Sustained Antibacterial Effect Research Articles

Dual-light photodynamic therapy administered daily provides a sustained antibacterial effect on biofilm and prevents Streptococcus mutans adaptation.

Antibacterial photodynamic therapy (aPDT) and antibacterial blue light (aBL) are emerging treatment methods auxiliary to mechanical debridement for periodontitis. APDT provided with near-infrared (NIR) light in conjunction with an indocyanine green (ICG) photosensitizer has shown efficacy in several dental in-office-treatment protocols. In this study, we tested Streptococcus mutans biofilm sensitivity to either aPDT, aBL or their combination dual-light aPDT (simultaneous aPDT and aBL) exposure. Biofilm was cultured by pipetting diluted Streptococcus mutans suspension with growth medium on the bottom of well plates. Either aPDT (810 nm) or aBL (405 nm) or a dual-light aPDT (simultaneous 810 nm aPDT and 405 nm aBL) was applied with an ICG photosensitizer in cases of aPDT or dual-light, while keeping the total given radiant exposure constant at 100 J/cm2. Single-dose light exposures were given after one-day or four-day biofilm incubations. Also, a model of daily treatment was provided by repeating the same light dose daily on four-day and fourteen-day biofilm incubations. Finally, the antibacterial action of the dual-light aPDT with different energy ratios of 810 nm and 405 nm of light were examined on the single-day and four-day biofilm protocols. At the end of each experiment the bacterial viability was assessed by colony-forming unit method. Separate samples were prepared for confocal 3D biofilm imaging. On a one-day biofilm, the dual-light aPDT was significantly more efficient than aBL or aPDT, although all modalities were bactericidal. On a four-day biofilm, a single exposure of aPDT or dual-light aPDT was more efficient than aBL, resulting in a four logarithmic scale reduction in bacterial counts. Surprisingly, when the same amount of aPDT was repeated daily on a four-day or a fourteen-day biofilm, bacterial viability improved significantly. A similar improvement in bacterial viability was observed after repetitive aBL application. This viability improvement was eliminated when dual-light aPDT was applied. By changing the 405 nm to 810 nm radiant exposure ratio in dual-light aPDT, the increase in aBL improved the antibacterial action when the biofilm was older. In conclusion, when aPDT is administered repeatedly to S. mutans biofilm, a single wavelength-based aBL or aPDT leads to a significant biofilm adaptation and increased S. mutans viability. The combined use of aBL light in synchrony with aPDT arrests the adaptation and provides significantly improved and sustained antibacterial efficacy.

Anti-caries effect of resin infiltrant modified by quaternary ammonium monomers

ObjectivesResin infiltrant is used in early enamel caries. However, commercial resin infiltrant lacks persistent antibacterial activity. Dimethylaminododecyl methacrylate (DMADDM) was added to resin infiltrant to give it sustainable antibacterial properties and inhibit demineralization. MethodsAfter the application of resin infiltrant to bovine enamel, cytotoxicity, surface roughness, and aesthetics were assessed. A multi-species biofilm was incubated on the enamel disk before and one month after microbial-aging. After a 48-h anaerobic incubation, biomass accumulation, metabolic activity, and lactic acid were analyzed using a crystal violet assay, an MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and a lactic acid assay. Biofilm structure and composition were determined by live/dead staining, exopolysaccharide (EPS) staining, scanning electron microscopy (SEM), and quantitative polymerase chain reaction (qPCR). The depth and content of demineralization were tested by transverse microradiography (TMR). ResultsIncorporating DMADDM did not increase the cytotoxicity or change the physical properties when the mass fraction of the DMADDM was 2.5–10 %. The modification decreased the amount of bacterial biofilm, metabolic activity, lactic acid production, EPS, and the proportion of Streptococcus mutans in the biofilms. It also provided anti-demineralization effects. The surface roughness and antibacterial ability were not changed after one month of microbial-aging. ConclusionThe incorporation of DMADDM improved the antibacterial and anti-demineralization effects of the material. It demonstrated a sustained antibacterial effect. Clinical significanceThe antibacterial modification might be a potential choice for future clinical applications to inhibit early enamel caries.

Highly transparent, highly flexible composite membrane with multiple antimicrobial effects used for promoting wound healing

In recent years, bacterial cellulose (BC)-based dressings or patches for skin or soft tissue repair have become investigative emphasis. However, most of the BC-based products used for biomedical applications present limitations due to their low flexibility, poor gas permeability and no inherent antibacterial activity. Herein, we proposed and designed a novel composite composed of natural bacterial cellulose (BC), polyethylene glycol (PEG) and polyhexamethylene biguanidine (PHMB) through new synthetic approaches. The composite membrane exhibited favorable physicochemical performance, especially transparency, water retention ability, flexibility as well as the characteristic of anti-adhesion. In vitro biochemical experiment results indicated that the composite had excellent biocompatibility and exhibited strong and sustained antibacterial effect. In vivo test further demonstrated that the composite could efficiently promote skin wound healing and regeneration in a rat model. This composite membrane possesses multiple mechanisms of promoting cutaneous wound healing and will provide new ideas for future development of wound dressings.

Antimicrobial Activity of 3D-Printed Poly(ε-Caprolactone) (PCL) Composite Scaffolds Presenting Vancomycin-Loaded Polylactic Acid-Glycolic Acid (PLGA) Microspheres.

BackgroundThe aim of this study was to design and test a novel composite scaffold with antibacterial efficacy for treating bone infections using a three-dimensional (3D) printed poly(ɛ-caprolactone) (PCL) scaffold coated with polydopamine (PDA) for the adsorption of polylactic acid-glycolic acid (PLGA) microspheres loaded with vancomycin.Material/MethodsVancomycin-loaded PLGA microspheres were produced by the double-emulsion method, and microsphere morphology, drug-loading dosage, encapsulation efficiency, average diameter, and release characteristics were examined. Composite scaffolds were prepared by adsorption of the microspheres on PDA-coated, 3D-printed PCL scaffolds, and scaffold morphology, biocompatibility, vancomycin release, and antibacterial efficacy were evaluated.ResultsThe vancomycin-loaded microspheres were smooth, round, uniform in size, and had no adhesion phenomenon, and exhibited sustained release of vancomycin from the microspheres for more than 4 weeks. Upon modification with PDA, the PCL scaffold changed from white to black, and after microsphere adsorption, dot-like white particles were seen. On scanning electron microscopy, PDA particles were observed on the PCL/PDA composite scaffolds, and PLGA microspheres were evenly dispersed over the PDA coating on the PCL/PDA/PLGA composite scaffolds. Cell viability assays showed that the adhesion and proliferation of rabbit bone mesenchymal stem cells were greater on the PCL/PDA scaffolds than on unmodified PCL scaffolds. Microsphere adsorption had no significant effect on cell proliferation. In vitro release of vancomycin from the composite scaffolds was observed for more than 4 weeks, and observation of the inhibition zone on agar plates of Staphylococcus aureus showed that the scaffolds maintained their antibacterial effect for more than 4 weeks.ConclusionsThe 3D-printed, PDA-coated PCL scaffold carrying vancomycin-loaded PLGA microspheres exhibited good biocompatibility and a sustained antibacterial effect in vitro.

Collagen-silica nanocomposites as dermal dressings preventing infection in vivo

The controlled delivery of multiple drugs from biomaterials is a timely challenge. In particular the nanocomposite approach offers a unique opportunity to combine the scaffold-forming ability and biocompatibility of hydrogels with the versatile and tunable drug release properties of micro- or nano-carriers. Here, we show that collagen-silica nanocomposites allowing for the prolonged release of two topical antibiotics are promising medicated dressings to prevent infection in wounds. For this purpose, core–shell silica particles loaded with gentamicin sulfate and sodium rifamycin were combined with concentrated collagen type I hydrogels. A dense fibrillar network of collagen exhibiting its typical periodic banding pattern and a homogenous particle distribution were observed by scanning electron microscopy. Antibiotics release from nanocomposites allowed a sustained antibacterial effect against Staphylococcus aureus over 10 days in vitro. The acute dermal irritation test performed on albino rabbit skin showed no sign of severe inflammation. The antibacterial efficiency of nanocomposites was evaluated in vivo in a model of cutaneous infection, showing a 2 log steps decrease in bacterial population when loaded systems were used. In parallel, the histological examination indicated the absence of M1 inflammatory macrophages in the wound bed after treatment. Taken together, these results illustrate the potentialities of the nanocomposite approach to develop collagen-based biomaterials with controlled dual drug delivery to prevent infection and promote cutaneous wound repair.

Preparation and properties of gum arabic cross-link binding nisin microparticles

Nisin is a small cationic peptide composed of 34 amino acid residues, it exhibits a wide spectrum antimicrobial activity against Gram-positive bacteria, but nisin has the disadvantages of poor stability and short duration of antibacterial activity. In order to improve the stability of nisin during food processing and storage period, the gum arabic (GA) is used to get GA-nisin microparticles. The analysis of zeta potential, SEM and FT-IR were used to characterize the combination of GA and nisin, test the antibacterial activity on Staphylococcus aureus and Escherichia coli, the bactericidal effect of GA-nisin microparticles decreased within 24 h compare to free nisin, however, GA-nisin microparticles after 121 °C treatment for 10 min, the activity loss rate is less than free nisin and has better sustained antibacterial effect at 25 °C. The results shown GA-nisin microparticles have better high-temperature stability and sustained bactericidal ability than the free nisin.

Composite Polyelectrolyte Multilayer and Mesoporous Bioactive Glass Nanoparticle Coating on 316L Stainless Steel for Controlled Antibiotic Release and Biocompatibility.

Bacterial infection in wounds or implants can cause osteomyelitis, eventually leading to orthopedic implant failure. In this study, polyelectrolyte multilayer (PEM) coating comprising collagen as the cationic layer, chitosan as the barrier layer and γ-poly-glutamic acid as the anionic layer were fabricated onto a 316L stainless steel substrate by spin coating technique. Tetracycline-loaded 57S mesoporous bioactive glass nanoparticles (57S MBG, SiO₂:CaO:P₂O5 = 57:33:10 by wt%) were introduced into the γ-poly-glutamic acid layers. Herein, 57S MBG nanoparticles were successfully incorporated into the PEMs with a total thickness of ∼53 μm on 316L stainless steel (SS-PEMs-57S), which exhibited good hydrophilicity with a contact angle of 18.71°. The hardness of SS-PEMs-57S was 0.66 GPa while the Young's modulus was 11.5 GPa; these values are similar to those for the cortical bone. The surface roughness of MBG nanoparticle-incorporated PEMs increased from 231 to 384 nm. Controlled release of tetracycline loaded in MBG nanoparticles resulted in sustained antibacterial effect for up to 7 days, with higher release efficacy at low pH, which may be induced by inflammation or infection. Tetracycline loaded in SS-PEMs-57S showed good bacterial inhibition and maintained good cell viability in rat bone marrow mesenchymal stem cells (BMSCs) in the MTT assay. Moreover, SS-PEMs-57S also promoted mineralization of BMSCs. Therefore, this surface modification technology has great potential for endowing orthopedic implants with antibacterial and osteoconductive properties.

Pharmacodynamics of cefiderocol, a novel siderophore cephalosporin, in a Pseudomonas aeruginosa neutropenic murine thigh model

Cefiderocol is a siderophore cephalosporin that displays potent in vitro activity against multidrug-resistant (MDR) Gram-negative bacteria. This study aimed to describe the pharmacokinetics, pharmacodynamics and 24-h efficacy of cefiderocol using dose-ranging methods in a neutropenic murine thigh infection model. Infection was established in neutropenic mice (administered cyclophosphamide 150 mg/kg and 100 mg/kg at 4 days and 1 day prior to inoculation, respectively) with eight Pseudomonas aeruginosa isolates [minimum inhibitory concentration (MIC) range 0.063–0.5 µg/mL] that displayed variable in vivo activity against previously tested β-lactams with siderophore moieties. Renal excretion was controlled by administration of 5 mg/kg uranyl nitrate 3 days prior to inoculation. Cefiderocol was administered subcutaneously in eight escalating doses [4.2–166.7 mg/kg every 8 h (q8h)]. In pharmacokinetic studies, cefiderocol manifested similar pharmacokinetics across tested doses (4, 100 and 250 mg/kg) with a mean half-life of 0.86 h. In pharmacodynamic studies, the change in CFU after 24 h from the initial inoculum ranged from +3.4 to −3.1 log10 with doses of 4.2–166.7 mg/kg q8h. Dose–response curves for the eight isolates assumed the characteristic sigmoidal shape, with greater CFU reductions as the dose increased. Focusing on the previously defined efficacy parameter of fT > MIC (time that the free drug concentration exceeds the MIC) for this compound, targets for stasis and 1 log10 and 2 log10 reductions ranged from 44.4–94.7, 50.2–97.5 and 62.1–100, respectively. Cefiderocol displayed sustained antibacterial effects against these MDR P. aeruginosa isolates. These data support the cefiderocol dose selected for clinical trials.

Retention of lysozyme activity by physical immobilization in nanocellulose aerogels and antibacterial effects

Aerogels prepared from aqueous dispersions of anionic and cationic cellulose nanofibrils (CNFs) were investigated as solid supports for enzymes and silver nanoparticles and to elicit a sustained antibacterial effect. The imparted stabilization in dry conditions was studied with aerogels that were cast after mixing the enzymes with CNFs followed by dehydration (freeze-drying). The activity of lysozyme immobilized in the given CNF system was analyzed upon storage in liquid and air media. In contrast with aqueous solutions of free, unbound enzyme, which lost activity after the first day, the enzyme immobilized physically in unmodified and cationic CNF presented better stability (activity for a longer time). However, the enzyme activity was reduced in the case of anionic CNF, which was prepared by TEMPO-mediated oxidation (TO-CNF). Both humidity and temperature reduced the stability of the enzyme immobilized in the respective CNF aerogel. The antibacterial activity of CNF aerogels carrying lysozyme was also tested against gram-negative and gram-positive bacteria. The results were compared with those obtained from CNF systems loaded with silver nanoparticles (AgNP) after in situ synthesis via UV reduction. Storage in cold or dry conditions preserved the activity and antibacterial performance of enzyme-loaded CNF aerogels. As expected, the lysozyme-containing aerogels showed lower inhibition than the AgNP-containing aerogel. In this latter case, the antibacterial activity depended on the concentration and size of the nanoparticles. Compared to unmodified CNF and TO-CNF, the aerogels prepared with cationic CNF, loaded with either lysozyme or AgNPs, showed remarkably better antibacterial activity. Similar experiments were conducted with horseradish peroxidase, which confirmed, to different degrees, the observations derived from the lysozyme systems. Overall, the results indicate that non-toxic and biodegradable CNF is a suitable support for bio-active materials and is effective in protecting and retaining enzymatic and antibacterial activities.

PLLA microcapsules combined with silver nanoparticles and chlorhexidine acetate showing improved antibacterial effect

In this study, composite antibacterial microcapsules combining of two antibacterial agents: chlorhexidine acetate and silver nanoparticle were prepared. The chlorhexidine acetate was encapsulated inside of the microcapsules and nano-sized silver particles were modified on the surface of microcapsules by electrostatic adsorption methods. Results show that this method decreases the silver usage dramatically, and promises a sustained antibacterial effect >30days. These microcapsules can also be modified on the surface of polymer films easily, which demonstrated the potential in functionalizing the implanted materials with antibacterial property.

Fabrication and Appraisal of Poly (Lactic-Co-Glycolic Acid) - Moxifloxacin Nanoparticles using Vitamin E-TPGS: A Potential Intracanal Drug Delivery Agent.

Nanotechnology is gaining momentum in the search for ideal biomaterials by dental researchers. The expansible nature of Endodontology deems exploration, learning and scrutinizing newer avenues which have the potential to be applied and investigated. The popularity of polymers as drug delivery vehicles has opened avenues for their application in the root canal system. This study utilized application of biodegradable polymers as potential drug delivery vehicles against Enterococcus faecalis, one of the main reasons for post treatment disease. This study aimed at fabricating Poly (Lactic-co-Glycolic Acid) (PLGA)-moxifloxacin nanoparticles and assessing its sustained antimicrobial efficacy with calcium hydroxide and chitosan-moxifloxacin hydrogel against Enterococcus faecalis. PLGA (50:50) in a quantity of 100 mg was dissolved in 1 ml ethyl acetate and 45 ml of 0.3% w/v Vitamin-E Polyethylene Glycol 1000 Succinate (vitamin E-TPGS) was kept for magnetic stirring in separate beaker. Moxifloxacin (50 μl) was added to polymer PLGA following which vitamin E-TPGS was added to the polymer. Nanoparticles were fabricated using ultrasonication and collected by centrifugation. Surface characterization was assessed using scanning electron microscope. Results were obtained in the form of zone of inhibition by the nanoparticles against Enterococcus faecalis and comparisons were made with chitosan-moxifloxacin hydrogel and calcium hydroxide using Analysis of Variance (ANOVA) followed by Student t-test. Upon statistical analysis, the zone of inhibition against E. faecalis remained constant with PLGA-moxifloxacin nanoparticles for 14 days while it decreased with chitosan-moxifloxacin hydrogel and remained nil for calcium hydroxide (p<0.01). The study posits that PLGA encapsulated moxifloxacin nanoparticles showcased sustained antibacterial effect in low doses against the test pathogen. Its sustained and programmed release makes them unique contenders for further evaluation in Endodontics as potential intracanal medicaments.

&lt;I&gt;Cicer arietinum&lt;/I&gt; Leaf Extract Mediated Synthesis of Silver Nanoparticles and Screening of Their Antimicrobial Activity

Silver nanoparticles have received substantial attention for various reasons—like magnetic and optical property, electrical conductivity, catalysis, antimicrobial activities. The use of silver and other metal ions for their sustained antifungal, antibacterial and antiviral effects has also been evaluated. Silver nanoparticles synthesized from wet chemical method are quite often toxic and flammable, while green chemical approach for the synthesis of silver nanoparticles provides an opportunity for large scale production of nanoparticles without any conflicting effect. This process is simple, rapid, economic and environment friendly, so in this study we have synthesized Ag NPs from Cicer arietinum leaf extract, characterized using UV-Vis spectrophotometer, FTIR, XRD, SEM, EDS, AFM and evaluated its antimicrobial activity.

Build-up of an antimicrobial multilayer coating on a textile support based on a methylene blue–poly(cyclodextrin) complex

The aim of this work was to develop an antibacterial multilayer coating activated with methylene blue (MB) and based on chitosan (CHT) and cyclodextrin polyelectrolyte (polyCD) onto a non-woven polyethylene terephthalate (PET) textile support. The MB-free and MB-loaded systems were built-up by applying the dip-coating technique, alternating soak cycles of the PET textile preliminarily modified with carboxylate groups in CHT and in polyCD or polyCD/MB complex solutions. The layer-by-layer assembly build-up was followed by optical waveguide lightmode spectroscopy on the one hand and by gravimetry once it was applied on the textile substrate on the other hand. Two chitosan grades were used, low molecular weight (CHT-L) and medium molecular weight (CHT-M). The influence of the molar ratio CD/MB in the polyCD solutions was varied and finally the system underwent a post reticulation with genipin. Such parameters influences were investigated with regard to the loading capacity in MB of the systems, the release kinetics profiles of MB in pure water, phosphate buffer and MEM media, and the degradation of the self-assembled coating in the same media. Finally, biological and microbiological tests were performed to demonstrate the cytocompatibility of the systems and their ability to display a sustained antibacterial effect of the device through the MB prolonged release.

Light Therapy

Conventional antibacterial treatment fails to eradicate biofilms associated with common infections of the oral cavity. Unlike chemical agents, which are less effective than anticipated, owing to diffusion limitations in biofilms, light is more effective on bacteria in biofilm than in suspension. Effectiveness depends also on the type and parameters of the light. We tested the phototoxic effects of non-coherent blue light (wavelengths, 400-500 nm) and CO(2) laser (wavelength, 10.6 μm), which have different mechanisms of action on the oral bacterium Streptoccocus mutans, in biofilm and on tooth enamel. Exposure of S. mutans in biofilm to blue light had a delayed effect on bacterial viability throughout the biofilm and a sustained antibacterial effect on biofilm newly formed by previously irradiated bacteria. A synergistic antibacterial effect between blue light and H(2)O(2) may enhance the phototoxic effect, which involves a photochemical mechanism mediated by reactive oxygen species (ROS) formation. The effect of CO(2) laser irradiation on the viability of S. mutans in biofilm on enamel samples appeared to be higher in the deep layers, due to heating of the enamel surface by the absorbed energy. Biofilms do not interfere with the chemical changes resulting from irradiation, which may increase the enamel's resistance to acid attack.

Mesoporous silica nanoparticle-functionalized poly(methyl methacrylate)-based bone cement for effective antibiotics delivery

Poly(methyl methacrylate)-based bone cements are functionalized with mesoporous silica nanoparticles (MSN) to enable a highly efficient and sustained release of antibiotics to reduce the risk of post-operative joint infection. To overcome the limited drug release of 5% for only 1day with the current commercial-grade bone cements, a 8 wt% MSN-formulated bone cement is able to increase the drug release efficiency by 14-fold and sustain the release for up to 80days. The loaded MSN is suggested to build up an effective network of rod-shaped silica particles with uniformly arranged nanoporous channels, which is responsible for the effective drug diffusion and extend time-release to the external surfaces. MSN has no detrimental effect on the critical weight-bearing bending modulus and compression strength of bone cement. In vitro assay test results show a much sustained antibacterial effect and low cytotoxicity of MSN demonstrating the potential applicability of MSN-formulated bone cement.

Facile method of preparing silver-embedded polymer beads and their antibacterial effect

Research designed to prevent human beings from being infected by microorganisms such as bacteria, molds, yeasts, and viruses from the living environment has attracted tremendous interest. Therefore, many researchers have tried to develop novel and effective antimicrobial materials with free of resistance and low cost [1, 2]. One of the most widely used antibacterial materials is based on silver (silver ions or silver nanoparticles) which exhibits strong biocidal effects towards a broad range of microorganisms, along with advantages such as a lack of odor, taste, and color [3– 6]. Until now, various routes for preparing antimicrobial silver compounds or silver nanoparticles (NPs) have been reported [7, 8]. Especially, silver NPs have more severe effects on bacterial cells than silver ions [9]. However, silver NPs are easily aggregated which causes the deterioration of their chemical properties and decreases their antimicrobial properties. Moreover, the fate of silver NPs for biological applications is still debatable [10, 11]. In addition, some synthetic methods of silver NPs as antimicrobial materials are time-consuming and require expensive instruments. In addition, silver NPs can easily become aggregated, which causes the deterioration of their chemical properties and decreases their antimicrobial properties. To solve these problems, silver has been introduced onto stable supporting materials, in which the antimicrobial mechanism is closely related to the release of silver ions. These methods have several advantages, such as sustained antibacterial effects based on the release of silver ions, good mechanical properties and inexpensive and easy manufacturing processes for industrial applications [12–17]. Recently, many different methods have been proposed to introduce silver NPs into polymers. Among the various polymers, polystyrene (PS)–divinylbenzene (DVB) porous resin is particularly useful, due to its large surface area, chemical stability, and low cost. Moreover, silver NPs can be easily embedded on it after sulfonation, and their size and the loading amount can be adjusted by changing of reaction condition [18]. The deposition of silver on polymer materials has been enhanced by the activation of the surface-functional groups. Among the various functional groups, sulfonated groups are good candidates to introduce silver NPs for the purpose of producing antibacterial materials. Recently, we introduced silver NPs into sulfonated PS–DVB resins (4–8 lm) with mild reduction using the polyol method for use as surface-enhanced Raman scattering (SERS) active materials for multiplex protein analysis [18, 19]. In this study, silver NPs embedded into ion-exchange resin (Ag-IER) (ca. 0.9 mm) were readily prepared by the polyol method and characterized by several instrumental analyses, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray emission (EDX), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Then, their anti-bacterial activity was tested using Escherichia coli, which is well known as indicator bacteria. Moreover, we investigated their antibacterial effect at a low silver loading level and silver ion release conditions. B.-H. Jun J. Y. Kim H.-J. Park J. Yoon Y.-S. Lee (&) School of Chemical and Biological Engineering, Seoul National University, Seoul 151-747, Korea e-mail: yslee@snu.ac.kr

Sustained antibacterial effect of a hand rub gel incorporating chlorhexdine-loaded nanocapsules (Nanochlorex ®)

In the present study, an original chlorhexidine-loaded nanocapsule-based gel (Nanochlorex ®) was tested as hand rub gel against the resident skin flora in comparison with 2-propanol 60% (v/v) and 62% (v/v) ethanol-based gel (Purell ®). After 30-s hand rub, the immediate bactericidal effect of Nanochlorex ® was found comparable to 2-propanol 60% (v/v) (reduction factor, RF: 0.30 ± 0.35 versus 0.38 ± 0.55, P > 0.05) against aerobic bacteria, whereas the post-values of surviving anaerobes were shown significantly lower from Nanochlorex ® ( P < 0.001) and insignificant from 2-propanol 60% (v/v) ( P > 0.05). Sustained antibacterial effect of Nanochlorex ® was confirmed against the resident and transient hand flora in two sets of experiment. In the first, the results obtained with the glove-juice technique showed that the bactericidal effect induced by Nanochlorex ® hand rub persisted throughout 3-h period, while Purell ® failed to reduce significantly the post-values of surviving bacteria. In the second, repeated artificial contaminations with Staphylococcus epidermidis was carried out onto ex vivo human skin pre-treated by either Nanochlorex ® or Purell ® for 5 min, then maintained in cell diffusion apparatus for 4 h. The log 10 reduction of surviving bacteria was significantly higher with Nanochlorex ® than that determined with Purell ® after three successive contaminations (from ∼5.5 to 1.5 log 10 reduction for Nanochlorex ® between the first and the third contamination; ∼1 log 10 reduction for Purell ® throughout the experiment), confirming the sustained antibacterial effect of chlorhexidine-loaded nanocapsule-based gel. The immediate and sustained antibacterial effect of Nanochlorex ® was explained by chlorhexidine carrier system which improved the drug targeting to bacteria and reduced from osmotic gel further bacterial growth on the skin. Nanochlorex ® might constitute a promising approach for hygienic hand disinfection in care practice performing multiple procedures.

Bactericidal efficacy of 5 per cent povidone iodine cream in Pseudomonas aeruginosa burn wound infection

A new topical antiseptic agent, 5 per cent polyvinylpyrrolidone-iodine (PVP-I) cream, with altered physicochemical properties, incorporated in a different carrier base has proved in vivo to be more effective in controlling burn wound infections than 10 per cent PVP-I ointment. Important biodynamic properties of the new formulation have not, however, been elucidated in vivo. Hence the need for a controlled study to evaluate the bioavailability of the active component after penetration through burn eschar; the bactericidal efficacy of the cream and determination of the bactericidal time of the cream in comparison with 10 per cent PVP-I ointment. A modified Walker burn wound model was used to define the rate of trans-eschar penetration, biodynamic availability and bactericidal efficacy 5 per cent povidone iodine cream in established Pseudomonas aeruginosa burn wound infection. In vitro penetration confirmed the effective diffusion of PVP-I cream through 1.5 mm eschar within 6 h. A single topical application of PVP-I cream resulted in a 98.8 per cent (6.088 × 10 9 c.f.u./g of tissue to 7.367 × 10 7 c.f.u./g of tissue) reduction in intra-eschar viable organisms within 18 h after application. A second topical application of PVP-I cream at 18 h resulted in a total reduction of 99.8 per cent in viable organisms (2.90 × 10 9 c.f.u./g of tissue to 7.009 × 10 6 c.f.u./g of tissue) within 48 h. Comparing the in vitro bactericidal time of povidone iodine ointment with cream against Pseudomonas aeruginosa, Staphylococcus aureus and a Klebsiella pneumoniae revealed that the PVP-I cream killed organisms ten-fold more quickly than the ointment. It is concluded that 5 per cent PVP-I in an oil/water emulsion cream base is very effective in terms of rapid trans-eschar penetration, rapid killing and sustained antibacterial effect.