The interaction of wood nanocellulose dressings and the wound pathogen P. aeruginosa

Chronic wounds pose an increasingly significant worldwide economic burden (over £1 billion per annum in the UK alone). With the escalation in global obesity and diabetes, chronic wounds will increasingly be a significant cause of morbidity and mortality. Cellulose nanofibrils (CNF) are highly versatile and can be tailored with specific physical properties to produce an assortment of three-dimensional structures (hydrogels, aerogels or films), for subsequent utilization as wound dressing materials. Growth curves using CNF (diameter 0.05) over 24 h. These data demonstrate the potential of nanocellulose materials in the development of novel dressings that may afford significant clinical potential

Cellulose nanofibril formulations incorporating a low molecular weight alginate oligosaccharide modify bacterial biofilm development

Cellulose nanofibrils (CNFs) from wood pulp are a renewable material possessing advantages for biomedical applications, due to their customizable porosity, mechanical strength, translucency and environmental biodegradability. Here we investigated the growth of multi-species wound biofilms on CNF formulated as aerogels and films incorporating the low molecular weight alginate oligosaccharide OligoG CF-5/20 to evaluate their structural and antimicrobial properties. Overnight microbial cultures were adjusted to 2.8 x 109 colony forming units (cfu) mL-1 in Mueller Hinton broth and growth rates of P. aeruginosa PAO1 and S. aureus 1061A monitored for 24 h in CNF dispersions sterilized by γ-irradiation. Two CNF formulations were prepared (20 g m-2) with CNF as air-dried films or freeze-dried aerogels, with or without incorporation of an antimicrobial alginate oligosaccharide (OligoG CF-5/20) as a surface coating or bio-nanocomposite respectively. The materials were structurally characterized by Scanning Electron Microscopy (SEM) and laser profilometry (LP). The antimicrobial properties of the formulations were assessed using single- and mixed-species biofilms grown on the materials and analysed using LIVE/DEAD® staining with confocal laser scanning microscopy (CLSM) and COMSTAT software. OligoG-CNF suspensions significantly decreased the growth of both bacterial strains at OligoG concentrations >2.58% (P<0.05). SEM showed that aerogel-OligoG bio-nanocomposite formulations had a more open 3-dimensional structure, while LP showed film formulations coated with OligoG were significantly smoother than untreated films or films incorporating PEG400 as a plasticizer (P<0.05). CLSM of biofilms grown on films incorporating OligoG demonstrated altered biofilm architecture, with reduced biomass and decreased cell-viability. The OligoG-CNF formulations as aerogels or films both inhibited pyocyanin production (P<0.05). These novel CNF formulations or bio-nanocomposites were able to modify bacterial growth, biofilm development and virulence factor production in vitro. These data support the potential of OligoG and CNF bio-nanocomposites for use in biomedical applications where prevention of infection or biofilm growth is required

Bacterial Load in Daily Urine Samples of Patients Infected with Mycoplasma genitalium, Mutation Analysis, and Response to Treatment

Objective. Increasing macrolide resistant strains of Mycoplasma genitalium is a challenge, and to differentiate between treatment failure and reinfection a timely test of cure (TOC) is warranted. The aim of this study was to evaluate the best time for TOC after five days’ treatment of Mycoplasma genitalium infection with azithromycin. Methods. Nineteen patients with positive PCR for Mycoplasma genitalium in urine provided urine samples daily for 2 weeks and on days 21, 28, and 35. Samples were tested by a commercial qPCR and by sequencing of the 23S rRNA gene. Results. Eight patients with a wild type of Mycoplasma genitalium responded successfully within four days after treatment initiation. Eleven patients had a mutation in the 23S rRNA gene. These samples exhibited high variations in bacterial load, and some patients tested negative at several time points during the observation period. Conclusions. Day-to-day fluctuations in the mutation samples allow for false negative TOC during the first 5 weeks after start of treatment. Due to increasing macrolide resistance of Mycoplasma genitalium, pretreatment mutation analysis is recommended. When a wild type is verified, TOC performed one week after initiation of treatment is suggested

Bacterial Load in Daily Urine Samples of Patients Infected with Mycoplasma genitalium, Mutation Analysis, and Response to Treatment

Objective. Increasing macrolide resistant strains of Mycoplasma genitalium is a challenge, and to differentiate between treatment failure and reinfection a timely test of cure (TOC) is warranted. The aim of this study was to evaluate the best time for TOC after five days’ treatment of Mycoplasma genitalium infection with azithromycin. Methods. Nineteen patients with positive PCR for Mycoplasma genitalium in urine provided urine samples daily for 2 weeks and on days 21, 28, and 35. Samples were tested by a commercial qPCR and by sequencing of the 23S rRNA gene. Results. Eight patients with a wild type of Mycoplasma genitalium responded successfully within four days after treatment initiation. Eleven patients had a mutation in the 23S rRNA gene. These samples exhibited high variations in bacterial load, and some patients tested negative at several time points during the observation period. Conclusions. Day-to-day fluctuations in the mutation samples allow for false negative TOC during the first 5 weeks after start of treatment. Due to increasing macrolide resistance of Mycoplasma genitalium, pretreatment mutation analysis is recommended. When a wild type is verified, TOC performed one week after initiation of treatment is suggested

Evaluation of treatment with two weeks of doxycycline on macrolide-resistant strains of Mycoplasma genitalium: a retrospective observational study

Background Increasing macrolide resistance makes treatment of Mycoplasma genitalium infections challenging. The second-line treatment is moxifloxacin, an antibiotic drug best avoided due to the potential of severe side effects and interactions. This study evaluates the effects of treatment with doxycycline 100 mg twice daily for 2 weeks as an alternative to moxifloxacin. Methods This retrospective observational study examined the medical records of patients testing positive for macrolide resistant Mycoplasma genitalium from January 1st, 2016 to September 1st, 2019 in Trondheim, Norway. Information regarding symptoms as well as clinical and microbiological cure was collected. Results 263 infections from 259 patients (161 females/98 males) were examined. 155 (58.9%) had a negative test of cure following treatment. 34.7% of symptomatic patients not achieving microbiological cure experienced symptom relief or clearance. There was no statistical difference between bacterial loads in symptomatic versus asymptomatic patients. The mean difference was 1.6 × 105 copies/ml (95% CI − 1.4 × 105–4.8 × 105, p = 0.30) for women and 1.4 × 106 copies/ml (95% CI -4.0 × 105–3.2 × 106, p = 0.12) for men. Conclusions The cure rate of doxycycline in this study is higher than previously reported. This adds support to doxycycline’s role in treatment before initiating treatment with less favorable drugs such as moxifloxacin

Cytotoxicity and effect on wound re-epithelialization after topical administration of tranexamic acid

Background Topical administration of tranexamic acid (TXA) reduces bleeding from surgical wounds similarly to intravenous use, but with negligible risk of adverse systemic events. Topical use is expanding, but is off‐label. Surgeons lack guidelines regarding safe topical dosages and modes of administration. The effects of topical TXA on skin cells and wound healing are unknown. This study investigated whether topical TXA might be cytotoxic or affect wound re‐epithelialization. Methods Human keratinocytes and fibroblast cell cultures and an ex vivo human skin wound model were subjected to both short (limited) and long (chronic) exposure to various clinically relevant concentrations of TXA to mimic different modalities of topical administration. Cytotoxicity and effects on wound re‐epithelialization were evaluated. Results In cell culture, toxicity from chronic exposure was associated with increasing concentration and exposure time. Limited exposure to TXA did not cause significant cytotoxicity even at high concentrations. Re‐epithelialization was completely absent in wounds chronically exposed to TXA concentrations of 25 mg/ml or above, and 50–100 mg/ml induced epidermolysis of normal epithelium, possibly by a non‐toxic mechanism. Wound re‐epithelialization was slightly delayed, but not impaired, by limited exposure to 100 mg/ml or chronic exposure to 6·25 mg/ml. Conclusion Although short exposure to even high concentrations of topical TXA seems well tolerated in vitro, prolonged exposure can be cytotoxic and may affect wound re‐epithelialization. Surgeons should adjust the TXA concentration to the planned mode of topical administration in clinical practice

Hyperspectral characterization of re‐epithelialization in an in vitro wound model

In vitro wound models are useful for research on wound re‐epithelialization. Hyperspectral imaging represents a non‐destructive alternative to histology analysis for detection of re‐epithelialization. This study aims to characterize the main optical behavior of a wound model in order to enable development of detection algorithms. K‐Means clustering and agglomerative analysis were used to group spatial regions based on the spectral behavior, and an inverse photon transport model was used to explain differences in optical properties. Six samples of the wound model were prepared from human tissue and followed over 22 days. Re‐epithelialization occurred at a mean rate of 0.24 mm2/day after day 8 to 10. Suppression of wound spectral features was the main feature characterizing re‐epithelialized and intact tissue. Modeling the photon transport through a diffuse layer placed on top of wound tissue properties reproduced the spectral behavior. The missing top layer represented by wounds is thus optically detectable using hyperspectral imagin

Producing ultrapure wood cellulose nanofibrils and evaluating the cytotoxicity using human skin cells

Wood cellulose nanofibrils (CNF) have been suggested as a potential wound healing material, but its utilization is limited by FDA requirements regarding endotoxin levels. In this study a method using sodium hydroxide followed by TEMPO mediated oxidation was developed to produce ultrapure cellulose nanofibrils, with an endotoxin level of 45 endotoxin units/g (EU/g) cellulose. Scanning transmission electron microscopy (S(T)EM) revealed a highly nanofibrillated structure (lateral width of 3.7 ± 1.3 nm). Assessment of cytotoxicity and metabolic activity on Normal Human Dermal Fibroblasts and Human Epidermal Keratinocytes was done. CNF-dispersion of 50 μg/ml did not affect the cells. CNF-aerogels induced a reduction of metabolic activity by the fibroblasts and keratinocytes, but no significant cell death. Cytokine profiling revealed no induction of the 27 cytokines tested upon exposure to CNF. The moisture-holding capacity of aerogels was relatively high (∼7500%), compared to a commercially available wound dressing (∼2500%), indicating that the CNF material is promising as dressing material for management of wounds with a moderate to high amount of exudate

Ultrapure Wood Nanocellulose - Assessments of Coagulation and Initial Inflammation Potential

Using a lepirudin-based human whole blood model, we evaluated the initial inflammatory and coagulation responses of dense and porous ultrapure (<50 endotoxin units/grams) cellulose nanofibrils (CNF), of carboxylated grade. The CNF was compared to the wound dressing AquaCel because it is a potential wound-healing material. The porous CNF aerogels induced the strongest coagulation potential measured as prothrombin factor 1.2 (PTF1.2). AquaCel induced the strongest complement response by terminal complement complex (TCC) and surface C3c. All materials activated leukocytes CD11b, while the levels of only 3 of 27 cytokines were significantly changed, limited to (i) an elevation of the monocyte chemoattractant protein-1 (MCP-1/CCL) by the CNF aerogel, (ii) a reduction of eosinophil chemotactic proteins (eotaxin/CCL11) by the CNF aerogel, and (iii) a reduction of platelet-derived growth factor BB (PDGF-BB) by all CNF materials. In conclusion, the CNF materials and AquaCel differently activate coagulation, complement, and cytokines, improving the selection possibilities in various treatment situations of wound healing

Hyperspectral characterization of an in vitro wound model

Wound healing is a complex process not fully understood. There is a need of better methods to evaluate the different stages of healing, and optical characterization is a promising tool in this respect. In this study hyperspectral imaging was employed to characterize an in vitro wound model. The wound model was established by first cutting circular patches of human abdominal skin using an 8mm punch biopsy tool, and then creating dermal wounds in the center of the skin patches using a 5mm tool. The wounds were incubated in medium with 10% serum and antibiotics. Hyperspectral images were collected every three days using a push broom hyper spectral camera (Hyspex VNIR1600). The camera had a spectral resolution of 3.7 nm and was fitted with a close up lens giving a FOV of 2.5 cm and a spatial resolution of 29 micrometer. Samples for histology were collected throughout the measurement period, which was 21 days in total. Data were processed in ENVI and Matlab. A successful classification based on hyperspectral imaging of the implemented model is presented. It was not possible to see the healing zone in the in vitro model with the naked eye without dying. The hyperspectral results showed that newly formed epithelium could be imaged without any additional contrast agents or dyes. It was also possible to detect non-viable tissue. In vitro wound models and hyperspectral imaging can thus be employed to gain further insight in the complicated process of healing in different kinds of wounds. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only