Valappil, Valappil, Pickup, D. M., Carroll, Donna L., Hope, Chris K., Pratten, Jonathan, Newport, Robert J., Smith, Mark E., Wilson, Michael and Knowles, Jonathan C. (2007) Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses. Antimicrobial Agents and Chemotherapy, Vol.51 (No.12). pp. 4453-4461. doi:10.1128/AAC.00605-07 ISSN 0066-4804.

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Abstract

Staphylococcus aureus can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 µg·mm–2·h–1) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (20 µm) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by 31P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections.

Item Type:	Journal Article
Subjects:	Q Science > QR Microbiology
Divisions:	Administration > University Executive Office Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Silver, Staphylococcus aureus
Journal or Publication Title:	Antimicrobial Agents and Chemotherapy
Publisher:	American Society for Microbiology
ISSN:	0066-4804
Official Date:	December 2007
Dates:	Date Event December 2007 Published
Volume:	Vol.51
Number:	No.12
Number of Pages:	9
Page Range:	pp. 4453-4461
DOI:	10.1128/AAC.00605-07
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)
Funder:	Engineering and Physical Sciences Research Council (EPSRC)
Grant number:	GR/T21080/01, EP/C000714/1 and EP/C000633/1

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