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
www.hsl.gov.uk
AnAn
Agency
of theof
Health
and Safety
Executive
Agency
the Health
and
Safety
Executive
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
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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
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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
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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)
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How do available systems match up
against each other?
Observed log reduction by fumigation system and organism
L
o
g
8
6
R
e
d
u
c
t
i
o
n
4
2
0
Geobacillus
C. difficile
H2O2a
H2O2b
M. fortuitum
Organism
Vaccinia
CL02
Formaldehyde
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 work
Home Office wished us to consider the following:

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.
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The test chamber – furnished room
examples
Domestic set up.
Office set up
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Laboratory 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 +
mechanical ventilation
Airflow
Direction
of airflow
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-
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
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Surfaces and location are important
 Microbial challenges mainly presented dried down on 2cm x 2cm square
coupons – Ikea furniture a popular material choice!!
Room Setting
Laboratory
Material
Stainless steel
Stainless steel
Formica
Formica
Office
Domestic
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Safety vinyl
Billy
Billy
Vika
Vika
Safety vinyl
Billy
Billy
Vika
Glass
Safety vinyl
Location
Top of cupboard
Inside centrifuge, with lid
almost closed
On top of cupboard
Inside
cupboard,
near
back, doors - nearly closed
On floor
Top of bookcase
Inside drawer, slightly ajar
On desktop
On shelf on bookcase
On floor, under desk
Top of bookcase
Inside drawer, slightly ajar
On table
Inside mattress
On floor
Good H&S - fumigant levels should be
known ......whether at peak or residual
Several systems were evaluated for formaldehyde fumigant
monitoring
Minirae
2000PID monitor:
potential for routine
hand held or static
monitoring
Bruel and Kjaer (type 1302)
multigas monitor – used for
accurate comparative monitoring
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PortaSens II
monitor:
potential for
routine hand
held or static
monitoring
The Gasmet IR monitor
Performance of sensors
Only two instruments able to cope with fumigant and humidity
levels:

X
Minirae
2000PID monitor:
potential for routine
hand held or static
monitoring
PortaSens II
monitor:
potential for
routine hand
held or static
monitoring

X
Bruel and Kjaer (type 1302)
multigas monitor – used for
accurate comparative monitoring
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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)
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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
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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
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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 3rd party Framework Supplier
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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
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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
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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….!!
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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)
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