JAC Advance Access originally published online on June 4, 2007
Journal of Antimicrobial Chemotherapy 2007 60(2):447; doi:10.1093/jac/dkm203
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Correspondence |
Comment on: The increasing use of silver-based products as antimicrobial agents: a useful development or a cause for concern?
1 Biomaterials-Related Infection Group, Division of Orthopaedic and Accident Surgery, School of Medical and Surgical Sciences, C Floor West Block, Queen's Medical Centre, University Hospital Nottingham, Nottingham NG7 2UH, UK 2 School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK
* Corresponding author. E-mail: roger.bayston{at}nottingham.ac.uk
Keywords: biomaterials , toxicity , infection
We read the article by Chopra1 on the increasing use of silver-based products with interest and we would like to make some observations.
The title of the article asked whether there was cause for concern, and, understandably, the issue of resistance was raised in this respect. Chopra makes a case for using dressings that release high concentrations of silver in order to overcome this, yet, in certain circumstances, this could raise the possibility of toxicity. Silver-processed products range from wound dressings to catheters, and the individual exposure to silver will vary enormously. Systemic toxicity (argyria) is rare but has been reported after topical use.2,3 Although reports of actual morbidity due to argyria are rare, neuropathy has been reported from topical use and from the use of silver in bone cement.3,4 Of equal concern is the selective deposition of silver in the CNS5–7 associated with the use of intracranial catheters, two of which are now available (Silverline, Spiegelberg GmbH; Vygon Expert, Vygon GmbH). In addition, local cytotoxicity has been demonstrated8 when silver-coated implants have been evaluated. It appears that the window between minimum concentrations lethal to microbes and those lethal to host cells is narrow and is easily missed in practice. In most cases this will not be clinically important, but in some it will be.
The design of the silver release system is also important. For example, if the aim is to kill microbes that impinge on the device, such as in a catheter, then low rates of release of silver ions from perhaps a nanoparticle system9,10 might suffice, but if the effect of silver is to be exerted in the surrounding tissue or exudates, as in a dressing, then greater amounts of silver must be released and this might be best in the form of a silver salt.
Finally, Chopra discussed the zones of inhibition expected from silver systems, yet one would not see a zone of inhibition from a nanoparticle system despite its ability to kill attached microbes,11 but one might with a silver salt system. The diversity of silver systems available and the often inadequate understanding of their modes of action have in our view led to confusion over the clinical efficacy of silver. Chopra's article is timely in that it raises the issue and hopefully will stimulate debate.
None of the authors has received financial or other support in connection with this research.
References
1
Chopra I. The increasing use of silver-based products as antimicrobial agents: a useful development or a cause for concern? J Antimicrob Chemother (2007) 59:587–90.
2 Tomi NS, Kränke B, Aberer W. A silver man. Lancet (2004) 363:532.[CrossRef][Web of Science][Medline]
3 Rowland Payne CME, Bladin C. Argyria from excessive use of topical silver sulphadiazine. Lancet (1992) 340:126.[Web of Science][Medline]
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7 Rungby J, Slomianka G, Danscher A, et al. A quantitative evaluation of the neurotoxic effect of silver on the volumes of the components of the developing rat hippocampus. Toxicology (1987) 43:261–8.[CrossRef][Web of Science][Medline]
8 Heidenauer F, Mittelmeier W, Detsch R, et al. A novel antibacterial titania coating: metal ion toxicity and in vitro surface colonization. J Mater Sci Mater Med (2005) 16:883–8.[CrossRef][Web of Science][Medline]
9
Furno F, Morley KS, Wong B, et al. Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection? J Antimicrob Chemother (2004) 54:1019–24.
10 Guggenbichler J-P, Böswald M, Lugauer S, et al. A new technology of microdispersed silver in polyurethane induces antimicrobial activity in central venous catheters. Infection (1999) 27(Suppl 1):S16–23.[CrossRef][Web of Science][Medline]
11 Mills AJ, Ashraf W, Bayston R, et al. Evaluation of the antimicrobial activity of silver-impregnated ventricular catheters. J Hosp Infect (2006) 64:S63–4.
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