Workshop on the biology of anthrax, Cardiff – 12.03.14
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Transcript of Workshop on the biology of anthrax, Cardiff – 12.03.14
An Agency of the Health and Safety Executive www.hsl.gov.ukAn Agency of the Health and Safety Executive
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
An Agency of the Health and Safety Executive
Outline of today’s presentationOutline of today’s presentation
Who we are
What we did and why we did it
Main findings
Implications
A workable SOP to take forward
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HSL: who are we, where are we?HSL: who are we, where are we?
320+ staff
90+ PhDs
80+ MScs
550 acre site in
the Derbyshire
Peak District, UK
Widest science base of any equivalent European Laboratory – www.hsl.gov.uk
A big site for (some) big experimentsBut we do small stuff too….!
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The context - use of whole room fumigationThe 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
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What we need from a fumigation systemWhat we need from a fumigation system
Routine decontamination, e.g. for maintenance
Consistent, reproducible and effective killEasily removed from the treated/contained areaLeave room/laboratory and it’s equipment undamaged (ideally)
Emergency decontamination (e.g. lab spill or other release)
All of the aboveQuick and easy to deploy (ideally without requiring entry intothe room if CL3-based)Reliable (especially if equipment is to be resident in room orleft for long periods unused)
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How do available systems match up How do available systems match up against each other?against each other?
Observed log reduction by fumigation system and organism
0
2
4
6
8 L o g R e d u c t i o n
Geobacillus C. difficile M. fortuitum Vaccinia Organism
H2O2a CL02 Formaldehyde
H2O2b H2O2c Ozone Error bars represent interquartile range Dashed line represents four-log reduction
See Beswick et al. (2011). Applied Biosafety. Volume 16 (3); 139-157.
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Aims of biosecurity-related workAims 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:
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The test chamber – furnished room The test chamber – furnished room examplesexamples
Domestic set up.
Office set up Externally monitoring fumigant levels
Laboratory set up
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Fumigation delivery and removalFumigation 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
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Microbiological challengesMicrobiological 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
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Surfaces and location are importantSurfaces and location are important
Microbial challenges mainly presented dried down on 2cm x 2cm square coupons – Ikea furniture a popular material choice!!
Room Setting Material Location Laboratory Stainless steel Top of cupboard
Stainless steel Inside centrifuge, with lid almost closed
Formica On top of cupboard Formica Inside cupboard, near
back, doors - nearly closed Safety vinyl On floor
Office Billy Top of bookcase Billy Inside drawer, slightly ajar Vika On desktop Vika On shelf on bookcase Safety vinyl On floor, under desk
Domestic Billy Top of bookcase Billy Inside drawer, slightly ajar Vika On table Glass Inside mattress Safety vinyl On floor
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Good H&S - fumigant levels should be Good H&S - fumigant levels should be known ......whether at peak or residualknown ......whether at peak or residual
Minirae 2000PID monitor: potential for routine hand held or static monitoring
PortaSens II 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
Several systems were evaluated for formaldehyde fumigant monitoring
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Performance of sensorsPerformance of sensors
Minirae 2000PID monitor: potential for routine hand held or static monitoring
PortaSens II 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
Only two instruments able to cope with fumigant and humidity levels:
X
X
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Findings - fumigant removal similar Findings - fumigant removal similar regardless of method used 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)
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Were microorganisms killed by Were microorganisms killed by formaldehyde?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
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Implications of findingsImplications 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
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The next step – using the developed The next step – using the developed SOP in a ‘real’ buildingSOP 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 3rd party Framework Supplier
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A practical output from experimental A practical output from experimental evaluationevaluation
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
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The practicalities of effective The practicalities of effective fumigant deliveryfumigant 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
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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 outcome of independent The outcome of independent testingtesting
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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)