Copper Continuously Limits the Concentration of Bacteria Resident on Bed Rails within the Intensive Care Unit

Abstract

Cleaning is an effective way to lower the bacterial burden (BB) on surfaces and minimize the infection risk to patients. However, BB can quickly return. Copper, when used to surface hospital bed rails, was found to consistently limit surface BB before and after cleaning through its continuous antimicrobial activity.

Full text

Copper Continuously Limits the Concentration of Bacteria Resident on Bed Rails within the
Intensive Care Unit
Author(s): Michael G. Schmidt, PhD; Hubert H. Attaway III, MS; Sarah E. Fairey, BS; Lisa L.
Steed, PhD; Harold T. Michels, PhD; Cassandra D. Salgado, MD, MS
Source:
Infection Control and Hospital Epidemiology,
Vol. 34, No. 5, Special Topic Issue: The
Role of the Environment in Infection Prevention (May 2013), pp. 530-533
Published by: The University of Chicago Press on behalf of The Society for Healthcare Epidemiology
of America
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infection control and hospital epidemiology may 2013, vol. 34, no. 5
concise communication
Copper Continuously Limits the
Concentration of Bacteria Resident on
Bed Rails within the Intensive Care
Unit
Michael G. Schmidt, PhD;
1
Hubert H. Attaway III, MS;
1
Sarah E. Fairey, BS;
1
Lisa L. Steed, PhD;
2
Harold T. Michels, PhD;
3
Cassandra D. Salgado, MD, MS
4
Cleaning is an effective way to lower the bacterial burden (BB) on
surfaces and minimize the infection risk to patients. However, BB
can quickly return. Copper, when used to surface hospital bed rails,
was found to consistently limit surface BB before and after cleaning
through its continuous antimicrobial activity.
Infect Control Hosp Epidemiol 2013;34(5):530-533
Microbes have an intrinsic ability to survive and colonize
commonly touched surfaces in hospitals. To prevent health-
care-associated infections (HAIs), infection control (IC)
guidelines recommend that, in concert with hand hygiene,
attention be paid to disinfection of patient-care surfaces, es-
pecially those designated high-touch objects (HTOs).
1
Such
objects could contribute to transmission by contaminating
the hands of healthcare workers (HCWs) who subsequently
contact patients.
2
Routine and terminal cleaning of surfaces
and objects within the room using a hospital-grade disinfec-
tant has been an accepted method for controlling and limiting
the spread of infectious agents.
1
A concentration of less than
250 aerobic colony-forming units (cfu) of bacteria per 100
cm
2
has been proposed as a benchmark where infectious risk
to patients is low.
3
In 2008, the United States Environmental Protection
Agency (US-EPA) registered 5 families of copper-containing
alloys as antimicrobial, which established that products man-
ufactured from these alloys kill 99.9% (log
10
2.0) of bacteria
within 2 hours of exposure.
4
Subsequently, copper has been
used to limit bacterial burden (BB) found on commonly
touched surfaces and objects in healthcare. Casey et al
5
ob-
served a median microbial reduction between 90% and 100%
(log
10
1.95 to log
10
2.0) on copper-surfaced push plates, faucet
handles, and toilet seats, whereas Schmidt et al
6
demonstrated
an 83% (log
10
1.93) reduction in BB for copper-surfaced ob-
jects over the course of a 43-month multicenter trial.
Cleaning can effectively remove pathogens from surfaces,
but studies have shown that, more than half of the time,
surfaces were not adequately terminally cleaned and may be-
come recontaminated within minutes.
7,8
The rails of hospital
beds, as a consequence of coincident interactions with pa-
tients, HCWs, and visitors, are one of the most frequently
touched items in the patient care environment. In this study,
we quantitatively assessed the BB present on bed rails to
evaluate the effectiveness of the antimicrobial properties of
metallic copper to continuously limit the concentration of
bacteria resident before and after routine cleaning.
material and methods
This institutional review board–approved study was con-
ducted within a 17-bed medical intensive care unit (MICU)
of a 660-bed academic hospital. In accordance with hospital
policy, visitors were permitted between 8 am and 8 pm at the
discretion of staff. Each single-patient room contained an In
Touch Critical Care Bed (Stryker). Routine patient care was
provided throughout the course of the study, including teach-
ing rounds, resulting in numerous patient visits with direct
contact between the healthcare team, patients, and built
environment.
Standard In Touch beds have 4 plastic rails. Three beds
were custom fitted with copper (UNS# C110 99.9% metallic
copper) surface caps on the rails as described elsewhere by
Schmidt et al.
6
In accordance with MICU policy, all objects and surfaces
within the patient’s room, including the study bed rails, were
cleaned at least daily and upon patient discharge from the
hospital (ie, terminally cleaned) using the US-EPA–registered
disinfectant Virex II 256, which was dispensed from an au-
tomated dilution system (Use Solution, 0.07% n-alkyl di-
methyl benzyl ammonium chloride and 0.07% didecyl di-
methyl ammonium chloride; Johnson Diversey) as prescribed
by the manufacturer.
Bed rail sampling was conducted in candidate rooms if the
patient housed there would be continuously occupying the
room for the next 8 hours and if sampling at 2-hour intervals
would not affect care. Cleaning staff were not made aware
of the study. Plastic (control) and copper bed rails were sam-
pled immediately before cleaning (time 0) and then at 30
minutes and 2.5, 4.5, and 6.5 hours after cleaning. Samples
were taken on 5 separate occasions over a 3-month period.
Three patient-occupied beds with plastic rails (controls) and
3 with copper rails were sampled on each occasion, resulting
in evaluation of 30 beds. Samples were collected and pro-
cessed as described elsewhere.
6,8
The effectiveness with which copper reduced resident BB
was calculated by measuring the difference between the BB
on copper bed rails and that on plastic bed rails. A mean
reduction in BB was calculated for each type of bed rail and
compared using the Mann-Whitney and Wilcoxon rank test
(Epi Info, version 3.5.1). In a previous study, copper surfaces
were associated with an 83% (log
10
1.92) reduction in BB,
compared with plastic surfaces.
6
Based on this, we calculated
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copper continuously limits bacterial burden 531
figure 1. Copper continuously limits the concentration of bacteria on bed rails. Shown are the average total aerobic colony-forming
units per 100 cm
2
recovered from standard plastic bed rails (filled circles) and copper bed rails (open circles) before and after cleaning
with Virex 256. Five independent replicates are shown, and 3 beds of each type were sampled per time period. Dashed line represents the
suggested bacterial burden desired immediately after terminal cleaning (250 colony-forming units per 100 cm
2
).
table 1. Assessment of the Antimicrobial Activity of Copper to Control the Bacterial Burden betweenCleanings
with Virex 256
Plastic bed rails Copper bed rails
Time point
Colony count,
mean cfu/100 cm
2
(ⳲSE) Reduction, %
Colony count,
mean cfu/100 cm
2
(ⳲSE) Reduction, % P
Precleaning 6,102 Ⳳ2,572 698 Ⳳ368 .006
Hour 0.5 1,112 Ⳳ802 82 362 Ⳳ282 48 .069
Hour 2.5 1,560 Ⳳ936 74 530 Ⳳ530 24 .012
Hour 4.5 2,396 Ⳳ1,502 61 224 Ⳳ94 68 .013
Hour 6.5 5,198 Ⳳ2,386 15 434 Ⳳ236 38 .002
note. SE, standard error.
that a sample size of 7 beds per group was necessary to have
at least 90% power to detect an absolute BB decrease of 83%
between copper-surfaced bed rails and standard plastic bed
rails at a 5% significance level.
results
Average length of stay was 7.3 days for patients cared for in
the plastic-railed beds and 8.6 days for patients cared for in
the copper-railed beds. Compared with the mean BB found
on plastic rails, the mean found immediately before cleaning
on copper rails was significantly lower (6,102 cfu per 100 cm
2
or log
10
3.79 per 100 cm
2
vs 698 cfu per 100 cm
2
or log
10
2.84
per 100 cm
2
; Figure 1). Subsequent cleaning of bed rails re-
sulted in an immediate decrease in BB regardless of the bed
rail surface. The mean reduction was 82% (1,112 cfu per 100
cm
2
or log
10
3.05 per 100 cm
2
) on plastic rails and 48% (362
cfu per 100 cm
2
or log
10
2.56 per 100 cm
2
) on copper rails.
Continued sampling subsequent to cleaning found that the
mean BB on copper rails remained significantly lower than
that on plastic rails (Table 1). Among the beds with unmo-
dified plastic rails, the highest initial BB recorded at any time
over the study period was 32,400 cfu per 100 cm
2
(log
10
4.51
per 100 cm
2
), whereas the lowest was undetectable for 5
(6.6%) of the 75 plastic-railed beds. Among copper beds, the
highest initial BB was 5,310 cfu per 100 cm
2
(log
10
2.56 per
100 cm
2
), whereas the lowest was undetectable for 37 (49.3%)
of 75 copper-railed beds sampled.
In assessing the frequency with which the BB on the sur-
faces of bed rails was below a proposed value that was sug-
gested as low risk immediately after terminal cleaning, 250
cfu per 100 cm
2
, it was found that the difference observed
between the copper-surfaced and plastic-surfaced rails was
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532 infection control and hospital epidemiology may 2013, vol. 34, no. 5
table 2. Frequency Bacterial Burden Was Below Suggested Terminal Cleaning Standard Immediately before and after Routine
Cleaning Conducted during Routine Patient Care
Bed rails with colony count !250 cfu/100 cm
2
Time point
Plastic rails associated
with 15 beds
Bed rail colony count
!250 cfu/100 cm
2
,%
Copper rails associated
with 15 beds
Bed rail colony count
!250 cfu/100 cm
2
,% P(2-tailed)
Precleaning 4 27 10 67 .067
Hour 0.5 10 67 13 87 .86
Hour 2.5 7 47 12 80 .13
Hour 4.5 8 53 11 73 .44
Hour 6.5 5 33 12 80 .02
Overall 34/75 45 58/75 77 .0001
note. cfu, colony-forming units.
significant ( ). A total of 77% of copper-surfacedPp.0001
rails were below this level, whereas only 45% of plastic rails
were below this critical threshold (Table 2).
discussion
The patient room is a kinetic reservoir where hard surfaces,
equipment, furniture, and the belongings of patients serve as
fomites where casual touch may transfer resident microbes
to patients and HCWs. Here, we report the quantitative ef-
fectiveness with which copper surfaces were able to augment
routine cleaning practices to continuously limit the BB res-
ident on the rails of patient beds.
Bacteria responsible for many HAIs can survive for days,
weeks, or months on hospital surfaces in spite of the best
efforts of the healthcare team to keep the BB within limits
considered safe for patient care.
3
Some have argued that ter-
minal cleaning must achieve a threshold where fewer than
250 cfu per 100 cm
2
of aerobic bacteria are detectable to
minimize risk of transfer to HCWs or patients.
9
In previous
work, we described the rapid reestablishment of bacteria on
bed rail surfaces after cleaning with a hospital-grade disin-
fectant.
8
These data suggested that, to keep the BB below the
risk-based threshold, surfaces would require cleaning at en-
hanced intervals and that this would result in increased work-
load for HCWs and environmental services. The current study
would suggest that this cleaning interval would need to com-
mence between every 2.5 and 4.5 hours for beds with standard
plastic rails. However, in concert with once-daily cleaning,
copper bed rails were routinely able to maintain a BB below
a low-risk threshold for the entire shift. Low-risk concentra-
tions were associated with 77% of the sampled copper beds.
The use of copper to control BB on surfaces found in
healthcare has been recently reviewed.
10
Here, we demonstrate
that the antimicrobial activity was continuous in its ability
to limit BB found on bed rails. Weber and Rutala,
11
in their
commentary of work conducted by Karpanen et al,
12
argued
that it was impractical or impossible to coat each environ-
mental surface with copper. However, the data provided here
and in other studies suggest that the strategic placement of
copper in key high-touch areas offers a novel strategy to limit
BB on a continuous basis.
6
Other no-touch methods for room
disinfection (hydrogen peroxide vapor [HPV] and UV light)
rely on discontinuous modalities of application to reduce
environmental BB.
13
Consequently, like the US-EPA–regis-
tered disinfectants that are regularly used to disinfect patient
rooms subsequent to cleaning, both UV and HPV will likely
have the same limitation of rapid restoration of BB intrinsic
to HTOs. In contrast, copper-alloyed surfaces offer a contin-
uous way to limit and/or control the environmental burden.
Hospital and environmental services need not perform ad-
ditional steps, follow complex treatment algorithms, obtain
“buy-in” from other providers, or require additional training
or oversight.
It is intuitive to argue that, to minimize infectious risk to
a patient, any method that augments the effectiveness of hand
hygiene and routine cleaning will likely translate into lower
rates of HAIs and/or hospital-acquired colonizations with
epidemiologically important pathogens. The continuous an-
timicrobial activity of copper surfaces demonstrated here
should enhance routine and terminal-cleaning practices re-
quired of hospitals.
acknowledgments
We acknowledge the assistance of Janet Byrne and the staff of the MUSC
MICU as well as Chuck Stark, Dennis Simon, and Kathy Zolman of Advanced
Technologies Institute; Adam Estelle, Wilton Moran, and Jim Michel of the
Copper Development Association; and Peter Sharpe of Sharpe and Associates
for assistance with developing the copper alloyed bed rails.
Financial support. Supported by the US Army Materiel Command Con-
tract W81XWH-07-C-0053. The views, opinions and/or findings presented
here are those of the authors and should not be construed as an official US
Department of the Army position.
Potential conflicts of interest. H.T.M. is senior vice president for research
and development for the Copper Development Association and was the
principal investigator of the funds awarded to support the study. Heprovided
expertise for antimicrobial alloy specifications. Similar to other authors, he
received salary support and funds to purchase supplies and materials. None
of the other authors received funds from the Copper Development Asso-
ciation for the conduct of this research. The Copper Development Association
did not provide any funds for the conduct of this research. In full disclosure,
the employer of H.T.M. promotes the active use of copper for industrial
applications. All other authors report no conflicts of interest relevant to this
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copper continuously limits bacterial burden 533
article. All authors submitted the ICMJE Form for Disclosure of Potential
Conflicts of Interest, and the conflicts that the editors consider relevant to
this article are disclosed here.
Affiliations: 1. Department of Microbiology and Immunology, Medical
University of South Carolina, Charleston, South Carolina; 2. Department of
Pathology and Laboratory Medicine, Medical University of South Carolina,
Charleston, South Carolina; 3. Copper Development Association, New York,
New York; 4. Division of Infectious Diseases, Department of Medicine, Med-
ical University of South Carolina, Charleston, South Carolina.
Address correspondence to Michael G. Schmidt, PhD, Medical University
of South Carolina, Department of Microbiology and Immunology, 173 Ashley
Avenue, BSB 319G, Charleston, SC 29425 (schmidtm@musc.edu).
Received June 3, 2012; accepted August 26, 2012; electronically published
April 9, 2013.
䉷2013 by The Society for Healthcare Epidemiology of America. All rights
reserved. 0899-823X/2012/3405-0016$15.00. DOI: 10.1086/670224
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