Reuse of Disposable Isolation Gowns in Rodent Facilities during a Pandemic

Abstract

Reuse of disposable personal protective equipment is traditionally discouraged, yet in times of heightened medical applications such as the SARS CoV-2 pandemic, it can be difficult to obtain. In this article we examine the reuse of disposable gowns with respect to still providing personnel protection. XR7, a fluorescent powder, was used to track contamination of gowns after manipulation of rodent cages. Mouse cages were treated with XR7 prior to manipulations. Disposable gowns were labeled for single person use and hung in common procedure spaces within the vivarium between usages. A simulated rack change of 140 cages was completed using XR7-treated cages. One individual changed all cages with a break occurring after the first 70 cages, requiring the gown to be removed and reused once. To simulate research activities, 5 individuals accessed 3 XR7-treated cages daily for 5 d. Each mouse in the XR7-treated cages was manipulated at least once before returning cages to the housing room. Disposable gowns were reused 5 times per individual. Gowns, gloves, clothing, bare arms, and hands were scanned for fluorescence before and after removing PPE. Fluorescence was localized to gloves and gown sleeves in closest contact with animals and caging. No fluorescence was detected on underlying clothing, or bare arms and hands after removing PPE. Fluorescence was not detected in procedure spaces where gowns were hung. The lack of fluorescence on personnel or surfaces indicate that gowns can be reused 1 time for routine husbandry tasks and up to 5 times for research personnel. A method for decontamination of used gowns using Vaporized Hydrogen Peroxide (VHP) was also validated for use in areas where animals are considered high risk such as quarantine, or for fragile immunocompromised rodent colonies.

The development of allergies is a common risk associated with handling laboratory animals.^1,4 A report by the Division of Occupational Health and Safety (OSHA) states that 1 out of every 3 to 5 individuals who work with laboratory animals will develop allergic symptoms, and that the best approach to reducing the development of allergies is to eliminate or minimize exposure through the use of engineering controls and PPE such as masks, gowns and gloves.⁴ PPE when used in combination with engineering controls, such as the use of biosafety cabinets (BSCs), increased room ventilation rates, and individually ventilated caging (IVC) systems, helps provide an extra barrier for personnel from hazards such as allergens. When hazards such as allergens cannot be controlled by other means, PPE serves as the last means of protecting personnel from exposure to laboratory animal allergens (LAA).¹¹ According to a national survey of 198 organizations, the most commonly used PPE items to control exposure were uniform/clothing covers and gloves.¹⁵ This further solidifies the importance of PPE items such as isolation gowns, in minimizing personnel exposure to LAA and further confirms the need to maintain a supply of gowns for personnel use. When considering the reuse of disposable gowns, it is important to determine if the item can provide an effective barrier and minimize personnel exposure to LAA.

Current requirements for animal care technicians at this institution include changing into scrubs prior to working in the animal vivarium, with minimum PPE requirements for entering a sterile or barrier housing room being a disposable gown, surgical facemask, hair bonnet, and gloves.⁹ Research staff are not required to change into scrubs but are held to the same minimum PPE requirements. Scrubs for animal care technicians are donned in a common use locker room outside of the animal facility. PPE is not required to enter the vivarium but is required before entering the animal housing spaces. PPE is typically donned before entering the animal housing spaces directly outside of the animal room door. Disposable PPE is required to be discarded after a single use and work uniforms worn by animal care technicians are required to be removed prior to leaving and laundered at the facility as another measure to minimize exposure to LAA. All barrier rodent housing rooms and procedure rooms are ventilated rooms with a minimum of 10 to 15 air exchanges and use engineering controls such as BSCs when handling rodents. For these studies, the air changes per hour (ACH) in procedure spaces (n = 20) were measured at 44.38 ± 0.9 ACH and at 14.3 ± 0.2 ACH in animal rooms (n = 39). In addition, 98% of rodent housing rooms use IVC systems which have been proven to minimize allergen exposure and decrease health risks among personnel.^6,7 Studies have also shown that building ventilation in conjunction with the use of IVC systems function to reduce disease spread within animal populations.⁵ The use of different engineering controls within our facilities made the reuse of PPE items such as disposable gowns a viable option without compromising personnel or animal health.

Recent global impacts of the novel coronavirus SARS-CoV-2 (COVID-19) have resulted in shortages and significant price increases for single-use PPE items such as isolation gowns, surgical face masks and eye protection.¹³ Isolation gowns accounted for the largest expenditure in the PPE budget at our institution, indicating the significance of this item for working in the animal facility.⁹ A recent inhouse survey on the utilization of PPE by facility staff, performed prior to the COVID-19 pandemic and this study, found that each animal care technician (n = 26) used an average of 5.7 gowns per day, while each veterinary technician (n = 5) used an average of 4.9 gowns per day. This further supports the importance and need to maintain a supply of isolation gowns for staff use. Prior to COVID-19, gown expenditure was $63.90 per day for staff including both animal care and veterinary technicians. Current expenditure for disposable gowns using the average gown usage for facility staff prior to COVID-19 and current prices for isolation gowns, equates to $369.58 per day, a 4-fold increase. The high rate of use for disposable gowns, in combination with current shortages and high prices, prompted the decision to reevaluate gown use requirements in the rodent vivarium. The goal of this study was to develop practices to prevent a lapse in supply while continuing to protect personnel from contaminants such as LAA. Current CDC guidelines for optimizing supplies of isolation gowns recommend strategies such as alternatives, reusable cloth, and reuse of disposable gowns.¹²

This study was designed to evaluate the disposable isolation gown’s ability to provide protection to personnel from exposure to contaminants, such as LAA, after multiple uses. This process requires an assessment of the level and distribution of contamination after use, and during storage between uses. XR7 contamination powder, a nontoxic, inexpensive, fluorescent powder was used to simulate possible contaminants such as LAA. Fluorescent dyes and powders, such as XR7, are used frequently in hospital and medical settings as a means of demonstrating environmental contamination due to its ease of use and ability to simulate contaminants on different surfaces.⁹

Finally, in collaboration with another institution, this study tested a method to decontaminate isolation gowns using Vaporized Hydrogen Peroxide (VHP) and thereby to extend the life of single use gowns used in areas for restricted animal populations. Decontamination of used isolation gowns can be considered for those facilities that wish to extend the reuse period in areas where animals are considered high risk, such as quarantine, or for fragile immunocompromised rodent colonies. Decontamination may also allow the reuse of gowns in specific situations working with particular “restricted” mouse populations such as Corynebacterium bovis, and murine norovirus negative animals.

Given a strict barrier facility, with increased air exchanges, ventilated caging, and the use of BSCs when performing animal use activities, we hypothesized that extending the use of disposable isolation gowns would have minimal impact on exposure of personnel to particulates generated during manipulation of rodent cages. We also hypothesize that extending the use of disposable isolation gowns will have a substantial impact on PPE expenditure, which will help facilities to continue to purchase PPE items such as disposable isolation gowns, on limited budgets.

Materials and Methods

Participants.

This study was approved by the Institutional Review Board human research protection program. Participants were volunteers currently employed by the institution and were informed that they were participating in a study prior to their involvement. Volunteers were not compensated and were not graded on their performance of tasks. No identifiable information was recorded for any participant.

Ethical statement.

All procedures were reviewed and approved by the Ohio State University’s IACUC prior to study initiation. The program is AAALAC accredited and compliant with all applicable federal regulations. The procedures for the sterilization and reuse of PPE were reviewed and approved by the Colorado State University’s Institutional Biosafety Committee.

Animals and housing.

For the simulation of cage changing activities (husbandry tasks), male and female mice (10 cages at a density of 2 to 5 mice per cage) were used for the first trial (time point 1). Male and female mice (99 cages at a density of 1 to 5 mice per cage) were used for the second and third trials (time point 2 and 3). For the simulation of investigator activities (research tasks), male and female (5 cages at a density of 4 to 5 mice per cage) mice were used. Various strains of mice were used for both simulations. All mice were donated from the institutions teaching colony and other protocols and had no experimental manipulations. Mice were housed in Allentown NexGen IVC rack caging system (Allentown, NJ). Animal health was monitored using dirty bedding sentinels and exhaust air dust sampling quarterly.

Materials.

XR7 fluorescent powder was used as an identifier of contamination in the study (Black Light World, Cub Run, KY). Contamination powder is milled at a 325-to-2500 mesh, which approximates a 44-μm final size. XR7 glows blue under black light (365nm). XR7 was used to mimic airborne particulate transfer from rodent cages during manipulation. Standard cloth-type polypropylene isolation gowns (MedSupply Partners, Atlanta, GA) were used for cage change and investigator simulated activities, in addition to bonnets, surgical face masks, and gloves (Lighthouse Life Sciences, Woburn, MA). Command small wire hooks (3M, St Paul, MN) were used for hanging gowns throughout the animal spaces. Wypall wipes (Kimberly-Clark, Roswell, GA) and Spor-Klenz (Steris Life Sciences, Mentor, OH) were used to disinfect the BSC, mouse cages, and gloves during handling. The VHP 1000-ARD Biodecontamination unit (Steris Life Sciences, Mentor, OH) designed to use Vaporized Hydrogen Peroxide (VHP) was used for decontamination of gowns. Steraffirm VH2O2 Process Indicators and Spordex VH202 Biologic Indicators containing Geobacillus stearothermophilus spores (Steris Life Sciences, Mentor, OH) were used as chemical and biologic indicators to validate the VHP process.

Preparation of experimental cages.

One teaspoon (4 g) of XR7 was added directly to the bedding of all mouse cages at least 30 min before any manipulations. For husbandry tasks, XR7 was added to the cage on the morning of cage changes for time point 1 and on the day before cage changes for time points 2 and 3. For research tasks, XR7 was added at least 30 mins before any manipulations on the first day of the 5-d study period. The cages used in the research tasks were checked daily with a black light, prior to the start of manipulations, to determine if additional XR7 needed to be added to the cage. No reduction in cage fluorescence was detected over the course of the 5-day study; therefore, additional XR7 was not added to these cages during the study. A preliminary study performed at the collaborating institution found that one teaspoon of XR7 was an adequate amount to achieve even distribution throughout the cage. Prior to the start of all experiments, the mice and cage environment were evaluated with a black light for fluorescence to ensure the presence and even distribution of XR7.

Husbandry tasks.

This experiment was designed to evaluate the contamination of disposable gowns and personnel after performing a routine standard husbandry task such as changing dirty cages. Husbandry tasks were was repeated 3 times by a single individual at 3 separate time points. At time point 1, a single individual completed 140 cage changes and at time points 2 and 3, 99 cages were changed. A total of 10 XR7-treated cages were used for time point 1, with 8 of the cages containing 5 mice each and 2 cages containing 2 mice each. A total of 99 XR7-treated cages were used for time points 2 and 3, with cages containing 1 to 5 mice per cage. The number of cages changed was selected to represent an entire rack (140 cages) or to mimic the maximum number of cages changed in a single day (83 cages ± 4) by staff (n = 22) at our largest rodent facility. Staff at our largest rodent facility are expected to change at least 80 cages per day depending on the room capacity and research personnel activity in the room. Due to the number of research personnel needing access to the biosafety cabinet, husbandry personnel at our facility stagger cage changes throughout the week. The number of cages included in this study exceeds the number of cages that staff are expected to change daily. Clean dark scrubs were worn at all time points to maximize visibility of any potential fluorescence. For all time points, staff donned a new unused set of PPE (hair bonnet, facemask, disposable gown, and gloves) before entering the room and before beginning cage changes. Setup for cage changes consisted of stacks of 5 clean cages, containing bedding and a cotton square with a lid covering the topmost cage. All cage changes were performed in a class II type A2 BSC (SterilGARD III Advance, The Baker Company, Sanford, ME) that had been disinfected using a Spor-klenz soaked Wypall prior to performing cage changes. Each Allentown NexGen IVC rack holds 140 ventilated mouse cages.

A total of 10 cages were used for time point 1 to simulate a complete rack change. All 140 cage changes were performed by a single individual on that day. Mouse cages were treated with XR7 and marked to ensure that mice were not mixed between cages during the simulation. Treated cages were placed on a clean rack and allowed to rest for 30 min before starting the simulation to allow time for distribution of XR7 throughout the cage. The outer surface of the cages and gloves were wiped with a Spor-klenz soaked Wypall before opening the cage and handling the mice. All cages were carried by the technician from the IVC rack to the BSC where cages were changed. Mice were transferred from cages containing XR7 to a clean unused cage within a BSC, and the new clean cage placed back on the rack. Mice were transferred between cages by gently grasping each mouse by the base of the tail and placing them into the new cage. Mice were allowed to rest in the new cages for at least 10 min before further manipulation. After the rest period, mice were transferred back to their original “dirty” cage containing XR7 and then allowed to rest again for 10 min. This process was repeated 14 times per cage. Empty XR7-treated “dirty” cages were stacked on a cart outside of the BSC between cage changes to mimic usual husbandry practices. A lid was placed on the topmost cage to prevent aerosolization of particulates from the dirty bedding during the wait times. After 70 cage changes, the staff member had a break so that the gown could be removed, hung up, and redonned to imitate breaks within a normal workday. Before the break, PPE was evaluated for fluorescence, photographed, and then removed. The gloves and hair bonnet were discarded, and the gown was hung on a hook in a designated area. To comply with newly implemented COVID-19 recommendations, the mask was worn continuously. Scrubs, arms, and hands were evaluated for fluorescence and photographed prior to exiting the room. After the break, the original process was repeated until all cages were “changed.”

A total of 99 cages were used at time points 2 and 3 to mirror the maximum number of cages changed in a single day by staff. Mouse cages were treated with XR7 and handled using the same methods as described above at time point 1. Mice were transferred from XR7-treated cages to a clean unused cage within a BSC, and the new clean cage placed back on the rack, in contrast to being transferred back to original “dirty cages” as described above at time point 1. The technician did not take a break during the time needed to change all 99 cages. PPE was evaluated for fluorescence, photographed, and then removed using the same procedures described above at time point 1.

Rotation of the mice between XR7-treated cages and clean cages at the first time point allowed a reduction in the number of animals and materials required for the study. The mice used for time point 1 were a part of the teaching colony and are handled frequently, making them highly accustomed to human handling. The animal technician was very experienced, and handling of mice was quick and as gentle as possible to minimize stress in the animals while maintaining cage change procedures. Mice from all trials were carefully evaluated for health concerns or overt signs of stress after all cage changes.

Research tasks.

This experiment was designed to examine the amount of contamination from mouse cages to gowns and underlying clothing that might occur when performing a common research activity. A total of 5 cages of mice, 4 cages with 5 mice each and 1 cage with 4 mice, were used. Tumor measurement was selected as the handling activity for manipulation of mice. The 5 participants chosen to participate in this task consisted of veterinarians and medicine technicians who were familiar with the process of performing tumor measurements. Research tasks were repeated once daily for 5 d, with 5 different participants handling 3 different cages once each day. To mimic the daily influx of research staff, different time points for manipulation were chosen throughout the day with starting time points spread between the morning (9 AM) and the afternoon (12 PM). Scrubs and PPE worn by the participants were consistent with those previously described for the husbandry tasks. The gloves, mask and hair bonnet were replaced daily, but the disposable gown was labeled, and the same gown was used for the entire time period. 3 cages were selected at random from the 5 available for the handling activity.

Selected cages were removed from the rack, placed on a cart, and transferred to the minor procedure room for manipulation in the BSC. All manipulations were performed within a class II type A2 BSC (SterilGARD III Advance, The Baker Company, Sanford, ME) that had been disinfected using a Spor-klenz soaked Wypall prior to performing cage changes. All tumor measurements were performed using a ruler device designed inhouse. Tumor measurement was a simulation; none of the mice used in this experiment had actual tumors present. The simulation was designed to mimic the handling that would occur during tumor measurement. Staff were allowed to select the location for “tumor measurement;” different locations were chosen for “tumor growth” varying from flank to inguinal regions. To simulate differences in tumor measurement methods between research labs, study participants performed the sham measurement by selecting their own technique without any guidance or instruction. Thus, techniques used for restraint, measuring, and preference for sitting or standing at the BSC varied between participants. Restraint methods varied between a classic scruff and utilization of the cage wire to help stabilize and restrain the mouse. No restraint devices were used. The outer surface of the cages and gloves were wiped with a Spor-klenz soaked Wypall before opening the cage and handling the mice. Mice were selected at random from each cage for sham tumor measurements, and each mouse was measured once per day. Each mouse was restrained by hand, the measurement was made in the manner of choice, and the mouse was returned to its original home cage. This process was repeated for all 3 cages and then cages were transferred by cart back to the original housing locations. At this point, all PPE was evaluated for fluorescence and photographed. Gloves and hair bonnet were discarded, and the gown was hung on a hook in the procedure room. Scrubs, arms, and hands were also evaluated for fluorescence and photographed before exiting the room. To remain compliant with newly implemented COVID-19 recommendations, the mask was worn continuously.

The location for hanging the gowns in the procedure room was selected in an attempt to minimize disturbance and aerosolization of gown contaminants caused by drafts generated by opening and closing of the procedure room door. Gowns were left hanging in procedure spaces for the entire study period. Gowns were removed from their hooks only to perform cage manipulations. Normal activity and movement in the procedure room (moving supplies, personnel movement, etc) was allowed to continue while the gowns were hanging. The procedure room was located within the animal housing suite, which permitted personnel to use the same pattern for donning and doffing of PPE before reuse. Gowns, gloves, underlying scrubs, arms, and hands of all participants were photographed daily to aid in monitoring changes in fluorescence over time. The photographs were used to determine how many times the gowns could be reused while still providing protection to personnel. All contact and surrounding spaces were evaluated daily for fluorescence as well.

Quantification of XR7 on gowns and surfaces.

XR7 is a white powder, that in small quantities, is invisible in regular room light, but fluoresces a bright blue color when under a black light (365 nm). To facilitate visualization of the XR7, items were examined in a completely dark room against a dark background, with no light interference. To further aid in evaluating gown contamination, participants wore dark gray or black scrubs. Gowns, scrubs, and surfaces were scanned with a black light and photographed in the dark in the procedure rooms of the animal housing space. Black tint was placed over any windows and black heavy duty trash bags were used to seal the bottom of the door to prevent light from filtering into the room and to ensure that the room was completely dark when the lights were turned off. Areas that fluoresced under black light were considered contaminated while no fluorescence was considered negative.

Data Evaluation.

Assessment and estimation of gown contamination in this study were based on subjective visual assessment of PPE images taken after the performance of husbandry and research tasks described above. This information was strictly observational and was not meant to provide a statistical evaluation. Photographs taken throughout the study were assessed by 2 individuals (TC and AS) to identify XR7 contamination on study participants and PPE. To ensure that images were consistent between all experiments, photographs were taken by one individual (TC) who used the same camera and camera settings throughout the study. The individuals evaluating the photos were not blind to the experimental conditions; however, we do not believe that this would have affected the outcome of the study because evaluators were only identifying the presence, location and intensity of fluorescence and had no input on how tasks were performed.

All photographs were assessed at the end of the study to allow more consistent comparisons between images. Intense fluorescence was used to describe PPE items that appeared to glow more brightly than other PPE items that were positive for fluorescence. Items that appeared less bright were described as having minor fluorescence. Brighter fluorescence of some parts of the PPE versus others was attributed to the presence of more XR7 powder accumulation on that particular surface. Using the images provided, PPE items were identified as negative for fluorescence (no XR7 contamination) or positive for fluorescence (XR7 contamination present). PPE items positive for fluorescence were rated as intense fluorescence or minor fluorescence.

Storage and labeling of gowns for reuse.

Hooks and dry erase markers were placed in designated areas in all rodent housing facilities for hanging and labeling of gowns after use. Hooks for gowns were placed in areas with minimal drafts and traffic to reduce the chances of aerosolizing contaminants that may be attached to hanging gowns. Facility staff and research personnel labeled their gowns using a dry erase marker before placing it on the hook. A dry erase marker was used so that ink inadvertently marked onto walls or other surfaces could easily be removed while maintaining a permanent marking on the gowns. Labeling of gowns was to minimize handling and allow individuals to identify and wear their own gowns.

Cost analysis and cost savings.

The recent COVID-19 pandemic has caused significant increases in single use PPE items such as facemasks and single use isolation gowns. A cost analysis was performed to determine cost savings that would occur if gown reuse policies were implemented. Room entry requires personal card swipe access that allows identification of anyone entering the animal housing space. To determine the economic impact of gown reuse, user entry for one of the rodent animal housing rooms was evaluated for a 2-wk time period. These entries were separated into research staff and facility staff with the assumption that every entrance into the animal room required the use of one set of PPE. Gown expenditure was determined per person at pre-pandemic and post-pandemic prices. Gown prices, along with facility entry data, were used to determine the change in cost when shifting from gown disposal after single use to wearing a single gown several times.

% increase in cost = prices/person COVID (single use)

− gown prices/person pre-COVID (single use)

× 100 gown prices/person pre-COVID (single use)

% decrease in cost = gown prices/person COVID (single use)

− gown prices/person COVID (reuse)

× 100 gown prices/person pre-COVID

VHP gown decontamination.

Decontamination of used polypropylene cover gowns and coated isolation gowns made of a combination of polypropoylene and polyethylene (Medline Industries Mundelein, IL) was performed in a decontamination room adjacent to the ABSL3 space of the Rocky Mountain Regional Biocontainment Laboratory (Colorado State University, Fort Collins, CO). The decontamination rooms are approximately 8ft × 10ft with the capacity for at least 3 rows of shower rods to hang gowns and 4 shelf racks to stack gowns. The room was sealed using Frog Tape (Shurtech Brands, Avon, OH) to prevent leakage of vaporized hydrogen peroxide (VHP) from the room during the decontamination process. The VHP unit was placed outside of the sealed room and connected to the intake and exhaust ports of the decontamination room. Our VHP unit uses a closed-loop configuration with conditioned air as a carrier to deliver Vaprox hydrogen peroxide sterilant vapor to exposed surfaces (STERIS Life Sciences, Mentor, OH). This closed-loop configuration also allows the decontamination process to take place at or near atmospheric pressure. Gowns were either hung or stacked for decontamination. Gowns were hung about 4 inches apart or stacked loosely, 3 to 4 gowns high, on racks. Each VHP decontamination cycle took approximately 5 h to complete. To validate gown decontamination, up to 10 chemical and biologic indicators were used for each decontamination cycle. Spordex VH202 biologic and Steraffirm VH202 chemical indicators were placed in the corners of the room and within the gowns during each cycle for validation. Indicators were taped to the inside of gowns that were on hangers, and in the middle of those that were stacked. Chemical indicators were assessed prior to entry to retrieve the biologic indicators. Biologic indicators were removed 24 h after the decontamination cycle and incubated at 56 °C for 7 d to check for growth. After 7 d without growth, the gowns were folded, placed in a 48-quart Sterilite container (Sterilite Corporation, Townsend MA) and removed from the decontamination chamber for reuse. A new cycle was not initiated until biologic indicators from the previous cycle were evaluated and negative for growth. Each decontamination cycle took approximately 8 d including room staging, VHP decontamination, bacterial culturing, and repackaging. A total of 8 decontamination cycles have been completed over a period of 90 d.

Results

Examination of caging and mice prior to starting any manipulations demonstrated fluorescence throughout the bedding, on the cage wire and on the food (Figure 1). Fluorescence was also observed on the snout, footpads, and tail of the mice in the cage (Figure 1).

Figure 1.

(A) XR7 distribution and fluorescence in a treated cage compared with a control cage with no XR7 added. XR7 is shown to have dispersed throughout the bedding in the treated cage. (B) and (C) A mouse in white light compared with a mouse under UV light demonstrating dispersal of fluorescence on the snout and footpads of mice in XR7-treated cages.

Husbandry tasks.

Evaluation of Components of the PPE were evaluated for fluorescence after 70 cage changes (time point 1, before the break). The hair bonnet and surgical facemask were negative for fluorescence. Gloves fluoresced on the top surface of the glove and on the palms, with most fluorescence occurring at the fingers and fingertips of the dominant hand (Figure 2) . Fluorescent areas of the gown were mostly restricted to the medial surface of both right and left lower sleeves near the hands (Figure 2). No other areas of the gown, including the front, fluoresced. This distribution is consistent with the areas of the body that were in closest contact with the XR7-treated mice and mouse cages and therefore were at the highest risk of being contaminated. The affected areas were always those that were in the BSC when animal work was being performed, indicating minimal risk of personnel exposure to contaminants. Evaluation of the scrubs, bare arms, and hands showed no discernable fluorescence, indicating that XR7 did not transfer from the gown to underlying clothing or skin when taking the gown off or putting the gown back on (Figure 3). This indicates that particulates generated during the change out process are unlikely to transfer from the gown to other surfaces.

Figure 2.

Demonstrates intense fluorescence of gowns and gloves after performing husbandry and research tasks. Fluorescent areas of the gown were mostly contained to the inner surface of both right and left lower sleeves (A). Fluorescence of gloves was noted on the palms (B) and on the top surface of the glove (C) with the most fluorescence occurring at the fingers and fingertips of the dominant hand.

Figure 3.

No discernable fluorescence was noted during evaluation of scrubs (A) or bare arms and hands (B and C) after completion of the cage changes (husbandry tasks).

Evaluation of PPE after the break for time point 1 was consistent with results seen before the break, with similar areas of fluorescence noted on the gown and gloves. Scrubs, bare arms, and hands remained negative for fluorescence. Evaluation of the individual gown, gloves, scrubs, and bare skin after time points 2 and 3 followed the same pattern as seen for time point 1. Fluorescence of gloves was mostly contained to the fingers and fingertips while gown fluorescence was contained to the medial surface of both right and left lower sleeves near the hands. No discernable fluorescence was present on the scrubs or bare skin. Because these procedures represent the “dirtiest” task performed by animal technicians on any given day, these results indicate that husbandry personnel can use a single gown throughout a single day.

Research tasks.

Scrubs, bare arms, and hands were evaluated before starting manipulations each day and were negative for fluorescence. The most fluorescent portion of the gowns for the 5 participants was localized to the medial surface of both right and left lower sleeves, near the hands. One of the 5 gowns had intense fluorescence on the front portion of the gown, with a majority of the contamination centering around the waist region, and 2 other gowns had fluorescence on the upper left shoulder area, with minor fluorescence of the front portion (waist and lap region) of the gown. This distribution was determined to be due to differences in the position of the operator while performing manipulations (sitting compared with standing), as the 3 gowns with contamination on the front surfaces of the gowns belonged to individuals who performed the task while sitting down. This observation indicated that individuals performing measurements while sitting were more likely to have contamination on the front surface of the gown. Variations in area of mouse tumor measurement (flank compared with groin) did not have any affect on contamination of the gown with the XR7. The gloves of all 5 participants had intense fluorescence even though all participants wiped their gloves with a Spor-klenz soaked Wypall between cages. This finding is consistent with expectations, as the gloves were in closest contact with the XR7-treated mice and mouse cages and were at the highest risk of being affected by contaminants. Fluorescence of gloves was detected on the top surface of the gloves and on the palms. The predominant areas of fluorescence occurred on the palms and at the fingers (usually the inner surface of the thumb), and fingertips of the hand used for restraint. Even though gloves were heavily contaminated with XR7, the outside of manipulated cages was minimally contaminated with XR7. All hair bonnets and facemasks were negative for fluorescence. Examination of scrubs, bare arms, and hands had no discernable fluorescence. Spaces in the immediate vicinity of the hanging gowns, including the floor, wall, and worktable, were scanned for fluorescence daily to aid in determining whether contaminants would be able to aerosolize from the hanging gowns to nearby surfaces. No fluorescence was detected on the wall, floor, or worktable in the immediate vicinity of the hanging gowns. This finding indicates that contaminants do not appear to transfer from the gown to nearby surfaces, even with drafts created by normal movement within the space. Underlying clothing and bare skin remained negative for fluorescence after handling used gowns throughout the study. According to vivarium entry data for the facility, researchers enter the vivarium an average of 4 times (4.3 ± 0.5, n = 48) per week (7 d), indicating that researchers should be able to reuse one gown for up to one week before requiring a new gown. Thus, researchers can reuse gowns a maximum of 5 times without increasing the risk of personnel exposure to contaminants.

Cost analysis and cost savings for gown resuse.

Facility entry data and gown expenditure were used to calculate cost and determine cost savings between single use and reuse gown practices. Isolation gowns at our institution have increased from $0.37 to $3.37, an 8-fold increase in price. Some research facilities may have difficulty in budgeting for PPE due to the significant increases in price. Cost was not a primary consideration for implementing the reuse of gowns for this study, but cost savings is nonetheless an important consideration when evaluating PPE requirements, especially with recent events and recent price increases. A total of 206 entries into the facility by research staff (n = 48) over the 2-wk period required the use of 206 sets of PPE. The average number of times per week that any individual entered the facility was 4.3 ± 0.5, supporting the recommendation for reuse of gowns up to 5 times within a 7-d period. Based on our costs, the single use of isolation gowns at a price of $0.37 per gown would cost $1.58 per person per week and $14.46 per person per week at $3.37 per gown. Allowing research staff to reuse 1 gown a maximum of 5 times decreases gown expenditure to $3.37 per person per week. To determine cost savings due to gown reuse, the cost of using 4 gowns per week at $3.37 per gown was compared with reusing 1 gown per week at $3.37 per gown, totaling a savings of 77% on gown expenditure (Table 1). Facility staff had 296 total entries into the facility (n = 33) over the 2-wk period requiring the use of 296 sets of PPE. The average number of times per week that any individual entered the facility was 9.0 ± 3.1. The single use of isolation gowns at a price of $0.37 per gown would cost $3.32 per person per week and $30.20 per person per week at $3.37 per gown. Facility staff are only allowed to reuse gowns 1 time per day. Allowing facility staff to reuse gowns 1 time per day decreases the gown expenditure to $16.85 per person per week. To determine cost savings with the implementation of gown reuse, the cost of using 9 gowns per week at $3.37 per gown was compared with the cost of using 5 gowns per week (1 gown per day) at $3.37 per gown, for a total savings of 44% on gown expenditure (Table 2). Total cost savings for both facility staff and research staff combined would equate to $24.43 per person per week. A total cost savings of this magnitude can have a substantial economic impact for budgeting for PPE items.

Table 1.

Research personnel cost comparison.

	Single gown use, Pre-COVID-19 cost	Single gown use, COVID-19 cost	Reuse of 1 gown for 7 d (5 times), COVID-19 cost
Price per gown	$0.37	$3.37	$3.37
Gowns used per week	206	206	1
Weekly cost per person	$1.58	$14.46	$3.37
Weekly cost increase at current pricing:		+815.02%	+113.29%
Weekly expenditure with gown reuse at current pricing:			−76.69%

Supply demands during the COVID-19 pandemic led to an 8-fold increase in cost per gown. Cost comparisons of previous and revised guidelines were based on data averaged from 4.29 ± 0.5 weekly entrances of n = 48 research personnel calculated over a 2-wk period.

Table 2.

Facility staff cost comparison.

	Single gown use, Pre-COVID-19 cost	Single gown use, COVID-19 cost	Reuse of 1 gown for 7 d (5 times), COVID-19 cost
Price per gown	$0.37	$3.37	$3.37
Gowns used per week	296	296	5
Weekly cost per person	$3.32	$30.20	$16.85
Weekly cost increase at current pricing:		+810.81%	+408.26%
Weekly expenditure with gown reuse at current pricing:			−44.2%

Cost comparisons of previous and revised guidelines were based on data averaged from 8.96 ± 3.1 weekly entrances of n = 33 facility staff calculated over a 2-wk period.

VHP gown decontamination.

Gowns were prepared for VHP decontamination by either hanging them on a shower rod or stacking them on a shelf rack. Chemical indicators placed with polypropylene gowns in either configuration demonstrated exposure to hydrogen peroxide, and the biologic indicators were routinely negative. Chemical indicators placed with the gowns made of a combination of polypropylene and polyethylene did not demonstrate exposure to hydrogen peroxide when they were stacked on the shelf. Similarly, the biologic indicators had positive culture results when stacked on the shelf rack, but not when they were hung. These results indicate that VHP can penetrate the polypropylene, but is less permeable to the combination material, which is more fluid resistant. An average of 350 gowns were processed in each cycle. The number was limited to the number of polypropylene and polyethylene gowns that could be hung on the rack and the number of polyethylene gowns that could be stacked on the shelves. The integrity of the gowns was assessed visually for effects of the VHP process on the gown material. The VHP process did not appear to result in a degradation of the materials.

Discussion

The COVID-19 pandemic has resulted in shortages and major price increases for single-use PPE items such as disposable isolation gowns. Research facilities that require gowns as part of its PPE may find it challenging to purchase enough gown supplies, as companies may not be able to fill all request, or the prices may be exorbitant. According to the Food and Drug Administration (FDA), gowns are a critical element of PPE and are intended to pose a physical barrier to the transfer of microorganisms and other material.¹⁰ Given the importance of providing personnel with an additional layer of protection against exposure to contaminants, such as LAA and the difficulty in acquiring gowns from suppliers, we decided to consider the reuse of single-use isolation gowns.

Our results indicate that gowns can be reused a maximum of 5 times by research staff and a maximum of 1 d for facility staff without contamination of underlying clothing or arms and hands. The fluorescent powder (XR7) used to track particulate transfer was chosen based on availability, ease of use, and appropriate size. XR7 is almost invisible in white light, but clearly visible under black light illumination and fluoresces blue in color. XR7 is very light, easily aerosolized, and easily attaches to many different surfaces. According to the manufacturer, Blacklight World, XR7 is about 44μm in diameter.⁹ Airborne rodent allergens found in a wide range of particle sizes can be carried substantial distances in animal facilities.¹⁸ While some reports indicate a varied particle size for allergens, other sources report LAA in particles less than 10 to 20 μm.^3,4,11,18 Although the particle size of XR7 is larger than what may be expected for typical LAA, its ability to be aerosolized and ease of tracking made this an ideal choice for tracking contamination aerosolized from the rodent cage during handling.

Animal use activities were evaluated to determine the amount and area of gown contamination that occurred during a standard husbandry task such as changing soiled rodent caging and research activities such as tumor measurements. Both of these tasks are considered high risk for exposure to LAA due to the disturbance of allergen-contaminated materials and close contact with the animals. These activities are considered the “dirtiest” task that personnel perform on any given day. A lack of contamination of underlying clothing, bare arms, and hands after performing the procedures indicate that gown reuse is a reasonable consideration. Strict use of the BSC and the appropriate use of disinfectants were used whenever cages were opened and animals were handled. All materials and individuals were scanned before the start of each simulation to ensure that absence of fluorescence. PPE that was in closest contact with the experimental cages showed the highest levels of fluorescence. The most affected area of the gowns was the lower sleeves near the hands. Minor fluorescence was detected at the waist and upper shoulder of 3 gowns worn by individuals performing research tasks, which was perhaps due to the differences in technique that were used when measuring tumors. Some individuals chose to stand while performing measurements, while others chose to sit. Standing or sitting could influence how cages and animals are handled in the BSC. Individuals who chose to sit had a tendency to hold animals closer to the front of the BSC, allowing more opportunity for contaminants to aerosolize onto gowns and other PPE items outside of the BSC. Carrying the cages from the IVC rack to the BSC cabinet is another time at which contaminants may aerosolize onto gowns; however, fluorescence was not observed on the front of the gown of the individual in this portion of the study, perhaps because the individual was aware of their movements and careful when handling the cages during transfer from the rack to the BSC. However, this was not considered to be a significant factor in our findings.

Gloves fluoresced on the top surface of the hand, the palms and the fingers with the dominant hand showing the more intense fluorescence. Gloves maintained a high level of fluorescence despite being wiped with a disinfectant soaked cloth between cages. This high level of glove contamination was expected because the gloves were in closest contact with the XR7-treated animals and cage materials. Even though gloves had a high degree of contamination, minimal contamination was transferred to the outer surface of cages during handling, perhaps because of the wiping of the outer surface of the caging with a disinfectant soaked cloth prior to opening the cage and beginning manipulations. Standard cage handling procedures require that cages be wiped with a disinfectant before removing the cage lid to avoid the transfer of unwanted organisms into the cage environment. Fluorescence was not detected on the underlying scrubs or arms and hands of any of the individuals, indicating that contaminants did not transfer from the gown to underlying clothing or skin.

An important aspect of reducing the transfer of contaminants, such as LAA, from PPE items such as gowns is careful and methodical donning and doffing of PPE. PPE should be removed in a way that minimizes the aerosolization of allergens. Individuals were asked to put on a gown, bonnet, facemask, and gloves without any guidance as to the order or method. A majority of individuals in this study put on their gown first, bonnet second and gloves last. This order is consistent with a previous study reporting that most personnel put on the gown first followed by the hair bonnet and gloves.⁹ All individuals entered the facility already wearing facemasks to remain compliant with face covering guidelines due to COVID-19. When removing PPE, a small portion of individuals removed their gown first and gloves last. Although some individuals removed their gloves last, they did not contaminate scrubs or bare skin during the process. This indicates that the risk of personnel exposure to contaminants is low even when gowns are contaminated, especially if donning and doffing of used gowns is performed in a careful and methodical manner.

Gowns were also evaluated daily for fluorescence to determine if the intensity or area of fluorescence changed. Intensity of fluorescence was judged subjectively using pictures taken during evaluation of gowns with a black light. The intensity and pattern of fluorescence on the gowns did not appear to change at any point during the 5-d study period. The pattern of fluorescence remained consistent throughout the study period with the lower sleeve of the gown being the most affected. Observations from these animal handling experiments demonstrate the importance of the BSC for reducing contamination of PPE by particulates including LAA. The use of the BSC restricted the exposed areas of PPE to the lower portion of gown sleeves and the gloves. Decreasing surfaces exposed to contaminants through use of engineering controls minimizes personnel exposure and reinforces the need for multiple mechanisms to control the exposure of personnel to contaminants.

Gown storage areas were evaluated to determine if hanging and reusing gowns would allow aerosolization of contaminants to nearby surfaces. The failure to detect fluorescence indicates that actions such as opening and closing doors, movement of personnel and supply carts, and shuffling of gowns during retrieval for donning, do not cause aerosolization of particulates to other surfaces. Higher ventilation rates in animal use areas also aid in minimizing exposure of personnel to contaminants, such as LAA, that have the potential to be aerosolized.

Implementation of engineering controls such as BSCs, IVC systems, and the use of appropriate PPE has led to a decrease in exposure to and prevalence of LAA.^4,11,17 Even with decreased prevalence, LAA continues to pose a health risk to those that work with laboratory animals, specifically laboratory rodents. Continued efforts to minimize and prevent personnel exposure to contaminants, such as LAA, are extremely important and the reason that this study focused on LAA as the primary contaminant when proposing the reuse of gowns throughout rodent facilities. A combination of measures to control allergen exposure have become an integral component of a program for LAA management, as reviewed previously.⁸ Many believe that the best approach to the problem of LAA is prevention.^2,3,15 Engineering controls are the first line of defense against contaminants like LAA. PPE should be viewed as a supplement to engineering controls and appropriate procedural processes.^9,14,16 If animal users are properly and consistently using engineering controls, together with practices that prevent and minimize LAA exposure, then minimal contamination of gowns should occur when performing animal handling activities. Training of staff and researchers on the use of engineering controls and the proper way to use PPE are also important in ensuring that personnel are adequately protected from exposure to contaminants.

Control of infectious disease spread among the animal population was not considered to be a significant risk due to the use of BSCs when handling animals. The use of IVC caging for a majority of the rodent population provides each cage with its own supply of HEPA filtered air with up to 120 air changes per hour.⁵ Each cage is individually sealed when docked on the rack, allowing each cage to function as its own biocontainment unit.⁵ The use of IVC caging reduces the risk of cage-to-cage disease transmission when compared with rodents housed in other caging systems (static isolator, open-top).⁵ Due to the use of IVC systems for 98% of rodent housing at ours institution, in combination with the use of BSCs for all rodent handling, concern for the spread of infectious disease in animal populations due to gown reuse was minimal. With adequate controls already in place to control infectious disease in the animal populations at the facility, this was not a focus in this study. Gown reuse may not be appropriate for specific situations such as biohazard facilities. In these situations, a risk assessment should be performed to determine if reuse of gowns can be considered.

Decontamination of single use disposable gowns is a consideration for facilities that want to reuse gowns in restricted animal populations such as quarantine, Corynebacterium bovis and murine norovirus negative spaces or facilities, and the possibility of opportunistic organisms that cause disease among fragile or immunocompromised mouse strains. This process can also be considered when gown supplies are difficult to maintain due to shortages or expense. The method of decontamination described allows for the decontamination of multiple gowns at once using VHP. One cycle, which included decontamination of gowns with VHP and evaluation of biologic indicators, takes about 8 d to complete. Several types of gowns as well as different configurations for decontamination were evaluated. Both stacking and hanging of gowns allowed for effective decontamination of polypropylene gowns. Gowns made from other materials, such as polyethylene plastic, were not decontaminated as effectively as polypropylene gowns and may require a different sterilant or configuration for effective decontamination. How often gowns can be sterilized and reused to prevent LAA or the spread of restricted organisms was not evaluated in this study, nor was the integrity of the gowns over repeated VHP decontamination other than visual examination. Evaluation of this frequency and gown integrity is important before deciding that decontamination of gowns is sufficient to extend beyond single use for use in restricted animal populations.

The costs for VHP decontamination of approximately 600 used gowns, including labor, chemicals, and indicators, was about $702. While the costs of VHP decontamination of gowns appears relatively cost effective at $1.17 per gown compared with the $3.37 cost for a new gown, this cost does not consider costs of the decontamination, the equipment to generate the VHP, or personnel training. Furthermore, the sterilization and reuse of PPE should be implemented only when availability is an issue. VHP is an effective method of decontamination for polypropylene gowns; this method has been used and validated for 8 successful cycles at the collaborating institution and can be considered when it is difficult to maintain gown supplies.

Hanging gowns for reuse in a common hallway could provide a vector for COVID-19; however, animal housing spaces at our institution are supplied with 100% fresh air and have at least 10 to 15 air changes per hour. For these studies, the air changes per hour (ACH) in procedure spaces (n = 20) were measured at 44 ± 1 ACH and at 14 ± 0.0 ACH in animal rooms (n = 39). In addition, all personnel are required to undergo daily temperature checks and are required to certify that they have been free from symptoms before being allowed on campus. All personnel are also required to wear a face mask at all times and are expected to follow distancing policies that include limiting the number of individuals that can be present in a space at one time. All gowns were labeled with the name of the staff or research member to minimize handling and allow individuals to identify and wear their own gowns. These precautions help to reduce the risk of transmission of SARS-CoV2 from reused gowns. Testing the possibility that hanging gowns act as a vector for coronavirus was beyond the scope of this study.

Results of this study, combined with previous research on the prevention and minimization of personnel exposure to LAA, allowed veterinarians at our institution to feel confident in the safe reuse of gowns a maximum of once per 7 d (average use of 4.3 ± 0.5, n = 48) for researchers and a single gown for all task in a single day for facility staff, with differences in reuse stipulations for researchers performing research related activities and facility staff performing husbandry related activities. Individuals participating in the research tasks portion of the study reused the same gown 5 times within 1 wk without contaminating underlying clothing, bare skin, and hands. In this study, 5 times in a week was more than the average expected use based on vivarium entry data for a 2-wk time period. Individuals participating in the husbandry tasks donned a new gown before performing cage changes; the findings indicated that gowns could be reused multiple times within a single day, with the assumption that cage changing was the “dirtiest” activity that would be performed by staff on any given day. Results from time point 1 of husbandry tasks demonstrated that underlying clothing and bare skin and hands remained negative after reusing the same PPE from before the break during cage changes. Even though participants in this study were aware of their movement and processes when performing cage changes and tumor measurements, we do not expect this would have changed the outcome of the results as participants were following standard operating procedures.

All gowns are collected from designated hanging areas every 7 d and discarded to ensure compliance with reuse guidelines. Other PPE items (bonnets and gloves) were not approved for reuse and are still disposed of before exiting the facility. Gowns are not reused if handling biohazard materials. Gowns should also be discarded if they are heavily soiled or have tears or rips in the fabric as this may allow penetration of the gown by contaminants. Laminated signs were posted on all PPE cabinets in rodent housing facilities detailing the results of these studies. Hooks and dry erase markers were also placed in designated areas in all rodent housing facilities for hanging and labeling of gowns after use (Figure 4). Even though results of these studies show that surface contamination from hanging gowns is unlikely, even in high traffic areas, hooks for gowns were placed in areas with minimal drafts and minimal traffic. This was an extra precaution to minimize and prevent exposure of personnel to aerosolized contaminants, which was still a top priority. Implementation of gown reuse throughout rodent facilities has had a significant economic impact that allowed the facility to continue to operate within the budget and decrease gown usage without compromising personnel or animal health. The reuse of gowns has also allowed the facility to support green initiatives by reducing waste. Based on findings in this study, we can recommend that disposable gowns be reused a maximum of 5 times for research staff and a maximum of 1 d for facility staff as long as gowns are not heavily soiled or torn. Future studies are needed to determine if gowns can be used for longer periods of time. PPE is typically donned directly outside of the animal room door before entering the animal housing spaces at this facility. Further evaluation would be needed to evaluate the use of a central donning-doffing location. Decontamination of gowns with VHP can also extend the life of gowns, as our collaborators found that this option does provide a safe reuse option for technicians and research staff. The reuse of gowns is not expected to affect personnel or animal health as long as proper precautions are followed, and gowns are used in combination with other controls to help protect personnel from exposure to contaminants.

Figure 4.

Hooks used to hang used gowns in vivaria in areas with minimal traffic and minimal drafts. Expo marker located above gowns used to label gowns for individual use.