Photocatalytic, antimicrobial and antibiofilm activities of MgFe2O4 magnetic nanoparticles.

This study reports the antibacterial and antibiofilm activities of Magnesium ferrite nanoparticles (MgFe2O4) against gram-positive and gram-negative bacteria. The photocatalytic degradation of Carbol Fuchsin (CF) dye (a class of dyestuffs that are resistant to biodegradation) under the influence of UV-light irradiation is also studied. The crystalline magnesium ferrite (MgFe2O4) nanoparticles were synthesized using the co-precipitation method. The morphology of the resulting nanocomposite was examined using scanning electron microscopy (SEM), while transmission electron microscopy (TEM) was employed for further characterization of particle morphology and size. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were utilized to analyze the crystalline structure, chemical composition, and surface area, respectively. Optical properties were evaluated using UV-Vis spectroscopy. The UV-assisted photocatalytic performance of MgFe2O4 nanoparticles was assessed by studying the decolorization of Carbol fuchsin (CF) azo dye. The crystallite size of the MgFe2O4 nanoparticles at the (311) plane, the most prominent peak, was determined to be 28.5 nm. The photocatalytic degradation of 10 ppm CF using 15 mg of MgFe2O4 nanoparticles resulted in a significant 96% reduction after 135 min at ambient temperature (25 °C) and a pH value of 9. Additionally, MgFe2O4 nanoparticles exhibited potent antibacterial activity against E. coli and S. aureus in a dose dependent manner with maximum utilized concentration of 30 µg/ml. Specifically, MgFe2O4 nanoparticles demonstrated substantial antibacterial activity via disk diffusion and microbroth dilution tests with zones of inhibition and minimum inhibitory concentrations (MIC) for E. coli (26.0 mm, 1.25 µg/ml) and S. aureus (23.0 mm, 2.5 µg/ml), respectively. Moreover, 10.0 µg/ml of MgFe2O4 nanoparticles elicited marked percent reduction in biofilm formation by E. coli (89%) followed by S. aureus (78.5%) after treatment. In conclusion, MgFe2O4 nanoparticles demonstrated efficient dye removal capabilities along with significant antimicrobial and antibiofilm activity against gram-positive and gram-negative bacterial strains suggesting their potential as promising antimicrobial and detoxifying agents.

Tannic acid modified keratin/sodium alginate/carboxymethyl chitosan biocomposite hydrogels with good mechanical properties and swelling behavior.

Natural polymer-based hydrogels have demonstrated great potential as wound-healing dressings. They help to maintain a moist wound environment as well as promote faster healing. In this work, a multifunctional hydrogel was prepared using keratin, sodium alginate, and carboxymethyl chitosan with tannic acid modification. Micro-morphology of hydrogels has been performed by scanning electron microscopy. Fourier Transform Infrared Spectroscopy reveals the presence of hydrogen bonding. The mechanical properties of the hydrogels were examined using a universal testing machine. Furthermore, we investigated several properties of the modified hydrogel. These properties include swelling rate, water retention, anti-freezing properties, antimicrobial and antioxidant properties, hemocompatibility evaluation and cell viability test in vitro. The modified hydrogel has a three-dimensional microporous structure, the swelling rate was 1541.7%, the elastic modulus was 589.74 kPa, the toughness was 211.74 kJ/m3, and the elongation at break was 75.39%, which was similar to the human skin modulus. The modified hydrogel also showed inhibition of S. aureus and E. coli, as well as a DPPH scavenging rate of 95%. In addition, the modified hydrogels have good biological characteristics. Based on these findings, the K/SA/CCS hydrogel holds promise for applications in biomedical engineering.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus.

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

Nanofiber-reinforced self-healing polysaccharide-based hydrogel dressings for pH discoloration monitoring and treatment of infected wounds.

The escalating global health concern arises from chronic wounds induced by bacterial infections, posing a significant threat to individuals. Consequently, an imperative exist for the development of hydrogel dressings to facilitate prompt wound monitoring and efficacious wound management. To this end, pH-sensitive bromothymol blue (BTB) and pH-responsive drug tetracycline hydrochloride (TH) were introduced into the polysaccharide-based hydrogel to realize the integration of wound monitoring and controlled treatment. Polysaccharide-based hydrogels were formed via a Schiff base reaction by cross-linking carboxymethyl chitosan (CMCS) on an oxidized sodium alginate (OSA) skeleton. BTB was used as a pH indicator to monitor wound infection through visual color changes visually. TH could be dynamically released through the pH response of the Schiff base bond to provide effective treatment and long-term antibacterial activity for chronically infected wounds. In addition, introducing polylactic acid nanofibers (PLA) enhanced the mechanical properties of hydrogels. The multifunctional hydrogel has excellent mechanical, self-healing, injectable, antibacterial properties and biocompatibility. Furthermore, the multifaceted hydrogel dressing under consideration exhibits noteworthy capabilities in fostering the healing process of chronically infected wounds. Consequently, the research contributes novel perspectives towards the advancement of intelligent and expeditious bacterial infection monitoring and dynamic treatment platforms.

A transparent p-coumaric acid-grafted-chitosan coating with antimicrobial, antioxidant and antifogging properties for fruit packaging applications.

The study aimed to develop a novel, transparent and non-toxic coating with antimicrobial, antioxidant, and antifogging properties. The p-coumaric acid-grafted chitosan (CS-PCA) was synthesized via a carbodiimide coupling reaction and then characterized. The CS-PCA coatings were further prepared using the casting method. The CS-PCA coatings obtained exhibited excellent transparency, UV-light barrier ability, and antifogging properties, as confirmed by spectroscopy and antifogging tests. The CS-PCA coatings showed stronger antioxidant capacity and antimicrobial properties against Escherichia coli, Staphylococcus aureus and Botrytis cinerea compared to CS. The multifunctional coatings were further coated on the polyethylene cling film and their effectiveness was confirmed through a strawberry preservation test. The decay of the strawberries was reduced by CS-PCA coated film at room temperature.

Borate bonds-containing pH-responsive chitosan hydrogel for postoperative tumor recurrence and wound infection prevention.

Chitosan has been widely used in biomedical fields due to its good antibacterial properties, excellent biocompatibility, and biodegradability. In this study, a pH-responsive and self-healing hydrogel was synthesized from 3-carboxyphenylboronic acid grafted with chitosan (CS-BA) and polyvinyl alcohol (PVA). The dynamic boronic ester bonds and intermolecular hydrogen bonds are responsible for the hydrogel formation. By changing the mass ratio of CS-BA and PVA, the tensile stress and compressive stress of hydrogel can controlled in the range of 0.61 kPa - 0.74 kPa and 295.28 kPa - 1108.1 kPa, respectively. After doping with tannic acid (TA)/iron nanocomplex (TAFe), the hydrogel successful killed tumor cells through the near infrared laser-induced photothermal conversion and the TAFe-triggered reactive oxygen species generation. Moreover, the photothermal conversion of the hydrogel and the antibacterial effect of CS and TA give the hydrogel a good antibacterial effect. The CS-BA/PVA/TAFe hydrogel exhibit good in vivo and in vitro anti-tumor recurrence and antibacterial ability, and therefore has the potential to be used as a powerful tool for the prevention of local tumor recurrence and bacterial infection after surgery.

Synthesis and characterization of honey based hybrid dental implants with enhanced antibacterial activity.

Dental implants are commonly used for tooth replacement tools due to their good oral rehabilitation and reconstruction capacities. Dental implants treatment for natural teeth is desired to achieve successful implants treatment with improved osseointegration through promotion of mammalian cell activity and prevention of bacterial activity. Honey is potentially known for its antimicrobial and antibacterial potential, specifically for burns and wound healing. In this study, honey based silver nanoparticles were synthesized using various concentrations of honey. The synthesized HNY-AgNPs, MSN and HNY-AgMSN were characterized for their surface Plasmon resonance using UV spectroscopy, Hydrodynamic diameter using Zetasizer. Morphology using AFM. Furthermore, surface functional groups were characterized using FTIR spectroscopy at 4cm-1 resolutions. The developed hybrid nanoparticles were tested for their anti-bacterial activity at concentration of 3000µg/mL. It was found HNY-AgNPs was active against both bacterial strains i.e, Streptococcus mutans and streptococcus aureus. HNY-AgNPs-MSN hybrid implant demonstrated potential new type of dental implants, which can offer an effective design for the fabrication of advanced dental implants.

The effect of 3D printing speed and temperature on transferability of Staphylococcus aureus and Escherichia coli during 3D food printing.

The current study aimed to determine if the 3D-printing speed and temperature would impact the transferability of foodborne pathogens from the stainless-steel (SS) food cartridge to the 3D-printed food ink. Staphylococcus aureus and Escherichia coli were inoculated onto the interior surface of the SS food cartridges. Subsequently, a model food ink was extruded with a recommended macronutrient contribution of 55.8, 23.7, and 20.5% of carbohydrates, proteins, and fat, respectively. The impact of 3D-printing temperatures and speeds on transfer rates was analysed using a Two-Way ANOVA. S. aureus was transferred more from the cartridge to the food ink with a population of 3.39, 2.98, and 3.09 log CFU/g compared to 2.03, 2.06, and 2.00 log CFU/g for E. coli at 2000, 3000, and 4000 mm/s printing speed, respectively, at 25 °C. A Kruskal-Wallis Test was employed to investigate the effect of different speeds and temperatures on the transferability of S. aureus and E. coli. Speed was the main factor affecting S. aureus transferability, while temperature (25 and 50 °C) had the greatest impact on E. coli transferability. This research seeks to advance the understanding of 3D-printing parameters in pathogen transferability and help the food industry move towards this technology's quick and safe adoption.

Characterisation of a SapYZU11@ZnFe2O4 biosensor reveals its mechanism for the rapid and sensitive colourimetric detection of viable Staphylococcus aureus in food matrices.

Although bacteriophage-based biosensors hold promise for detecting Staphylococcus aureus in food products in a timely, simple, and sensitive manner, the associated targeting mechanism of the biosensors remains unclear. Herein, a colourimetric biosensor SapYZU11@ZnFe2O4, based on a broad-spectrum S. aureus lytic phage SapYZU11 and a ZnFe2O4 nanozyme, was constructed, and its capacity to detect viable S. aureus in food was evaluated. Characterisation of SapYZU11@ZnFe2O4 revealed its effective immobilisation, outstanding biological activity, and peroxidase-like capability. The peroxidase activity of SapYZU11@ZnFe2O4 significantly decreased after the addition of S. aureus, potentially due to blockage of the nanozyme active sites. Moreover, SapYZU11@ZnFe2O4 can detect S. aureus from various sources and S. aureus isolates that phage SapYZU11 could not lyse. This may be facilitated by the adsorption of the special receptor-binding proteins on the phage tail fibre and wall teichoic acid receptors of S. aureus. Besides, SapYZU11@ZnFe2O4 exhibited remarkable sensitivity and specificity when employing colourimetric techniques to rapidly determine viable S. aureus counts in food samples, with a detection limit of 0.87 × 102 CFU/mL. Thus, SapYZU11@ZnFe2O4 has broad application prospects for the detection of viable S. aureus cells on food substrates.

Effective of different industrial disinfection in subzero cold-chain environment.

Effective disinfection methods are crucial in the cold chain transportation process of food due to the specificity of temperature and the diversity of contaminated flora. The objective of this study was to investigate the sanitizing effect of different disinfectants on various fungi at - 20 °C to achieve accurate disinfection of diverse bacterial populations. Peracetic acid, hydrogen peroxide, and potassium bisulfate were selected as low-temperature disinfectants and were combined with antifreeze. The sanitizing effect of these cryogenic disinfectants on pathogens such as Bacillus subtilis black variant spores (ATCC9372), Staphylococcus aureus (ATCC 6538), Candida albicans (ATCC 10231), Escherichia coli (8099), and poliovirus (PV-1) was sequentially verified by bactericidal and virus inactivation experiments. After a specified time of disinfection, a neutralizing agent was used to halt the sanitizing process. The study demonstrates that different disinfectants exhibit selective effects during the low-temperature disinfection process. Peracetic acid, hydrogen peroxide, and potassium monopersulfate are suitable for the low-temperature environmental disinfection of bacterial propagules, viruses, and fungal contaminants. However, for microorganisms with strong resistance to spores, a low-temperature disinfectant based on peracetic acid should be chosen for effective disinfection treatment. Our results provide a valuable reference for selecting appropriate disinfectants to sanitize various potential pathogens in the future.

Effectiveness of cephalosporins in hydrolysis and inhibition of Staphylococcus aureus and Escherichia coli biofilms.

IMPORTANCE: Staphylococcus aureus and Escherichia coli contribute to global health challenges by forming biofilms, a key virulence element implicated in the pathogenesis of several infections. OBJECTIVE: The study examined the efficacy of various generations of cephalosporins against biofilms developed by pathogenic S. aureus and E. coli. METHODS: The development of biofilms by both bacteria was assessed using petri-plate and microplate methods. Biofilm hydrolysis and inhibition were tested using first to fourth generations of cephalosporins, and the effects were analyzed by crystal violet staining and phase contrast microscopy. RESULTS: Both bacterial strains exhibited well-developed biofilms in petri-plate and microplate assays. Cefradine (first generation) showed 76.78% hydrolysis of S. aureus biofilm, while significant hydrolysis (59.86%) of E. coli biofilm was observed by cefipime (fourth generation). Similarly, cefuroxime, cefadroxil, cefepime, and cefradine caused 78.8%, 71.63%, 70.63%, and 70.51% inhibition of the S. aureus biofilms, respectively. In the case of E. coli, maximum biofilm inhibition (66.47%) was again shown by cefepime. All generations of cephalosporins were more effective against S. aureus than E. coli, which was confirmed by phase contrast microscopy. CONCLUSIONS AND RELEVANCE: Cephalosporins exhibit dual capabilities of hydrolyzing and inhibiting S. aureus and E. coli biofilms. First-generation cephalosporins exhibited the highest inhibitory activity against S. aureus, while the third and fourth generations significantly inhibited E. coli biofilms. This study highlights the importance of tailored antibiotic strategies based on the biofilm characteristics of specific bacterial strains.

Antibacterial and Anti-Inflammatory Properties of Flavonoids from Streptomyces chartreusis RH3.5.

<b>Background and Objective:</b> The RH3.5 was isolated from the rhizosphere of <i>Boesenbergia rotunda</i> (L.) Mansf. and identified to be <i>Streptomyces chartreusis</i> via analysis of its 16S rDNA sequence, chemotaxonomy and morphology. The aim of this study was to identify the major compounds of RH3.5 and assess their biological activities. <b>Materials and Methods:</b> Silica gel column chromatography and thin-layer chromatography were used to purify major compounds, elucidate 5,7,2'-trihydroxy-8-methoxyflavanone (compound <b>1</b>) and 5',2',5'-trihydroxy-7,8-dimethoxyflavanone (compound <b>2</b>). Subsequently, mass spectrometry and NMR techniques were used to identify the structure of these compounds. Antimicrobial, anti-inflammatory and cytotoxic properties were carried out using <i>in vitro</i> assays. <b>Results:</b> The bioassays revealed the antimicrobial effect of compounds <b>1</b> and <b>2</b> on MRSA and <i>Staphylococcus aureus</i>. The minimum inhibitory concentration and minimum bactericidal concentration was calculated in the range of 32-64 and 128-256 µg/mL, respectively. The compounds <b>1</b> and <b>2</b> also exhibited anti-inflammatory potential by inhibiting NO, IL-1ß and TNF-α production in LPS-stimulated RAW264.7 cells in a dose-dependent manner. Additionally, they had mild cytotoxic action against Vero and L929 cell lines with IC₅₀ values greater than 512 µg/mL. <b>Conclusion:</b> These findings showed that flavonoids of <i>Streptomyces</i> <i>chartreusis</i> RH3.5 exhibited antibacterial and anti-inflammatory activities with low cytotoxicity against healthy cells. Thorough research on these compounds could result in the creation of useful methods for treating microbial infections and acute inflammatory responses.

The Role of CCL Chemokines in Experimental Staphylococcus aureus Endophthalmitis.

Purpose: To test the hypothesis that (C-C motif) ligand 2 (CCL2) and CCL3 impact retinal function decline and inflammation during Staphylococcus aureus endophthalmitis. Methods: Experimental endophthalmitis was initiated by intravitreal injection of 5000 colony-forming units of S. aureus into the eyes of C57BL/6J, CCL2-/-, or CCL3-/- mice. At 12 and 24 hours post-infection, retinal function, bacterial load, and myeloperoxidase levels were quantified. Results: During S. aureus endophthalmitis, we observed a significant improvement in retinal function in CCL2-/- mice relative to C57BL/6J mice at 12 hours but not at 24 hours. In CCL3-/- mice, retinal function was significantly improved relative to C57BL/6J mice at 12 and 24 hours. The absence of CCL2 did not alter intraocular S. aureus intraocular concentrations. However, CCL3-/- mice had significantly lower intraocular S. aureus at 12 hours but not at 24 hours. No difference in myeloperoxidase levels was observed between C57BL/6J and CCL2-/- mice at 12 hours. CCL3-/- mice had almost no myeloperoxidase at 12 hours. At 24 hours, increased myeloperoxidase was observed in CCL2-/- and CCL3-/- mice relative to C57BL/6J mice. Conclusions: Although the absence of CCL2 resulted in improved retinal function retention at 12 hours, CCL3 deficiency resulted in improved retinal function at 12 and 24 hours. CCL3 deficiency, but not CCL2 deficiency, resulted in almost no inflammation at 12 hours. However, at 24 hours, the absence of CCL2 or CCL3 resulted in significantly increased inflammation. These results suggest that, although both CCL2 and CCL3 impact intraocular infection outcomes, CCL3 may have a more significant impact in S. aureus endophthalmitis.

Tailoring bisphosphonate-doped titanium films to optimally couple cellular responses and antibacterial activity for biomedical applications.

Titanium (Ti) is widely utilized as an implant material; nonetheless, its integration with bone tissue faces limitations due to a patient's comorbidities. To address this challenge, we employed a strategic approach involving the growth of thin films by spin-coating and surface functionalization with etidronate (ETI), alendronate (ALE), and risedronate (RIS). Our methodology involved coating of Ti cp IV disks with thin films of TiO2, hydroxyapatite (HA), and their combinations (1:1 and 1:2 v/v), followed by surface functionalization with ETI, ALE, and RIS. Bisphosphonate-doped films were evaluated in terms of surface morphology and physical-chemical properties by techniques such as electron microscopy, confocal microscopy, and x-ray photoelectron spectroscopy. The antibacterial potential of bisphosphonates alone or functionalized onto the Ti surface was tested against Staphylococcus aureus biofilms. Primary human bone mesenchymal stem cells were used to determine in vitro cell metabolism and mineralization. Although RIS alone did not demonstrate any antibacterial effect as verified by minimum inhibitory concentration assay, when Ti surfaces were functionalized with RIS, partial inhibition of Staphylococcus aureus growth was noted, probably because of the physical-chemical surface properties. Furthermore, samples comprising TiO2/HA (1:1 and 1:2 v/v) showcased an enhancement in the metabolism of nondifferentiated cells and can potentially enhance the differentiation of osteoblastic precursors. All samples demonstrated cell viability higher than 80%. Addition of hydroxyapatite and presence of bisphosphonates increase the metabolic activity and the mineralization of human bone mesenchymal cells. While these findings hold promise, it is necessary to conduct further studies to evaluate the system's performance in vivo and ensure its long-term safety. This research marks a significant stride toward optimizing the efficacy of titanium implants through tailored surface modifications.

Use of Antimicrobial Silver Coatings on Fixed Orthodontic Appliances, Including Archwires, Brackets, and Microimplants: A Systematic Review.

Orthodontic treatments, while essential for achieving optimal oral health, present challenges in infection control due to the propensity for bacterial adhesion and biofilm formation on orthodontic appliances. Silver-coated orthodontic materials have emerged as a promising solution, leveraging the potent antimicrobial properties of silver nanoparticles (AgNPs). Antibacterial coatings are used in orthodontics to prevent the formation of bacterial biofilms. This systematic review evaluated the literature on antimicrobial silver coatings on fixed orthodontic appliances, including archwires, brackets, and microimplants. Two evaluators, working independently, rigorously conducted a comprehensive search of various databases, including PubMed, PubMed Central, Embase, Scopus and Web of Science. This systematic review comprehensively examined in vitro studies investigating the antimicrobial efficacy of silver-coated orthodontic archwires, brackets, and microimplants. The review registered in PROSPERO CRD42024509189 synthesized findings from 18 diverse studies, revealing consistent and significant reductions in bacterial adhesion, biofilm formation, and colony counts with the incorporation of AgNPs. Key studies demonstrated the effectiveness of silver-coated archwires and brackets against common oral bacteria, such as Streptococcus mutans and Staphylococcus aureus. Microimplants coated with AgNPs also exhibited notable antimicrobial activity against a range of microorganisms. The systematic review revealed potential mechanisms underlying these antimicrobial effects, highlighted implications for infection prevention in orthodontic practice, and suggested future research avenues. Despite some study heterogeneity and limitations, the collective evidence supports the potential of silver-coated orthodontic materials in mitigating bacterial complications, emphasizing their relevance in advancing infection control measures in orthodontics.

Bacterial Aggregation in Cerebral Spinal Fluid: The Extent it Occurs and the Clinical Ramifications.

Bacteria can form aggregates in synovial fluid that are resistant to antibiotics, but the ability to form aggregates in cerebral spinal fluid (CSF) is poorly defined. Consequently, the aims of this study were to assess the propensity of four bacterial species to form aggregates in CSF under various conditions. To achieve these aims, bacteria were added to CSF in microwell plates and small flasks at static and different dynamic conditions with the aid of an incubating shaker. The aggregates that formed were assessed for antibiotic resistance and the ability of tissue plasminogen activator (TPA) to disrupt these aggregates and reduce the number of bacteria present when used with antibiotics. The results of this study show that under dynamic conditions all four bacteria species formed aggregates that were resistant to high concentrations of antibiotics. Yet with static conditions, no bacteria formed aggregates and when the CSF volume was increased, only Staphylococcus aureus formed aggregates. Interestingly, the aggregates that formed were easily dispersed by TPA and significant (p < 0.005) decreases in colony-forming units were seen when a combination of TPA and antibiotics were compared to antibiotics alone. These findings have clinical significance in that they show bacterial aggregation does not habitually occur in central nervous system infections, but rather occurs under specific conditions. Furthermore, the use of TPA combined with antibiotics may be advantageous in recalcitrant central nervous system infections and this provides a pathophysiological explanation for an unusual finding in the CLEAR III clinical trial.

Synergistic stabilization of a menthol Pickering emulsion by zein nanoparticles and starch nanocrystals: Preparation, structural characterization, and functional properties.

A Pickering emulsion was synergistically stabilised with zein nanoparticles (ZNPs) and starch nanocrystals (SNCs) to prepare it for menthol loading. After response surface optimisation of the emulsion preparation conditions, a Pickering emulsion prepared with a ZNPs:SNCs ratio of 1:1, a particle concentration of 2 wt% and a water:oil ratio of 1:1 provided the highest menthol encapsulation rate of the emulsions tested (83%) with good storage stability within 30 days. We examined the bilayer interface structure of the emulsion by optical microscopy, scanning electron microscopy, and confocal laser scanning microscopy. The results of simulated digestion experiments showed that the release rate of free fatty acid was 75.06 ± 1.23%, which ensured bioavailability. At the same time, the emulsions facilitated the slow release of menthol. Bacteriostatic studies revealed that the Pickering emulsion had a protective effect on menthol, with the most significant inhibitory effects on Escherichia coli and Staphylococcus aureus under the same conditions. Overall, this study proposes a novel approach for the application and development of l-menthol by combining it with Pickering emulsion.

Structural basis of promoter recognition by Staphylococcus aureus RNA polymerase.

Bacterial RNAP needs to form holoenzyme with σ factors to initiate transcription. While Staphylococcus aureus σA controls housekeeping functions, S. aureus σB regulates virulence, biofilm formation, persistence, cell internalization, membrane transport, and antimicrobial resistance. Besides the sequence difference, the spacers between the -35 element and -10 element of σB regulated promoters are shorter than those of σA regulated promoters. Therefore, how σB recognizes and initiates transcription from target promoters can not be inferred from that of the well studied σ. Here, we report the cryo-EM structures of S. aureus RNAP-promoter open complexes comprising σA and σB, respectively. Structural analyses, in combination with biochemical experiments, reveal the structural basis for the promoter specificity of S. aureus transcription. Although the -10 element of σA regulated promoters is recognized by domain σA2 as single-stranded DNA, the -10 element of σB regulated promoters is co-recognized by domains σB2 and σB3 as double-stranded DNA, accounting for the short spacers of σB regulated promoters. S. aureus RNAP is a validated target of antibiotics, and our structures pave the way for rational drug design targeting S. aureus RNAP.

Effectiveness of laser pulsed irradiation for antimicrobial photodynamic therapy.

The aim of this study was to compare two types of light irradiation devices for antimicrobial photodynamic therapy (aPDT). A 660-nm light-emitting diode (LED) and a 665-nm laser diode (LD) were used for light irradiation, and 0.1 mg/L TONS 504, a cationic chlorin derivative, was used as the photosensitizer. We evaluated the light attenuation along the vertical and horizontal directions, temperature rise following light irradiation, and aPDT efficacy against Staphylococcus aureus under different conditions: TONS 504 only, light irradiation only, and TONS 504 with either LED (30 J/cm2) or LD light irradiation (continuous: 30 J/cm2; pulsed: 20 J/cm2 at 2/3 duty cycle, 10 J/cm2 at 1/3 duty cycle). Both LED and LD light intensities were inversely proportional to the square of the vertical distance from the irradiated area. Along the horizontal distance from the nadir of the light source, the LED light intensity attenuated according to the cosine quadrature law, while the LD light intensity did not attenuate within the measurable range. Following light irradiation, the temperature rise increased as the TONS 504 concentration increased in the order of pulsed LD < continuous LD < LED irradiation. aPDT with light irradiation only or TONS 504 only had no antimicrobial effect, while aPDT with TONS 504 under continuous or pulsed LD light irradiation provided approximately 3 log reduction at 30 J/cm2 and 20 J/cm2 and approximately 2 log reduction at 10 J/cm2. TONS 504-aPDT under pulsed LD light irradiation provided anti-microbial effect without significant temperature rise.

Staphylococcus aureus carriage and prevalence of skin and soft tissue infections among people who inject drugs: a longitudinal study.

People who inject drugs are frequently colonized with Staphylococcus aureus and have an increased risk for skin and soft tissue infections. This longitudinal study aims to describe S. aureus carriage in this group and the risk for infections during a 1-year follow-up. We included 61 participants from the Malmö Needle Exchange Program. Mapping of S. aureus carriage was conducted by screening cultures every third month and S. aureus growth was semi-quantified. Data regarding infections and living conditions were collected from structured interviews. Statistics included univariate analysis with the Fischer's exact test, univariate logistic regression and multivariate logistic regression. S. aureus carriage was detected in 46-63% of participants, and 75% reported one or more infections during the study period. Self-reported infections were associated with carriage in perineum (OR 5.08 [95% CI 1.45-17.73]), in skin lesions (OR 1.48 [95% CI 1.21-1.81]), and unstable housing situation (OR 12.83 [95% CI 1.56-105.81]). Thus, people who inject drugs are frequent carriers of S. aureus and report a surprisingly high prevalence of skin and soft tissue infections. Homeless people and those with skin carriage seem to be at highest risk. Effective clinical interventions are needed, aiming at preventing infections in this vulnerable group.