23 research outputs found
Galleria mellonella: an in vivo model for accessing the efficacy of colistin in combination with broad spectrum antibiotics against biofilm forming Acinetobacter baumannii infections
Get PDFThe emergence of opportunistic nosocomial bacteria Acinetobacter baumannii, which causes infections in critically ill patients with compromised immune systems, is one of the most clinically challenging pathogens to treat effectively.
Most nosocomial pathogens grow as monoculture or poly-species biofilms in infections and the biofilm mode of existence for A. baumannii may almost certainly contribute to its increased multi-drug resistant (MDR), although resistance can also be attributed to many contributing factors including overuse and misuse of antibiotics in hospitals and the community.
In vitro methods for studying microbial biofilms have developed to include the CDC biofilm reactor, Flow cell devices and MBECâ„¢ but in vivo biofilm model development has been very limited. Few simple animal models are available which reflect either the biofilm nature of growth of pathogens or the treatment of infection influenced by biofilm development in vivo. Biofilm formation is a critical virulence and defence strategy for bacteria, the present study focuses on working towards establishing a biofilm generated in-vivo model to assess the efficacy of antimicrobials against A. baumannii infections.
The present study looks at the effects of broad spectrum antibiotics (BSA) and colistin combinations against lethal planktonic or biofilm A. baumannii infections with a pre-clinical insect model, Galleria mellonella (Greater wax moth larvae). The work shows colistin to be an important synergist both in vitro and in a simple in vivo model. This work is the first to describe a model biofilm associated infection in G. mellonella
Influencing the attachment of bacteria through laser surface engineering
Get PDFAlso published in Journal of Laser Applications (2017). eISSN - 1938-1387.Bacteria have evolved to become proficient at adapting to both extracellular and environmental conditions, which has made it possible for them to attach and subsequently form biofilms on varying surfaces. This has resulted in major health concerns and economic burden in both hospital and industrial environments. Surfaces which prevent this bacterial fouling through their physical structure represent a key area of research for the development of antibacterial surfaces for many different environments. Laser surface treatment provides a potential candidate for the production of anti-biofouling surfaces for wide ranging surface applications within healthcare and industrial disciplines. In the present study, a KrF 248 nm Excimer laser was utilized to surface pattern Polyethylene terephthalate (PET). The surface topography and roughness were determined with the use of a Micromeasure 2, 3D profiler. Escherichia coli (E. coli) growth was analysed at high shear flow using a CDC Biofilm reactor for 48 hours, scanning electron microscopy was used to determine morphology and total viable counts were made. Through this work it has been shown that the surface modification significantly influenced the distribution and morphology of the attached E. coli cells. What is more, it has been evidenced that the laser-modified PET has been shown to prevent E. coli cells from attaching themselves within the laser-induced micro-surface-features
High speed CO2 laser surface modification of iron/cobalt co-doped boroaluminosilicate glass
Get PDFThis document is the Accepted Manuscript version of a published work that appeared in final form in Laser Physics Letters. To access the final edited and published work see http://dx.doi.org/10.1088/1612-2011/13/7/076102A preliminary study into the impact of high speed laser processing on the surface of iron and cobalt co-doped glass substrates using a 60 W continuous wave (cw) CO2 laser. Two types of processing, termed fill-processing and line-processing, were trialled. In fill-processed samples the surface roughness of the glass was found to increase linearly with laser power from an Sa value of 20.8 nm–2.1 μm at a processing power of 54 W. With line processing, a more exponential-like increase was observed with a roughness of 4 μm at 54 W. The change in surface properties of the glass, such as gloss and wettability, have also been measured. The contact angle of water was found to increase after laser processing by up to 64°. The surface gloss was varied between 45 and 100 gloss units (GUs)
Surface treatments to modulate bioadhesion: A critical review
Get PDFOn account of the recent increase in importance of biological and microbiological adhesion in industries such as healthcare and food manufacturing many researchers are now turning to the study of materials, wettability and adhesion to develop the technology within these industries further. This is highly significant as the stem cell industry alone, for example, is currently worth £3.5 million in the United Kingdom (UK) alone. This paper reviews the current state-of-the-art techniques used for surface treatment with regards to modulating biological adhesion including laser surface treatment, plasma treatment, micro/nano printing and lithography, specifically highlighting areas of interest for further consideration by the scientific community. What is more, this review discusses the advantages and disadvantages of the current techniques enabling the assessment of the most attractive means for modulating biological adhesion, taking in to account cost effectiveness, complexity of equipment and capabilities for processing and analysis
Chaotic zone boundary for low free eccentricity particles near an eccentric planet
Full text linkWe consider particles with low free or proper eccentricity that are orbiting
near planets on eccentric orbits. Via collisionless particle integration we
numerically find the location of the boundary of the chaotic zone in the
planet's corotation region. We find that the distance in semi-major axis
between the planet and boundary depends on the planet mass to the 2/7 power and
is independent of the planet eccentricity, at least for planet eccentricities
below 0.3. Our integrations reveal a similarity between the dynamics of
particles at zero eccentricity near a planet in a circular orbit and with zero
free eccentricity particles near an eccentric planet. The 2/7 law has been
previously explained by estimating the semi-major at which the first order mean
motion resonances are large enough to overlap. Orbital dynamics near an
eccentric planet could differ due to first order corotation resonances that
have strength proportional to the planet's eccentricity. However, we find the
corotation resonance width at low free eccentricity is small. Also the first
order resonance width at zero free eccentricity is the same as that for a zero
eccentricity particle near a planet in a circular orbit. This accounts for
insensitivity of the chaotic zone width to planet eccentricity. Particles at
zero free eccentricity near an eccentric planet have similar dynamics to those
at zero eccentricity near a planet in a circular orbit.Comment: accepted for publication in MNRA
An Integrated Approach to Understand Relationships Between Shallow Water Benthic Community Structure and Ecosystem Function SERDP Project SI-1335
Get PDFHuman activities along our nation\u27s coasts often lead to habitat modification, pollution, and overexploitation of living resources in coastal and estuarine waters (U.S. Commission on Ocean Policy 2004). Coastal areas are the most developed regions of the United States. In addition to recreational and leisure activities, these areas support commercial fishing, aquaculture, shipping, and defense activities. Numerous human activities can have detrimental effects on biodiversity and the provision of ecosystem services that support and sustain human populations. Given their proximity to the land and human population centers, nearshore estuarine ecosystems are especially vulnerable. Effective management can be improved with a better understanding of relationships between ecological integrity and human pressures in these ecosystems (National Estuary Program 2007). Ecologists, coastal managers, and policy-makers are working together to develop better ways to measure and manage human effects on estuarine and coastal ecosystems. Management strategies can be framed in the context of human actions (pressure or stressor), resulting effects on community structure and ecosystem functions (state or condition), and management response
Action 3:30R: Results of a cluster randomised feasibility study of a revised teaching assistant-led extracurricular physical activity intervention for 8 to 10 year olds
Get PDFMany children are not sufficiently physically active. We conducted a cluster-randomised feasibility trial of a revised after-school physical activity (PA) programme delivered by trained teaching assistants (TAs) to assess the potential evidence of promise for increasing moderate-to-vigorous physical activity (MVPA). Participants (n = 335) aged 8–10 years were recruited from 12 primary schools in South West England. Six schools were randomised to receive the intervention and six acted as non-intervention controls. In intervention schools, TAs were trained to deliver an after-school programme for 15 weeks. The difference in mean accelerometer-assessed MVPA between intervention and control schools was assessed at follow-up (T1). The cost of programme delivery was estimated. Two schools did not deliver the intervention, meaning four intervention and six control schools were analysed at T1. There was no evidence for a difference in MVPA at T1 between intervention and control groups. Programme delivery cost was estimated at £2.06 per pupil per session. Existing provision in the 12 schools cost £5.91 per pupil per session. Action 3:30 was feasible to deliver and considerably cheaper than existing after-school provision. No difference in weekday MVPA was observed at T1 between the two groups, thus progression to a full trial is not warranted
Using sub-micron silver-nanoparticle based films to counter biofilm formation by Gram-negative bacteria
Get PDFComposite films comprised of silver nanoparticles (AgNPs) grown using a low-cost straightforward chemical bath based method have been deposited on glass microscope slides to investigate their potential as a sacrificial antibacterial coating. The as-deposited films have been characterised using scanning electron microscopy (SEM) and optical profilometry. These suggested that the films were relatively uniform in coverage. Chemical composition of the AgNP films has been studied by using x-ray photoelectron spectroscopy (XPS). The XPS analysis indicated that the Ag was in a metallic form able to sustain plasmon behaviour, and that low levels of residual nanoparticle precursors were present. Particle size was characterised using transmission electron microscopy (TEM) which showed an average particle size of 10.6 nm. The effectiveness of the films as an antibacterial coating was tested against Escherichia coli. The AgNP film was determined to be effective in the killing of E.coli cells over a 24 hour period when compared to equivalent samples that contained no silver. Of particular note was that only minimal bacterial growth was detected over the first 12 hours of testing, up to 78.6 times less than the control samples, suggesting the film is very efficient at slowing initial biofilm formation. The use of AgNP based films that have been synthesised using a novel low-cost, low-temperature and highly upscalable method is demonstrated as a promising solution for the deployment of silver as an effective sacrificial antimicrobial coating to counter the formation of potentially hazardous Gram negative biofilms
Risk estimation of distant metastasis in node-negative, estrogen receptor-positive breast cancer patients using an RT-PCR based prognostic expression signature
Get PDF<p>Abstract</p> <p>Background</p> <p>Given the large number of genes purported to be prognostic for breast cancer, it would be optimal if the genes identified are not confounded by the continuously changing systemic therapies. The aim of this study was to discover and validate a breast cancer prognostic expression signature for distant metastasis in untreated, early stage, lymph node-negative (N-) estrogen receptor-positive (ER+) patients with extensive follow-up times.</p> <p>Methods</p> <p>197 genes previously associated with metastasis and ER status were profiled from 142 untreated breast cancer subjects. A "metastasis score" (MS) representing fourteen differentially expressed genes was developed and evaluated for its association with distant-metastasis-free survival (DMFS). Categorical risk classification was established from the continuous MS and further evaluated on an independent set of 279 untreated subjects. A third set of 45 subjects was tested to determine the prognostic performance of the MS in tamoxifen-treated women.</p> <p>Results</p> <p>A 14-gene signature was found to be significantly associated (p < 0.05) with distant metastasis in a training set and subsequently in an independent validation set. In the validation set, the hazard ratios (HR) of the high risk compared to low risk groups were 4.02 (95% CI 1.91–8.44) for the endpoint of DMFS and 1.97 (95% CI 1.28 to 3.04) for overall survival after adjustment for age, tumor size and grade. The low and high MS risk groups had 10-year estimates (95% CI) of 96% (90–99%) and 72% (64–78%) respectively, for DMFS and 91% (84–95%) and 68% (61–75%), respectively for overall survival. Performance characteristics of the signature in the two sets were similar. Ki-67 labeling index (LI) was predictive for recurrent disease in the training set, but lost significance after adjustment for the expression signature. In a study of tamoxifen-treated patients, the HR for DMFS in high compared to low risk groups was 3.61 (95% CI 0.86–15.14).</p> <p>Conclusion</p> <p>The 14-gene signature is significantly associated with risk of distant metastasis. The signature has a predominance of proliferation genes which have prognostic significance above that of Ki-67 LI and may aid in prioritizing future mechanistic studies and therapeutic interventions.</p
