Infection Control & Hospital Epidemiology
Medical Center, a 215-bed acute-care facility. The radiology department contains 20 patient rooms, including 5 computed tomography rooms, 2 angiography suites, 5 digital radiography rooms, 6 ultrasound rooms, and 2 magnetic resonance imaging rooms. Environmental services personnel clean all radiology rooms at the end of each work day and provide additional cleaning as needed, including after procedures for patients on contact precautions. Bleach disinfectant wipes are used after CDI patients complete procedures, and quaternary ammonium disin- fectant wipes are used for all other cleaning. Radiology staff have access to disinfectant wipes and are responsible for assisting in keeping their imaging equipment clean. BBL CultureSwabs (Becton Dickinson, Cockeysville, MD) pre-
moistened with sterile normal saline were used to collect cultures from 5×10 cm areas of 5–6 sites on central procedure tables in 10 radiology department rooms during the work day. The sites inclu- ded areas commonly touched by patients (eg, head rest, body of table, foot of table) and the table control buttons that are commonly touchedbypersonnel. Thecultureswereprocessed forMRSA, VRE, fluoroquinolone-resistant gram-negative bacilli, Clostridium difficile, and Candida spp using previously reported methods.1,17
Test strains used for comparison of UV devices
We studied 1 strain each of C. difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus faecium (VRE). The C. difficile strain was American Type Culture Collection (ATCC) strain 43598; the MRSA strain was a clinical isolate of pulse-field gel electrophor- esis (PFGE) type USA800; and the VRE strain was a clinical VanB-type VRE strain.
Preparation of C. difficile spores
Spores were prepared as described previously.18 The spores were stored in phosphate-buffered saline containing 0.1% (v/v) Tween 80 at −80°C. Prior to testing, spore preps were confirmed to be at least 99% dormant, bright-phase spores.18
Table 1. Characteristics of the Ultraviolet Light Devices Device
Standard vertical tower devices Pulsed xenon
Low-pressure mercury device 1 Low-pressure mercury device 2 Low-pressure mercury device 3 Low-pressure mercury device 4
Nonstandard devices Adjustable bulbsc 3 vertical towers
1
28 4
20 8b Comparison of irradiance measurements for the devices
Absolute spectral irradiance measurements were taken using an Ocean Optics JAZ spectrometer equipped with a cosine corrector and a UV+VIS grating (200–850 nm). All measured spectra were interpolated to 1 nm spacing over the range of 250–800 nm. The ambient fluorescent lighting in the test space remained on during the test, and the absolute spectral irradiance of the ambient light was also measured and was subtracted from the measured spectra of the disinfection devices. Measurements were taken at a height of 86.4 cm from the floor and 91.4 cm from the light-emitting portion of the devices. The average absolute irradiances in µW/cm2 for UV-C (250–279 nm), UV-B (280–319 nm), UV-A (320–399), and visible light (400–800 nm) were calculated based on readings taken over several seconds. For the nonstandard device with 3 vertical towers, we measured the irradiance for 1 of the towers with the bulbs in a fixed position directed at the detector.
Comparison of efficacy of multiple UV devices in a radiology procedure room
The efficacy evaluation protocol was approved by the institutional review board and the Biosafety Committee of the Cleveland VA Medical Center. We tested devices available at the Cleveland VA Medical Center or other local hospitals and invited manufacturers of other UV room decontamination devices to provide a device for testing. Table 1 shows characteristics of the 8 devices tested. The time required to move the devices from the corner of the room and set up for operation varied from 18 to 26 seconds for the standard vertical towers and from 26 to 59 seconds for the nonstandard devices. The manufacturers did not provide input on study design and were not provided with data from the study. The evaluations were conducted in a single procedure room used for computed tomography. Initial experiments were conducted with a single device to determine optimal placement of the device for reduction in pathogens placed at multiple locations on the patient exam table. For each pathogen, 10-μL aliquots containing 1×106 colony- forming units (CFU) in sterile water containing 5% tryptone,
159
No. of Bulbs Bulb Length, cm (inches) Highest in Use Bulb Height, cm (inches) Target Wavelength Set Up Time, sa 22.9 (9)
101.6 (40) 162.6 (64) 121.9 (48) 101.6 (40)
6 3d
45.7 (18) 109.2 (43)
137.2 63 (54) 160.0 (63) 182.8 (72) 175.3 (69) 165.1 (65)
221.0 (87) 193.0 (76)
200–315 254 254 254 254
254 254
25 26 25 25 18
39 26
aTime required to move the devices from the corner of the room and set up to begin the ultraviolet light cycle. bLow-pressure mercury device 4 can be used with 2 towers (16 bulbs total) but was tested as a single vertical tower. cThe device has 3 adjustable bulbs that can be oriented to provide closer proximity to the surface of interest; this device is the same device used for the robotic mobile unit that moves along
the side of the table during the cycle. dEach of the 3 vertical towers has 3 bulbs (ie, 9 total when operated with all 3 towers).
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