Antibacterial activity of novel self-disinfecting surface coatings

The antibacterial activities of different thin films (TiO2/CuO, Cu/SiO2 and Ag/SiO2) prepared by flame-assisted chemical vapour deposition (FACVD) and atmospheric pressure thermal (APT-FCVD) for TiO2/CuO films, were investigated against standard strains of bacteria used for disinfectant testing and against multi-antibiotic resistant bacteria that have been shown to persist in the hospital environment. These included; MRSA strains (EMRSA15 and two recent clinical isolates MRSA 1595 and MRSA 1669), extended spectrum β-lactamase (ESBL) producing Escherichia coli, a second (ESBL- 2 ) producing Escherichia coli, KPC+ (carbapenemase producing) Klebsiella pneumoniae, Stenotrophomonas maltophilia, Acinetobacter baumannii, Listeria monocytogenes, Salmonella enterica ser typhimurium, and vancomycin resistant Enterococcus faecium (VRE) . The Antimicrobial activity of the above coatings (Cu/SiO2 and Ag/SiO2) was investigated based on the BS ISO 22196:2009 and 2011 Plastics – Measurement of antibacterial activity on plastics and other porous surfaces. The activity of TiO2/CuO films was investigated based on the BS ISO 27447:2009 Test method for antibacterial activity of semiconducting photocatalytic materials. On the TiO2/CuO films, the bacteria were killed by UVA irradiation of the photocatalyst with a >5 log kill within 4-6 h except for the MRSA where a 2.3 log kill was obtained after 6 h increasing to >5 log after 24 h. There was antimicrobial activity in the dark which was enhanced by irradiation with fluorescent light. There was also activity at 5ºC under UVA but activity was lower when fluorescent light was used for illumination. The Cu/SiO2 coating showed a >5 log reduction in viability after 4 h for the disinfectant test strain (E.coli) and for some pathogenic strains include; Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia. However, their activity against the other hospital isolates was slower but still gave a >5 log reduction for extended spectrum β-lactamase producing Escherichia coli and Salmonella enterica typhimurium, and > 2.5 log reduction for vancomycin resistant Enterococcus faecium, Listeria and methicillin resistant Staphylococcus aureus within 24 h. The coating was also active at 5ºC but was slow compared to room temperature. The highest activity of copper /silica films was seen at 35ºC, but bacterial cells were also killed on the control surfaces. The Ag/SiO2 coating was also active against pathogenic bacteria; however the coating was not hard or durable as other coatings used. The activity on natural contamination in an in use test in a toilet facility was also determined for coated ceramic tiles (Cu/SiO2 and Ag/SiO2) and coated steel. The results demonstrated that the tiles were highly active for the first 4 months period and the contamination was reduced by >99.9%. However, tiles lost some of their activity after simulated ageing and washing cycles. The Cu/SiO2 coated ceramic tiles placed in Manchester Royal Infirmary also showed antimicrobial activity and no indicator organisms were detected. The coatings had a good activity against both standard test strains and clinical isolates. The coatings (copper surfaces in particular), may have applications in health care by maintaining a background antimicrobial activity between standard cleaning and disinfection regimes. They may also have applications in other areas where reduction in microbial environmental contamination is important, for example, in the food industry. However, the optimum composition for use needs to be a balance between activity and durability.Keywords: TiO2, CuO, Ag, Antimicrobial; Chemical vapour deposition; Copper; Disinfection surface; Pathogenic bacteria (hospital pathogen)

Dual functionality anti-reflection and biocidal coatings

A thin film combination of anti-reflection (AR) and biocidal properties would be of particular interest to reduce the transfer of infection and improve readability of public high use touch screens. In this paper we describe the development of a dual functionality film of silica (AR) and copper oxide (biocidal). Deposition was via flame assisted chemical vapour deposition (FACVD) which has the advantages of being a cost efficient atmospheric pressure technique enabling use of non-volatile precursors and that no closed reaction cell is required so making it ideal for integration into industrial production lines. The resulting films were characterized by a range of techniques including optical spectroscopy, electron microscope and X-ray fluorescence. Biocidal behavior was tested by determining the kill rate of Escherichia coli. A 3 layer stack on glass of silica/copper oxide/silica had better adhesion and lower reflection than a comparable 2 layer stack. This multilayer film led to a > 2% drop in reflection from that of uncoated glass, similar to that of silica only film. In addition, showed a > 6 log10 kill between 6 and 24 h for as deposited and annealed samples

Effects of silver sulphadiazine on production of extracellular proteins by strains of Staphylococcus aureus isolated from burns wound

Previous studies had shown that sub-inhibitory concentrations of silver sulphadiazine (AgSD) stimulated the production of Toxic Shock Syndrome Toxin-1 in certain strains (responder strains)of S.aureus and that protease production was also affected. No changes were detected in other strains (non-responders). Extracellular proteins from eleven responder and non-responder strains grown with and without AgSD were separated by SDS PAGE.There were three classes of response, responder strains that showed enhancement of synthesis of certain proteins, non-responder strains that showed no change and responder strains that showed a general decrease in exoprotein production in the early stages of growth.The results showed that the effects of AgSD were complex and that S. aureus strains were heterogenous with respect to their response to sub-inhibitory concentrations of AgSD

Novel antibacterial silver-silica surface coatings prepared by chemical vapour deposition for infection control

Aims: Environmental contamination plays an important role in the transmission of infections, especially healthcare-associated infections. Disinfection transiently reduces contamination, but surfaces can rapidly become re-contaminated. Antimicrobial surfaces may partially overcome that limitation. The antimicrobial activity of novel surface coatings containing silver and silica prepared using a flame-assisted chemical vapour deposition method on both glass and ceramic tiles was investigated. Methods and Results: Antimicrobial activity against a variety of bacteria including recent clinical isolates was investigated based on the BS ISO 22196:2007 Plastics – Measurement of antibacterial activity on plastics surfaces, British Standards Institute, London, method. Activity on natural contamination in an in use test in a toilet facility was also determined. Activity on standard test strains gave a log10 reduction of five after 1–4 h. The hospital isolates were more resistant, but MRSA was reduced by a log10 reduction factor of >5 after 24 h. Activity was maintained after simulated ageing and washing cycles. Contamination in situ was reduced by >99�9% after 4 months. Activity was inhibited by protein, but, although this could be overcome by increasing the amount of silver in the films, this reduced the hardness of the coating. Conclusions: The coatings had a good activity against standard test strains. Clinical isolates were killed more slowly but were still sensitive. The optimum composition for use therefore needs to be a balance between activity and durability. Significance and Impact of the Study: The coatings may have applications in health care by maintaining a background antimicrobial activity between standard cleaning and disinfection regimes. They may also have applications in other areas where reduction in microbial contamination is important, for example, in the food industry

Antimicrobial activity against hospital-related pathogens of dual layer CuO/TiO2 coatings prepared by CVD

Photocatalytically active films of TiO2/CuO grown by atmospheric pressure thermal (APT)CVD are investigated for activity against multiple antibiotic-resistant pathogens namely, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, vancomycin-resistant enterococci (VRE), and a recent isolate of methicillin-resistant Staphylococcus aureus (MRSA), that have been shown to persist in the hospital environment. The bacteria are killed by UVA irradiation of the photocatalyst with a>5 log kill within 4–6 h except for the MRSA where a 2–3 log kill is obtained after 6 h increasing to >5 log after 24 h. There is antimicrobial activity in the dark which is enhanced by irradiation with fluorescent light. There is also activity at 5 8C under UVA, but activity is lower when fluorescent light is used for illumination