Terminal Decontamination of Patient Rooms by Using a Mobile Ultraviolet Light Unit

Background: Cleaning/disinfection of environmental surfaces in patient care areas is recognized as an important element of infection control programs, but housekeepers often do not clean surfaces as recommended.

Objective: Determine the ability of a mobile ultraviolet light (UV) light unit to reduce bacterial contamination of environmental surfaces in patient rooms.

Methods: An automated mobile UV light unit that emits UV-C (254 nm range) light was placed in patient rooms after patient discharge and terminal cleaning had been performed.  UV intensity was set at a target of 22,000 microwatts/cm² to eradicate spores.  D/E neutralizing agar rodac plates were used to obtain cultures of 5 standardized high-touch surfaces in each room before and after UV light decontamination (UVLD).  Aerobic colony counts (ACC) were calculated for each surface. To determine log reductions achieved, a modification of ASTM E-2197 quantitative disk carrier test method was used. Stainless steel disk carriers were inoculated with ~ 10⁵ CFUs of Clostridium difficile spores, air-dried, placed in sterile petri dishes and then placed in shadowed and non-shadowed areas of the patient room and bathroom. Three control disks (not exposed to UV light) and 5 disks from each decontaminated room were placed in phosphate buffered saline with 0.1% Tween 80 and vortexed to elute the spores. The eluates were serially diluted and the entire contents were filtered and cultured to determine log reductions achieved.  In-room ozone concentrations during UVLD were measured by using a portable ozone monitor (lower limit of detection, 5 PPB).  

Results: Preliminary findings are based on UVLD of 5 patient rooms, with cycle times of 40-50 min.  Results of ACC are shown below.

Site Sampled	Median ACC (Range)  Before UV Decontamination	Median ACC (Range) After UV Decontamination
Bedside rail	10 CFUs (0-53)	0 CFUs (0)
Overbed table	3 CFUs (0-26)	0 CFUs (0)
Television remote	18 CFUs (1-104)	0 CFUs (0-1)
Bathroom grab bar	164 CFUs (9-300)	44 CFUs (0-160)
Toilet seat	11 CFUs (0-300)	0 CFUs (0-17)

12 (92%) of 13 contaminated high-touch surfaces in patient rooms yielded no growth, and 1 surface yielded 1 colony after UVLD. 2 surfaces were culture-negative before and after UVLD.  3 (38%) of 8 contaminated high-touch surfaces in patient bathrooms yielded no growth after UVLD.  4 of the 5 surfaces in bathrooms that yielded growth after UVLD were rough-surfaced grab bars located in shadowed areas.  Log₁₀ reductions of C. difficile spores on carrier disks ranged from 0.4 to 2.3. In-room ozone concentrations during UVLD ranged from undetectable to 0.008 PPM.

Conclusions:   Our preliminary findings revealed that the mobile UV-C light unit eliminated aerobic bacteria from most of the high-touch surfaces sampled, except bathroom grab bars located in shadowed areas. Further evaluation of this technology is warranted to establish its role in terminal decontamination of patient rooms.