Antimicrobial activity of copper-nickel coated door handles: a blinded, randomized controlled study in a clinical setting.

Abstract

Background: Prevention of nosocomial infections continues to be crucial to ensure patient safety and improve healthcare outcomes. In this regard, surface contamination plays an important role in the undetected transmission of nosocomial pathogens as a continuous, sporadic event or in the context of outbreaks. However, the impact of reducing bacterial contamination through copper-coated surfaces remains controversial.

Methods: A pilot study was set up in a blinded, randomized controlled design to elucidate the antimicrobial activity of door handles coated with a copper-nickel alloy. Twelve doors in a specialized department of tumor and revision surgery of a German orthopedic hospital were randomly selected to install visually indistinguishable stainless-steel door handles, either without coating (control group, n=6) or with an alloy coating consisting of 30% copper and 70% nickel (study group, n=6). Patients, all involved personnel and investigators were blinded with regard to the assignment of door handles. Door handles were sampled for viable microorganisms at 24 h after disinfection by (i) consecutive use of wet and dry swabs and (ii) contact agar slides. Bacterial growth was detected and bacteria were identified using MALDI-TOF mass spectrometry. In addition, contamination kinetics of door handles were determined by ATP measurement at time points 0 h, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h after disinfection. Each technique was used on three subsequent days.

Results: Using swab method, the mean total number of colony forming units (cfu) of control and copper-nickel alloy surfaces was 2.14 cfu/cm² and 0.67 cfu/cm², respectively, yielding a difference of 68.7% (p=0.27). Bacterial counts from contact agar slide samples resulted in 0.86 cfu/cm² on control and 0.6 cfu/cm² on coated door handles which equals a difference of 30.2% (p=0.31). ATP bioluminescence measured over three subsequent days from coated door handles showed a decreased bioburden by 70.8%, 23.1%, 55.5%, 79.7%, 45.9%, 56.0%, and 68.3% of relative light units compared to control door handles at time points 0 h (before disinfection), 0 h (after disinfection), 1 h, 2 h, 4 h, 8 h, and 12 h, respectively. Statistically significant differences (p<0.05) were obtained for time points 4 h and 12 h.

Conclusion: Our data indicate a trend of reduced bacterial and overall bioburden on copper-nickel-coated door handles. Further, larger randomized controlled trials are warranted to investigate the influence of copper-coated surfaces on the prevention of hospital-acquired infections.