Boolean connectors to gather and summarize the information. Of the 31 native and naturalized species in the Flora of Mozambique, 17 are used in different regions of Africa and were described for their traditional uses. They were reported to treat more than 20 diseases, mostly infectious, in the gastrointestinal and oral cavity compartments. This work provides an overview of the therapeutical potential of Diospyros species and explores novel insights on the antimicrobial potential of extracts and/or isolated compounds of these Mozambican species.

Low Allergenicity in Processed Wheat Flour Products Using Tannins from Agri-Food Wastes

The present study aimed to investigate the effect of the addition of tannins from unutilized resources on wheat allergen reduction, antioxidant properties, and quality by substituting 3%, 5%, and 10% of the flour with chestnut inner skin (CIS) and young persimmon fruit (YPF) powders to produce cookies. The enzyme-linked immunosorbent assay and Western blotting showed significantly lower wheat allergen content in CIS- or YPF-substituted cookies than in control cookies, and this effect was pronounced for CIS-substituted cookies. In addition, the tannin content and antioxidant properties of the CIS- or YPF-substituted cookies were markedly higher than those of the control cookies. Quality analysis of the CIS- and YPF-substituted cookies showed that the specific volume and spread factor, which are quality indicators for cookies, were slightly lower in the CIS- and YPF-substituted cookies than in the control cookies. Compared to the control, CIS substitution did not affect the breaking stress and total energy values of the cookies; however, YPF substitution at 10% increased these values. Color was also affected by the addition of CIS and YPF. The results suggest that the addition of CIS and YPF can reduce wheat allergens in cookies and improve tannin content and antioxidant properties.

Fabrication of Co-Assembly from Berberine and Tannic Acid for Multidrug-Resistant Bacteria Infection Treatment

Long-term antibiotic use induces drug resistance in bacteria. This has given rise to the challenge of refractory infections, which have become a global health threat. Berberine (BBR) and tannic acid (TA) from plants exhibit promising antibacterial activities and may overcome antibiotic resistance. However, poor solubility and/or low penetration capability have limited their application. Carrier-free co-assembled nanocomposites composed entirely of BBR and TA exhibit improved or new properties and produce improved efficacy. Herein, we demonstrated that an ordered nanostructure could be spontaneously co-assembled by the solvent evaporation method using the two natural products. These co-assembled berberine-tannic acid nanoparticles (BBR-TA NPs) exhibited the best antibacterial effect compared with the corresponding physical mixture, pristine BBR, and some first-line antibiotics (benzylpenicillin potassium-BP and ciprofloxacin-Cip) against Staphylococcus aureus (S. aureus) and multidrug-resistant Staphylococcus aureus (MRSA). Even if the concentration of BBR-TA NPs was as low as 15.63 μg/mL, the antibacterial rate against S. aureus and MRSA was more than 80%. In addition to the synergistic effect of the two compounds, the antibacterial mechanism underlying the nanostructures was that they strongly adhered to the surface of the bacterial cell wall, thereby inducing cell membrane damage and intracellular ATP leakage. Furthermore, the in vivo wound healing effect of BBR-TA NPs was verified using an MRSA wound infection mouse model. The BBR-TA NPs achieved the best efficacy compared with BP and Cip. Moreover, cytotoxic and histopathological evaluations of mice revealed that the nanodrug had good biological safety. This facile and green co-assembly strategy for preparing nanoparticles provides a feasible reference for the clinical treatment of bacterial infection.

Unraveling the mechanisms of inhibition of silver-doped bioactive glass-ceramic particles

Infections are a major concern in orthopedics. Antibacterial agents such as silver ions are of great interest as broad-spectrum biocides and have been incorporated into bioactive glass-ceramic particles to control the release of ions within a therapeutic concentration and provide tissue regenerative properties. In this work, the antibacterial capabilities of silver-doped bioactive glass (Ag-BG) microparticles were explored to reveal the unedited mechanisms of inhibition against methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial properties were not limited to the delivery of silver ions but rather a combination of antibacterial degradation by-products. For example, nano-sized debris punctured holes in bacteria membranes, osmotic effects, and reactive oxygen species causing oxidative stress and almost 40% of the inhibition. Upon successive Ag-BG treatments, MRSA underwent phenotypic and genomic mutations which were not only insufficient to develop resistance but instead, the clones became more sensitive as the treatment was re-delivered. Additionally, the unprecedented restorative functionality of Ag-BG allowed the effective use of antibiotics that MRSA resists. The synergy mechanism was mainly identified for combinations targeting cell-wall activity and their action was proven in biofilm-like and virulent conditions. Unraveling these mechanisms may offer new insights into how to tailor healthcare materials to prevent or debilitate infections and join the fight against antibiotic resistance in clinical cases.

Unveiling major ethnopharmacological aspects of genus Diospyros in context to its chemical diversity: A comprehensive overview

Diospyros species (DS), "Ebenaceae," were known for their therapeutic uses in folk medicine since days of yore. Thereafter, scientific evidence related their health benefits to a myriad of chemical classes, for instance, naphthoquinones, flavonoids, tannins, coumarins, norbergenin derivatives, sterols, secoiridoids, sesquiterpenes, diterpenoids, triterpenoids, volatile organic compounds (VOCs), and carotenoids. The available literature showed that more than 200 compounds were isolated and identified via spectroscopic techniques. Many pharmacological activities of DS have been previously described, such as antioxidant, neuroprotective, antibacterial, antiviral, antiprotozoal, antifungal, antiinflammatory, analgesic, antipyretic and cosmeceutical, investigated, and confirmed through versatile in vitro and in vivo assays. Previous studies proved that genus Diospyros is a rich reservoir of valuable bioactive compounds. However, further comparative studies among its different species are recommended for more precise natural source-based drug discovery and clinical application. Accordingly, this review is to recall the chemical abundance and diversity among different members of genus Diospyros and their ethnopharmacological and pharmacological uses. PRACTICAL APPLICATIONS: Practically, providing sufficient background on both secondary metabolites divergence and pharmacological properties of genus Diospyros has many fruitful aspects. As demonstrated below, extracts and many isolated compounds have significant curative properties, which can lead to the discovery of pharmaceutically relevant alternative substitutes to conventional medicine. Consequently, molecular docking on various receptors can be applied. On the grounds, Naoxinqing tablets, a standardized herbal product containing D. kaki leaves extract, have been patented and recorded in Chinese Pharmacopeia as an approved Traditional Chinese Medicine (TCM) for the treatment of cerebro- and cardiovascular diseases, although the underlying mechanism remains under advisement. Moreover, the antimicrobial applications of DS are of considerable concern; since the widespread use of antibiotics resulted in different forms of bacterial resistance, hence, limiting and compromising effective treatment. In addition, as a result of contemporary rampant memory disorders, neuroprotective activities of different extracts of DS became of great emphasis.

Garlic essential oil in water nanoemulsion prepared by high-power ultrasound: Properties, stability and its antibacterial mechanism against MRSA isolated from pork

Food-borne methicillin-resistance Staphylococcus aureus (MRSA) has caused significant health threats and economic loss in livestock and poultry products. Garlic essential oil (GEO) is an effective antibacterial agent but presents strong instability and hydrophobicity. In this study, GEO in water nanoemulsion (GEON) with good stability was produced by emulsification technique of high-power ultrasound. Its antibacterial activity and underlying mechanism against MRSA isolated from retailed pork were investigated. Results showed that ultrasonic treatment significantly reduced the particle size of GENO from 820.3 to 215.0 nm as time increased from 0 to 10 min. Comparatively, GEON of 10 min ultrasound was more stable than other GEONs (0, 1, 5 min) during 30 d storage. It also displayed good thermal stability and relatively good ion stability (NaCl, MgCl₂, and glucose). Antibacterial analysis showed that GEON (10 min) exhibited the best anti-MRSA activity among all GEONs, and the minimum inhibitory concentration of GEO in this nanoemulsion was 0.125 % (1.25 mg/mL). Treatment of GEON (10 min) significantly suppressed the cell proliferation of MRSA, which was mainly achieved by damaging the cell membrane as evidenced by membrane depolarization and considerable leakage of intracellular nucleic acids and protein. Laser scanning confocal microscope and scanning electron microscopy showed that treatment of GEON (10 min) significantly altered the membrane integrity and severely damaged the cellular membrane and structure. The present work illustrated that GEON produced by ultrasonic emulsification is a promising alternative to inhibit the contamination and spread of MRSA in livestock and poultry products.

From Diospyros kaki L. (Persimmon) Phytochemical Profile and Health Impact to New Product Perspectives and Waste Valorization

Persimmon (Diospyros kaki L.) fruit's phytochemical profile includes carotenoids, proanthocyanidins, and gallic acid among other phenolic compounds and vitamins. A huge antioxidant potential is present given this richness in antioxidant compounds. These bioactive compounds impact on health benefits. The intersection of nutrition and sustainability, the key idea behind the EAT-Lancet Commission, which could improve human health and decrease the global impact of food-related health conditions such as cancer, heart disease, diabetes, and obesity, bring the discussion regarding persimmon beyond the health effects from its consumption, but also on the valorization of a very perishable food that spoils quickly. A broad option of edible products with better storage stability or solutions that apply persimmon and its byproducts in the reinvention of old products or even creating new products, or with new and better packaging for the preservation of food products with postharvest technologies to preserve and extend the shelf-life of persimmon food products. Facing a global food crisis and the climate emergency, new and better day-to-day solutions are needed right now. Therefore, the use of persimmon waste has also been discussed as a good solution to produce biofuel, eco-friendly alternative reductants for fabric dyes, green plant growth regulator, biodegradable and edible films for vegetable packaging, antimicrobial activity against foodborne methicillin-resistant Staphylococcus aureus found in retail pork, anti-Helicobacter pylori agents from pedicel extracts, and persimmon pectin-based emulsifiers to prevent lipid peroxidation, among other solutions presented in the revised literature. It has become clear that the uses for persimmon go far beyond the kitchen table and the health impact consumption demonstrated over the years. The desired sustainable transition is already in progress, however, mechanistic studies and clinical trials are essential and scaling-up is fundamental to the future.

Antibacterial films made with persimmon (Diospyros kaki L.), pectin, and glycerol: An experimental design approach

Persimmon is among the fruits with a significant postharvest loss over the last few years. Thus, it is important to investigate new technical feasibilities to obtain products with higher added value from this fruit. In this study persimmon puree films (Diospyros kaki L.) incorporated with glycerol and pectin by casting technique were formulated using a Plackett-Burman design and characterized. The puree showed high carbohydrate content (175.70 g/kg). In descending order, fructose, glucose, and maltohexaose were the sugars found in persimmon. All the independent variables studied-puree concentration, pectin, glycerol, and temperature-statistically influenced the tensile strength (0.75-1.30 MPa), elongation at break (17.69-26.02%), and Young's modulus (3.34-10.94 MPa) of the films. Water solubility ranged from 68.80% to 80.86%, which were very similar to other films based on puree fruit in the literature. Samples presented high vapor permeability (5.77-6.63 × 10^-6 g/h/m/Pa) when compared to biodegradable films. Scanning electron microscopy showed smooth surfaces and good plasticizer dispersion. The colorimetric coordinates indicated the films are reddish and yellowish, giving them an orange-ish visual aspect. The films exhibited antimicrobial activity, especially against Escherichia coli and Staphylococcus aureus. These results indicate that the developed films might be a good candidate for antimicrobial food packaging improving food quality and safety. PRACTICAL APPLICATION: The production of fruit-film packaging with functional and biodegradable characteristics might reduce postharvest loss of fruit and have the potential to develop active food packaging. In this sense, this study is in line with precepts of the circular economy, once it takes advantage of exceeded resources that would be discarded by generating biodegradable films which can be used as edible packaging. Furthermore, given the antimicrobial potential of the films developed, they might be applied as active packaging to improve food safety and extend shelf life.

Antimicrobial and Antibiofilm Activities and Mechanism of Action of Chelerythrine Against Carbapenem-Resistant Serratia marcescens In Vitro

Aim: To evaluate the antimicrobial and antibiofilm effects of chelerythrine (CHE) against carbapenem-resistant Serratia marcescens (CRSM). Materials and Methods: The minimum inhibitory concentration (MIC) of CHE against CRSM was determined using the agar dilution method. Changes in intracellular adenosine triphosphate (ATP) concentration, intracellular pH, cell membrane potential, and cell membrane integrity were investigated to assess the influence of CHE on the cell membrane. The effects of CHE on cell morphology were observed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy. The antibiofilm formation of CHE was measured by crystal violet staining and visualized with confocal laser scanning microscopy (CLSM) and FESEM. The influence of CHE on biofilm components was further investigated using CLSM specific combined with double-dyeing methods. Results: Our results showed that CHE had an MIC at 125 μg/mL against CRSM was capable of inhibiting the growth of CRSM and destroying its cell membrane integrity, as well as obviously changing the cell morphology. Sub-MIC CHE displayed robust inhibitory effects against CRSM biofilm formation by mediating the production of biofilm components. In addition, CLSM- and FESEM-mediated evaluation of the damage of biofilm cells and biofilm persistence revealed that at high concentrations, CHE could compromise the cells within biofilms and remove preformed biofilms. Conclusion: CHE shows promise as a natural antimicrobial substance against biofilm-positive CRSM, with the potential to serve as an alternative therapeutic agent.

New insights into thermo-acidophilic properties of Alicyclobacillus acidoterrestris after acid adaptation

Alicyclobacillus acidoterrestris has unique thermo-acidophilic properties and is the main cause of fruit juice deterioration. Given the acidic environment and thermal treatment during juice processing, the effects of acid adaptation (pH 3.5, 3.2, and 3.0) on the resistance of A. acidoterrestris to heat (65 °C, 5 min) and acid (pH = 2.2, 1 h) stresses were investigated for the first time. The results showed that acid adaptation induced cross-protection against heat stress of A. acidoterrestris and acid tolerance response, and the extent of induced tolerance was increased with the decrease of adaptive pH values. Acid adaptation treatments did not disrupt the membrane potential stability and intracellular pH homeostasis, but reduced intracellular ATP concentration, increased cyclic fatty acids content, and changed the acquired Fourier transform infrared spectra. Transcription levels of stress-inducible (dnaK, grpE, clpP, ctsR) genes and genes related to spore formation (spo0A, ctoX) were up-regulated after acid adaptation, and spore formation was observed by scanning electron microscopy. This study revealed that the intracellular microenvironment homeostasis, expression of chaperones and proteases, and spore formation played a coordinated role in acid stress adaptive responses, with implications for applications in fruit juice processing.

Metabolomics analysis to evaluate the antibacterial activity of the essential oil from the leaves of Cinnamomum camphora (Linn.) Presl

ETHNOPHARMACOLOGY RELEVANCE

Cinnamomum camphora (Linn.) Presl (C. camphora) is one of the oldest herbal medicines used as a traditional medicine, owning a wide range of biological functions including anti-bacterial, anti-oxidative, anti-fungal, anti-inflammatory, insecticidal and repellent activities.

OBJECTIVE

The aim of this study was to investigate the antibacterial activity and mechanism of action of the essential oil (EO) from C. camphora.

MATERIALS AND METHODS

The EO was isolated from the leaves of C. camphora by hydrodistillation, and the chemical compositions of the EO were analyzed by gas chromatography-mass spectrometry (GC-MS). The minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) values of the EO were estimated by the microbroth dilution method. Growth curve was investigated by turbidimetry. Apoptosis was measured by flow cytometry. Morphological change of bacteria was observed by field emission scanning electron microscopy and transmission electron microscopy. The integrity of cell membrane was evaluated by NanoDrop and BCA Protein Assay Kit. The methicillin-resistant Staphylococcus aureus (MRSA) metabolic profile in the presence of the EO was explored by GC-MS-based metabolomics. Isocitrate dehydrogenase (ICDH), α-ketoglutarate dehydrogenase (α-KGDH), succinic dehydrogenase (SDH) and malic dehydrogenase (MDH) activities were detected by commercial kits.

RESULTS

The main components of the EO from the leaves of C. camphora were identified to be linalool (26.6%), eucalyptol (16.8%), α-terpineol (8.7%), isoborneol (8.1%), β-phellandrene (5.1%), and camphor (5.0%). The EO had good activity against MRSA, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Salmonella gallinarum and Escherichia coli. MRSA was selected as the model bacterium to illustrate antibacterial mechanism of action of the EO, and the MIC and MBC values was 0.8 and 1.6 mg/mL, respectively. Apoptosis rate of MRSA increased in a concentration-dependent manner after the addition of EO. The cell morphology was damaged by the EO. There were 74 significantly different metabolites, including 29 upregulated and 45 downregulated metabolites in the result of metabolomics evaluation. Seven pathways were enriched by shared differential metabolites. The EO enhanced the activity of ICDH by 47.35%, while weaken MDH, SDH and α-KGDH by 72.63%, 31.52% and 63.29%, respectively.

CONCLUSIONS

The EO from C. camphora showed anti-MRSA activity via damaging cell membranes and disturbing the amino metabolism.

Antimicrobial and Antibiofilm Activities of Citral Against Carbapenem-Resistant Enterobacter cloacae

Citral that is produced in the essential oils of plants is an isomeric mixture of geranial and neral. Few recent studies exhibited robust antibacterial activity of citral against several pathogens. However, little is reported about effects of citral on carbapenem-resistant Enterobacter cloacae (CREC). The purpose of this study was to assess antibacterial and antibiofilm activities of citral against CREC. Here, minimum inhibitory concentrations (MICs) of citral against CREC were determined by the agar dilution method. Antibacterial mode of citral against CREC was elucidated by evaluating changes in intracellular adenosine triphosphate (ATP) concentration, intracellular pH (pH_in), membrane potential, membrane integrity, and cell morphology. In addition, CREC cell damage within biofilms was examined by confocal laser scanning microscopy (CLSM). The results showed that the MIC of citral against CREC was 1000 μg/mL. Citral inhibited CREC growth and destroyed its cell membrane integrity, as measured by the decrease of intracellular ATP, pH, and membrane potential as well as distinctive deformation in cellular morphology. CLSM images demonstrated that citral could inactivate CREC cells within biofilms. These results revealed that citral exhibits potent antibacterial and antibiofilm activity against CREC, and thus has potential to be used as natural food preservatives to control CREC-associated infection spread.

Antimicrobial activity of eugenol against carbapenem-resistant Klebsiella pneumoniae and its effect on biofilms

A preliminary study found that eugenol expressed an antibacterial activity against Klebsiella pneumoniae. However, the mechanism of action of eugenol against K. pneumoniae still remains unexplored. The aim of this study was to gain further insight into the antibacterial effect of eugenol against carbapenem-resistant Klebsiella pneumoniae (CRKP) and possible mode of action. Here, minimum inhibitory concentration (MIC) of eugenol against CRKP strains was determined using the agar dilution method. Moreover, variations in intracellular ATP concentration, intracellular pH (pH_in), membrane potential and membrane integrity were measured to evaluate the effect of eugenol on cell membrane. Besides, changes in cell structure and biofilm formation of CRKP as well as biofilm-associated cell damage were determined using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and confocal laser scanning microscopy (CLSM). Finally, gene expression of biofilm-related biosynthesis was investigated. The results showed that MICs of eugenol against four tested CRKP were 0.2 mg/mL. Eugenol damaged the cell membrane of CRKP, as evidenced by decreased intracellular ATP concentration, reduced pH_in and cell membrane hyperpolarization, coupled with enhanced membrane permeability. Furthermore, eugenol compromised cell structure and induced loss of intracellular components of CRKP. Additionally, eugenol inhibited biofilm formation and inactivated biofilm CRKP cells. Finally, eugenol presented strong inhibitory effects on biofilm formation and biofilm-associated gene expression, and inactivated CRKP cells growing in biofilms. These findings suggest that eugenol exhibits antimicrobial effect against CRKP strains and could be potentially used to control CRKP-related infections.

In Vitro Antibacterial Activity and Mechanism of Vanillic Acid against Carbapenem-Resistant Enterobacter cloacae

Vanillic acid (VA) is a flavoring agent found in edible plants and fruits. Few recent studies exhibited robust antibacterial activity of VA against several pathogen microorganisms. However, little was reported about the effect of VA on carbapenem-resistant Enterobacter cloacae (CREC). The purpose of the current study was to assess in vitro antimicrobial and antibiofilm activities of VA against CREC. Here, minimum inhibitory concentrations (MIC) of VA against CREC was determined via gradient diffusion method. Furthermore, the antibacterial mode of VA against CREC was elucidated by measuring changes in intracellular adenosine triphosphate (ATP) concentration, intracellular pH (pH_in), cell membrane potential and membrane integrity. In addition, antibiofilm formation of VA was measured by crystal violet assay and visualized with field emission scanning electron microscopy (FESEM) and confocal laser scanning microscopy (CLSM). The results showed that MIC of VA against E. cloacae was 600 μg/mL. VA was capable of inhibiting the growth of CREC and destroying the cell membrane integrity of CREC, as confirmed by the decrease of intracellular ATP concentration, pH_in and membrane potential as well as distinctive variation in cellular morphology. Moreover, crystal violet staining, FESEM and CLSM results indicated that VA displayed robust inhibitory effects on biofilm formation of CREC and inactivated biofilm-related CREC cells. These findings revealed that VA exhibits potent antibacterial activity against CREC, and thus has potential to be exploited as a natural preservative to control the CREC associated infections.

Possible mechanisms of the antimicrobial effects of polypeptide‑enriched Gastrodia elata Blume extracts

The present study aimed to evaluate the antimicrobial activity and the possible mechanisms of activity of polypeptide‑enriched Gastrodia elata extracts (GEP) against the gram‑negative bacteria Escherichia coli and Pseudomonas aeruginosa, the gram‑positive bacterium Staphylococcus aureus and the fungus Candida albicans. The antimicrobial activity of GEP was first confirmed by determining the minimum inhibitory concentration by growth curve analysis. GEP was found to damage the cell wall and membrane of the microorganisms tested, as revealed by the morphological changes visible through scanning electron microscopy, and by the observed leakage of alkaline phosphatase and β‑galactosidase from cells. GEP was demonstrated to perturb the metabolism of the microorganisms, especially the tricarboxylic acid cycle, as indicated by the reduced intracellular activity of succinate dehydrogenase, malate dehydrogenase and ATPases, including the Na+/K+‑ATPase and the Ca2+‑ATPase. In addition, GEP caused the leakage of the genetic material of the bacteria and the fungus, as indicated by the increased OD260. The results of the present study indicated that GEP may exert its antimicrobial activity by damaging cell walls and membranes, causing the leakage of genetic material, and by perturbing cellular metabolism.