Infection control is an area of increasing interest due to the failure of traditional disinfection and sterilisation methods, and of course, the significant problems associated with microbial multiple-antibiotic resistance. This study investigated light-based methods for the inactivation of a range of medically important bacteria. Initial investigations involved the design and development of a PUV-light airdisinfection system for the control and prevention of airborne infection. This system was tested in-situ for its efficiency to decontaminate air in university lecture theatres. Results demonstrated an 80% reduction in the level of airborne bacterial population, with the majority of the surviving isolates being saprophytic, pigmented Micrococcus spp. which pose no risk to human health. The second, and most significant, area of this study was the discovery, development and application of a visible-light treatment for the inactivation of MRSA and other medically important Gram-positive bacteria including Clostridium, coagulasenegative Staphylococcus, Streptococcus and Enterococcus species. The lethality of blue-light, and white-light containing blue-light, for these organIsms was demonstrated through a series of filter studies, and identification of the causative wavelengths to within a 10 nm bandwidth allowed the selection of a more efficient high-intensity narrow-band light source, now termed HlNS-light. Based on experimental data obtained from this study, it is proposed that Staphylococcus inactivation by blue light is brought about through singlet oxygen e02) generation by the photo-excitation of naturally-occurring endogenous porphyrins within the bacteria. This process has not previously been documented as a possible inactivation pathway for Staphylococcus aureus. Although not as germicidally efficient as UV-light, this HlNS-light system has the great advantage of being non-detrimental to human health, thus posing no problems with continuous exposure in occupied rooms, such as hospital wards. Consequently, HINS-light may prove to be an effective, non-harmful method for the control and prevention of MRSA transmission within the health-care environment.

No description available.

No description available.

Hospital acquired infection affects approximately 10% of patients admitted to hospital, and is responsible for over 5000 deaths in the UK annually. The cost to the NHS has been estimated at around £1 bn per year. Infections acquired during invasive procedures have particularly high mortality rates, and the majority of these infections are thought to be caused by airborne bacteria present during procedures. High-intensity narrow-spectrum (HINS) light is a novel light-based disinfection system which may be able to aid in the continuous battle against bacteria. HINS-light has been shown to have bactericidal properties, causing near complete inactivation of a number of medically relevant bacteria. The purpose of this study was to investigate potential patient-based applications of HINS-light, to establish if HINS-light could be used during invasive procedures where exposure of tissue to HINS-light would occur. The effect of HINS-light on wound healing was investigated with a fibroblast populated collagen lattice (FPCL) wound model. High intensities of HINS-light (15 mWcm-2: 1 hour exposure) were found to delay FPCL contraction, inhibit α-smooth muscle actin expression and reduce cell viability. Exposure to intensities at and below 5 mWcm-2 for 1 hour had no significant inhibitory effects on any measured aspect of fibroblast function. Infection is a significant risk in orthopaedic joint replacement procedures. To establish if HINS-light could be employed to reduce the number of bacteria present during these procedures without damaging exposed bone tissue, osteoblast cells were exposed to HINS-light. Cell viability was assessed via alkaline phosphatase assay, osteoblast collagen production, osteocalcin expression, and microscopy techniques. Exposure to 15 mWcm-2 HINS-light for 1 hour was found to have inhibitory effects, while exposure to 5 mWcm-2 and below for 1 hour had no significant effects. Having established that 5 mWcm-2 HINS-light could be applied to mammalian cells for 1 hour without significant detrimental effects, this dose was applied to polyester prosthetic vascular graft materials. This dose of HINS-light had no significant effects on the mechanical properties of the tested materials, and caused no visible damage. Extracts produced after treatment of the materials with HINS-light did not cause cytotoxicity to human aortic smooth muscle cells. The bactericidal effects of 5 mWcm-2 HINS-light were investigated on various clinically relevant bacterial species with variable success. Significant reductions in populations of Staphylococcus epidermidis, Staphylococcus aureus and Methicillin resistant Staph. aureus could be achieved when exposed to HINS-light in liquid suspension, with lesser inactivation of Acinetobacter baumannii and Pseudomonas aeruginosa, and no effect on populations of Escherichia coli. However, reduced inactivation rates for all bacteria were observed when exposing the bacteria on agar surfaces, a situation which closer resembles the wound environment. Despite showing that a bactericidal level HINS-light exposure could be established that would not be detrimental to living tissue, the bactericidal benefits of this dose may not be sufficiently beneficial for medical use in practice. Reduced bacterial inactivation by HINS-light in nutritious environments such as a wound bed, combined with the limited penetration into tissue, suggest that the ability of HINS-light to reduce the number of bacteria in a wound would be limited. It is suggested that medical uses of HINS-light should focus on environmental disinfection, and decontamination of medical devices, rather than direct disinfection of wounds.

Hygienic food contact surfaces are inert, hard and easy to clean. Aggressive cleaning and disinfection regimes, and general usage and wear, may damage the integrity of the surface, and the resultant defects – pits or scratches – increase the roughness of the surface and potentially affect subsequent cleanability by retaining microorganisms and organic soil. It is generally acknowledged that an increase in surface roughness, often measured using the Ra parameter (the average departure of the surface profile from a centre line) increases the retention of microorganisms on a surface, although feature dimension may also have some influence. The retention of more amorphous organic (food) soil is less affected by the feature dimension, but is likely to be enhanced by any increase in Ra value. The aim of this project was to explore the relationship between surface topography and microbial cell retention on surfaces via the use of surfaces with defined linear features, and with defined chemical properties. Stainless steel is the most commonly used material for hygienic surfaces, but its surface chemistry can be complex. Thus, in order to explore the effect of topography in a controlled manner, test surfaces were coated with titanium, using plasma vapour deposition. A novel impression technique was developed, using acetate softened with acetone pressed against in-use stainless steel surfaces, which when hardened could be removed and examined using atomic force microscopy and scanning electron microscopy. The diameter and profile of typical linear features were measured, enabling model surfaces to be constructed in vitro. Thirty micrometre diameter features were reproduced using nano-indentation, but microorganisms tended to be retained on the edges of the features, rather than within them, because there was accumulation of debris at the edges whose smaller feature size provided increased surface area for microbial retention. Consequently, attention was focused on linear features of microbial dimensions approximating to one and 0.5 micrometer width. These were conveniently obtained by titanium-coating CDs (feature size 1.02 µm, Ra 0.042 µm) and DVDs (feature size 0.59 µm, Ra 0.024 µm) respectively. Escherichia coli did not adhere well to the titanium-coated test surfaces. When stainless steel surfaces were coated with titanium, the same phenomenon was observed: thus it was the surface chemistry rather than topography which reduced microbial retention. In the presence of an organic (meat) soil, retention was again lower on the titanium surface. Thus E.coli was not used in subsequent work, although the potential for titanium coatings to reduce fouling by this species should be explored further. Listeria monocytogenes and Staphylococcus sciuri were used subsequently, representing different shaped microorganisms related to food-borne illness (S.scuiri being related to Staphylococcus aureus). Retention of bacteria on the test surfaces was assessed by incubating cells and surfaces for 1h, gently rinsing, and examining and enumerating retained cells via scanning electron microscopy. Retention was related to cell size and feature size: the spherical staphylococci were preferentially retained on the 1.0 micrometer featured surfaces, being effectively wedged within the features, whilst L.monocytogenes was preferentially retained on the 0.5micrometer featured surfaces, because cell-surface contact was maximised by the increased density of ‘peaks’ on the surface, with the rod-shaped cells lying across and along the linear features. Epifluorescence microscopy was attempted, after staining attached cells with acriding orange, but the relationship between cells and surface features could not be visualised. The strength of attachment rather than the amount of attachment was measured using atomic force microscopy, by application of an increasing lateral force on attached cells, and assessment of the number of scans required to remove cells. Results were similar to those obtained in retention assays, with the S. sciuri retained in highest numbers on the 1 µm features and the least on the 0.5 µm features, emphasising the importance of the relationship between cell size and feature size. Again E.coli could not be used, since it did not adhere: when combined with organic material, the AFM probe could not be used. A more realistic physical removal strategy was applied via repeated physical ‘wipes’ with a mechanised device and water, subsequent to fouling of surfaces with soil, or cells, or a cell-soil mixture. Different fluorescent stains were applied that stained either soil or cells, enabling differential analysis of the area of a microscopic field covered by cells or soil. Whether there was a single fouling event, or sequential fouling-cleaning events, increasing wipes removed increasing amounts of cells and/or soil, and wipes applied along surface features were more effective at removal than wipes applied across the features. Results have revealed that the relationship between cell size and linear feature width and orientation is key to determining whether or not cells are retained on surfaces: the Ra value is of less importance. The direct relationship that is often proposed to exist between Ra value and cell retention is only likely to be true within particular ranges: if the surface features are larger than microbial cells, the cells may not be retained; similarly with features smaller than the diameter of cells. If features are of microbial dimensions, then enhanced retention might be anticipated. Organic food soil is more heterogeneous, thus is retained in features irrespective of feature size, although removal is improved from larger features. Thus rather than merely measuring the Ra, it would appear to be important to assess feature dimension in relation to the size of the microorganism of concern in a given environment. The range of methods used in this study have helped interpretation of a complex interaction between cells, soil, surface and its topography and chemistry. The work described will be useful for exploring these phenomena further, and in the assessment of the effectiveness of putative novel antimicrobial surfaces and/or cleaning regimens used in different environments.

Healthcare associated infections (HCAI) are a significant problem facing modern healthcare settings; therefore it is important to develop strategies aimed at reducing the number of patients contracting HCAIs. This study investigates the use of essential oils (EO) as antimicrobial additives for polymer materials, including surface coatings (paints), silicone elastomer and a thermoplastic. Conferring antimicrobial properties to surfaces made from such materials, would help to reduce the number of bacteria, reduce the risk of cross infection and therefore limit the number of HCAIs. The antimicrobial efficacies of five EOs (manuka (MO), oregano (OO), rosewood (RO), lavender (LO) and geranium (GO)) were examined individually against three microorganisms associated with HCAI (MRSA, Acinetobacter baumannii, and Pseudomonas aeruginosa). Oregano oil provided the highest level of antimicrobial activity, inhibiting the growth of all three bacteria at 2.5 % (v/v). In an attempt to reduce the concentration of oil required for inhibition of growth, blends of the EO have been explored. A blend of oregano oil and rosewood oil exhibited the strongest synergistic antimicrobial effect at a ratio of 3:1, and was selected as the antimicrobial to be added to the polymer materials. EOs are volatile, direct addition to polymers may allow the EO to bloom to the surface and rapidly evaporate from the polymer, resulting in loss of antimicrobial activity. Furthermore thermoplastics are processed at high temperatures which can result in degradation of the EO. Encapsulation strategies for the EO were therefore investigated in order to promote both sustained release of the EO and protection against degradation / volatilisation during blending in to thermoplastic materials. Considering the latter in particular, inorganic adsorbents were selected and the adsorption characteristics of the EOs onto a range of natural and synthetic montmorillonite type layered silicates were investigated. Using gas chromatography and flow micro-calorimetry their suitability as controlled release reservoirs was investigated. Rockwood Additives Laponite® RD provided the highest levels of adsorption, achieving approximately 170 mg.g-1 for oregano oil and 140 mg.g-1 for rosewood oil. Organic modification (via cation exchange) of the layered silicates with alkyl ammonium surfactants did not give the anticipated increase in the level of EO adsorption from solution. However the strength of adsorption was in some cases increased. Laponite® RD with 50 % 2HT2M organic modification (modified via cation exchange using dihydrogenated tallow dimethyl ammonium chloride) was selected as the adsorption substrate for the EO based antimicrobial. Samples of linear low density polyethylene (LLDPE), silicone elastomer (SE) and a solvent based paint were formulated containing the oregano oil:rosewood oil blend pre-adsorbed onto Laponite® RD with 50 % 2HT2M organic modification. These materials were tested for antimicrobial efficacy against MRSA and A. baumannii, and the results were compared to control polymers where the EO blend had been added directly. P. aeruginosa was found to be unsuitable as a test organism for the polymer samples. All of the polymer samples containing the EO blend exhibited antimicrobial activity, with SE containing the pre-adsorbed EO blend performing the best achieving a 3 log reduction in MRSA cells. The SE and paint materials containing the preadsorbed EO blend outperformed the directly added EO controls; however the reverse was true for LLDPE. The release rates of the EO molecules from the polymers were investigated using headspace gas chromatography, and it was found that pre-adsorption of the EO onto the organically modified Laponite® RD more than doubled the time the EO molecules were retained in comparison to the directly added controls. It has been shown that EO can be used to obtain antimicrobials with broad spectrum antimicrobial activity, and that said activity can be successfully conferred onto polymer materials. Adsorption of the EO onto layered silicates before addition to polymers improved the retention of the EO molecules, thereby increasing the antimicrobial lifetime. Further work will be undertaken to optimise the EO polymer formulations, to combine the best possible antimicrobial activity with EO molecule retention that will make the materials a viable commercial product. The mechanical properties of the polymers; such as hardness, strength and toughness, will be optimised to ensure commercial viability.

The effect of X-ray irradiation on Campylobacter jejuni, Campylobacter coli, Arcobacter butzleri and Salmonella Typhimurium was examined by measuring the recovery on ifferent media. Irradiation doses (1.0-7.0 kGy) caused a significant reduction in icrobial counts irrespective of the media used for recovery. Recovery was highest on Blood Mueller Hinton Agar (D-value being 3.30,3.32,3.56 and 6.86 kGy for C jejuni, C. coli, A. butzleri and S. Typhimurium respectively) and lowest on selective media (Dvalue being 3.20, 3.08, 3.36 and 3.20 kGy for C. jejuni, C. coli, A. butzleri, and S. lurium respectively).

No description available.

This programme of research consists of eight studies which sought to determine how healthcare professionals' hand hygiene practice might be improved. The Theory of Planned Behaviour was used to isolate perceived cognitive and physical factors that may explain the variance in their hand hygiene behaviour. Practice was observed and healthcare professionals' understanding of the hand hygiene policy to which they were expected to adhere was assessed. Messages on hand hygiene posters were analysed. The effect of two educational interventions on students' attitudes was tested. Achieving change will be challenging for several reasons. Healthcare professionals hold false perceptions about their hand hygiene behaviour; they think it is better than it is but their practice is unrelated to their intentions and self-reports of behaviour. Adherence to the national guideline was poor and practice was neither rational nor informed by risk assessment, even when caring for patients colonised with methicillin-resistant Staphylococcus aureus. Student nurses' attitudes towards the importance of hand hygiene showed progressively downward trends between three cohorts in their first, second and third years of training. The difference was particularly pronounced between first and second years. Their attitudes also showed optimistic bias and false consensus beliefs. For all but one of the 11 clinical procedures measured, they said that they value hand hygiene practice significantly more than other nurses and doctors they work alongside. A microbiology laboratory practical and a demonstration using a fluorescent cream and an ultraviolet light hand inspection cabinet were equally effective at enhancing students' attitudes towards hand hygiene, but the improvement was quickly eroded by their first experience of clinical practice. Various factors in the clinical setting impact negatively on healthcare professionals' attitudes and practice and undermine the principles taught in the pre-clinical phase of training. These include poor role models, ambiguous hand hygiene policies and inappropriately framed messages on hand hygiene posters which lead to confusion in the minds of healthcare professionals about when hands should be washed. In order to improve healthcare professionals' hand hygiene behaviour, it is necessary to disambiguate their understanding about when hands should be washed. There needs to be more emphasis on infection prevention. An active process called the Dynamic Assessment Strategy for Hand Hygiene (DASHH) offers one way of changing poor practice. It does this by teaching healthcare professionals to consider hand hygiene before and after care as separate activities requiring separate risk assessment. Such a strategy provides them with a simple mind map to make the quick informed decisions that are required on a busy ward. The effectiveness of the strategy needs to be evaluated. Observation should form part of the assessment to ensure that there is a beneficial outcome and that good practice is becoming a habit.

De nombreux travaux ont démontré que l'utilisation des SHA réduit le taux d'infections nosocomiales. Cependant, la qualité de friction avec SHA a été rarement évaluée. Un des objectifs de ce travail est d'évaluer la qualité de friction et la tolérance cutanée aux SHA sur le long terme. Lors d'une utilisation intensive en milieu hospitalier, les conséquences du passage systémique de l'éthanol par pénétration cutanée ou par inhalation restent encore un sujet de débat. Le second objectif est d'évaluer l'exposition aux SHA, dans des conditions expérimentales, et dans les conditions réelles de travail en milieu hospitalier. Ce travail a démontré une baisse de la qualité de friction à trois ans de la formation. L'utilisation des SHA augmente l'hydratation de la peau. Les SHA sont tolérées par les soignants. Les mesures réalisées en laboratoire, ont montré que l'exposition a l'éthanol des SHA est de brève durée mais à des concentrations importantes. La quantification d'éthanol dans l'air ambiant d'une chambre de patient, durant 8 heures d'utilisation intensive de SHA, a montré que le patient et le soignant sont exposés à la même quantité de vapeurs d'éthanol, cependant cette quantité est inférieure à la valeur limite d'exposition professionnelle française. L'étude réalisée au CHU, a montré que l'exposition des soignants aux SHA à court terme, ne conduit pas à une absorption décelable de l'éthanol et de ses métabolites. La concentration d'éthanol dans l'air inhalé, reste inférieure aux valeurs limites réglementaires françaises. L'ensemble de ce projet se déroule sur 10 ans, il permettra de vérifier les possibles effets secondaires liés à l'utilisation des SHA sur le long terme / Previous studies have shown that the use of Acohol-Based Hand Rubs (ABHRs) has been associated with reduced rates of nosocomial infections. However, the quality of hand rubbing with ABHRs has rarely been evaluated. The first aim of this work is to evaluate the quality of hand rubbing and skin tolerance to ABHRs in the long term. The consequences of systemic passage of alcohol by inhalation or dermal absorption during intensive use of these products in hospitals remain a subject of debate. The second aim of our work is to assess the exposure of Healthcare Workers (HCWs) to ABHRs, under experimental conditions in the laboratory and under a real situation of work shift in hospital. Our study demonstrated a decrease in the quality of hand rubbing. The use of these products increases skin hydration. ABHRs are well tolerated by HCWs and do not dry the skin.The measurements made in the laboratory showed that exposure to ethanol during ABHRs handling is of short duration but at high concentrations. The quantification of ethanol in ambient air of a patient room for eight hours of ABHRS intensive use showed that the patient and HCW are exposed to the same amount of ethanol vapours. However this amount remains far inferior to the French guidelines for professional exposure limits to ethanol over 8 hours. The hospital study showed that exposure of HCWs to ABHR at short term does not lead to detectable absorption of ethanol and its metabolites. Quantification of ethanol vapour in the inhaled air remains well below the levels known to be toxic in humans. The whole project takes place over 10 years; it will verify the potential side effects associated with the ABHRs use for a long-term