Evaluation of a hand-held far-ultraviolet radiation device for decontamination of Clostridium difficile and other healthcare-associated pathogens

Abstract

Background: Environmental surfaces play an important role in transmission of healthcare-associated pathogens. There is a need for new disinfection methods that are effective against Clostridium difficile spores, but also safe and rapid. The Sterilray™ Disinfection Wand device is a hand-held room decontamination technology that utilizes far-ultraviolet radiation (185-230 nm) to kill pathogens.

Methods: We examined the efficacy of disinfection using the Sterilray device in the laboratory, in rooms of hospitalized patients, and on surfaces outside of patient rooms (i.e. keyboards and portable medical equipment). Cultures for C. difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) were collected from commonly-touched surfaces before and after use of the Sterilray device.

Results: On inoculated surfaces in the laboratory, application of the Sterilray device at a radiant dose of 100 mJ/cm(2) for ~ 5 seconds consistently reduced recovery of C. difficile spores by 4.4 CFU log10, MRSA by 5.4 log(10)CFU and of VRE by 6.9 log10CFU. A >3 log10 reduction of MRSA and VRE was achieved in ~2 seconds at a lower radiant dose, but killing of C. difficile spores was significantly reduced. On keyboards and portable medical equipment that were inoculated with C. difficile spores, application of the Sterilray device at a radiant dose of 100 mJ/cm(2) for ~ 5 seconds reduced contamination by 3.2 log10CFU. However, the presence of organic material reduced the lethal effect of the far-UV radiation. In hospital rooms that were not pre-cleaned, disinfection with the Sterilray device significantly reduced the frequency of positive C. difficile and MRSA cultures (P =0.007).

Conclusions: The Sterilray™ Disinfection Wand is a novel environmental disinfection technology that rapidly kills C. difficile spores and other healthcare-associated pathogens on surfaces. However, the presence of organic matter reduces the efficacy of far-UV radiation, possibly explaining the more modest results observed on surfaces in hospital rooms that were not pre-cleaned.

Figure 1

Picture of the Sterilray™ Disinfection Wand far-ultraviolet radiation device. The portable device includes a disinfecting wand weighing 4 pounds attached to a wheeled power pack. The radiant dose (mJ/cm²) of far-ultraviolet irradiation is dependent upon the amount of time and the distance the device is held from the surface being treated.

Figure 2

Mean reduction (log₁₀colony-forming units (CFU)/cm²in recovery of multiple strains ofClostridium difficilespores, methicillin-resistantStaphylococcus aureus(MRSA), and vancomycin-resistantEnterococcus(VRE) suspended in phosphate-buffered saline. The Sterilray far-ultraviolet irradiation device was operated at radiant doses ranging from 10 to 100 mJ/cm² for ~5 seconds.