Antimicrobial surfaces: much has been written or presented about antimicrobial systems for surface application and many of the claims seem overrated such as 'the answer to MRSA'. Dr Terence Child has reviewed and put into perspective the technologies available today for applications in hospitals and care homes.

It is a myth that antimicrobial surfaces are the single answer to infection control in hospitals and care homes. Claims that they are the Holy Grail to combat MRSA have damaged the credibility of technologies that are available from reputable companies who are aware of the place for antimicrobial

surfaces within an infection control programme. This paper was written following an in-depth review of technical papers, patents, company literature, trade articles and discussions with manufacturers and infection control nurses. It provides a balanced view of the technologies available, shows their essential differences and indicates where successful applications have been made.

MAJOR CATEGORIES

There are two major categories of antimicrobial surfaces, those resulting from incorporation of the biocide throughout the whole of the article and those with only a surface coating. Examples of totally incorporated biocides would be impregnated materials such as plastics and laminates. Surfaces coatings could in the form of paints, or special applications involving spraying, padding or dipping.

EFFICACY AND DURABILITY

Claims are varied. A disinfective action is claimed by some systems whereas a biostatic action is claimed by most well-established products on the market. None of the claims may be compared directly because there is no internationally recognised performance standard for evaluating antimicrobial surfaces. An internet review of claims for durability shows a vast range, from 7 days to 30 years, depending on the type of product. Paints based on polyurethanes, epoxy materials or styrene acrylics claim, on average, a 10 year lifespan.

APPLICATION AREAS

Paints have been used for coating many areas such as walls, ceilings and floors. Addition of biocide to powder coating treatments has found application in items such as shelving and bed frames. A variety of biocidal treatments has been used for clothing, kitchen utensils, medical devices, bandages, surgical instruments and implants.

TOTALLY EMBEDDED VERSUS SURFACE COATED SYSTEMS

Objects with biocide distributed throughout the body of the material rely on the surface population of biocide to provide the antimicrobial effect. The biocides are tied into the polymer matrix in a manner which is not completely understood and some migration can occur within polymer interstices and in the amorphous parts of the matrix (Watterson and Hanrahan, 2002; Ong and Hanrahan, 2004). The biocides on the surface are fixed and therefore enable food contact approvals and compliance with the Medical Products Directive. In the event of abrasion or wear over a period of time, a degree of self-repair is possible by exposing more biocidal material from beneath the surface. The biocidal action will therefore remain for the lifetime of the product.