High-Intensity Ultraviolet Light as an Adjunct to Conventional Cleaning Methods in a Laboratory Animal Facility

Ferguson, L., Faseeh, I., Cox, M., Herbert, J., Daisley, S., Sharp, P., and Trasti, S. Animal Resources Centre, Perth, WA, Australia

Abstract

Introduction

Materials & Methods

In recent years due in small part to regional spread of Ebola into 1st world countries, a novel method of sanitization has been developed and garnered attention. Hospitals, cruise lines, and other industries have begun to utilize high-intensity ultraviolet light in cleaning and decontamination procedures. The practice has been shown to enhance conventional cleaning methods to further reduce pathogen levels1,3. The current study compares bacterial counts on the walls, floors, and benchtops in high traffic areas of an animal facility. Surfaces were sanitized with conventional cleaning agents both with and without subsequent exposure to high-intensity ultraviolet light from the TORCH™ by ClorDiSys, Inc. Results indicate that high-intensity ultraviolet light can be a useful adjunct to conventional cleaning methods as well as an alternative for rapid decontamination.

Commercially available RODAC (Replicate Organism Detection and Counting, Becton Dickinson, Inc.) plates were used to measure bacteria levels on multiple surfaces (benchtop, floor, wall) in two high traffic areas of a dedicated animal facility (Diagnostic Laboratory and Cage Wash). RODAC plate samples were collected by gently touching the convex agar surface to the area of interest. Bacterial colonies were counted on each plate after incubation of 48 hours at 37 degrees Celsius. Any plate with greater than 50 colonies was designated Too Numerous to Count (TNTC), comparable to a “poor” level of sanitation in standard RODAC assays. For calculations, TNTC was represented as 51 colonies which was used to formulate graphical illustrations. Commercially available chemical detergents (Monofoil, TEGO, Quatricide, AJAX Spray&Wipe, F-10, Virkon) were prepared and used according to manufacturer’s label. Experiments looked at each surface before and after cleaning with a commercial disinfectant, HIUVL exposure, or both. Ultraviolet decontamination was performed by The TORCH™ (ClorDysis, Inc.). The TORCH is a portable disinfection system containing eight high powered UVC (ultraviolet C) lamps. These lamps produce intense radiation that is able to get a (calculated) 99% reduction in bacterial contamination within 10 feet (quote from ClorDiSys brochure). Each area was exposed to ultraviolet light for 45 minutes which represents a median level required to achieve a 6 Log reduction in bacterial numbers according to manufacturer’s literature5.

Laboratory animal facilities go to great lengths to eliminate, minimize the spread of, and prevent exposure to pathogens in rodent colonies in order to maintain Specific Pathogen Free (SPF) status. In order to decontaminate new facilities or “reset” animal rooms after depopulation, traditionally an area is physically/chemically cleaned and then exposed to either vaporized hydrogen peroxide or to chlorine dioxide gas1,2. These procedures involve considerable time1, hazardous chemicals, and are costly. Having a quick, safe and efficacious device with which to decontaminate facilities could generate substantial savings of time and resources. This study looks at the use of a high-intensity ultraviolet light (HIUVL) device (The TORCH™) for decontamination of areas within a dedicated animal facility. Ultraviolet light exposure causes damage to nucleic acids and leads to cell death. UVC light is known to be both bactericidal and virucidal (germicidal) 6. Contemporary animal facilities utilize RODAC (replicate organism detection and counting) culture plates to monitor and evaluate the efficacy of cleaning and decontamination protocols. This study uses RODAC plates to evaluate and compare UV light exposure alone and along with chemical agents in a modern laboratory animal facility.

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Figure 1: Torch™ device operating in a darkened room

Figure 2: Average colony counts before and after UV exposure alone.

Figure 3: Average colony counts from floor sampling

Figure 5: Average colony counts from wall sampling

Figure 4: Average colony counts from benchtop sampling

Figure 6: RODAC plates from a non-treated, a chemical decontamination, and a chemical + UV exposed floor sample. The plates show a clear reduction in bacterial colony counts after chemical decontamination and reduction to zero colony counts after chemical decontamination and UV exposure.

Conclusions

Discussion

• High-intensity UV light exposure is comparable in efficacy

to many commercially available chemical agents. • HIUVL used in addition to chemical agents produces

greatly reduced colony numbers to chemical agents alone and in many cases reduced bacterial counts to zero.

• HIUVL as an adjunct to traditional methods can enhance the efficacy of the cleaning program as well as allow for quick decontamination.

• HIUVL may provide a useful alternative or adjunct to traditional decontamination methods in laboratory animal facilities.

References

1. Non-manual techniques for room disinfection in healthcare facilities: a review of clinical effectiveness and guidelines. Rapid Response Report. Canadian Agency for Drugs and Technologies in Health.2014.

2. Decontamination systems comparison: Hydrogen peroxide vapor (HPV) vs. ultraviolet radiation(UVC). Bioquell white sheet.2012.

3. Jinadatha et al. Evaluation of a pulsed-xenon ultraviolet room disinfection device for impact on contamination levels of methicillin-resistant Staphylococcus aureus. BMC Infectious Diseases. 2014, 14:187.

4. Owens et. Al. High-dose ultraviolet c light inactivates spores of Bacillus atrophaeus and Bacillus anthracis on non-reflective surfaces. Applied Biosafety. 2005. 10(4)240-247.

5. TORCH™ User Manual. ClorDiSys, Inc. 6. Rutala, W. et al. Guidelines for Disinfection and Sterilization in

Healthcare Facilities, 2008. Center for Disease Control. 2008.

In the current study a commonly used validation method (RODAC assay) was used to evaluate whether high intensity ultraviolet light (HIUVL) could be utilized for decontamination of high traffic areas of a laboratory animal facility. Results showed that when used alone, HIUVL was successful at significantly reducing colony counts on multiple surfaces in the areas tested. When HIUVL was used along with a chemical method, bacterial counts were nearly universally eliminated. HIUVL alone seemed to have it’s limits as the areas that were most highly colonized (floors) showed around a 60% reduction in colony count, whereas areas cleaner to begin with (walls) showed a complete elimination of colonies on in the RODAC assay. It should be noted that both wall and floor results would be considered “acceptable” or “good” levels of sanitation in most RODAC assays. The current study has limitations in that the virucidal activity of HIUVL was not evaluated (UVC is known to be virucidal6) and results could have been more qualitative if a “seeded” group of bacteria of a known concentration was placed on test surfaces4. In this study it is assumed that a relatively uniform population of bacteria is present on the tested surfaces which is unlikely but does reflect “real world” scenario in that areas tested were currently operational. Results obtained in this study represent a proof of concept that high intensity ultraviolet light can be used as a tool for decontaminating modern laboratory animal facilities. Also shown is that when HIUVL is used in combination with chemical agents, near sterile surfaces can be the result. Finally, with HIUVL an area can be decontaminated much faster than with gas or vapor methods which may allow for savings of time and funds. Further studies with more specifics are indicated.