Novel sampling technique maintaining the two-dimensional organization of microbes during cultivation from chronic wounds: The Imprint method

This study aimed to develop and validate "the Imprint method,", a technique for sampling microbes from chronic wounds while preserving their two-dimensional spatial organization. We used nylon filters to sample bacteria and compared with sampling using Eswabs in 12 patients. The Imprint method identified a mean of 0.93 unique species more than Eswab (4.3 ± 2.2 and 3.4 ± 1.4 unique species, respectively; mean ± SD; n = 30). Accuracy between the Eswab and the Imprint method was 93.2% and in cases of disagreement between methods, Imprint had a higher sensitivity in 6/8 of the most prevalent species. In vitro validation confirmed that the Imprint method could transfer bacterial colonies while replicating their two-dimensional organization and the area covered by bacteria on the plate sampled. Clinical testing demonstrated that the imprint method is a rapid and feasible technique that identified more unique bacterial species than Eswab with a good agreement between methods but that Imprint was better at detecting important pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa. The Imprint method is a novel technique that cultures and records the two-dimensional organization of microbes, providing an alternative or supplement to conventional surface culture using Eswab.

Pharmacokinetics of Locally Applied Antibiotic Prophylaxis for Implant-Based Breast Reconstruction

Importance

Antibiotic irrigation of breast implants is widely used internationally, but no clinical study has investigated the pharmacokinetics of antibiotic prophylaxis in the breast implant pocket.

Objectives

To evaluate how long locally applied gentamicin, cefazolin, and vancomycin concentrations in the implant pocket remain above the minimum inhibitory concentration (MIC) for the most common bacterial infections and to measure systemic uptake.

Design, Setting, and Participants

This prospective cohort study was performed at the Department of Plastic Surgery and Burns Treatment, Rigshospitalet, Copenhagen, Denmark, between October 25, 2021, and September 22, 2022, among 40 patients undergoing implant-based breast reconstruction who were part of the ongoing BREAST-AB trial (Prophylactic Treatment of Breast Implants With a Solution of Gentamicin, Vancomycin and Cefazolin Antibiotics for Women Undergoing Breast Reconstructive Surgery: a Randomized Controlled Trial). Patients were randomized to receive locally applied gentamicin, cefazolin, and vancomycin or placebo. Samples were obtained from the surgical breast drain and blood up to 10 days postoperatively.

Exposures

The breast implant and the implant pocket were irrigated with 160 μg/mL of gentamicin, 2000 μg/mL of cefazolin, and 2000 μg/mL of vancomycin in a 200-mL saline solution.

Main Outcomes and Measures

The primary outcome was the duration of antibiotic concentrations above the MIC breakpoint for Staphylococcus aureus according to the Clinical and Laboratory Standards Institute: gentamicin, 4 μg/mL; cefazolin, 2 μg/mL; and vancomycin, 2 μg/mL. Secondary outcomes included the time above the MIC for Pseudomonas aeruginosa and other relevant bacteria, as well as systemic uptake.

Results

The study included 40 patients (median age, 44.6 years [IQR, 38.3-51.4 years]; median body mass index, 23.9 [IQR, 21.7-25.9]) with a median number of 3 drain samples (range, 1-10 drain samples) and 2 blood samples (range, 0-6 blood samples). Vancomycin and cefazolin remained above the MIC for S aureus significantly longer than gentamicin (gentamicin, 0.9 days [95% CI, 0.5-1.2 days] for blood samples vs 6.9 days [95% CI, 2.9 to 10.9 days] for vancomycin [P = .02] vs 3.7 days [95% CI, 2.2-5.2 days] for cefazolin [P = .002]). The gentamicin level remained above the MIC for P aeruginosa for 1.3 days (95% CI, 1.0-1.5 days). Only cefazolin was detectable in blood samples, albeit in very low concentrations (median concentration, 0.04 μg/mL [range, 0.007-0.1 μg/mL]).

Conclusions and Relevance

This study suggests that patients treated with triple-antibiotic implant irrigation during breast reconstruction receive adequate prophylaxis for S aureus and other common implant-associated, gram-positive bacteria. However, the protection against P aeruginosa may be inadequate.

Single cells and bacterial biofilm populations in chronic wound infections

Chronic wounds and chronic ulcers are an increasing problem associated with high health care burden and patient burden. The arrested healing of chronic wounds has, in part, been attributed to the presence of biofilms. Substantial research has documented the presence of biofilms in chronic wounds, and many mechanisms of host-pathogen interactions have been uncovered to explain the arrested healing. However, the paradigm of whether biofilms are only observed in chronic infections was recently challenged when biofilms were also observed in acute infections. Here, we characterize the distribution of bacteria in lower leg wounds with particular emphasis on Pseudomonas aeruginosa and Staphylococcus aureus by confocal laser scanning microscopy combined with PNA-FISH staining and routine culture of bacteria. We show that 40% of wounds contained either P. aeruginosa or S. aureus biofilms and demonstrate the presence of scattered single cells in tissues stained with a universal bacterial PNA-FISH probe. Thus, we demonstrate that chronic wounds do not only harbor bacteria organized in biofilms, but also carry populations of scattered single cells and small cell clusters of only a few bacteria. Our findings may influence diagnostic tools being developed to only target biofilms, where single-cell subpopulations thus may be overlooked and possibly lead to false-negative results.

What's in a name? Characteristics of clinical biofilms

In vitro biofilms are communities of microbes with unique features compared to individual cells. Biofilms are commonly characterized by physical traits like size, adhesion, and a matrix made of extracellular substances. They display distinct phenotypic features, such as metabolic activity and antibiotic tolerance. However, the relative importance of these traits depends on the environment and bacterial species. Various mechanisms enable biofilm-associated bacteria to withstand antibiotics, including physical barriers, physiological adaptations, and changes in gene expression. Gene expression profiles in biofilms differ from individual cells but, there is little consensus among studies and so far, a 'biofilm signature transcriptome' has not been recognized. Additionally, the spatial and temporal variability within biofilms varies greatly depending on the system or environment. Despite all these variable conditions, which produce very diverse structures, they are all noted as biofilms. We discuss that clinical biofilms may differ from those grown in laboratories and found in the environment and discuss whether the characteristics that are commonly used to define and characterize biofilms have been shown in infectious biofilms. We emphasize that there is a need for a comprehensive understanding of the specific traits that are used to define bacteria in infections as clinical biofilms.

The non-attached biofilm aggregate

Biofilms have conventionally been perceived as dense bacterial masses on surfaces, following the five-step model of development. Initial biofilm research focused on surface-attached formations, but detached aggregates have received increasing attention in the past decade due to their pivotal role in chronic infections. Understanding their nature sparked fervent discussions in biofilm conferences and scientific literature. This review consolidates current insights on non-attached aggregates, offering examples of their occurrence in nature and diseases. We discuss their formation and dispersion mechanisms, resilience to antibiotics and immune-responses, drawing parallels to surface-attached biofilms. Moreover, we outline available in vitro models for studying non-attached aggregates.

A collagen-based layered chronic wound biofilm model for testing antimicrobial wound products

A new in vitro chronic wound biofilm model was recently published, which provided a layered scaffold simulating mammalian tissue composition on which topical wound care products could be tested. In this paper, we updated the model even further to mimic the dynamic influx of nutrients from below as is the case in a chronic wound. The modified in vitro model was created using collagen instead of agar as the main matrix component and contained both Staphylococcus aureus and Pseudomonas aeruginosa. The model was cast in transwell inserts and then placed in wound simulating media, which allowed for an exchange of nutrients and waste products across a filter. Three potential wound care products and chlorhexidine digluconate 2% solution as a positive control were used to evaluate the model. The tested products were composed of hydrogels made from completely biodegradable starch microspheres carrying different active compounds. The compounds were applied topically and left for 2-4 days. Profiles of oxygen concentration and pH were measured to assess the effect of treatments on bacterial activity. Confocal microscope images were obtained of the models to visualise the existence of microcolonies. Results showed that the modified in vitro model maintained a stable number of the two bacterial species over 6 days. In untreated models, steep oxygen gradients developed and pH increased to >8.0. Hydrogels containing active compounds alleviated the high oxygen consumption and decreased pH drastically. Moreover, all three hydrogels reduced the colony forming units significantly and to a larger extent than the chlorhexidine control treatment. Overall, the modified model expressed several characteristics similar to in vivo chronic wounds.

Protocol to assess metabolic activity of Pseudomonas aeruginosa by measuring heat flow using isothermal calorimetry

Here, we present a protocol for assessing metabolic activity of bacterial populations by measuring heat flow using isothermal calorimetry. We outline the steps for preparing the different growth models of Pseudomonas aeruginosa and performing continuous metabolic activity measurements in the calScreener. We detail simple principal component analysis to differentiate between metabolic states of different populations and probabilistic logistic classification to assess resemblance to wild-type bacteria. This protocol for fine-scale metabolic measurement can aid in understanding microbial physiology. For complete details on the use and execution of this protocol, please refer to Lichtenberg et al. (2022).¹.

Adaptation of Pseudomonas aeruginosa biofilms to tobramycin and the quorum sensing inhibitor C-30 during experimental evolution requires multiple genotypic and phenotypic changes

In the present study we evaluated the fitness, antimicrobial susceptibility, metabolic activity, gene expression, in vitro production of virulence factors and in vivo virulence of experimentally evolved Pseudomonas aeruginosa PAO1. These strains were previously evolved in the presence of tobramycin and the quorum sensing inhibitor furanone C-30 (C-30) and carried mutations in mexT and fusA1. Compared to the wild-type (WT), the evolved strains show a different growth rate and different metabolic activity, suggesting they have an altered fitness. mexT mutants were less susceptible to C-30 than WT strains; they also show reduced susceptibility to chloramphenicol and ciprofloxacin, two substrates of the MexEF-OprN efflux pump. fusA1 mutants had a decreased susceptibility to aminoglycoside antibiotics, and an increased susceptibility to chloramphenicol. The decreased antimicrobial susceptibility and decreased susceptibility to C-30 was accompanied by a changed metabolic activity profile during treatment. The expression of mexE was significantly increased in mexT mutants and induced by C-30, suggesting that MexEF-OprN exports C-30 out of the bacterial cell. The in vitro production of virulence factors as well as virulence in two in vivo models of the strains evolved in the presence of C-30 was unchanged compared to the virulence of the WT. Finally, the evolved strains were less susceptible towards tobramycin (alone and combined with C-30) in an in vivo mouse model. In conclusion, this study shows that mutations acquired during experimental evolution of P. aeruginosa biofilms in the presence of tobramycin and C-30, are accompanied by an altered fitness, metabolism, mexE expression and in vitro and in vivo antimicrobial susceptibility.

Inoculum Concentration Influences Pseudomonas aeruginosa Phenotype and Biofilm Architecture

In infections, bacterial cells are often found as relatively small multicellular aggregates characterized by a heterogeneous distribution of phenotype, genotype, and growth rates depending on their surrounding microenvironment. Many laboratory models fail to mimic these characteristics, and experiments are often initiated from planktonic bacteria given optimal conditions for rapid growth without concerns about the microenvironmental characteristics during biofilm maturation. Therefore, we investigated how the initial bacterial concentration (henceforth termed the inoculum) influences the microenvironment during initial growth and how this affects the sizes and distribution of developed aggregates in an embedded biofilm model-the alginate bead biofilm model. Following 24 h of incubation, the viable biomass was independent of starting inoculum but with a radically different microenvironment which led to differences in metabolic activity depending on the inoculum. The inoculum also affected the number of cells surviving treatment with the antibiotic tobramycin, where the highest inoculum showed higher survival rates than the lowest inoculum. The change in antibiotic tolerance was correlated with cell-specific RNA content and O2 consumption rates, suggesting a direct role of metabolic activity. Thus, the starting number of bacteria results in different phenotypic trajectories governed by different microenvironmental characteristics, and we demonstrate some of the possible implications of such physiological gradients on the outcome of in vitro experiments. IMPORTANCE Biofilm aggregates grown in the alginate bead biofilm model bear resemblance to features of in vivo biofilms. Here, we show that changing the initial concentration of bacteria in the biofilm model leads to widely different behavior of the bacteria following an incubation period. This difference is influenced by the local conditions experienced by the bacteria during growth, which impact their response to antibiotic treatment. Our study provides a framework for manipulating aggregate sizes in in vitro biofilm models. It underlines the importance of how experiments are initiated, which can profoundly impact the outcomes and interpretation of microbiological experiments.

Nitric-oxide-driven oxygen release in anoxic Pseudomonas aeruginosa

Denitrification supports anoxic growth of Pseudomonas aeruginosa in infections. Moreover, denitrification may provide oxygen (O₂) resulting from dismutation of the denitrification intermediate nitric oxide (NO) as seen in Methylomirabilis oxyfera. To examine the prevalence of NO dismutation we studied O₂ release by P. aeruginosa in airtight vials. P. aeruginosa rapidly depleted O₂ but NO supplementation generated peaks of O₂ at the onset of anoxia, and we demonstrate a direct role of NO in the O₂ release. However, we were not able to detect genetic evidence for putative NO dismutases.

The supply of endogenous O₂ at the onset of anoxia could play an adaptive role when P. aeruginosa enters anaerobiosis. Furthermore, O₂ generation by NO dismutation may be more widespread than indicated by the reports on the distribution of homologues genes. In general, NO dismutation may allow removal of nitrate by denitrification without release of the very potent greenhouse gas, nitrous oxide.

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Pseudomonas aeruginosa was found to release O₂ at the onset of anoxia

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Peaks of O₂ were amplified in a nitric oxide reductase (NOR) mutant

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The O₂ release was mediated by nitric oxide (NO)

In-Situ Metatranscriptomic Analyses Reveal the Metabolic Flexibility of the Thermophilic Anoxygenic Photosynthetic Bacterium Chloroflexus aggregans in a Hot Spring Cyanobacteria-Dominated Microbial Mat

Chloroflexus aggregans is a metabolically versatile, thermophilic, anoxygenic phototrophic member of the phylum Chloroflexota (formerly Chloroflexi), which can grow photoheterotrophically, photoautotrophically, chemoheterotrophically, and chemoautotrophically. In hot spring-associated microbial mats, C. aggregans co-exists with oxygenic cyanobacteria under dynamic micro-environmental conditions. To elucidate the predominant growth modes of C. aggregans, relative transcription levels of energy metabolism- and CO₂ fixation-related genes were studied in Nakabusa Hot Springs microbial mats over a diel cycle and correlated with microscale in situ measurements of O₂ and light. Metatranscriptomic analyses indicated two periods with different modes of energy metabolism of C. aggregans: (1) phototrophy around midday and (2) chemotrophy in the early morning hours. During midday, C. aggregans mainly employed photoheterotrophy when the microbial mats were hyperoxic (400–800 µmol L⁻¹ O₂). In the early morning hours, relative transcription peaks of genes encoding uptake hydrogenase, key enzymes for carbon fixation, respiratory complexes as well as enzymes for TCA cycle and acetate uptake suggest an aerobic chemomixotrophic lifestyle. This is the first in situ study of the versatile energy metabolism of C. aggregans based on gene transcription patterns. The results provide novel insights into the metabolic flexibility of these filamentous anoxygenic phototrophs that thrive under dynamic environmental conditions.

Lactobacillus rhamnosus strains of oral and vaginal origin show strong antifungal activity in vitro

Background: Intake of probiotic bacteria may prevent oral Candida infection. Objective: To screen the antifungal activity of 14 Lactobacillus candidate strains of human origin, against six opportunistic C. albicans and non-albicans species. A second aim was to study the acid production of the four strains showing the strongest antifungal activity. Methods: We used an agar overlay growth inhibition assay to the assess the antifungal activity of the lactobacilli. The acid-producing capacity was measured with pH micro-sensors. Results: All 14 Lactobacillus candidates inhibited the growth of the Candida spp. The four best-performing strains were L. rhamnosus DSM 32992 (oral origin), L. rhamnosus DSM 32991 (oral), L. jensenii 22B42 (vaginal), and L. rhamnosus PB01 (vaginal). The difference between L. rhamnosus DSM 32992 and the other three strains was statistically significant (p < 0.001). The Candida spp. differed in susceptibility; C. parapsilosis was highly inhibited, while C. krusei was not or slightly inhibited. The oral L. rhamnosus DSM 32992 and DSM 32991 strains showed the lowest pH-values. Conclusion: Screening of probiotic lactobacilli showed significant strain-dependent variations in their antifungal capacity in a pH-dependent mode. Two strains of oral origin were most effective. A further characterization seems justified to elaborate on their probiotic properties.

Do Mixed-Species Biofilms Dominate in Chronic Infections?-Need for in situ Visualization of Bacterial Organization

Chronic infections present a serious economic burden to health-care systems. The severity and prevalence of chronic infections are continuously increasing due to an aging population and an elevated number of lifestyle related diseases such as diabetes. Treatment of chronic infections has proven difficult, mainly due to the presence of biofilms that render bacteria more tolerant toward antimicrobials and the host immune response. Chronic infections have been described to harbor several different bacterial species and it has been hypothesized that microscale interactions and mixed-species consortia are present as described for most natural occurring biofilms i.e., aquatic systems and industrial settings, but also for some commensal human biofilms i.e., the mouth microbiota. However, the presence of mixed-species biofilms in chronic infections is most often an assumption based on culture-based methods and/or by means of molecular approaches, such as PCR and sequencing performed from homogenized bulk tissue samples. These methods disregard the spatial organization of the bacterial community and thus valuable information on biofilm aggregate composition, spatial organization, and possible interactions between different species is lost. Hitherto, only few studies have made visual in situ presentations of mixed-species biofilms in chronic infections, which is pivotal for the description of bacterial composition, spatial distribution, and interspecies interaction on the microscale. In order for bacteria to interact (synergism, commensalism, mutualism, competition, etc.) they need to be in close proximity to each other on the scale where they can affect e.g., solute concentrations. We argue that visual proof of mixed species biofilms in chronic infections is scarce compared to what is seen in e.g., environmental biofilms and call for a debate on the importance of mixed-species biofilm in chronic infections.

Vertical Distribution and Diversity of Phototrophic Bacteria within a Hot Spring Microbial Mat (Nakabusa Hot Springs, Japan)

Phototrophic microbial mats are assemblages of vertically layered microbial populations dominated by photosynthetic microorganisms. In order to elucidate the vertical distribution and diversity of phototrophic microorganisms in a hot spring-associated microbial mat in Nakabusa (Japan), we analyzed the 16S rRNA gene amplicon sequences of the microbial mat separated into five depth horizons, and correlated them with microsensor measurements of O₂ and spectral scalar irradiance. A stable core community and high diversity of phototrophic organisms dominated by the filamentous anoxygenic phototrophs, Roseiflexus castenholzii and Chloroflexus aggregans were identified together with the spectral signatures of bacteriochlorophylls (BChls) a and c absorption in all mat layers. In the upper mat layers, a high abundance of cyanobacteria (Thermosynechococcus sp.) correlated with strong spectral signatures of chlorophyll a and phycobiliprotein absorption near the surface in a zone of high O₂ concentrations during the day. Deeper mat layers were dominated by uncultured chemotrophic Chlorobi such as the novel putatively sulfate-reducing “Ca. Thermonerobacter sp.”, which showed increasing abundance with depth correlating with low O₂ in these layers enabling anaerobic metabolism. Oxygen tolerance and requirements for the novel phototroph “Ca. Chloroanaerofilum sp.” and the uncultured chemotrophic Armatimonadetes member type OS-L detected in Nakabusa hot springs, Japan appeared to differ from previously suggested lifestyles for close relatives identified in hot springs in Yellowstone National Park, USA. The present study identified various microenvironmental gradients and niche differentiation enabling the co-existence of diverse chlorophototrophs in metabolically diverse communities in hot springs.

In Situ Monitoring of the Antibacterial Activity of a Copper-Silver Alloy Using Confocal Laser Scanning Microscopy and pH Microsensors

The antibacterial efficacy of a copper-silver alloy coating under conditions resembling build up of dry surface bacterial biofilms is successfully demonstrated according to US EPA test methods with a ≥99.9% reduction of test organisms over a 24 h period. A tailor-made confocal imaging protocol is designed to visualize in situ the killing of bacterial biofilms at the copper-silver alloy surface and monitor the kinetics for 100 min. The copper-silver alloy coating eradicates a biofilm of Gram-positive bacteria within 5 min while a biofilm of Gram-negative bacteria are killed more slowly. In situ pH monitoring indicates a 2-log units increase at the interface between the metallic surface and bacterial biofilm; however, the viability of the bacteria is not directly affected by this raise (pH 8.0-9.5) when tested in buffer. The OH- production, as a result of the interaction between the electrochemically active surface and the bacterial biofilm under environmental conditions, is thus one aspect of the contact-mediated killing of the copper-silver alloy coating and not the direct cause of the observed antibacterial efficacy. The combination of oxidation of bacterial cells, release of copper ions, and local pH raise characterizes the antibacterial activity of the copper-silver alloy-coated dry surface.

Optical Properties of Corals Distort Variable Chlorophyll Fluorescence Measurements

Pulse-amplitude-modulated (PAM) fluorimetry is widely used in photobiological studies of corals, as it rapidly provides numerous photosynthetic parameters to assess coral ecophysiology. Coral optics studies have revealed the presence of light gradients in corals, which are strongly affected by light scattering in coral tissue and skeleton. We investigated whether coral optics affects variable chlorophyll (Chl) fluorescence measurements and derived photosynthetic parameters by developing planar hydrogel slabs with immobilized microalgae and with bulk optical properties similar to those of different types of corals. Our results show that PAM-based measurements of photosynthetic parameters differed substantially between hydrogels with different degrees of light scattering but identical microalgal density, yielding deviations in apparent maximal electron transport rates by a factor of 2. Furthermore, system settings such as the measuring light intensity affected F ₀, F_m , and F_v /F_m in hydrogels with identical light absorption but different degrees of light scattering. Likewise, differences in microalgal density affected variable Chl fluorescence parameters, where higher algal densities led to greater F_v /F_m values and relative electron transport rates. These results have important implications for the use of variable Chl fluorimetry in ecophysiological studies of coral stress and photosynthesis, as well as other optically dense systems such as plant tissue and biofilms.

Light Sheet Microscopy Imaging of Light Absorption and Photosynthesis Distribution in Plant Tissue

In vivo variable chlorophyll fluorescence measurements of photosystem II (PSII) quantum yields in optically dense systems are complicated by steep tissue light gradients due to scattering and absorption. Consequently, externally measured effective PSII quantum yields may be composed of signals derived from cells differentially exposed to actinic light, where cells located deeper inside tissues receive lower irradiance than cells closer to the surface and can display distinct photophysiological status. We demonstrate how measured distributions of PSII quantum yields in plant tissue change under natural tissue light gradients as compared with conventionally measured quantum yields with even exposure to actinic light. This was achieved by applying actinic irradiance perpendicular to one side of thallus cross sections of the aquatic macrophyte Fucus vesiculosus with laser light sheets of defined spectral composition, while imaging variable chlorophyll fluorescence from cross sections with a microscope-mounted pulse amplitude-modulated imaging system. We show that quantum yields are highly affected by light gradients and that traditional surface-based variable chlorophyll fluorescence measurements result in substantial underestimations and/or overestimations, depending on incident actinic irradiance. We present a method for using chlorophyll fluorescence profiles in combination with integrating sphere measurements of reflectance and transmittance to calculate depth-resolved photon absorption profiles, which can be used to correct apparent PSII electron transport rates to photons absorbed by PSII. Absorption profiles of the investigated aquatic macrophyte were different in shape from what is typically observed in terrestrial leaves, and based on this finding, we discuss strategies for optimizing photon absorption via modulation of the structural organization of phytoelements according to in situ light environments.

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O₂, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, E_k, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments.

Diffusion or advection? Mass transfer and complex boundary layer landscapes of the brown alga Fucus vesiculosus

The role of hyaline hairs on the thallus of brown algae in the genus Fucus is long debated and several functions have been proposed. We used a novel motorized set-up for two-dimensional and three-dimensional mapping with O2 microsensors to investigate the spatial heterogeneity of the diffusive boundary layer (DBL) and O2 flux around single and multiple tufts of hyaline hairs on the thallus of Fucus vesiculosus. Flow was a major determinant of DBL thickness, where higher flow decreased DBL thickness and increased O2 flux between the algal thallus and the surrounding seawater. However, the topography of the DBL varied and did not directly follow the contour of the underlying thallus. Areas around single tufts of hyaline hairs exhibited a more complex mass-transfer boundary layer, showing both increased and decreased thickness when compared with areas over smooth thallus surfaces. Over thallus areas with several hyaline hair tufts, the overall effect was an apparent increase in the boundary layer thickness. We also found indications for advective O2 transport driven by pressure gradients or vortex shedding downstream from dense tufts of hyaline hairs that could alleviate local mass-transfer resistances. Mass-transfer dynamics around hyaline hair tufts are thus more complex than hitherto assumed and may have important implications for algal physiology and plant-microbe interactions.

The effectiveness of the paclitaxel-coated Luminor® balloon catheter versus an uncoated balloon catheter in superficial femoral and popliteal arteries in preventing vessel restenosis or reocclusion: study protocol for a randomized controlled trial

BACKGROUND

The aim of this investigator-initiated trial is to evaluate the safety and efficacy of the novel Luminor® paclitaxel-coated drug-eluting balloon (DEB) catheter (iVascular, S.L.U., Barcelona, Spain) in inhibiting restenosis and in ensuring long-term vascular patency.

METHODS/DESIGN

This is a multicenter randomized controlled trial to evaluate the Luminor® paclitaxel-coated DEB catheter for stenotic or occlusive lesions (length ≤15 cm) in the superficial femoral artery (SFA) and the popliteal artery (PA) up to the P1 segment compared to the noncoated, plain old balloon angioplasty (POBA) catheter. In total 172 subjects will be treated with either the DEB catheter or the POBA catheter in 11 German study centers in a 1:1 randomization study design. The primary endpoint is late lumen loss (LLL) at 6 months. Secondary endpoints are patency rate, target lesion/vessel revascularization, quality of life (assessed with the Walking Impairment Questionnaire (WIQ) and the EQ-5D), change of Rutherford stage and ankle-brachial index, major and minor amputation rate at the index limb, number of dropouts and all-cause mortality.

DISCUSSION

EffPac represents a randomized controlled trial that will provide evidence on the effectiveness of the Luminor® paclitaxel-coated DEB catheter for the reduction of restenosis compared to the POBA catheter for the SFA and the PA. The results of EffPac will allow direct comparison to other already-completed RCTs applying paclitaxel-coated DEBs from different manufacturers with different coating technologies in the same target vessel.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02540018 , registered on 17 August 2015. Protocol version: CIP Version Final04, 11 February 2016. EUDAMED No: CIV-15-03-013204.

Nanoparticle-based measurements of pH and O2 dynamics in the rhizosphere of Zostera marina L.: effects of temperature elevation and light-dark transitions

Seagrasses can modulate the geochemical conditions in their immediate rhizosphere through the release of chemical compounds from their below-ground tissue. This is a vital chemical defence mechanism, whereby the plants detoxify the surrounding sediment. Using novel nanoparticle-based optical O2 and pH sensors incorporated in reduced and transparent artificial sediment, we investigated the spatio-temporal dynamics of pH and O2 within the entire rhizosphere of Zostera marina L. during experimental manipulations of light and temperature. We combined such measurements with O2 microsensor measurements of the photosynthetic productivity and respiration of seagrass leaves. We found pronounced pH and O2 microheterogeneity within the immediate rhizosphere of Z. marina, with higher below-ground tissue oxidation capability and rhizoplane pH levels during both light exposure of the leaf canopy and elevated temperature, where the temperature-mediated stimuli of biogeochemical processes seemed to predominate. Low rhizosphere pH microenvironments appeared to correlate with plant-derived oxic microzones stimulating local sulphide oxidation and thus driving local proton generation, although the rhizoplane pH levels generally where much higher than the bulk sediment pH. Our data show that Z. marina can actively alter its rhizosphere pH microenvironment alleviating the local H2 S toxicity and enhancing nutrient availability in the adjacent sediment via geochemical speciation shift.

Photosynthetic Acclimation of Symbiodinium in hospite Depends on Vertical Position in the Tissue of the Scleractinian Coral Montastrea curta

Coral photophysiology has been studied intensively from the colony scale down to the scale of single fluorescent pigment granules as light is one of the key determinants for coral health. We studied the photophysiology of the oral and aboral symbiont band of scleractinian coral Montastrea curta to investigate if different acclimation to light exist in hospite on a polyp scale. By combined use of electrochemical and fiber-optic microsensors for O2, scalar irradiance and variable chlorophyll fluorescence, we could characterize the physical and chemical microenvironment experienced by the symbionts and, for the first time, estimate effective quantum yields of PSII photochemistry and rates of electron transport at the position of the zooxanthellae corrected for the in-tissue gradient of scalar irradiance. The oral- and aboral Symbiodinium layers received ∼71% and ∼33% of surface scalar irradiance, respectively, and the two symbiont layers experience considerable differences in light exposure. Rates of gross photosynthesis did not differ markedly between the oral- and aboral layer and curves of PSII electron transport rates corrected for scalar irradiance in hospite, showed that the light use efficiency under sub-saturating light conditions were similar between the two layers. However, the aboral Symbiodinium band did not experience photosynthetic saturation, even at the highest investigated irradiance where the oral layer was clearly saturated. We thus found a different light acclimation response for the oral and aboral symbiont bands in hospite, and discuss whether such response could be shaped by spectral shifts caused by tissue gradients of scalar irradiance. Based on our experimental finding, combined with previous knowledge, we present a conceptual model on the photophysiology of Symbiodinium residing inside living coral tissue under natural gradients of light and chemical parameters.

Fiber-Optic Probes for Small-Scale Measurements of Scalar Irradiance

A new method for producing fiber-optic microprobes for scalar irradiance (=fluence rate) measurements is described. Such fine-scale measurements are important in many photobiological disciplines. With the new method, it is possible to cast spherical 30-600 μm wide light integrating sensor tips onto tapered or untapered optical fibers. The sensor tip is constructed by first casting a clear polymethyl methacrylate (PMMA) sphere (~80% of the size of the final probe tip diameter) onto the optical fiber via dip-coating. Subsequently, the clear sphere is covered with light diffusing layers of PMMA mixed with TiO₂ until the fiber probe exhibits a satisfactory isotropic response (typically ±5-10%). We also present an experimental setup for measuring the isotropic response of fiber-optic scalar irradiance probes in air and water. The fiber probes can be mounted in a syringe equipped with a needle, facilitating retraction of the spherical fiber tip. This makes it, e.g. possible to cut a hole in cohesive tissue with the needle before inserting the probe. The light-collecting properties of differently sized scalar irradiance probes (30, 40, 100, 300 and 470 μm) produced by this new method were compared to probes produced with previously published methods. The new scalar irradiance probes showed both higher throughput of light, especially for blue light, as well as a better isotropic light collection over a wide spectral range. The new method also allowed manufacturing of significantly smaller scalar irradiance microprobes (down to 30 μm tip diameter) than hitherto possible, and such sensors allow minimally invasive high-resolution scalar irradiance measurements in thin biofilms, leaves and animal tissues.

Pronounced gradients of light, photosynthesis and O2 consumption in the tissue of the brown alga Fucus serratus

Macroalgae live in an ever-changing light environment affected by wave motion, self-shading and light-scattering effects, and on the thallus scale, gradients of light and chemical parameters influence algal photosynthesis. However, the thallus microenvironment and internal gradients remain underexplored. In this study, microsensors were used to quantify gradients of light, O2 concentration, variable chlorophyll fluorescence, photosynthesis and O2 consumption as a function of irradiance in the cortex and medulla layers of Fucus serratus. The two cortex layers showed more efficient light utilization compared to the medulla, calculated both from electron transport rates through photosystem II and from photosynthesis-irradiance curves. At moderate irradiance, the upper cortex exhibited onset of photosynthetic saturation, whereas lower thallus layers exhibited net O2 consumption. O2 consumption rates in light varied with depth and irradiance and were more than two-fold higher than dark respiration. We show that the thallus microenvironment of F. serratus exhibits a highly stratified balance of production and consumption of O2 , and when the frond was held in a fixed position, high incident irradiance levels on the upper cortex did not saturate photosynthesis in the lower thallus layers. We discuss possible photoadaptive responses and consequences for optimizing photosynthetic activity on the basis of vertical differences in light attenuation coefficients.

Combination of rotational atherothrombectomy and Paclitaxel-coated angioplasty for femoropopliteal occlusion

OBJECTIVE

The rotational atherothrombectomy with Straub Rotarex^® is a safe and efficient treatment of acute/subactute vascular occlusions. The purpose of this study was to evaluate the benefit of paclitaxel-coated angioplasty after rotational atherothrombectomy over an observation period of six months.

MATERIALS AND METHODS

Overall, 29 patients were treated with the Rotarex catheter in combination with paclitaxel-coated angioplasty. All patients had acute/subacute and chronic occlusions of the superficial femoral artery (SFA) and/or popliteal arteries. The ankle-brachial index (ABI) was detected before the intervention, after the procedure, and after six months. Also clinical examination and ultrasound scans were done in the observation period.

RESULTS

There were no technical failures. The ABI shows a significant increase from 0.52 ± 0.17 to 0.91 ± 0.25 in the follow-up. By ultrasound examination, there were found two (6.9%) restenoses during the follow-up. There was one dissection during the intervention (3.5%).

CONCLUSION

The rotational atherothrombectomy in combination with paclitaxel-coated angioplasty might be an effective and safe method with a promising low rate of restenosis at six months.

Radiative energy budget reveals high photosynthetic efficiency in symbiont-bearing corals

The light field on coral reefs varies in intensity and spectral composition, and is the key regulating factor for phototrophic reef organisms, for example scleractinian corals harbouring microalgal symbionts. However, the actual efficiency of light utilization in corals and the mechanisms affecting the radiative energy budget of corals are underexplored. We present the first balanced light energy budget for a symbiont-bearing coral based on a fine-scale study of the microenvironmental photobiology of the massive coral Montastrea curta. The majority (more than 96%) of the absorbed light energy was dissipated as heat, whereas the proportion of the absorbed light energy used in photosynthesis was approximately 4.0% under an irradiance of 640 µmol photons m(-2) s(-1). With increasing irradiance, the proportion of heat dissipation increased at the expense of photosynthesis. Despite such low energy efficiency, we found a high photosynthetic efficiency of the microalgal symbionts showing high gross photosynthesis rates and quantum efficiencies (QEs) of approximately 0.1 O2 photon(-1) approaching theoretical limits under moderate irradiance levels. Corals thus appear as highly efficient light collectors with optical properties enabling light distribution over the corallite/tissue microstructural canopy that enables a high photosynthetic QE of their photosynthetic microalgae in hospite.

Superficial femoral artery TASC D Registry: twelve-month effectiveness analysis of the Pulsar-18 SE nitinol stent in patients with critical limb ischemia

AIM

Single center observational study analyzing the primary patency rate and freedom from target lesions revascularization rate of the Pulsar-18 nitinol stent after recanalization of long superficial femoral artery (SFA) occlusions (TASC D) in 22 patients with critical limb ischemia (CLI).

METHODS

Between 1/2011 and 7/2011, 22 consecutive patients (9 male, 13 female) with chronic total occlusions (CTO) of the femoro-popliteal arteries presenting with CLI (17 patients with Rutherford 4 score, and 5 patients with Rutherford 5 score) were enrolled and successfully recanalized using the Pulsar-18 self-expanding (SE) nitinol stent (BIOTRONIK AG, Buelach, Switzerland). Primary patency at 12 months was defined as no binary restenosis (>50%) on Duplex ultrasound (PSVR<2.5) and respectively no target lesion revascularization performed within 12 months. The average lesion length of the treated femoro-popliteal segment was 315 mm. Performing spot stenting average stent length in all patients was 245 mm (minimal 215 mm, maximal 315 mm).

RESULTS

Technical success, with establishing an antegrade straight line flow to the foot through a reopened SFA, was achieved in all 22 patients. Subintimal and intraluminal recanalization techniques were used. Two patients with Rutherford 5 score had a minor amputation shortly after the recanalization procedure. All other patients had a complete wound healing of their lesions during a 6 month follow-up. After 12 month follow-up the primary patency rate of the Pulsar-18 SE nitinol stent was 77% with a per protocol restenosis in 5 of 22 patients. Seventeen patients showed a walking capacity on treadmill test >300 meters (Rutherford II). Two patients with a documented restenosis were Rutherford, these patients were treated conservatively. Three patients with restenosis and a Rutherford III score were scheduled for an endovascular target lesion revascularization leading to a freedom from target lesion revascularization rate of 86%.

CONCLUSION

Endovascular intervention of long SFA occlusions using subintimal or intraluminal recanalization technique with implantation of the Pulsar-18 SE nitinol stent in CLI patients is safe and clinically effective with a primary patency rate after 12 months of 77% and a freedom from target lesion revascularization rate of 86%.

The Parkinson's disease protein LRRK2 impairs proteasome substrate clearance without affecting proteasome catalytic activity

Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common known cause of Parkinson's disease (PD). The clinical features of LRRK2 PD are indistinguishable from idiopathic PD, with accumulation of α-synuclein and/or tau and/or ubiquitin in intraneuronal aggregates. This suggests that LRRK2 is a key to understanding the aetiology of the disorder. Although loss-of-function does not appear to be the mechanism causing PD in LRRK2 patients, it is not clear how this protein mediates toxicity. In this study, we report that LRRK2 overexpression in cells and in vivo impairs the activity of the ubiquitin-proteasome pathway, and that this accounts for the accumulation of diverse substrates with LRRK2 overexpression. We show that this is not mediated by large LRRK2 aggregates or sequestration of ubiquitin to the aggregates. Importantly, such abnormalities are not seen with overexpression of the related protein LRRK1. Our data suggest that LRRK2 inhibits the clearance of proteasome substrates upstream of proteasome catalytic activity, favouring the accumulation of proteins and aggregate formation. Thus, we provide a molecular link between LRRK2, the most common known cause of PD, and its previously described phenotype of protein accumulation.

[Results of surgical treatment of dislocation fractures of the ankle joint]

The authors have made evaluation of the surgical treatment of luxation fractures of the ankle in the period 1979-1987 in 105 patients (60 female, 45 male patients) in the age range from seventeen to eighty-one years, with the most frequent representation of the age group ranging from thirty-five to forty-five years. The group comprised 2,70 percent of fractures of type Weber A, 31.53 percent of fractures of type Weber B and 65.77 percent of fractures of type Weber C. 53 percent of patients were operated on the day of injury, 24.8 percent of patients were transferred with a delay from other clinics and in the rest of the patients the timely operation was contraindicated because of the poor local or general condition. The results were processed according to a uniform worksheet by the computer. On the basis of the evaluation there were found out 87.62 percent of successful and 12.38 percent of poor results. 93.3 percent of patients resumed their original jobs and there was no patient eligible for a full disability pension. The main cause of failure was the osteoarthritis of the ankle joint found out in connection with the inaffestable factors (such as defects of cartilage, nature of the bone lesion, luxation of talus, age and sex of the patient) and affectable factors (infection, failure of osteosynthesis, pseudoarthrosis of medial malleolus, non-anatomical position in the area of tibiofibular syndesmosis). The incidence of these negative factors may be reduced by a timely operation, precise surgical strategy and technique and proper post-operative treatment.