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Workshop on the biology of anthrax, Cardiff – 12.03.14 Decontamination challenges: if you can kill Bacillus anthracis endospores you can probably kill most pathogens - but how best to achieve it? The Health & Safety Laboratory Alan Beswick
Outline of today’s presentation • Who we are • What we did and why we did it • Main findings • Implications • A workable SOP to take forward
HSL: who are we, where are we? 320+ staff 90+ PhDs 80+ MScs 550 acre site in the Derbyshire Peak District, UK A big site for (some) big experiments But we do small stuff too….! Widest science base of any equivalent European Laboratory – www.hsl.gov.uk
The context - use of whole room fumigation • Decontamination can include use of whole room fumigation • This must be able to combat potentially malicious microbiological release for bio-security applications • Some examples of whole room fumigants: • H2O2 – Hydrogen peroxide – as vapour & dry mist (multiple systems) • ClO2 – Chlorine dioxide - a true gas • CH2O - Formaldehyde vapour
What we need from a fumigation system • Routine decontamination, e.g. for maintenance • Consistent, reproducible and effective kill • Easily removed from the treated/contained area • Leave room/laboratory and it’s equipment undamaged (ideally) • Emergency decontamination (e.g. lab spill or other release) • All of the above • Quick and easy to deploy (ideally without requiring entry into • the room if CL3-based) • Reliable (especially if equipment is to be resident in room or • left for long periods unused)
How do available systems match up against each other? Observed log reduction by fumigation system and organism See Beswick et al. (2011). Applied Biosafety. Volume 16 (3); 139-157.
Aims of biosecurity-related work • Biocidal efficacy of formaldehyde vapour against a range of challenge microorganisms and room scenarios • Using HSL’s Controlled Atmosphere Chamber to evaluate methods for formaldehyde fumigant delivery and removal • From the steps above - develop a Standard Operating Procedure (SOP) that could be used by third party decontamination contractors. Home Office wished us to consider the following:
The test chamber – furnished room examples Domestic set up. Laboratory set up Office set up Externally monitoring fumigant levels
Fumigation delivery and removal Wok fumigation + ammonia from Formaflow VAP2 Device The Walker’s Whole Room Fumigation System with ammonia delivery & carbon bed Wok fumigation + Airflow - mechanical ventilation Direction of airflow
Microbiological challenges • Some of the surrogate pathogens used to provided relevant challenges for the testing: • Bacillus atrophaeus – a spore forming surrogate for B. anthracis • Pantoea agglomerans – bacterial surrogate for Yersinia pestis • Coxiella burnetii – bacterial agent of Q Fever; 9 mile strain used (non-infectious; supplied by B Heinzen, US Rocky Mountain labs) • Vaccinia virus – as a surrogate for Variola (smallpox) virus • Geobacillus stearothermophilus – a standard reference strain & resilient bacterial spore former
Surfaces and location are important • Microbial challenges mainly presented dried down on 2cm x 2cm square coupons – Ikea furniture a popular material choice!!
Good H&S - fumigant levels should be known ......whether at peak or residual Several systems were evaluated for formaldehyde fumigant monitoring PortaSens II monitor: potential for routine hand held or static monitoring Minirae 2000PID monitor: potential for routine hand held or static monitoring Bruel and Kjaer (type 1302) multigas monitor – used for accurate comparative monitoring The Gasmet IR monitor
Performance of sensors Only two instruments able to cope with fumigant and humidity levels: X PortaSens II monitor: potential for routine hand held or static monitoring Minirae 2000PID monitor: potential for routine hand held or static monitoring X Bruel and Kjaer (type 1302) multigas monitor – used for accurate comparative monitoring The Gasmet IR monitor
Findings - fumigant removal similar regardless of method used • Mechanical air flow alone rapidly reduced formaldehyde fumigant to low levels (0-5ppm) – so often above WEL (2ppm) on completion • Ammonia easy to deliver and effective for rapid neutralisation of fumigant – but can form 2o by-products that mimic formaldehyde • Addition of a large carbon filter bed – in addition to ammonia – gave no obvious additional benefits to ammonia alone • Off gassing often observed from soft materials in room - usually <10ppm and localised but often persistent (up to 96 hrs post treatment)
Were microorganisms killed by formaldehyde? • Microbiological reductions >6-Log were possible with formaldehyde for most test challenges • Some variation in efficacy noted - dependent on microbiological type and location – 4 to 5 log reduction not unusual • Samples located within the drawer unit exhibited some of the lowest kill – indicative of limited penetration
Implications of findings • Choice of monitoring equipment for measuring levels of fumigant is critical for efficacy and safety during treatment delivery • Only certain fumigant monitors are ‘up to the job’ • Formaldehyde is an effective fumigant but there is potential for variation in efficacy depending on location/room layout etc. – validation can help • Methods for removing formaldehyde must be in place before fumigation. Aeration is as effective as any method, if it is physically possible • Furnishings should be checked for off gassing effects – some exposed materials may require disposal or extended periods of aeration • Knowledge gained allowed preparation of Draft SOP document
The next step – using the developed SOP in a ‘real’ building • Involvement in a GDS-led WASA exercise taught HSL much about SOP preparation and presentation • GDS asked HSL to road test the Draft SOP in a real building situation before inflicting it on a 3rdparty Framework Supplier
A practical output from experimental evaluation • Optimisation of v1 of SOP allowed preparation of an improved v2 document for use by contract decontamination teams • We realised - having the right information is important but front end document has to be simple and easy to follow – e.g. flow charts
The practicalities of effective fumigant delivery The optimised SOP was evaluated as part of a recent project funded by GDS – independent contractors used This has included ‘real’ building tests (150m3 volume) Considered – Risk assessment; PPE; sealing of doors & windows; levels of fumigant required; explosive risk; aeration of room; working above ground level
The outcome of independent testing Building layout during contractor fumigation tests: The four locations of the 1.5cm steel coupons seeded with Bacillus spores are indicated by small red circles; - floor - high shelf - window ledge - worktop 7-log reduction of B. atrophaeus achieved in all room locations Independent users happy with SOP Result….!!
The Health & Safety Laboratory Acknowledgements Thanks to: S Casey & J Caddick (GDS) J Gawn (HSE) C Makison Booth (HSL) J Farrant (HSL) G Frost (HSL) J Holroyd (HSL)