copper as a self-disinfecting surface 773
(1) the effectiveness of the self-disinfecting surface to kill or inhibit microbes artificially placed on the self-disinfecting surface, (2) the level of contamination on self-disinfecting surfaces in actual patient rooms compared to a “control” surface and (3) most importantly, clinical trials of a self-disinfecting surface to reduce HAIs. Copper is an essential trace element in most living organ- isms, and >30 types of copper-containing proteins have been
described.20 The use of copper by humans dates back to the fifth and sixth millennia BC.23 Ancient civilizations used copper or copper compounds to prevent the growth of barnacles on the hulls of ships and as a medicinal agent.20 In the 19th and 20th centuries, inorganic copper preparations were used to treat chronic adenitis, eczema, impetigo, tuberculous infec- tions, and syphilis.23 The cause of bacterial cell death to exposure to copper may relate to its ability to accept and donate single electrons leading to the generation of reactive oxygen species, resulting is cell lysis.14,20,21,23 In healthcare facilities, the most well-studied use of copper has been as a “self-disinfecting” surface, but many other uses have been studied, including copper-containing paints, fabrics, hand rubs, microfiber cleaning cloths, pens, and fins within air-conditioning units.20 Multiple studies have assessed the contact killing of
microbes by copper surfaces.23 Contact with copper has been demonstrated to kill a variety of healthcare-associated patho- gens including Staphylococcus aureus (including methicillin- resistant S. aureus), Enterococcus spp, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aerugi- nosa, and Mycobacterium tuberculosis.20 In general, contact killing of vegetative bacteria and fungi occurs rapidly with >6-log10 inactivation per hour. Spores (eg, C. difficile) are inactivated more slowly, but >3-log10 are inactivated within 24 hours.23,24 In this issue of Infection Control and Hospital Epidemiology,
Souli et al25 report on the frequency and level of contamina- tion of multiple copper-coated surfaces (ie, patient beds, side table, IV pole, side cart handles, and manual antiseptic dispenser) compared to control surfaces in a patient room in an intensive care unit.25 The study was performed in a Greek ICU setting in which evidence showed that the environment was considerably more contaminated than other settings and where highly resistant organisms predominated. For example, 62% of K. pneumoniae isolated from the environment were resistant to carbapenems and 100% were multidrug resistant; similarly, 98% of A. baumannii were resistant to carbapenems and 99% were multidrug resistant. Their study was conducted in 2 phases: In phase 1, enhanced environmental sampling was performed to identify the most microbiologically con- taminated items to ‘copperize’; this targeted use of copper items is an important strength of the study. Phase 2 was the intervention phase; in phase 2a, copper-coated objects were placed next to uncoated objects (controls); and in phase 2b, cooper-coated objects were all placed in a single ICU com- partment and non–copper-coated objects were placed in a
different ICU compartment (controls). Combining the data for phases 2a and 2b revealed that copper-coated surfaces were less likely to be microbially contaminated (ie, 55.6% vs 72.5% for controls, P<.0001). Copper-coated surfaces were sig- nificantly less likely to be contaminated with gram-negative bacilli or Enterococcus spp, but no statistical reduction for A. baumannii, K. pneumoniae,or S. aureus was observed. Overall, the level of contamination was reduced by ~0.7-log10 (P=.049). Importantly, no significant reduction was observed in phase 2a, in which copper items were placed next to uncoated objects, suggesting a possible interaction between the number of copper items and the level of reduction, which requires further investigation. The statistical approach used did not take into account the full range of variables; most importantly, indicators of hand-hygiene compliance and patient-level variables could have been included in a model with copper items as a separate variable. Souli et al reported no difference in hand-hygiene compliance during the study, but the effectiveness of environmental clean/disinfection was not assessed. Other limitations include the use of alcohol spray for daily disinfection of surfaces, which is an unusual approach and may limit the generalizability of the study; lack of rando- mization of patients to beds with copper items; and the lack of clinical and cost-effectiveness outcomes. Multiple studies of copper-coated surfaces or devices have
been conducted in the healthcare setting comparing the level and frequency of surface contamination to control surfaces (for a review of studies, seeWeber and Rutala,20 Humphreys,21 Muller et al,22 Weaver et al,24 and O’Gorman and Hum- phreys26). Studies have either used concurrent non–copper- coated control surfaces or a crossover design. Muller et al22 reported that 5 of 7 copper studies of copper-coated surfaces or fabrics reviewed demonstrated a significant reduction
in quantitative bacterial contamination of <1-log10 (range, <1-log10 to 2-log10). Limitations of the studies noted by Muller et al22 included lack of blinding, lack of randomization, and in general, failure to measure potential confounding factors (eg, hand hygiene compliance, effectiveness of cleaning by environmental services) or reported any patient-level data. Similar to previous studies, 2 more recent studies also demonstrated significant reductions of microbial contamina- tion on copper-coated surfaces compared to control surfaces of 1- to 2-log10.27,28 In addition, 3 clinical trials have been published in the
English literature that assessed the effectiveness of cooper- coated surfaces to reduce HAIs (Table 1).23–31 Of these 3 trials, 2 reported that the intervention arm (ie, copper) had a decreased incidence of HAIs,30,31 and 1 trial reported no significant reduction in HAIs.29 Importantly, none of the trials assessed the effectiveness of environmental cleaning and disinfection using fluorescent dye or ATPase measurements, and 1 did not assess compliance with hand hygiene.31 Although Salgado et al31 described their trial as a randomized clinical trial, Muller et al22 described this study as “low-quality evidence due to inappropriate randomization and lack of
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