Effect of APTES modified TiO2 on antioxidant enzymes activity secreted by Escherichia coli and Staphylococcus epidermidis.

In this work, the impact of APTES-modified TiO2 photocatalysts on antioxidant enzymes (catalase and superoxide dismutase) activity secreted by bacteria was presented. Microbial tests has been examined using Escherichia coli (ATCC 29425) and Staphylococcus epidermidis (ATCC 49461) as model organisms. It was found that APTES-TiO2 affected the activity of antioxidant enzymes. Additionally, obtained APTES-TiO2 photocatalysts were capable of total E. coli and S. epidermidis inactivation under artificial solar light irradiation. The sample modified with the concentration of APTES equals 300 mM (TiO2-4h-120°C-300mM) showed the strongest photocatalytic activity toward both bacteria species. The two-stage photocatalytic mechanism of bacteria response to photocatalysts was proposed.

In-depth analysis of antibacterial mechanisms of laser generated shockwave treatment.

Background and Objectives Laser generated shockwave (LGS) is a novel modality for minimally invasive disruption of bacterial biofilms. The objectives of this study are to determine the mechanisms behind LGS treatment and non-biofilm effects on bacterial disruption, including (1) comparing bacterial load with and without LGS in its planktonic form and (2) estimating bacterial cell permeability following LGS. Study Design/Materials and Methods For the first study, planktonic S. epidermidis were treated with gentamicin (0, 8, 16, 32, 64 µg/ml) with and without LGS (1064 nm Nd:YAG laser, 110.14 mJ/mm2 , pulse duration 9 ns, spot size 3 mm, n = 8/group), and absorbances at 600 nm compared. For the second study, four samples of planktonic S. epidermidis were treated with LGS (same settings). Propidium iodide (PI) uptake via flow cytometry as a measure of cell permeability was measured at 0, 10, and 20 minutes following LGS. RESULTS: In comparing corresponding gentamicin concentrations within both LGS-treated samples and controls at 0 hours, there were no differences in absorbance (P = 0.923 and P = 0.814, respectively). Flow cytometry found modest PI uptake (10.4 ± 2.5%) immediately following LGS treatment, with time-dependent increase and persistence of the signal at 20 minutes (R2 = 0.449, P = 0.048). CONCLUSION: Taken together, LGS does not appear to have direct bacteriocidal properties, but rather by allowing for biofilm disruption and bacterial cell membrane permeabilization, both of which likely increase topical antibiotic delivery to pathogenic organisms. Insight into the mechanisms of LGS will allow for improved clinical applications and facilitate safe and effective translation of this technology. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

Carbon Nanomaterials and LED Irradiation as Antibacterial Strategies against Gram-Positive Multidrug-Resistant Pathogens.

BACKGROUND: Due to current antibiotic resistance worldwide, there is an urgent need to find new alternative antibacterial approaches capable of dealing with multidrug-resistant pathogens. Most recent studies have demonstrated the antibacterial activity and non-cytotoxicity of carbon nanomaterials such as graphene oxide (GO) and carbon nanofibers (CNFs). On the other hand, light-emitting diodes (LEDs) have shown great potential in a wide range of biomedical applications. METHODS: We investigated a nanotechnological strategy consisting of GO or CNFs combined with light-emitting diod (LED) irradiation as novel nanoweapons against two clinically relevant Gram-positive multidrug-resistant pathogens: methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). The cytotoxicity of GO and CNFs was studied in the presence of human keratinocyte HaCaT cells. RESULTS: GO or CNFs exhibited no cytotoxicity and high antibacterial activity in direct contact with MRSE and MRSA cells. Furthermore, when GO or CNFs were illuminated with LED light, the MRSE and MRSA cells lost viability. The rate of decrease in colony forming units from 0 to 3 h, measured per mL, increased to 98.5 ± 1.6% and 95.8 ± 1.4% for GO and 99.5 ± 0.6% and 99.7 ± 0.2% for CNFs. CONCLUSIONS: This combined antimicrobial approach opens up many biomedical research opportunities and provides an enhanced strategy for the prevention and treatment of Gram-positive multidrug-resistant infections.

Efficiency of riboflavin and ultraviolet light treatment against high levels of biofilm-derived Staphylococcus epidermidis in buffy coat platelet concentrates.

BACKGROUND AND OBJECTIVES: Staphylococcus epidermidis forms surface-attached aggregates (biofilms) in platelet concentrates (PCs), which are linked to missed detection during PC screening. This study was aimed at evaluating the efficacy of riboflavin-UV treatment to inactivate S. epidermidis biofilms in buffy coat (BC) PCs. MATERIALS AND METHODS: Biofilm and non-biofilm cells from S. epidermidis ST-10002 and S. epidermidis AZ-66 were individually inoculated into whole blood (WB) units (~106 colony-forming units (CFU)/ml) (N = 4-5). One spiked and three unspiked WB units were processed to produce a BC-PC pool. Riboflavin was added to the pool which was then split into two bags: one for UV treatment and the second was untreated. Bacterial counts were determined before and after treatment. In vitro PC quality was assessed by flow cytometry and dynamic light scattering. RESULTS: Bacterial counts were reduced during BC-PC production from ~106 CFU/ml in WB to 103 -104 CFU/ml in PCs (P < 0·0001). Riboflavin-UV treatment resulted in significantly higher reduction of S. epidermidis AZ-66 than strain ST-10002 (≥3·5 log reduction and 2·6-2·8 log reduction, respectively, P < 0·0001). Remaining bacteria post-treatment were able to proliferate in PCs. No differences in S. epidermidis inactivation were observed in PCs produced from WB inoculated with biofilm or non-biofilm cells (P > 0·05). Platelet activation was enhanced in PCs produced with WB inoculated with biofilms compared to non-biofilm cells (P < 0·05). CONCLUSION: Riboflavin-UV treatment was similarly efficacious in PCs produced from WB inoculated with S. epidermidis biofilm or non-biofilm cells. Levels of biofilm-derived S. epidermidis ≥103 CFU/ml were not completely inactivated; however, further testing is necessary with lower (real-life) bacterial levels.

Laser-generated shockwaves enhance antibacterial activity against biofilms in vitro.

BACKGROUND AND OBJECTIVES: Bacterial biofilm formation within chronic wound beds, which provides an effective barrier against antibiotics, is a known cause of recalcitrant infections and a significant healthcare burden, often requiring repeated surgical debridements. Laser-generated shockwaves (LGS) is a novel, minimally invasive, and nonthermal modality for biofilm mechanical debridement which utilizes compressive stress waves, generated by photonic absorption in thin titanium films to mechanically disrupt the biofilm. Prior studies have demonstrated LGS monotherapy to be selectively efficacious for biofilm disruption and safe for host tissues. In this study, we sought to determine if LGS can enhance the antimicrobial activity and biofilm disruption capability of topical antibiotic therapy. STUDY DESIGN/MATERIALS AND METHODS: Staphylococcus epidermidis biofilms grown in vitro on glass were treated with topical gentamicin (31, 62, and 124 µg/ml) with and without LGS (n = 3-11/treatment group). Mechanical shockwaves were generated with a 1,064 nm Nd:YAG laser (laser fluence 110.14 mJ/mm2 , pulse duration 5 ns, spot size 3 mm). Following a 24-hour incubation period, bacterial viability was assessed by determining the number of colony-forming units (CFU) via the Miles and Misra method. Residual biofilm bioburden was analyzed using the crystal violet biofilm assay. RESULTS: With gentamicin monotherapy, CFU density (CFU/mm2 ) at 31, 62, and 124 µg/ml were (282 ± 84) × 104 , (185 ± 34) × 104 , and (113 ± 9) × 104 , respectively. With LGS and gentamicin therapy, CFU density decreased to (170 ± 44) × 104 , (89 ± 24) × 104 , and (43 ± 3) × 104 , respectively (P = 0.1704, 0.0302, and 0.0004 when compared with gentamicin alone). Biofilm burden as measured by the assay in the gentamicin 31, 62, and 124 µg/ml groups was reduced by 80%, 95%, and 98% when LGS was added (P = 0.0102, >0.0001, and 0.0001 for all groups when compared with gentamicin alone). Furthermore, samples treated with LGS saw an increase in susceptibility to gentamicin, in terms of reduced biofilm bioburden and CFU densities. CONCLUSION: LGS enhances the efficacy of topical antibiotics in an in vitro model. This has significant implications for clinical applications in the management of chronic soft tissue infections and recalcitrant chronic rhinosinusitis. Lasers Surg. Med. 49:539-547, 2017. © 2017 Wiley Periodicals, Inc.

The uses and limitations of a hand-held germicidal ultraviolet wand for surface disinfection.

The morbidity and mortality from healthcare associated infections has raised concern that conventional disinfection methods are inadequate and that other adjunct methods such as room fumigation and ultraviolet irradiation may be needed. There is also concern that these alternative methods may pose a risk to workers and patients. OBJECTIVES: (1) Determine the efficacy of a germicidal UV-C wand for surface disinfection, (2) evaluate changing relative humidity (RH) and different target distances on bacteria kill rates, and (3) assess potential exposure concerns. METHODS: This study investigates whether a hand-held germicidal wand can efficaciously disinfect surfaces treated with either a vegetative or spore forming bacterium and to evaluate the effect of changing environmental conditions such as relative humidity (RH), target position, and target distances on microbial kill rates. RESULTS: Kill rate was best at 40-65% RH at a temperature range of 21-24°C. Both high and low RH interfered with the ability of UV-C to kill the vegetative microbe. In the case of the spore forming bacterium, increased surface drying time was the most significant factor increasing kill rate. CONCLUSIONS: This research demonstrates that UV-C was efficacious under optimal conditions, a direct beam exposure, and a short target distance (12.7 cm). However, there are limitations when used in non-optimal conditions. Increased distance and indirect beam angles resulted in lower kill rates. It is also important to minimize unnecessary patient and worker exposure during its use.

Photodynamic UVA-riboflavin bacterial elimination in antibiotic-resistant bacteria.

BACKGROUND: To evaluate the bactericidal effect of clinical ultraviolet A (UVA) settings used in photoactivated chromophore for infectious keratitis (PACK)-collagen cross-linking (CXL) in antibiotic-resistant and non-resistant bacterial strains. METHODS: Well-characterized bacterial strains from clinical isolates, without and with antibiotic resistance, were studied in a pairwise comparison. The evaluated pathogens were Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis. Bacteria were dispersed in PBS and diluted to a concentration of approximately 4 × 105 /ml. Riboflavin was added to a concentration of 0.01%. By spreading the solution on a microscope slide, a fluid film layer, with a thickness of around 400 mm, was formed and UVA exposure followed. Eight separate exposures were made for each strain (n = 8). The degree of elimination in resistant and non-resistant pathogens was compared. RESULTS: The bactericidal efficacy of exposure differed between the tested microorganisms, and the mean elimination ranged between 60 and 92%, being most extensive in both of the evaluated Pseudomonas strains and least in the E. faecalis strains. Similar reductions were seen in antibiotic-resistant and non-resistant strains, with the exception of S. aureus, in which the resistant strain metchicillin-resistant Staphylococcus aureus (MRSA) was eradicated in a greater extent than the non-resistant strain (P = 0.030). CONCLUSION: UVA-riboflavin settings used in PACK-CXL are effective in reducing both antibiotic-resistant and non-resistant bacteria. Antibiotic resistance does not appear to be protective against the photooxidative exposure.

In vitro antibacterial properties and UV induced response from Staphylococcus epidermidis on Ag/Ti oxide thin films.

Implanted materials are susceptible to bacterial colonization and biofilm formation, which can result in severe infection and lost implant function. UV induced photocatalytic disinfection on TiO2 and release of Ag(+) ions are two promising strategies to combat such events, and can be combined for improved efficiency. In the current study, a combinatorial physical vapor deposition technique was utilized to construct a gradient coating between Ag and Ti oxide, and the coating was evaluated for antibacterial properties in darkness and under UV light against Staphylococcus epidermidis. The findings revealed a potent antibacterial effect in darkness due to Ag(+) release, with near full elimination (97%) of viable bacteria and visible cell lysis on Ag dominated surfaces. The photocatalytic activity, however, was demonstrated poor due to low TiO2 crystallinity, and UV light irradiation of the coating did not contribute to the antibacterial effect. On the contrary, bacterial viability was in several instances higher after UV illumination, proposing a UV induced SOS response from the bacteria that limited the reduction rate during Ag(+) exposure. Such secondary effects should thus be considered in the development of multifunctional coatings that rely on UV activation.

Experimental study on the effect of light source arrangements on the disinfection performance of upper-room 222 nm Far-UVC.

The air disinfection efficacy of upper-room 222 nm Far-UVC was experimentally investigated in a real-size chamber under well-mixed air conditions. Two bacteria (Escherichia coli, Staphylococcus epidermidis) and two bacteriophages (MS2, and P22) were selected for the test. The study considered different lamp source arrangements, including single and double sources, stationary and rotating operating modes, and an overlapping mode with a 45° irradiation angle. A numerical view-factor model was developed to analyze the irradiance distributions. Four irradiation angles, 30°, 45°, 60°, and 90°, were chosen. The results show that the lamps operating with an irradiation angle of 45° provide the highest chamber-averaged irradiance. This suggests an optimal irradiance level for a given room dimension, as inferred from the view factor model. Experimental results indicated that the overlapping mode with a 45° irradiation angle consistently outperformed both the stationary mode and rotating mode in disinfection. This can be attributed to the higher chamber-averaged irradiance, which is also supported by the numerical model predictions. The increment ratios ranged from 14.9 % to 42.9 % compared to the stationary mode. The susceptibility constants of Escherichia coli, Staphylococcus epidermidis, MS2, and P22 were measured as 0.572 m2/J, 0.099 m2/J, 0.060 m2/J, and 0.081 m2/J respectively.

405 nm Light exposure of osteoblasts and inactivation of bacterial isolates from arthroplasty patients: potential for new disinfection applications?

Infection rates after arthroplasty surgery are between 1-4 %, rising significantly after revision procedures. To reduce the associated costs of treating these infections, and the patients' post-operative discomfort and trauma, a new preventative method is required. High intensity narrow spectrum (HINS) 405 nm light has bactericidal effects on a wide range of medically important bacteria, and it reduced bacterial bioburden when used as an environmental disinfection method in a Medical Burns Unit. To prove its safety for use for environmental disinfection in orthopaedic theatres during surgery, cultured osteoblasts were exposed to HINS-light of intensities up to 15 mW/cm2 for 1 h (54 J/cm2). Intensities of up to 5 mW/cm2 for 1 h had no effect on cell morphology, activity of alkaline phosphatase, synthesis of collagen or osteocalcin expression, demonstrating that under these conditions this dose is the maximum safe exposure for osteoblasts; after exposure to 15 mW/cm2 all parameters of osteoblast function were significantly decreased. Viability (measured by protein content and Crystal Violet staining) of the osteoblasts was not influenced by exposure to 5 mW/cm2 for at least 2 h. At 5 mW/cm2 HINS-light is an effective bactericide. It killed 98.1 % of Staphylococcus aureus and 83.2 % Staphylococcus epidermis populations seeded on agar surfaces, and is active against both laboratory strains and clinical isolates from infected hip and knee arthroplasties. HINS-light could have potential for development as a method of disinfection to reduce transmission of bacteria during arthroplasty, with wider applications in diverse surgical procedures involving implantation of a medical device.

Understanding the dark and light-enhanced bactericidal action of cationic conjugated polyelectrolytes and oligomers.

A multiscale investigation was carried out to study the dark and light-enhanced bactericidal mechanisms of poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) and oligo-phenylene ethynylenes (OPEs). On the morphological scale, Gram-negative E. coli cells exposed to CPE and OPE compounds in the dark show damage to the cell envelope, plasma membrane, and in some cases the cytoplasm, while with UV-irradiation, E. coli sustained catastrophic damages to both the cell envelope and cytoplasm. In contrast, the Gram-positive S. epi bacteria appeared intact when exposed to CPE and OPE compounds in the dark but showed damages to the cell envelope with UV-irradiation. To better understand the molecular basis of CPE- and OPE-induced morphological changes and damages to bacteria, we investigated the effect of these compounds on model bacterial plasma membrane and bacterial proteins and plasmid DNA. Measurements of dark membrane perturbation activity of the CPEs and OPEs using model lipid membranes support a carpet or detergent-like mechanism by which the antimicrobial compounds induce membrane collapse and phase transitions. Under UV-irradiation, E. coli bacteria exposed to CPEs and OPEs showed covalent modifications and damages to both cellular protein and plasmid DNA, likely through oxidative pathways mediated by singlet oxygen and subsequent reactive oxygen species sensitized by the CPE and OPE compounds. Our finding thus show that the antimicrobial polymers and oligomers exert toxicity toward Gram-negative bacteria by disrupting the morphology and structures of cell envelope and cytoplasm, including cellular components such as proteins and DNA, while exert toxicity toward Gram-positive bacteria by binding to and disrupting just the cell wall.

[Suppression of viability of staphylococci cells by 1270 nm laser beam].

AIM: Study the effect of 1270 nm wavelength laser exposure on the viability of Staphylococcus aureus and S. epidermidis cells in vitro. MATERIALS AND METHODS: Reference strain S. aureus 209P and clinical isolate S. epidermidis 26/193 that form bacterial biofilm were used in the study. Ica gene presence in S. epidermidis 26/193 that controls biofilm formation was confirmed in the study by PCR with a primer that generates a specific 814 n.p. amplicon. Experimental device by "New surgical technologies, Ltd." was used as a source of emission. The device has a continuous emission mode of laser semiconductor diodes with 1270 nm wavelength. Maximum regulated power of the emission is up to 3 W. Emission power in the studies performed was 150 mW. The time of exposition was 5, 10, 15 and 30 minutes. The amount of viable cells in the experiment and control was determined by calculating CFU/ml. Evaluation of bacterial biofilm formation was performed by the method described in O'Toole G.A. et al. (2000). RESULTS: A decrease of the number of viable forms of S. aureus 209P by a mean of 52 +/- 6.0% and 76 +/- 4.0%, and of S. epidermidis 26/193 by a mean of 48 +/- 4% and 64 +/- 5% for 15 and 30 min exposition, respectively, and a significant suppression of biofilm formation by staphylococci was shown. CONCLUSION: Exposure to 1270 nm laser renders a moderate bactericidal effect on staphylococci cells and significantly suppresses their bacterial biofilm formation.

Application of 233 nm far-UVC LEDs for eradication of MRSA and MSSA and risk assessment on skin models.

A newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280-380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm2, the 233 nm light source reduced the viable microorganisms by a log10 reduction (LR) of 5 log10 levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5-3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.

Enhanced inactivation of bacteria by metal-oxide nanoparticles combined with visible light irradiation.

BACKGROUND: In recent years nano-metaloxides which easily penetrate into the cells with special interest due to their higher chemical reactivity as compared to that of similar materials in the bulk form. Of particular interest are nano-TiO(2) and ZnO, which have been widely used for their bactericidal and anticancerous properties. PURPOSE: The aim of the present study was to examine the bactericidal properties of nano-TiO(2) and ZnO combined with visible light on S. aureus and S. epidermitis, known for their high prevalence in infected wounds. STUDY: Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of TiO(2) and ZnO nanoparticle suspensions in water to produce reactive oxygen species (ROS) with and without visible light irradiation. The possibility of exciting these nanoparticles with visible light in order to enhance their antimicrobial activity was also tested. RESULTS: Electron-spin resonance measurements revealed that ZnO and TiO(2) nanoparticles are able to produce ROS in water suspension. A remarkable enhancement of ROS production was found following illumination with blue light. In addition, illumination significantly enhanced the antibacterial activity of the nanoparticles. CONCLUSION: The results suggest that nanoparticles combined with visible light can be used for sterilization purposes and may be effective for treating infected wounds.

Evaluation of antibacterial efficacy of photo-activated riboflavin using ultraviolet light (UVA).

BACKGROUND: To evaluate the antibacterial efficacy of photo-activated riboflavin using Ultraviolet A (UVA) on three bacterial strains commonly detected in keratitis. METHODS: Three bacterial strains (Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa) were cultured on blood/hematin-agar plates and dispersed in PBS. Dispersion was done of 10 microl of bacterial stock-solutions in 90 microl of RPMI, where different riboflavin molarities had been added, to achieve a bacterial concentration of 1-4 x 10 (4)/ml. Riboflavin end molarities before illumination were 0, 100, 200, 300 and 400 microM. Each solution had a negative control. The solutions were illuminated with UVA (365 nm) for 30 minutes (5.4 J/cm(2)) and then continued for a total time of 60 minutes (10.8 J/cm(2)). A count of CFU was conducted after incubation and results compared. RESULTS: In all tested strains, a slight decrease of bacteria was seen when exposed to UV for 30 minutes. A doubling of the UV dose showed a marked decrease of bacterial count in all bacteria tested. The combination of UV and riboflavin showed a more extensive reduction of CFU, confirming an interaction effect between UV and riboflavin. CONCLUSION: Riboflavin photo-activation using UVA (365 nm) can achieve an extensive eradication of bacteria, and the combination is more potent in reducing bacterial number than UV alone.

Sterilization of platelet concentrates at production scale by irradiation with short-wave ultraviolet light.

BACKGROUND: Bacterial contamination of platelet concentrates (PCs) is recognized as a serious threat to transfusion safety. We developed a simple method for sterilization of PCs with short-wave ultraviolet light (UVC). The effects of treatment on the sterility of contaminated PCs and in vitro platelet (PLT) variables were evaluated. STUDY DESIGN AND METHODS: Plasma-reduced PCs were prepared from pools of five buffy coats. Irradiation with UVC (wavelength, 254 nm) under vigorous agitation was from both sides of the irradiation bags. Kinetics of the inactivation of Bacillus cereus, Propionibacterium acnes, and Staphylococcus epidermidis were determined. PCs spiked with approximately 10 to 100 colony-forming units (CFUs)/mL of 10 bacteria species (n = 12/species) were irradiated with UVC doses between 0.25 and 0.4 J/cm(2) and tested for sterility by a commercially available bacterial detection system (BacT/ALERT, bioMérieux) after storage at 22 degrees C for 3 or 6 days. The influence of a dose of 0.3 J/cm(2) on PLT variables was investigated on Days 1, 4, and 6 after irradiation. RESULTS: At 0.3 J/cm(2) all bacteria species tested were inactivated by more than 4 log. At this dose the influence of UVC on in vitro PLT variables was marginal; the storage stability for up to 6 days after treatment was maintained. PCs spiked with approximately 10 to 100 CFUs/mL were reproducibly sterilized in the dose range tested. In individual experiments with the spore former B. cereus, PCs were, however, unsterile after treatment. CONCLUSION: Irradiation at UVC doses not detrimental to in vitro PLT variables sterilizes PCs contaminated with a wide range of different bacteria species.

Improved photodynamic inactivation of gram-positive bacteria using hematoporphyrin encapsulated in liposomes and micelles.

BACKGROUND AND OBJECTIVES: Antimicrobial photodynamic inactivation (PDI) is a promising treatment modality for local infections. To increase the efficacy of photosensitizer, hematoporphyrin (Hp) was used as a model drug and encapsulated in liposomes and micelles. The bactericidal efficacy of the carrier-entrapped Hp was assessed against gram-positive bacteria. STUDY DESIGN/MATERIALS AND METHODS: Hp was encapsulated in liposomes by a modified reversed-phase evaporation and extrusion method. Micelle-Hp was prepared by the reversed-phase evaporation method. Spectroscopic analysis was used to characterize the properties of Hp in PBS, liposome or micelle. The PDI efficacy was examined by using gram-positive pathogens including methicillin-susceptible, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. RESULTS: The absorption and fluorescence emission spectra indicated that Hp encapsulated in liposomes and micelles is less likely to exist in aggregated form compared to that generally seen in an aqueous medium. Liposome- or micelle-Hp can induce complete eradication of the bacteria above a critical Hp dose, which is significantly lower than the dose required when using the non-encapsulated Hp. Furthermore, the PDI effect of the Hp encapsulated in micelles was superior to the Hp encapsulated in liposomes at lower Hp doses. Similar PDI results were also found in S. epidermidis and S. pyogenes. CONCLUSIONS: Our results indicate that photosensitizer entrapped in micelle exert similar or better PDI efficacy than that of liposome, which indicates this formulation may be useful for the treatment of local infections in the future.

Decreased efficacy of UV inactivation of Staphylococcus aureus after multiple exposure and growth cycles.

UV disinfection is a relatively simple and cost-efficient disinfection method, especially for in-home greywater treatment. In this study, a bench scale experiment was performed using a LED collimated UV-C beam with a peak wavelength of 256 nm to determine if potentially pathogenic bacteria such as Staphylococcus aureus may become enriched in a semi-recirculating greywater system with UV as the sole disinfection step. A statistically significant (P < 0.001) decreasing trend in UV-C efficacy was observed between the 1st and 6th UV exposure-growth cycles of S. aureus (ATCC 25923), resulting in a 1.5 decrease in log10 removal (P < 0.00000) by the 5th iteration. An eleven-point dose-response curve of the 7th iteration of S. aureus was estimated and compared to the dose-response curve of the original strain; due to a longer apparent shoulder period and a decay constant of lesser degree, the dose required for a 4-log reduction of the enriched S. aureus was estimated to be ∼1.9 times greater (22.0 mJ⋅cm-2 versus 11.8 mJ⋅cm-2). However, experimental results with S. epidermidis (ATCC 12228) and two wild strains, S. aureus and S. warneri, exhibited no trend of increased resistance. UV doses exceeding 20 mJ⋅cm-2 are generally sufficient in achieving a 4-log reduction of bacteria in drinking water systems; however, the results exhibited in this study suggest that when recirculation is involved, there may be a need for UV doses exceeding what is necessary for a 4-log reduction to suppress the enrichment of strains which could pose a public health risk.

Atomic force microscopy study of the effect of pulsed electric field on Staphylococcus epidermidis.

The effect of a pulsed electric field (PEF) on Staphylococcus epidermidis was investigated by using an atomic force microscopy (AFM) image and force measurement under liquid. The changes in the bacterial envelope were probed in situ before and after applying different dosages of PEF. Our results indicated that PEF induced the changes of bacterial peptidoglycan layer and the exposure of plasma membrane. This conclusion was further confirmed by two control experiments: the effect of the lysozyme or heat on the bacterial envelope. Furthermore, our results demonstrated that AFM analysis including image and force measurement is helpful to explain the relationship between the chemical composition change of the cellular envelope and the external stimulation.

The effect of UVB radiation on skin microbiota in patients with atopic dermatitis and healthy controls.

OBJECTIVES: To investigate Staphylococcus aureus and Staphylococcus epidermidis quantitatively in adult patients with atopic dermatitis and in healthy controls treated with UVB radiation. STUDY DESIGN: Twenty-three adult patients (of these, 3 were excluded) with flexural atopic dermatitis and 20 healthy controls were randomly selected at the outpatient clinic of the Dermatological Department, University Hospital, North Norway. METHODS: Adult patients with atopic dermatitis (n = 20) and healthy controls (n = 20) were given 20 UVB treatments. Bacterial samples were collected before treatment, after 4 weeks of treatment, and finally after 2 weeks follow-up. RESULTS: The main bacteria found were Staphylococcus aureus and Staphylococcus epidermidis. 16 of the 20 patients with atopic dermatitis had Staphylococcus aureus in lesional skin and 12 in non-lesional skin. None of the healthy controls had Staphylococcus aureus in the sample from the flexural elbow. The Staphylococcus aureus counts decreased (not significant) in lesional skin after 4 weeks of treatment and Staphylococcus aureus counts were slightly higher after 2 weeks follow up. The same figures were also seen in non-lesional skin and forehead. CONCLUSIONS: Staphylococcus aureus is widely colonised in the skin of atopic dermatitis patients, but is rare in healthy adults. UVB treatment decreases the Staphylococcus aureus count in patients with atopic dermatitis.