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The Ebola Disinfection Booth: Evaluation of an Enclosed Ultraviolet Light Booth for Disinfection of Contaminated Personal Protective Equipment Prior to Removal

Published online by Cambridge University Press:  20 July 2015

Myreen E. Tomas,
Jennifer L. Cadnum,
Annette Jencson and
Curtis J. Donskey
Myreen E. Tomas
Affiliation:
Geriatric Research, Education, and Clinical Center, Cleveland Veterans Affairs Medical Center, Cleveland, Ohio
Jennifer L. Cadnum
Affiliation:
Case Western Reserve University School of Medicine, Cleveland, Ohio
Annette Jencson
Affiliation:
Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio
Curtis J. Donskey*
Affiliation:
Geriatric Research, Education, and Clinical Center, Cleveland Veterans Affairs Medical Center, Cleveland, OhioDivision of Infectious Diseases, Department of Medicine, Case Western Reserve University, Cleveland, Ohio.
*
Address correspondence to Curtis J. Donskey, MD, Geriatric Research, Education, and Clinical Center (1110 W), Cleveland Veterans Affairs Medical Center, 10701 East Boulevard, Cleveland, Ohio 44106 (curtisd123@yahoo.com).
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Abstract

A portable booth designed to disinfect full-body coverage protective equipment before removal using ultraviolet-C radiation resulted in at least 3 log reductions in bacteriophage MS2 and methicillin-resistant Staphylococcus aureus within 3 minutes. The booth could be useful for disinfection of contaminated protective equipment before removal during care of Ebola patients.

Infect Control Hosp Epidemiol 2015;36(10):1226–1228

Information

Type
Concise Communications
Information
Infection Control & Hospital Epidemiology , Volume 36 , Issue 10 , October 2015, pp. 1226 - 1228
Copyright
© 2015 by The Society for Healthcare Epidemiology of America. All rights reserved 

Contamination of the skin and clothing of healthcare personnel may occur during removal of personal protective equipment (PPE).Reference Williams, McGraw and Schneck 1 Such contamination may place healthcare personnel at risk, as illustrated by recent cases in which Ebola virus infection was acquired despite use of PPE.Reference Fischer, Hynes and Perl 2 To reduce the risk for contamination during care of patients with suspected or confirmed Ebola virus infection, the Centers for Disease Control and Prevention have recommended disinfection of gloves at multiple steps during PPE doffing. 3 Disinfection of other protective equipment with a disinfectant wipe or spray is recommended if visible contamination is present. However, pathogen contamination often occurs without visible soiling and application of effective quantities of liquid disinfectants to equipment such as gowns and face shields may not be feasible.Reference Tomas, Kundrapu and Thota 4

Ultraviolet C (UV-C) irradiation is effective in killing viruses, including Ebola, and may be more effective against enveloped viruses such as Ebola than against nonenveloped viruses. Reference Sagripanti and Lytle 5 – Reference Lytle and Sagripanti 6 In a previous study, a pulsed xenon UV room disinfection unit was effective in reducing a nonenveloped canine parvovirus on PPE.Reference Jinadatha, Simmons and Dale 7 However, room disinfection units do not provide an ideal method to deliver UV-C for PPE disinfection. The Daylight Disinfection Suite Model 1077-02 (Daylight Medical) is a novel, portable UV-C disinfection booth designed for disinfection of full-body coverage PPE prior to removal. Here, we tested the efficacy of the booth for reduction of microorganisms inoculated onto PPE and used photochromic detection strips to assess whether UV-C penetrated through PPE.

METHODS

The Daylight Disinfection Suite is a portable 4.5 ft deep×4.5 ft wide × 7.5 ft tall rectangular booth with an inner reflective surface that delivers UV-C radiation via 4 low-pressure UV-C lamps. The booth is designed to allow personnel wearing full-body coverage protective equipment to stand inside while the system disinfects outer equipment prior to removal. The maximal distance from the UV-C lamps is 2 feet at the center of the booth, and contaminated sites can be placed close to the lamps.

We examined the efficacy of the booth for killing microorganisms inoculated on sections of gloves or gowns and on steel disks. The test organisms included bacteriophage MS2 (American Type Culture Collection 15597-B1), a nonpathogenic surrogate for small RNA viruses such as EbolaReference O’Connell, Bucher and Anderson 8 ; and a clinical methicillin-resistant Staphylococcus aureus (MRSA) isolate from pulsed-field gel electrophoresis type USA300. Bacteriophage MS2 was propagated in Escherichia coli 15597 as previously described.Reference O’Connell, Bucher and Anderson 8 For MRSA, testing was performed in the presence or absence of 5% fetal calf serum.

Ten μL of phosphate-buffered saline or 5% fetal calf serum containing bacteriophage MS2 or MRSA was inoculated onto 1-cm2 sections of gloves and gowns and on 1-cm2 steel disks; the carriers were affixed to glass microscope slides. For each organism, the inoculum applied to the carriers was adjusted such that 5 to 6 log10 colony-forming units/cm2 were recovered from untreated controls. The carriers were positioned vertically at a height of 4 feet inside the booth at distances of 6 inches from one bulb or in the center of the booth at 2 feet from each of the 4 bulbs; for a subset of experiments, carriers were placed 2 feet from the bulbs at heights of 1, 2, 4, and 6 feet within the booth. The organisms were treated for 30 seconds or 1, 3, or 5 minutes. The carriers were each submersed in 1 mL of phosphate-buffered saline and vortexed for 1 minute; dilutions were plated onto selective media and enumerated as previously described.Reference O’Connell, Bucher and Anderson 8 – Reference Nerandzic, Cadnum, Pultz and Donskey 9 Following 24 hours of incubation for bacteriophage and 48 hours for MRSA, log10 plaque-forming unit or colony-forming unit reductions were calculated by comparing the recovery after UV-C disinfection with untreated controls.

Similar experiments were conducted in which the pathogens were inoculated onto a face shield and Tyvek coverall (DuPont) at the wrist, elbow, shoulder, chest, waist, knee, and ankle; the suit was suspended to mimic the position of a healthcare worker standing in the center of the UV-C booth and treated for 5 minutes. The suit and face mask were sampled using premoistened swabs and processed as described previously. All experiments were performed in triplicate. Data were analyzed using R, version 3.1.1.

To assess penetration of UV-C through PPE, we placed UV-C photochromatic detection strips (Daylight Medical) on the inner surface of gloves, gowns, and face shields during exposure for 5 minutes and evaluated for color change indicating UV-C exposure.

RESULTS

As shown in Figure 1, the UV-C disinfection booth reduced recovery of bacteriophage MS2 and MRSA with greater reductions occurring with increased exposure time and closer proximity to the UV-C lamps. A reduction in both pathogens of 3 or more log10 colony-forming units was achieved in 1 minute at 6 inches from a UV-C lamp and in 3 minutes at 2 ft from the lamps. The efficacy of the UV-C disinfection booth was not significantly reduced by the presence of 5% fetal calf serum or by placement at different heights within the booth (data not shown). On the face shield and Tyvek suit, a 5-minute exposure resulted in a reduction in MRSA of 4 or more log10 colony-forming units and a reduction in bacteriophage MS2 of 5 or more log10 plaque-forming units at all inoculation sites. Photochromatic detection strips demonstrated no evidence of UV-C penetration of PPE materials during 5 minutes of exposure.

FIGURE 1

The efficacy of an ultraviolet-C radiation disinfection booth for reduction of bacteriophage MS2 (A) and methicillin-resistant Staphylococcus aureus (MRSA) (B) with and (C) without organic load dried onto carriers including glove and gown material and steel disks. The log10 plaque-forming unit (PFU) and log10 colony-forming unit (CFU) reductions per square centimeter are shown for bacteriophage MS2 and MRSA, respectively. Carriers contained 5 to 6 log10 PFU or CFU of the organisms. The carriers were irradiated for 30 seconds or 1, 3, or 5 minutes at a distance of 6 inches from one of the ultraviolet-C lamps or in the center of the booth at 2 feet from each of the 4 ultraviolet-C lamps. The means of the data from experiments conducted in triplicate are presented. Error bars indicate standard error.

DISCUSSION

The UV-C disinfection booth reduced recovery of bacteriophage MS2 and MRSA by 3 logs or more on PPE materials within 1 minute at 6 inches from a UV-C lamp and within 3 minutes at 2 feet from the lamps. Reduction in MRSA was equivalent at different heights within the booth and was not significantly reduced by 5% fetal calf serum. These data suggest that the UV-C disinfection booth could be useful for rapid disinfection of contaminated full-body coverage PPE used in care of patients with suspected or confirmed Ebola virus infection prior to removal.

Our findings are consistent with a recent study that demonstrated that a pulsed xenon UV room disinfection unit was effective in reducing recovery of a nonenveloped canine parvovirus on PPE by more than 4 logs with a 5-minute exposure time at a distance of 2 meters.Reference Jinadatha, Simmons and Dale 7 The UV-C disinfection booth described here offers some potential advantages over room disinfection units. The booth is quiet and the exposure time of 3 minutes is feasible for busy personnel. The use of a booth limits the site of UV-C exposure to a small area, avoiding potential exposure of other personnel, while positioning of lamps on all 4 corners of the booth provides 360° UV-C exposure.

Our study has some limitations. First, although we demonstrated that UV-C did not penetrate through PPE used in our facility, other hospitals considering use of UV-C should verify that it does not penetrate their PPE. In addition, testing of penetration of UV-C should include wet or heavily soiled PPE. Although UV-C did not penetrate the face shield tested in this study, to minimize the risk of ocular exposure, additional protection such as UV-C filtering goggles might be reasonable. Second, although 5% fetal calf serum did not adversely affect the efficacy of disinfection, it is likely that efficacy would be reduced by heavy contamination with blood, stool, or vomitus. Thus, we recommend that physical cleaning of visibly contaminated areas be performed before PPE removal. Third, future studies are needed to evaluate the efficacy and feasibility of using the booth for disinfection of contaminated PPE worn by personnel in Ebola virus training sessions. In addition, studies are needed to evaluate strategies to optimize the safety of UV-C for PPE disinfection (eg, use of UV-C for disinfection of selected areas of PPE rather than for full-body disinfection).

ACKNOWLEDGMENTS

Daylight Medical provided the UV-C booth for testing and it was returned after completion of the experiments. The company did not have any role in planning or design of the study nor was any compensation received.

Financial support. Department of Veterans Affairs (Merit Review grant to C.J.D).

Potential conflicts of interest. C.J.D reports that he has received research grants from Steris, Clorox, Cubist, and Gojo and has served on scientific advisory boards for 3M, Cubist, and Merck. All other authors report no conflicts of interest relevant to this article.

References

REFERENCES

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Figure 0

FIGURE 1The efficacy of an ultraviolet-C radiation disinfection booth for reduction of bacteriophage MS2 (A) and methicillin-resistant Staphylococcus aureus (MRSA) (B) with and (C) without organic load dried onto carriers including glove and gown material and steel disks. The log10 plaque-forming unit (PFU) and log10 colony-forming unit (CFU) reductions per square centimeter are shown for bacteriophage MS2 and MRSA, respectively. Carriers contained 5 to 6 log10 PFU or CFU of the organisms. The carriers were irradiated for 30 seconds or 1, 3, or 5 minutes at a distance of 6 inches from one of the ultraviolet-C lamps or in the center of the booth at 2 feet from each of the 4 ultraviolet-C lamps. The means of the data from experiments conducted in triplicate are presented. Error bars indicate standard error.