An Overview of the Options for Antimicrobial Hard Surfaces in Hospitals - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 155

The regulatory position for copper AMS is currently different in the USA and
Europe. In the USA, the Copper Development Association obtained an EPA
registration for copper containing alloys allowing claims that copper when used
in accordance with the label 'kills 99.9 % of bacteria within two hours' in 2008
[ 93 ]. More recently, a manufacturer of copper-oxide impregnated surfaces received
the same registration [ 65 ]. However, in Europe, copper is one of the active agents
included on the list of items that should be phased out of use in private and public
health for disinfection (product type, PT 2) [ 94 ]. This means that the use of copper
for AMS is not permitted under current European Union legislation.

7.4.1.2 Silver

Silver is currently used as a component of some topical wound dressings, as an
ingredient in combination with other chemical in some 'no-touch' automated room
disinfection systems and as a coating on medical devices [ 58 , 95 ]. The exact
mechanism of antimicrobial activity for silver is controversial, but requires direct
contact between the silver and the microbial cell wall [ 81 ]. Hence, microbes
accumulate silver until the toxicity threshold is exceeded.
A number of options are available for producing silver impregnated AMS
for hospitals. A silver-containing liquid disinfectant has been evaluated in vitro
[ 96 , 97 ]. An in vitro study demonstrated clear residual activity for a disinfectant
containing 0.005 % silver, with a

4-log reduction on P. aeruginosa and S. aureus
[ 97 ]. However, the test was performed at high humidity (

>

80 %) to maintain the
viability of the test organisms, but may have over-estimated efficacy. In another
study, the use of silver impregnated microfiber mops and containers appeared to
limit microbial contamination of mops [ 96 ].
Also, there are a number of options for generating surface films and coatings
containing silver [ 98 , 99 ]. A study by Bright et al . found that stainless steel surfaces
coated with an absorbent material coated with 2.5 % silver and 14 % zinc ions
significantly reduced the survival of S. aureus within 1 h [ 99 ]. Another study of
similar surfaces indicated a < 1to > 5 log reduction of S. aureus, E. coli,
P. aeruginosa

>

4-log reduction on all
pathogens after 24 h [ 100 ]. However, the durability of this coating is questionable,
since scrubbing the surface reduced efficacy considerably, whereas wiping it did
not. Another option is chemical vapour deposition of silver coatings [ 98 ]. The
in vitro activity of various formulations of the coating varied with pathogen; a 5-log
reduction in MRSA was obtained after 24 h. This study found that silver concen-
tration correlated with efficacy, but that coating hardness (and hence, durability)
correlated negatively with silver concentration. An in situ study found that the
concentration of contamination was significantly lower on silver coated surfaces
placed in a toilet cubicle (Table 7.2 ).
An in situ study of items with silver ions manufactured in was performed in the
UK (Table 7.2 )[ 77 ]. This study, performed on two comparable outpatient units,
demonstrated that

and L. monocytogenes after 4 h, and

>

treated items in one of the units were significantly less