copper reduced surface colonization by mdro 767 Throughout the study,we used the definitions formultidrug
resistant (MDR) and extensively drug-resistant (XDR) bacteria proposed by Magiorakos et al.21
Statistical Analysis
Distributions of continuous characteristics were presented as means with standard deviations (SDs) or medians with inter- quartile ranges (IQRs). Differences in colonization rates between copper and noncopper surfaces were analyzed using t tests or Wilcoxon rank sum tests if assumptions of normality were not met. Categorical data were presented as relative frequencies, and differences were analyzed using the χ2 test or Fisher’sexact test if observations per cell were ≤5. SPSS version 23 software (IBM, Armonk, NY) was utilized, and a level of P<.05 was considered statistically significant for any association.
results Phase 1: Validation of Sampling Methodology
We confirmed that the recovery rate of traditional swabbing was very poor, allowing the recovery of viable colonies from an initial applied inoculum of ≥104 cfu, probably because bacteria were trapped within the cotton fibers. In contrast, using the sampling method of Hedin et al,19 we could recover viable colonies from an initial applied inoculum of as low as 103 cfu (Supplementary Table S1).
Phase 1: Burden of Environmental Contamination Before the Intervention
The results ofphase1areshowninSupplementary TableS2. Before any intervention, 121 of 130 (93.1%) samples taken from commonly touched items in the ICU were colonized at a mean number of 18,172 cfu/100cm2. The microbial burden of the clinical environment in the preintervention phase 1 was>70 times higher than the commonly accepted value of 250 cfu/100cm2.22 The most commonly isolated microorganisms were
coagulase-negative staphylococci, followed by K. pneumoniae, S. aureus, P. aeruginosa, and Acinetobacter spp. The most heavily colonized items were the bed electronic remote con- trols, the ECG apparatus and defibrillators, the manual anti- septic dispensers, the side tables, the i.v. poles, and the bed rails. The latter 4 items were proposed for copper coating.
Phase 2 (a and b): Burden of Environmental Contamination During the Intervention
In total, 24 patients were admitted to ICU compartments A and B during phase 2a of the study (8 in copper-coated beds) and 22 during phase 2b (12 in copper-coated beds). Table 1
depicts the clinical characteristics of those patients. We speci- fically recorded risk factors for colonization and spreading of colonizing bacteria to the surrounding surfaces. Although there was no formal randomization of patients to each type
of bed, there were no significant differences between the 2 groups. In total, 685 samples were collected during phase 2 (347 during
phase 2a and 338 during phase 2b). Among them, 311 were derived from coated surfaces and 374 from uncoated controls, whereas 596 were derived from surfaces at the vicinity of the patient, and 89 were derived from the handles of nurse’s cupboards. The number of samples from coated surfaces was not equal to that from control surfaces due to the occasional movement of furniture as necessitated by patient
care.Collectively, 444 samples (64.8%) revealed colonization: 128 (18.7%) with gram-negative bacteria, 23 (5.2%) with Enterococcus spp., and 3 (0.8%)with S. aureus (Table 2). The remaining samples revealed coagulase-negative staphylococci, streptococci, or gram-positive bacteria, which were not further characterized. Table 3 depicts the number of colonized surfaces and the microbial burden in phase 2. During phase 2a, 259 of 347 (74.6%) samples grew any bacteria, 70 (20.2%) grew gram- negative bacteria, 6 (1.7%) grew Enterococcus spp., and none grew S. aureus. The mean number of bacterial colonies was 4,601 cfu/100cm2, and the mean number of gram-negative colonies was 822 cfu/100cm2. During phase 2b, 185 of 338 samples (54.7%) were positive for bacterial growth (P<.0001 vs phase 2a), 58 (17.2%) grew gram-negative bacteria (P=.33 vs phase 2a), 15 (4.4%) grew Enterococcus spp. (P=.046 vs phase 2a), and 3 (0.9%) grew S. aureus. The mean number of bacterial colonies was 6,350 cfu/100cm2 (P=.33 vs phase 2a), and the mean number of gram-negative colonies was 798 cfu/ 100cm2 (P=.96 vs phase 2a). These results indicate that compared with noncoated controls, copper coating reduced the percentage of surfaces colonized with any bacteria by 16.9% (P<.0001), reduced the percentage of surfaces colonized with gram-negative organ- isms by 8.9% (P=.003), and reduced the percentage of surfaces colonized with enterococci by 3.2% (P=.014). This reduction was mainly driven by the effect of the arrangement of copper-coated beds and other items during phase 2b of the study. In this phase, when the ratio of copper-coated items near the patient increased, the percentage of surfaces colonized with any bacteria was reduced by 22.2% (P<.001), the per- centage of surfaces colonized with gram-negative isolates was reduced by 8.4% (P=.044), and the percentage of surfaces colonized with enterococci was reduced by 5.9% (P=.014). Even before the regular manual surface disinfection of the day, the mean numbers of gram-negative colonies on copper- coated surfaces (during both phases 2a and 2b) were close to the lower proposed standard of 250 cfu/100cm2.22 In phase 2a, 37.5% of copper-coated units (bed and/or
accessories) were colonized by MDR gram-negative bacteria, compared with 80% of noncopper-coated units (P=.058). In phase 2b, the rates of colonization were 41% with copper- coated units and 70% with noncopper-coated units (P=.185), respectively. This trend was mainly driven by A. baumannii colonization, which was 37.5% with copper-coated units versus 81.3% with noncopper-coated units in phase 2a (P=.047) and
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