Can pulsed xenon ultraviolet light systems disinfect aerobic bacteria in the absence of manual disinfection?

To determine if the PX-UV disinfection system can effectively reduce ABC without prior manual disinfection, a prospective pre–post study design was developed. The study site was a single Veterans Affairs facility located in Temple, Texas. A convenience sample of 38 recently vacated rooms (n = 38) that had not yet undergone any manual disinfection and had been occupied for a minimum of 48 hours were identified and before and after PX-UV surface samples were collected. The description of the device and the methodology used for disinfection was similar to those described in Jinadatha et al except there was no manual disinfection before PX-UV use. Five high-touch surfaces within each room were sampled before and after PX-UV disinfection. The surfaces included 3 in the patient room (ie, call button, bedrail, and tray table) and 2 in the bathroom (ie, handrail and toilet). Therefore, a total of 190 samples before and after PX-UV disinfection were obtained across 38 rooms.

Tryptic soy agar supplemented with lecithin and polysorbate 80 Rodac contact plates (Hardy Diagnostics, Santa Maria, Calif) were used for sampling of surfaces. If gross visible soiling was observed, such as food particles or spilt condiments, the area adjacent was sampled by press plate technique. Roll plate method was used for nonflat surfaces such as bedrails and handrails. Once the baseline samples were taken the PX-UV was used to disinfect the room and then post-PX-UV samples were collected in areas adjacent to the samples taken before disinfection.

The plates were then incubated for 48 hours at 37°C. After incubation the colonies were counted and recorded. The mean and the median aerobic bacteria CFU/25 cm² and 95% confidence intervals (CIs) were calculated for each surface type. An upper limit of 200 CFU was used for ABC counts exceeding this value. The effectiveness of PX-UV on the concentration of aerobic bacteria was assessed employing a Wilcoxon signed-rank test for all 190 pre–post samples in 38 rooms, as well as by surface location. A type 1 error of α = 0.05 was assumed. Data were analyzed using SAS version 9.2 (SAS Institute Inc, Cary, NC).

The overall mean ABC count across all 190 samples before PX-UV disinfection was 73.6 (95% CI, 63.8-83.4) (Table 1). The surface with greatest ABC count was the call button, with a mean of 88.5 (95% CI, 66.7-110.3), followed by the bedrail, with a mean 84.0 (95% CI, 61.6-106.4). The tray table had the lowest mean ABC count before PX-UV disinfection, with 54.5 (95% CI, 34.5-74.5). After disinfection, the call button had the greatest mean ABC count reduction of 72.4 (median reduction of 66.0; P < .01). All high-touch surfaces experienced a significant reduction in ABC count. Overall, before PX-UV disinfection, 187 (98.4%) of the surfaces were contaminated with aerobic bacteria; this was reduced to 169 (88.9%) surfaces after disinfection, leading to 18 (9.6%) contaminated surfaces now becoming free of aerobic bacteria after PX-UV disinfection. Levels of ABC were reduced from 74 ± 10 to no more than 20 ± 3 colonies overall, with the highest residual counts on bathroom surfaces. When the results from Table 1 were compared with ABC count reduction after standard manual disinfection without use of PX-UV disinfection, the results were similar (data not shown).

Surface contamination has been shown to play a significant role in the acquisition of hospital-acquired infections.^,  In fact, Huang et al showed a 40% increased odds of transmission for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci if the room's previous occupant was positive for either antibiotic-resistant bacteria. The current standard for disinfection in most hospitals is manual cleaning by Environmental Management Services staff with disinfectants. These methods are inconsistent and often inadequate in decreasing environmental bioburden.^,  Newer NTD technologies have the potential to supplement manual disinfection to provide enhanced disinfection.^{,  ,  ,}  Anderson et al showed that Hg-UV is effective at decreasing the ABC counts in hospital settings even in the absence of manual disinfection. However, until now research has been lacking for PX-UV disinfection systems. Our study results indicate that PX-UV disinfection reduces aerobic bacteria in the absence of manual disinfection. Our results were similar to the reduction of ABC counts seen in other studies that used a mercury-based no-touch UV disinfection device.^,  In our previous study, we evaluated a properly truncated aesthetic cleaning protocol supplemented by PX-UV disinfection in vacated hospital rooms. But we were not able to delineate if PX-UV was effective on surfaces where Environmental Management Services personnel did not apply a chemical disinfectant, which is part of standard cleaning protocol. It is highly unlikely that the UV light devices are going to be used alone without manual precleaning, for aesthetic reasons. Although our study is not intended to advocate abandoning manual disinfection practices altogether, it provides insight into what happens if a surface is missed by Environmental Management Services personnel during manual disinfection when PX-UV is subsequently deployed. Our study had several limitations, including no evaluation of organism-specific reduction. This study was conducted in a Veterans Affairs hospital setting and may not be generalizable to community hospitals. Although the sample size was small, it represents a larger cohort than other previously reported studies.^, 

Our study suggests that PX-UV effectively reduces ABC counts in the absence of manual disinfection. These data are important for hospitals that plan to adapt this technology as adjunct to routine manual disinfection and alleviate any fears that adapting this technology may actually harm patients because Environmental Management Services personnel may miss surfaces.

The authors thank Kimberly Sikes, Robin Keene, and Deana Hamson for collecting samples; Elicia Greene and the entire Infection Prevention and Control Department; Allen Lassiter and the Environmental Management Services team; and the nursing service personnel for their help in coordinating study activities.