key: cord-0960801-n7j1aa1t authors: Chakladar, Abhijoy; Jones, Claire G; Siu, Jimmy; Hassan-Ibrahim, Mohammed Osman; Khan, Mansoor title: Microbial contamination of powered air purifying respirators (PAPR) used by healthcare staff during the COVID-19 pandemic: an in situ microbiological study date: 2021-02-13 journal: Am J Infect Control DOI: 10.1016/j.ajic.2021.02.006 sha: e0321d50a4d4446a27d0c85e88c55f8bca926d91 doc_id: 960801 cord_uid: n7j1aa1t BACKGROUND: Powered air purifying respirators (PAPR) are an option for healthcare workers requiring respiratory protection during Covid-19; during the current pandemic, they are shared between multiple people. PAPR hoods are intended for multiple uses by a single user and may pose an infection risk between wearers. METHODS: Internal components of PAPR hoods and corrugated air supply hoses were swabbed for evidence of bacterial, fungal, common respiratory viruses and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) contamination. RESULTS: 25 PAPR hoods were swabbed; ten (40%) returned positive results. Bacterial growth was detected on six PAPR; five of the PAPR tested positive for fungal growth; all tested negative for SARS-CoV-2 and common respiratory viruses. CONCLUSIONS: Bacteria and fungi can remain on internal components of PAPR hoods and air supply hoses despite following recommended disinfection procedures. PAPR hoods have the potential to act as fomites, cross-infecting wearers and patients. Current guidelines for disinfecting PAPR hoods may not be effective for use in high risk healthcare environments. cross-infecting wearers and patients. Current guidelines for disinfecting PAPR hoods may not be effective for use in high risk healthcare environments. Powered air purifying respirator (PAPR) assemblies, also referred to as 'power hoods', are an option available to HCWs requiring high level respiratory protection and also those who fail a fit test for disposable respirators, or for whom prolonged use of a standard respirator is intolerable. PAPR are utilised during the highest risk aerosol generating procedures and have been shown to offer better conditions for the wearer when performing complex airway procedures compared to reusable respirators. 2, 3 There is evidence to suggest that females and non-Caucasian people are less likely to pass fit tests for FFP3 respirators. [4] [5] [6] [7] [8] [9] [10] [11] PAPR consist of powered fan units connected via tubing to hoods. Filtered air, under positive pressure is supplied to the wearer; this and the wearer's exhaled breath are expelled around the edges of the hood and through unshrouded expiratory valves; the hoods consist of a clear visor, stitched to fabric. PAPR and these hoods were originally developed to provide respiratory protection in industrial use to help combat pulmonary contamination by non-biological particulates. They have been adapted for use during the COVID-19 pandemic by upgrading the particulate filters, but the use of PAPR in clinical environments is not universally accepted. 12, 13 The fidelity of the hood relies on the assumption that high flow forced air prevents the wearer both from inhaling particles directly from the environment, and, importantly, from contaminating the internal surfaces of the tubing. Such protection may be nullified if users follow guidance to don hoods before activating the fan unit or the filter air inlet becomes obstructed during use. 14 These problems are of particular significance in the current pandemic because individuals can test COVID-19 positive but be clinically asymptomatic, 15 putting other staff sharing the same hood at risk. Healthcare workers have expressed other infection concerns about PAPRs, including fomite dispersal during handling, aerosol deposition of respiratory and other secretions, 13 and lack of confidence in the cleaning and decontamination process. Current local guidelines from infection control services recommend the use of disinfection wipes for cleaning and disinfection, but do not address how the internal parts of the power hoods should be treated. 16 There has been minimal research published examining the efficacy of different cleaning methods, although cleaning alone and cleaning plus disinfection have both been shown to be effective in removing the influenza virus from the external components of PAPR, 13 we can find no studies that have examined the contamination or disinfection of internal components. As PAPR hoods and air supply hoses are intended for multiple uses by a single user, the manufacturer has not determined how the internal surfaces of the PAPR components might be disinfected, 17 and so no evidence-based protocol exists for disinfecting the hoods before their re-use, when demand for high level respiratory protection outstrips supply. Evidence suggests that viral particles may persist on surfaces, in an infectious state, for prolonged periods. 18, 19 In addition, fomite and aerosol transmission is suspected for SARS-CoV-2, 20, 21 and therefore the probability exists that PAPRs may potentially contaminate sterile fields. 12 Given these concerns, we conducted a study to test our hypothesis that PAPR hoods and fan hoses could remain colonised with bacteria, fungi or detectable viral DNA/RNA following protocol-driven cleaning and disinfection. After approval from the Brighton and Sussex University Hospitals NHS Trust, UK, Executive Board, we conducted an observational, laboratory study to test the PAPR hoods in use in our institution. Over a 48 hour period in June 2020, 25 PAPR hoods and their attached corrugated fan hoses, approximately 25% of our institution's circulating stock, were tested for evidence of bacterial, fungal, respiratory viral and SARS-CoV-2 colonisation, generating a total of 100 swabs for analysis.. We examined the 3M Scott Safety FH1 and FH2 PAPR headtops, (3M Scott, Skelmersdale, UK) that are used at our institution. The FH1 headtop is a half hood that provides a loose neoprene seal around the face; the FH2 headtop has a shoulder cape that provides neck and shoulder protection (figure 1). Hood assemblies are cleaned with disinfectant wipes after use (benzalkonium chloride 0.54g, didecyldimonium chloride 0.54g, and phenoxyethanol 0.6g per 100g; GAMA Healthcare, Watford, UK). Each PAPR hood had four swabs: two charcoal and two viral, one of each from two pre-defined areas: first, inside of the clear plastic visor including the expiratory valve, and second, inside the corrugated air supply hose attached to the hood. The visor and expiratory valve were divided in to two halves, one for the charcoal swab, and one for the viral swab. The expiratory valve was swabbed first with care taken to apply the swabs uniformly over the surface and then over the respective side of the visor in linear, up-down, fashion with care taken to access any corners and cover the full area of the visor. The air supply hoses were also divided in two halves, one for each type of swab. The swab was passed from the rim down to approximately 10cm, the length of the swabs, with care taken to swab within the ridges of the hose corrugations. All samples were taken by consultant anaesthetists experienced in the wearing of FFP3 respirators and PPE, and conducting procedures with aseptic non-touch technique (ANTT). Investigators wore PPE to protect themselves from potentially colonised PAPR and to prevent inadvertent contamination of the equipment by the investigators. All investigators wore FFP3 respirators without an expiratory valve. The 'hood-holder' wore fresh non-latex sterile gloves, and eye protection; the 'swab-taker' wore fresh nonlatex sterile gloves, fresh surgical gowns, and eye protection; the investigator responsible for sample labelling and bagging wore non-sterile latex free gloves and eye protection. Swabbing was carefully planned and conducted so that each swab consistently sampled the same area of respective hoods and air supply hoses, minimising overlap and the potential to remove organisms. The location of PAPR across the Trust was identified. Hoods were marked with a unique code that corresponded with the code for their respective swabs and allowed for the location of any PAPR to be identified. For example, 'RSCH_ENT_1' refers to a PAPR that is kept in the ENT outpatients at the Royal Sussex County Hospital. Where the PAPR already had a number designation in a clinical area, this was reflected in the assigned code. Transwab® Amies Charcoal swabs were cultured onto Blood (OXOID Colombia Agar with horse blood, Code: PB0122, distributed by ThermoFisher, UK) and Chocolate (Oxoid Colombia Agar with Chocolated Horse Blood, Code: PB0124, ThermoFisher, UK) agar plates and incubated in carbon dioxide (CO 2 ) for 24 hours. Any growth was identified using the MALDI-TOF system (Bruker, USA). Testing for SARS-CoV-2 (COVID-19) was performed by real-time RT-PCR method. 400 µl of each of the Sigma Virocult® swabs with added 5µl internal control were extracted using the Kingfisher Transwab® Amies Charcoal swabs were cultured onto Sabouraud dextrose agar plates (Oxoid Sabouraud dextrose agar with Chloramphenicol, Code: PO0161, ThermoFisher, UK) and incubated in air at 35°C for 5 days. Any growth of fungi was then identified macroscopically and/or microscopically as appropriate. Of the 25PAPR hood and hose assemblies swabbed, ten (40%) returned a positive result (Table 1) . Five of the PAPR hoods were positive for fungal growth; all grew non-sporulating environmental mould (NSEM) which could not be identified. All PAPR hoods sampled tested negative for SARS-CoV-2 (COVID-19) and respiratory viral panel testing. To our knowledge, this is one of the first studies conducted during the COVID-19 pandemic to report contamination of PAPR hood assemblies. Despite cleaning and disinfection according to recommended protocols in the UK during the 2020 COVID-19 pandemic, bacteria and fungi remained at detectable levels on internal surfaces of the hoods and corrugated air supply hoses. Staphylococcus epidermidis, Kocuria rhizophilia, and Microcccus luteus are Gram positive cocci. Staphylococcus epidermidis is a skin commensal that can cause infections of intravenous lines and prosthetic materials, including artificial heart valves and orthopaedic joints. Kocuria rhizophiliais found in the oropharynx, oral mucosa, and skin, but does not usually cause human infections except rarely in severely immunocompromised patients. Microcccus luteus is part of the normal bacterial flora of human skin and is not generally pathogenic. Bacillus simplex and Bacillus weihenstephensis are gram positive bacilli that can colonise skin and are found in soil; they are unlikely to be pathogens in humans, although B. simplex has been implicated in food borne disease and as a potential cause of brain abscess. 22 The clinical impact of NSEMs is difficult to qualify; they do not sporulate, and so are difficult to differentiate. They are usually not pathogenic except occasionally in immunocompromised patients. Notably, however, NSEM survived optimal care in one hood (controlled storage, double cleaning and disinfection, tracked use, user log, cleaning diary), even though it had not been worn for 6 days. The risk to PAPR users, at our institution, of pathogenic cross infection during the study period seems minimal. However, we think that it is reasonable to infer from our results that more pathogenic organisms could survive cleaning and disinfection procedures, and risk cross-infecting subsequent users. Recent studies have demonstrated the ability of SARS-COV-2 to persist for prolonged periods of time in an infectious state on a variety of surfaces; 19 it is likely none of previous wearers of these hood systems was infected with SARS-CoV-2, but this is may be of greater concern as more virulent strains of SARS-CoV-2 arise. PAPRs are available to clinicians who conduct high risk (aerosol generating) procedures, 2, 3 or who fail fit-testing for disposable FFP3 respirators. Contamination of hood assemblies may be more likely if the hood is donned before the fan unit is activated (as advised by Health Protection Scotland), 14 and if the inlet to the air filter is blocked (allowing recirculation of exhaled breath inside the hood and fan tubing). Prominent noses are more likely to pass respirator fit tests, [23] [24] [25] [26] being the gender and racial phenotypes of the population trialled during PPE design i.e. Caucasian males. [4] [5] [6] [7] [8] [9] [10] Our results suggest that obligate PAPR wearing by non-Caucasians and women may place users at even further risk of pathogenic crosscontamination, and, potentially, COVID-19-related morbidity and mortality. 27, 28 There remains a dearth of comparative studies involving women and non-Caucasians, but a growing body of anecdotal and empirical evidence supporting suggestions of structural sex and racial bias in the provision of respiratory PPE internationally. 4, 5, [7] [8] [9] [10] [11] During this pandemic, confidence in PPE has been reduced by concerns over personal safety, 29 conflicting, frequently changing, advice, 30 difficulties with availability, 31 All hoods except one had been worn within 24 hours of testing but without adequate time logs, we were unable to ascertain how long; a longer time length of time since last use may reduce the chance of successfully culturing bacteria and after 72 hours it is difficult to retrieve viral materials from hard surfaces. One hood assembly was last worn 6 days before swabbing (one of several, tracked, PAPR), and this grew a NSEM. We examined 25 hoods and air supply hose assemblies, approximately 25% of our institution's circulating stock, and consider that this represented an adequate sample to test our hypothesis. PAPRs are an important component in the range of respiratory PPE available to healthcare staff in pandemics. 2, 3, 33, 34 It is our opinion that, given the constraints outlined by both the manufacturer and the distributor, the hoods tested cannot be adequately disinfected for use in high risk healthcare environments and the systems may support fomite transmission; in the short-term this may be overcome by issuing HCWs with personal PAPR hoods and air supply hoses. Urgent investment and research is required to develop more effective respirators that fit better, equipment designed for clinical environments that can be adequately disinfected and comparative studies to identify optimal equipment, cleaning, disinfection, and storage. This work cannot succeed in isolation and industry, the manufacturers of respirators, must be engaged to collaborate with clinicians to develop PAPR systems that are fit for purpose in high risk healthcare settings. This study demonstrates that disinfection guidelines in the UK during the COVID-19 pandemic may not be effective in disinfecting PAPR hood assemblies. Organisms that survive the disinfection process can persist for more than 5 days. 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None. Not required.