Biomedical Engineering Reference
In-Depth Information
blood agar plates to perform sampling of diverse sources: toilet bowl water (remarkably
clean), salad from the employees' cafeteria (heavily colonized), and doorknobs. Brass
(67 % copper and 33 % zinc) doorknob cultures showed scarce staphylococcal and
streptococcal growth while stainless steel (about 88 % iron and 12 % chromium)
doorknob cultures showed heavy growth of Gram-positive organisms and an array of
Gram-negative organisms. Under laboratory conditions, antimicrobial properties
of copper surfaces have been well established as outlined in the previous section.
However, antimicrobial copper surfaces must also show efficacy as an additional
barrier against microbes in healthcare settings. As an important caveat, it should be
mentioned that metallic copper surfaces cannot replace strict hygienic conditions but
instead act as an additional approach that can help further reduce microbial surface
burden and consequently be used to diminish infection rates in patients. It is known that
regular cleaning and proper hygiene conditions help to lower transmission-rates of
infectious diseases, but complete elimination of germs appears to be unrealistic
[
16
]. Hospital surfaces are highly contaminated with microorganisms, such as
C. difficile
,
Acinetobacter spp., Enterococcus spp
and
S. aureus,
capable to persist on
regular surfaces for months [
47
]. Therefore, the usage of a self-sanitizing antimicrobial
surface might strongly diminish transmission of microbes to humans by reducing
fomite contamination (Fig.
6.2
). Worldwide hospital trials confirmed the suitability
of use of metallic copper as an antimicrobial surface [
6
,
44
,
52
,
60
]. These trials were
able to validate that metallic copper surfaces effectively reduced surface burden
compared to control surfaces (such as stainless steel, aluminum and plastic). During
the 2010 trial in the Selly Oak Hospital in Birmigham, United Kingdom [
6
], recovery of
microbes was between 90 and 100 % lower from copper surfaces compared to control
surfaces. Copper surfaces remained active even when these surfaces were oxidized
(“aged”) over time. Similar positive results were obtained by [
44
], where copper alloys
(greater than or equal to 58 % copper) reduced microbial quantity on the surface
compared with control surfaces, as well as by [
52
], in a South African trial reporting
reduction of bacteria survival rate by 71 % on copper. The German trial also reported a
surface burden reduction in the magnitude of 63 % [
60
]. Furthermore, the repopulation
rate of copper surfaces was less than half compared to that of control surfaces.
There are still ongoing trials worldwide. Promising results were obtained in a trial
that involves three hospitals: the Memorial Sloan-Kettering Cancer Center in
New York City, the Medical University of South Carolina, and the Ralph H. Johnson
VA Medical Center, both in Charleston [
77
], where application of metallic copper
lowered infection-rates for patients in rooms with copper objects compared with the
ones without copper objects [
77
]. See Chap.
4
for more details.
6.6 Closing Remarks
Despite all the differences regarding the mechanism of copper surface-induced
inactivation of bacteria cells, it is clear that the use of metallic copper is an
important concept in the area of reducing healthcare acquired infections (HAI).
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