The results of this study suggest that six common, frequently touched objects with which HCWs, patients, and visitors routinely interact carry a substantial MB and thus present a risk to patients. These data underscore the need to ensure that cleaning is completed in an effective manner, as bacterial concentrations resident on items sampled were well above the values recommended immediately after terminal cleaning (11
). Concentrations of bacteria on objects differed substantially (). The stochastic behavior of the MB distributed across the three ICUs is likely attributable to the inherent dynamics of patient care, cleaning, and patient characteristics as well as to other, unknown factors.
Incorporation of inherently and continuously active antimicrobial copper onto frequently touched surfaces in the ICU offered an enhanced effect in combination with regular cleaning and infection control practices that resulted in significantly lower MB and potentially safer surfaces. Bed rails were the most heavily burdened control objects, with a maximum MB of 306,000 CFU/100 cm2
, 17 times higher than the maximum value observed from a copper-surfaced rail. In fact, 80% of plastic bed rails had bacterial concentrations above the risk threshold for transferring infectious bacteria (). In contrast, 83% of copper bed rails had levels below this threshold. Thus, generally, during the conduct of patient care, objects surfaced with copper carried concentrations of bacteria at or below the threshold recommended immediately after terminal cleaning (11
). The levels of antimicrobial activity of the metallic copper surfaces were equivalent throughout the course of the trial. This was evident from the observation that over the course of sampling, 46% of copper bedrails had no recoverable bacteria (). In contrast, only 3% of bed rails sampled in control rooms failed to yield viable bacteria.
Similarly, the five other copper items had remarkably lower burdens. The call button was the most heavily burdened of the copper-surfaced objects evaluated; however, 71% of the samples were below the proposed terminal cleaning threshold. The measured levels for 75% of chair arms sampled, 90% of tray tables, 91% of IV poles, and 90% of data input devices were below the proposed standard of <250 CFU/100 cm2. In total, 45% of control objects from the 511 rooms sampled exceeded an average MB considered to represent a risk to patients, compared to just 16% of copper-clad objects. The most surprising finding was the 64% decrease in MB between the preintervention and intervention phases in the control rooms. This might be accounted for as a consequence of a number of independent and uncontrolled variables: (i) the presence of copper on the unit might have resulted in better cleaning by the environmental services staff; (ii) the presence of copper might have resulted in an antimicrobial halo that limited the transfer of microbes between control rooms, as staff were common to both rooms; or (iii) variations in compliance with other infection control measures such as hand hygiene might account for the differences seen.
Unlike programs designed to improve compliance with infection control such as hand hygiene or barrier precautions, the antimicrobial activity of copper-surfaced objects was not dependent on additional training or supervision. It did not require alterations to existing cleaning practices or add to the annual environmental cleaning costs, as does the application of UV light and/or hydrogen peroxide vapor deposition for reduction in MB. Additionally, reductions to the MB manifested by the copper objects during active patient care approached the reduction level of 99.9% observed in tests conducted for registration of copper-based surfaces with the U.S. EPA.
Recent literature provides increased evidence that contaminated hospital surfaces may be a source of transmission of pathogens. Kramer et al. reported that, in hospitals, surfaces with hand contact are often contaminated with nosocomial pathogens and may serve as vectors for cross-transmission (17
). Stiefel et al. found that in patient rooms with MRSA carriers, HCWs are just as likely to contaminate their hands or gloves from contact with commonly touched environmental surfaces as from direct contact with colonized patients (35
). Boyce (6
) demonstrated that nurses frequently acquired MRSA on their gloves after touching surfaces near colonized patients, and a report by Bhalla and others found that 53% of hand imprint cultures were positive for one or more pathogens after contact with surfaces near hospitalized patients (2
). Other studies have found that patients treated in rooms previously occupied by individuals with colonization or infection with MRSA, VRE, and C. difficile
are at a higher risk of acquiring the organism than patients admitted to rooms where the previous occupant did not have colonization or infection (14
The use of copper to control or reduce the MB on surfaces in health care has been previously reported (10
). In a South African community health care facility, copper surfaces (desks, trolleys) were associated with a 71% reduction in MB compared to control surfaces when sampled every 6 weeks for a period of 6 months (20
). A recent crossover study in a 19-bed acute medical ward found that many copper surfaces were associated with significantly decreased MB compared to control surfaces when sampled weekly for 24 weeks, with reductions ranging from −0.4 CFU/cm2
to −80.3 CFU/cm2
). Also, as was seen in our study, copper surfaces were significantly less likely to be contaminated with indicator organisms such as VRE and coliforms. Our study differs from those previous studies in several respects. Sampling in our study was performed over a substantially longer period of time (21 months), and the objects surfaced with copper were often medical devices in close proximity to the patient and used routinely during direct patient care. Additionally, the populations cared for in the rooms involved in our study were critically ill and generally not ambulatory, which reduced the influence of their interactions with other environmental surfaces within and outside the room.
Reducing the overall MB on a continuous basis with the introduction of continuously active antimicrobial copper surfaces, as evidenced in this study and others, may provide a safer environment for hospital patients, HCWs, and visitors.