Synergistic Antimicrobial Effect Research Articles

Wide‐Spectrum Nano‐Antibiotics Based on TPA‐Py@AuNCs⊂BSA for Multimodal Synergistic Therapy of Drug‐Resistant Bacteria and Wound Infections

ABSTRACTTo meet the high requirements of biomedical applications in antimicrobial agents, it is crucial to explore efficient nano‐antimicrobial agents with no resistance and good biocompatibility for treating infected wounds. In this study, composite nano‐antibiotic TPA‐Py@AuNCs⊂BSA nanoparticles (TAB NPs) are prepared using hollow mesoporous Au nanocages (AuNCs) loaded with a photosensitizer (namely TPA‐Py) with D‐π‐A structure showing aggregation‐induced emission properties. When TPA‐Py is encapsulated in the cavity of AuNCs, its fluorescence is suppressed. In the presence of photothermal induction, TPA‐Py can be released from the AuNCs, allowing for the restoration of fluorescence illumination and the specific imaging of Gram‐positive bacteria. TAB NPs demonstrate outstanding antimicrobial activity against a variety of bacteria, and this multimodal antimicrobial property does not lead to the development of bacterial resistance. In vitro experiments show that TAB NPs could eliminate bacteria and ablate bacterial biofilm. In vivo experiments show that the synergistic antimicrobial effect of TAB NPs has a significant positive impact on the treatment of infected wounds, including rapid antibacterial action, promotion of M2 macrophage polarization, and enhancement of chronic wound healing. This study provides an effective strategy for developing wide‐spectrum nano‐antibiotics for the ablation of bacterial biofilms and the treatment of infected wounds.

Multifunctional Temporary Dental Nanofillers Enhanced with Synergistically Active Chlorine-Containing Molecules against Streptococcus mutans and Its Effects on Oral Epithelial Cells.

Temporary dental fillers are critical for safeguarding teeth during the period between caries removal and permanent restoration. However, conventional fillers often lack sufficient antimicrobial properties to prevent bacterial colonization. To address this issue, the study researches on the development of antimicrobial Temporary Dental Nano-Fillers (TDNF) capable of targeting multiple cariogenic pathogens, including Streptococcus mutans, Lactobacillus casei, Candida albicans, and mixed-species planktonic cells/biofilms, which play a significant role in the progression of dental caries. The TDNF was formulated using a combination of Chloramine-T (CRT) and Cetylpyridinium Chloride (CPC), both known for their antimicrobial efficacy, and embedded in a nanoparticle matrix of hydroxyapatite (HAP) and silicon dioxide (SiO2). The synergistic antimicrobial effect of CRT and CPC, with MIC90 values of 12.5 and 6.25 ppm, respectively, displayed potent activity against S. mutans. Proteomic analysis, including gene ontology and protein-protein interaction network evaluations, further confirmed significant disruptions in S. mutans metabolic and stress response pathways, highlighting the bactericidal effectiveness of the formulation against S. mutans. Additionally, the formulation demonstrated sustained antimicrobial efficacy against other cariogenic pathogens such as L. casei, C. albicans and mixed-species planktonic cells and biofilms over a 16-day period. The TDNF (HAP+SiO2+CRT+CPC matrix) exhibited superior mechanical properties with a compressive strength of 237.7 MPa, flexural strength of 124.3 MPa, and shear bond strength of 52 MPa. Biocompatibility tests conducted on human oral squamous carcinoma cells (OECM-1) indicated over 95% cell viability, affirming its safety for preclinical or clinical applications. The multifunctional TDNF developed in this study successfully combines mechanical reinforcement with broad-spectrum antimicrobial efficacy, offering a promising interim solution in dental restorations. Its ability to protect against microbial colonization, while maintaining structural stability, positions it as an effective temporary material that enhances patient outcomes during the period before permanent restoration.

Bacillus Cereus Control Using Lactoferrin and/or Propolis Incorporated Carboxymethyl Cellulose Edible Coating in Chilled Beef Fillets

Background: Bacillus cereus (B. cereus) is a major food poisoning bacterium that resists high cooking temperatures. The aim of this study was to prepare Carboxymethyl Cellulose (CMC) edible coats incorporated with lactoferrin, propolis and mixtures of them and evaluate their effects on B. cereu) experimentally inoculated in beef fillets stored in the refrigerator till spoilage. Methods: Prepare Carboxymethyl Cellulose (CMC) edible coats incorporated with lactoferrin, propolis and mixtures of them and evaluate their effects on bacillus cereus that experimentally inoculated in beef fillets stored refrigerated till spoilage. Results: The results revealed a significant and gradual increase in B. cereus count from ~8 log CFU/g. In first day the count reached a population of 9.69±0.12 and 9.27±0.02 log CFU/gm. at 9th day of storage in un-coated group (BF/BC) and blank coated group (CMC/BF/BC), respectively. While coated groups showed a significant decrease in B. cereus count from ~8 log CFU/gm. in first day of inoculation to 5.80±0.1, 5.41±0.06, 5.11±0.02 in CMC/BF/BC/LF, CMC/BF/BC/PR and CMC/BF/BC/LF/PR groups, respectively. The groups with coated beef showed a significant decrease (P<0.05) in B. cereus count from approximately 8 log CFU/g. On the first day of inoculation to 5.80, 5.41, and 5.11 in the Lactoferrin fortified CMC edible coating beef fillet, propolis fortified CMC edible coating beef fillet, and Lactoferrin/propolis fortified CMC edible coating beef fillet groups, respectively, on the 21st day of refrigerated storage. A synergistic antimicrobial effect between Lactoferrin and propolis was shown against B. cereus. Conclusion: It was revealed that CMC fortified with LF/PR plus its anti-B. cereus effect increased the shelf life and enhanced sensory profile of beef fillets during the 21 days of storage.

Synergistic antimicrobial effects of ammonium persulfate, ultrasound, and mild heat on Staphylococcus aureus under varied conditions

Synergistic antimicrobial effects of ammonium persulfate, ultrasound, and mild heat on Staphylococcus aureus under varied conditions

Effective combinations of silver nanoparticles and antimicrobial peptides against antibiotic-resistant bacteria

BACKGROUND: The problem of constantly growing resistance of microorganisms to the antibiotics used forces scientists to constantly search for new antimicrobial agents. AIM: To study the antimicrobial activity and toxicity of silver nanoparticles and antimicrobial peptides with a β-hairpin structure, and to characterize their combined antimicrobial action. MATERIALS AND METHODS: The antimicrobial activity of silver nanoparticles and antimicrobial peptides against antibiotic-resistant bacteria was assessed by serial dilutions in a liquid nutrient medium, and the combined antimicrobial activity – by serial dilutions according to the “checkerboard” method. The toxicity of the substances to human cells was determined using a hemolytic test. RESULTS: The studied silver nanoparticles have pronounced antimicrobial activity and low toxicity to human erythrocytes. Silver nanoparticles containing acetylcysteine are more active against gram-negative bacteria than against gram-positive ones. Synergism of the antibacterial action was detected with the combined use of silver nanoparticles stabilized with sodium oleate and protegrin-1. A synergistic antimicrobial effect was also noted for combinations of silver nanoparticles containing acetylcysteine with protegrin-1, ricaecilin and shuchin-4. CONCLUSIONS: Effective combinations of silver nanoparticles and antimicrobial peptides have been identified that act synergistically against antibiotic-resistant bacterial strains, i.e. they multiply the effect of each other. These combinations can be used as prototypes for the development of antibacterial drugs.

Synergistic antimicrobial effect of daptomycin and ethyl lauroyl arginate containing self-emulsifying drug delivery system against bacterial infections

This study aimed to enhance the antimicrobial properties of daptomycin by ion-pairing with ethyl lauroyl arginate (ELA) and incorporation in a self-emulsifying drug delivery system (SEDDS).Daptomycin was ion-paired with the ELA and the hydrophobic ion pair (HIP) was loaded into SEDDS. SEDDS 1 consisted of 15% oleic acid, 5% soy phosphatidylcholine, 10% cetyltrimethylammonium bromide (CTAB) in medium-chain triglycerides (MCT) at a concentration of 250 mg/ml, 20% benzyl alcohol, and 50% PG-4 caprate. SEDDS 2 comprised 10% soy phosphatidylcholine in MCT at a concentration of 53 mg/ml, 10% CTAB, 20% benzyl alcohol, and 60% PG-4 caprate. SEDDS were characterized regarding droplet size, polydispersity index (PDI), zeta potential, and stability. Cytotoxicity was evaluated on Caco-2, HeLa, and SW620 cells. Antimicrobial activity was assessed by agar diffusion studies and time-kill assays with Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Candida albicans.Both formulations showed a droplet size below 200 nm with a PDI < 0.4, a positive zeta potential, and robust thermodynamic stability. They exhibited low toxicity profiles while maintaining full antimicrobial efficacy on all tested pathogens. Compared to unformulated daptomycin, SEDDS 1 and 2 lowered the minimum inhibitory concentration (MIC) 5- and 8- fold for S. aureus and 10- and 30- fold for S. epidermidis, respectively. Bacterial killing time was 105 -fold shortened with SEDDS 1 and 106 -fold with SEDDS 2. Furthermore, HIP and SEDDS enhanced antibacterial activity against Candida albicans and Pseudomonas aeruginosa. According to these results, ion pairing of daptomycin with ELA and incorporation into SEDDS is a promising approach to improve the antimicrobial activity of this drug.

The autophagy-targeting compound V46 enhances antimicrobial responses to Mycobacteroides abscessus by activating transcription factor EB

Mycobacteroides abscessus (Mabc) is a rapidly growing nontuberculous mycobacterium that poses a considerable challenge as a multidrug-resistant pathogen causing chronic human infection. Effective therapeutics that enhance protective immune responses to Mabc are urgently needed. This study introduces trans-3,5,4′-trimethoxystilbene (V46), a novel resveratrol analogue with autophagy-activating properties and antimicrobial activity against Mabc infection, including multidrug-resistant strains. Among the resveratrol analogues tested, V46 significantly inhibited the growth of both rough and smooth Mabc strains, including multidrug-resistant strains, in macrophages and in the lungs of mice infected with Mabc. Additionally, V46 substantially reduced Mabc-induced levels of pro-inflammatory cytokines and chemokines in both macrophages and during in vivo infection. Mechanistic analysis showed that V46 suppressed the activation of the protein kinase B/Akt-mammalian target of rapamycin signaling pathway and enhanced adenosine monophosphate-activated protein kinase signaling in Mabc-infected cells. Notably, V46 activated autophagy and the nuclear translocation of transcription factor EB, which is crucial for antimicrobial host defenses against Mabc. Furthermore, V46 upregulated genes associated with autophagy and lysosomal biogenesis in Mabc-infected bone marrow-derived macrophages. The combination of V46 and rifabutin exerted a synergistic antimicrobial effect. These findings identify V46 as a candidate host-directed therapeutic for Mabc infection that activates autophagy and lysosomal function via transcription factor EB.

The study of honokiol as a natural product-based antimicrobial agent and its potential interaction with FtsZ protein.

Multidrug resistant bacteria have been a global health threat currently and frontline clinical treatments for these infections are very limited. To develop potent antibacterial agents with new bactericidal mechanisms is thus needed urgently to address this critical antibiotic resistance challenge. Natural products are a treasure of small molecules with high bioactive and low toxicity. In the present study, we demonstrated that a natural compound, honokiol, showed potent antibacterial activity against a number of Gram-positive bacteria including MRSA and VRE. Moreover, honokiol in combination with clinically used β-lactam antibiotics exhibits strong synergistic antimicrobial effects against drug-resistant S. aureus strains. Biochemical studies further reveal that honokiol may disrupt the GTPase activity, FtsZ polymerization, cell division. These biological impacts induced by honokiol may ultimately cause bacterial cell death. The in vivo antibacterial activity of honokiol against S. aureus infection was also verified with a biological model of G. mellonella larvae. The in vivo results support that honokiol is low toxic against the larvae and effectively increases the survival rate of the larvae infected with S. aureus. These findings demonstrate the potential of honokiol for further structural advancement as a new class of antibacterial agents with high potency against multidrug-resistant bacteria.

Synergistic Antimicrobial Effects of Phage vB_AbaSi_W9 and Antibiotics against Acinetobacter baumannii Infection.

Acinetobacter baumannii is a challenging multidrug-resistant pathogen in healthcare. Phage vB_AbaSi_W9 (GenBank: PP146379.1), identified in our previous study, shows lytic activity against 26 (89.66%) of 29 carbapenem-resistant Acinetobacter baumannii (CRAB) strains with various sequence types (STs). It is a promising candidate for CRAB treatment; however, its lytic efficiency is insufficient for complete bacterial lysis. Therefore, this study aimed to investigate the clinical utility of the phage vB_AbaSi_W9 by identifying antimicrobial agents that show synergistic effects when combined with it. The A. baumannii ATCC17978 strain was used as the host for the phage vB_AbaSi_W9. Adsorption and one-step growth assays of the phage vB_AbaSi_W9 were performed at MOIs of 0.001 and 0.01, respectively. Four clinical strains of CRAB belonging to different sequence types, KBN10P04948 (ST191), LIS2013230 (ST208), KBN10P05982 (ST369), and KBN10P05231 (ST451), were used to investigate phage-antibiotic synergy. Five antibiotics were tested at the following concentration: meropenem (0.25-512 µg/mL); colistin, tigecycline, and rifampicin (0.25-256 µg/mL); and ampicillin/sulbactam (0.25/0.125-512/256 µg/mL). The in vitro synergistic effect of the phage and rifampicin was verified through an in vivo mouse infection model. Phage vB_AbaSi_W9 demonstrated 90% adsorption to host cells in 1 min, a 20 min latent period, and a burst size of 114 PFU/cell. Experiments combining phage vB_AbaSi_W9 with antibiotics demonstrated a pronounced synergistic effect against clinical strains when used with tigecycline and rifampicin. In a mouse model infected with CRAB KBN10P04948 (ST191), the group treated with rifampicin (100 μg/mL) and phage vB_AbaSi_W9 (MOI 1) achieved a 100% survival rate-a significant improvement over the phage-only treatment (8.3% survival rate) or antibiotic-only treatment (25% survival rate) groups. The bacteriophage vB_AbaSi_W9 demonstrated excellent synergy against CRAB strains when combined with tigecycline and rifampicin, suggesting potential candidates for phage-antibiotic combination therapy in treating CRAB infections.

Synergistic Antimicrobial Activity of Biogenic Silver Nanoparticles and Acanthospermum australe Essential Oil against Skin Infection Pathogens.

In response to the steady increase in antimicrobial-resistant strains, the World Health Organisation has emphasised the need to investigate new antimicrobial agents and alternative therapies that improve the spectrum of activity and reduce the dose required, thus improving safety. This study focused on the characterisation of Acanthospermum australe essential oil and green-synthesis silver nanoparticles (AgNP), evaluating their cytotoxicity in human cells, antimicrobial activity and synergistic effect against pathogens causing skin infections. The main components of the essential oil were germacrene A (24.07%), γ-cadinene (21.47%) and trans-caryophyllene (14.97%). Spherical AgNP with a diameter of 15 ± 3 nm were synthesised. The essential oil showed antimicrobial activity against dermatophytes and Malassezia globosa, while AgNP were found to be active against bacteria, yeasts and dermatophytes. Both compounds were found to be primarily non-cytotoxic at the concentrations required to inhibit microbial growth. Furthermore, the combined use of essential oil and AgNP showed a synergistic antimicrobial effect against dermatophytes and M. globosa. In conclusion, the results suggest that the combined use of bioactive compounds from natural sources, such as essential oil and biogenic AgNP, has the potential to improve antimicrobial efficacy against specific skin pathogens, particularly Microsporum canis, Nannizzia gypsea and M. globosa.

Selective in vitro Synergistic Evaluation of Probiotic Tolerant morpholinyl- and 4-ethylpiperazinyl-Imidazole-chalcone Derivatives on Gastrointestinal System Pathogens

Imidazole-chalcone compounds are recognised for their broad-spectrum antimicrobial properties. Probiotic-friendly, selective new-generation antimicrobials prove to be more efficient in combating gastrointestinal system pathogens. The aim of this study is to identify imidazole-chalcone derivatives that probiotics tolerate and evaluate their in vitro synergistic antimicrobial effects on pathogens. In this study, fifteen previously identified imidazole-chalcone derivatives were analyzed for their in vitro antimicrobial properties against gastrointestinal microorganisms. Initially, the antimicrobial activity of pathogens was measured using the agar well diffusion method, while the susceptibility of probiotics was determined by microdilution. The chosen imidazole-chalcone derivatives were assessed for synergistic effects using the checkerboard method. Four imidazole-chalcone derivatives to which probiotic bacteria were tolerant exhibited antibacterial and antifungal activity against the human pathogens tested. To our knowledge, this study is the first to reveal the fractional inhibitory concentration (FIC) of combinations of imidazole-chalcone derivatives. Indeed, the minimum inhibitory concentrations (MIC) for morpholinyl- (ZDO-3f) and 4-ethylpiperazinyl- (ZDO-3 m) imidazole-chalcones were notably low when tested against E. coli and B. subtilis, with values of 31.25 μg/mL and 125 μg/mL, respectively. The combination of morpholinyl- and 4-ethylpiperazinyl derivatives demonstrated an indifferent effect against E. coli, but an additive effect was observed for B. subtilis. Additionally, it was observed that imidazole-chalcone derivatives did not exhibit any inhibitory effects on probiotic organisms like Lactobacillus fermentum (CECT-5716), Lactobacillus rhamnosus (GG), and Lactobacillus casei (RSSK-591). This study demonstrates that imidazole-chalcone derivatives that are well tolerated by probiotics can potentially exert a synergistic effect against gastrointestinal system pathogens.

Enhancing food preservation and safety: Synergistic effects of Allium-derived organosulfur compounds and outer membrane permeabilization peptide L-11

Ready-to-eat (RTE) foods, characterized by the lack of a terminal heating step prior to consumption, offer enhanced organoleptic qualities compared to their cooked counterparts, as they retain more of their natural flavors, textures, and nutritional content. However, these untreated products pose a risk for foodborne illnesses if not promptly consumed and/or adequately stored under refrigeration or in a frozen state. This investigation delves into the synergistic antimicrobial effects of a novel human-mimetic peptide, L-11, in conjunction with organosulfur compounds derived from Allium species—namely allicin, diallyl sulfide (DAS), dipropyl sulfide (DPS), propyl propane thiosulfinate (PTS), and propyl propane thiosulfonate (PTSO)—on the inhibition and control of Gram-negative foodborne pathogens across various food matrices. Notably, despite the minimal individual antimicrobial activity of peptide L-11 and the evaluated organosulfur compounds against target bacteria (Escherichia coli, Salmonella enterica, Yersinia enterocolitica, and Shigella sonnei), their combinations exhibited remarkable synergistic effects in vitro with until 32-fold reduction for some combinations. Specifically, combinations including PTS and PTSO demonstrated up to a 99% reduction in bacterial proliferation within RTE food models such as salmorejo, aioli, pumpkin cream, and spinach cream. These findings highlight the potential applications of these synergistic combinations in extending the shelf-life and enhancing the safety of RTE foods. To the best of our knowledge, this represents the inaugural report of such synergistic interactions between organosulfur compounds and peptides in extending the shelf-life of RTE foods.

Characterization of free and encapsulated cinnamon and clove essential oils for enhancing fresh sausage quality: A natural substitute for synthetic preservatives

This study aims to evaluate the properties of essential oils (EOs) from cinnamon (Cinnamomum cassia) and clove (Eugenia caryophyllus). Mixtures of cinnamon and clove EOs at ratios of 75:25, 50:50, and 25:75 were encapsulated and applied in fresh sausage. The research includes a kinetic examination of active component release and preservation parameter monitoring. Clove EO showed superior antioxidant activity (0.039 mg/mL), while cinamon oil exhibited promising bacterial inhibition (minimum inhibitory concentration lower 1.5). Combinations of cinnamon and clove EOs demonstrated synergistic antioxidant and antimicrobial effects. Encapsulation efficiency for the 25:75 cinnamon and clove oil mixture reached 89.4%, with 80.9% EO retention. The microencapsulated mixture displayed commendable antimicrobial and antioxidant activities, slowing compound release (>50% after 15 days). The encapsulated EOs (25:75) showed comparable results in lipid oxidation (0.194 mg malonaldehyde/kg) and microbial control to traditional curing salt, suggesting substitution potential. By encapsulating cinnamon and clove essential oils and evaluating their efficacy in fresh sausages, this research demonstrates their potential to enhance the safety and quality of meat products while addressing consumer demand for healthier and more natural food options.

Determination of cinnamaldehyde, thymol and eugenol in essential oils by LC–MS/MS and antibacterial activity of them against bacteria

Plant essential oils contain many secondary metabolites, some of which can effectively inhibit the growth of pathogenic microorganisms, so it is a very promising antibacterial agent. In this study, a qualitative and quantitative method based on high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was developed for the simultaneous determination of three bioactive substances, cinnamaldehyde (CNM), thymol (THY), and eugenol (EUG), in the essential oils of plants. Necessary tests for linearity, limit of quantification, recovery, carryover contamination and precision of the method were carried out. Then, the antibacterial activity of 3 bioactive compounds against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by minimal inhibitory concentration and the synergistic antimicrobial effect. The results indicated that CNM, THY and EUG had good antibacterial activity. According to the results of fractional inhibitory concentration index (FICI), it is considered that CNM + THY and CNM + THY + EUG has obvious synergistic inhibitory effect on E. coli, and CNM + THY and CNM + EUG has obvious synergistic inhibitory effect on S. aureus. Finally, we analyzed the effect of the bioactive compounds on trace elements in bacteria and found significant changes in magnesium, calcium, copper and iron.

Enhanced Antimicrobial Activity of Laser‐induced Graphene Wrapped Tri‐Metal Organic Framework Nanocomposites

Crystalline and porous metal‐organic frameworks (MOFs) are potential candidates for different antibacterial, photocatalytic, and adsorption applications. Moreover, multi‐principal element nanoparticles are effective against multidrug‐resistant bacteria, and combining metals with carbon nanomaterials can enhance activity. In this study, a Tri‐MOF comprised of iron, zinc, and cobalt and 2‐methyl imidazole was grown together with laser‐induced graphene (LIG) powder. Electron microscopy imaging showed the successful preparation and the crystalline nature of the LIG/Tri‐MOF composite. Fourier‐transform infrared and X‐ray photoelectron spectroscopy confirmed a non‐covalent mixture of LIG and Tri‐MOF. Compared with the negligible activity of LIG alone, low doses (0.91‐4.54 mg/mL) of the prepared LIG/Tri‐MOF composite showed excellent antibacterial activity (≥ 95% bacterial removal) and a MIC of 0.6 mg/mL, for Gram‐negative bacteria via the gradual leaching of metal ions and organic linker from the material enhanced by bacterial aggregation near the LIG/Tri‐MOF. Compared to a mixture of separately synthesized Tri‐MOF and LIG, the LIG/Tri‐MOF composite showed improved antibacterial effects. All materials showed cytotoxicity for L929 mouse cell lines, the solids showing a disrupting effect on cells grown in vitro. Performance‐enhancing combinations of various materials leading to synergistic or additive antimicrobial effects is an essential strategy for minimizing the possible emergence of antibiotic‐resistant strains.This article is protected by copyright. All rights reserved.

Infection-Free and Enhanced Wound Healing Potential of Alginate Gels Incorporating Silver and Tannylated Calcium Peroxide Nanoparticles.

The treatment of chronic wounds involves precise requirements and complex challenges, as the healing process cannot go beyond the inflammatory phase, therefore increasing the healing time and implying a higher risk of opportunistic infection. Following a better understanding of the healing process, oxygen supply has been validated as a therapeutic approach to improve and speed up wound healing. Moreover, the local implications of antimicrobial agents (such as silver-based nano-compounds) significantly support the normal healing process, by combating bacterial contamination and colonization. In this study, silver (S) and tannylated calcium peroxide (CaO2@TA) nanoparticles were obtained by adapted microfluidic and precipitation synthesis methods, respectively. After complementary physicochemical evaluation, both types of nanoparticles were loaded in (Alg) alginate-based gels that were further evaluated as possible dressings for wound healing. The obtained composites showed a porous structure and uniform distribution of nanoparticles through the polymeric matrix (evidenced by spectrophotometric analysis and electron microscopy studies), together with a good swelling capacity. The as-proposed gel dressings exhibited a constant and suitable concentration of released oxygen, as shown for up to eight hours (UV-Vis investigation). The biofilm modulation data indicated a synergistic antimicrobial effect between silver and tannylated calcium peroxide nanoparticles, with a prominent inhibitory action against the Gram-positive bacterial biofilm after 48 h. Beneficial effects in the human keratinocytes cultured in contact with the obtained materials were demonstrated by the performed tests, such as MTT, LDH, and NO.

Synergistic antibacterial activity of cell wall hydrolase Lys14579 combined with cinnamaldehyde against emetic Bacillus cereus and their application in foods

Synergistic antibacterial effect as a promising strategy against foodborne pathogens is compelling since the development of novel antibacterial agents is not so easy. Here we investigated the synergistic effect of cell wall hydrolase Lys14579 and cinnamaldehyde (CAL) against emetic Bacillus cereus. The MICs of Lys14579 and CAL against emetic B. cereus were 25 and 200 μg/mL, respectively. The combination of Lys14579 and CAL displayed a synergistic antimicrobial effect with a Fractional Inhibitory Concentration Index (FICI) of 0.375. Bactericidal assays revealed that this combination had better bactericidal performance than either substance alone. Furthermore, the combination of Lys14579 and CAL effectively inhibited the biofilm formation of emetic B. cereus at the concentrations of 6.25 and 50 μg/mL, respectively. Additionally, it down-regulated the cereulide synthetase gene (cesB) expression at the transcription level and reduced swarming motility by 55%. Scanning electron microscope and PI uptake assays further demonstrated that the combination accelerated the disruption of emetic B. cereus cells. Finally, the synergistic preservative effect of this combinational was observed in boiled rice and fresh lean beef. Thus, the combination of Lys14579 and CAL represents a potential synergistic strategy for controlling emetic B. cereus contamination in the food industry.

Multidrug-Resistant Escherichia coli Remains Susceptible to Metal Ions and Graphene-Based Compounds.

Escherichia coli is listed as a priority 1 pathogen on the World Health Organization (WHO) priority pathogen list. For this list of pathogens, new antibiotics are urgently needed to control the emergence and spread of multidrug-resistant strains. This study assessed eighteen metal ions, graphene, and graphene oxide for their antimicrobial efficacy against E. coli in both planktonic and biofilm growth states and the potential synergy between metal ions and graphene-based compounds. Molybdenum and tin ions exhibited the greatest antimicrobial activity against the planktonic states of the isolates with minimal inhibitory concentrations (MIC) ranging between 13 mg/L and 15.6 mg/L. Graphene oxide had no antimicrobial effect against any of the isolates, while graphene showed a moderate effect against E. coli (MIC, 62.5 mg/L). Combinations of metal ions and graphene-based compounds including tin-graphene, tin-graphene oxide, gold-graphene, platinum-graphene, and platinum-graphene oxide exhibited a synergistic antimicrobial effect (FIC ≤ 0.5), inhibiting the planktonic and biofilm formation of the isolates regardless of their antibiotic-resistant profiles. The bactericidal effect of the metal ions and the synergistic effects when combined with graphene/graphene oxide against medically relevant pathogens demonstrated that the antimicrobial efficacy was increased. Hence, such agents may potentially be used in the production of novel antimicrobial/antiseptic agents.

The synergistic antimicrobial effects and mechanism of cinnamon essential oil and high voltage electrostatic field and their application in minced pork

Spice essential oils (EOs) have potent antimicrobial ability, but their application as food preservatives was severely limited by strong sensory properties. In this study, high voltage electrostatic field (HVEF) was applied to strengthen the antimicrobial effect of EOs while reducing their additive dosage. First, cinnamon essential oil (CEO) was selected from ten spice EOs because of its strongest inhibition against bacteria (Escherichia coli and Staphylococcus aureus) and molds (Penicillium citrinum and Aspergillus niger) common in foods. Then, the antimicrobial effect and mechanism of CEO and HVEF used alone or in combination were investigated. The results exhibited that the antimicrobial effect of CEO was dramatically enhanced by combining with HVEF, as the required concentration for the same antimicrobial effect was only 1/4∼1/3 of that when used alone. Both CEO and HVEF treatments changed the permeability of the microbial cell wall as well as the permeability and integrity of the cell membrane, resulted in the change in membrane protein structure, led to the increase in content of reactive oxygen species in the microbial cells, while the combined treatment of HVEF and CEO (HVEF + CEO) caused the significantly greater effect on microbes than two treatments applied alone. Finally, HVEF was found to substantially improve the preservative effect of CEO, allowing CEO to prolong the shelf life of minced pork from about 3 d to 7 d without compromising its original sensory quality.

Polyphenolic compounds in the combat of foodborne infections - An update on recent evidence.

In recent years, the incidence of food-borne bacterial enteric diseases has increased worldwide causing significant health care and socioeconomic burdens. According to the World Health Organization, there are an estimated 600 million cases of foodborne illnesses worldwide each year, resulting in 420,000 deaths. Despite intensive efforts to tackle this problem, foodborne pathogenic microorganisms continue to be spread further. Therefore, there is an urgent need to find novel anti-microbial non-toxic compounds for food preservation. One way to tackle this issue may be the usage of polyphenols, which have received increasing attention in the recent years given their pleotropic health-promoting properties. This prompted us to perform a literature search summarizing studies from the past 10 years regarding the potential anti-microbial and disease-alleviating effects of plant-derived phenolic compounds against foodborne bacterial pathogens. The included 16 studies provide evidence that polyphenols show pronounced anti-bacterial and anti-oxidant effects against both Gram-positive and Gram-negative bacterial species. In addition, synergistic anti-microbial effects in combination with synthetic antibiotics were observed. In conclusion, phenolic compounds may be useful as natural anti-microbial agents in the food, agricultural, and pharmaceutical industries in the combat of foodborne infections.