An Overview of the Options for Antimicrobial Hard Surfaces in Hospitals - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 152

that copper pens were not significantly less contaminated immediately after the
shift, but they were after storage. This suggests, as you would expect from in vitro
studies, that even copper surfaces take some time to exert antimicrobial activity.
However, since the pens were in frequent use, rapid and high-level deposition of
microbes also seems likely in this study.
Whilst differences in the inherent capacity of the various AMS that have
been tested by in situ studies combined with differences in study design make
comparison of studies difficult, a number of common principles emerge (Table 7.2 ).
AMS are typically associated with a 1-3 log reduction in TAC. The levels of
reduction in situ are generally less than the levels achieved in vitro , most likely
due to the presence of organic soiling [ 69 , 74 , 75 ]. For example, in a study of a
polycationic AMS, inocula applied using a swab from a water suspension exhibited
a 3-log reduction, whereas inocula applied using a swab from a wound or immersed
in urine exhibited only a 1-log reduction [ 69 ].
The impact seems to be greater on more contaminated surfaces, suggesting
that there may be an irreducible minimum level of contamination, which perhaps
represents continual deposition of contamination [ 43 , 76 ]. Longitudinal studies
have identified evidence of reducing levels of contamination over a period of
days and weeks, which may be due to the accumulation effects, which is plausible
when an AMS is applied regularly [ 68 , 70 ]. One interesting finding is that untreated
objects adjacent or close to AMS objects have significantly lower counts than
untreated objects that are not adjacent or close to AMS objects [ 43 , 77 ]. This
so-called 'halo' effect may be due to reduced transmission of microbes between
surfaces via the hands of healthcare personnel.
7.3.3 Clinical Impact
Before AMS are adopted widely in healthcare, studies demonstrating that their
introduction is associated with reduced acquisition of pathogens are necessary.
To date, only one study evaluating the clinical impact of AMS (copper) has been
published, and the methods of analysis have received criticism [ 31 , 78 , 79 ].
More studies evaluating the clinical impact of AMS are necessary.
7.3.4 Cost-Effectiveness
Even if clinical benefit associated with the introduction of AMS can be demon-
strated, cost-effectiveness studies will be necessary before widespread adoption.
The cost of AMS may be incrementally small, but the total cost of implementation
could be substantial and would need to be justified. However, it may be that AMS
could be introduced a no additional cost during the manufacturing process - or even
with an associated saving for some items. For example, data from the 1980s