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Improved Bio-Agent Recovery From Simulated Environmental Surfaces
with Liquid Rinse Vacuum Collection System
Jared G. MaughanVP of Microbiology and Operations
Microbial-Vac Systems, Inc.Email: [email protected]
Detection Technologies 2008
Phoenix, AZ
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Why are We Talking About Sampling Why are We Talking About Sampling at a Detection Conference?at a Detection Conference?
• All detection starts with sampling• If you can’t COLLECT it, you can’t
DETECT it• If the capabilities of modern
detection equipment are to be realized then we need to start with a quality sample
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Calculating Efficiency: Sampling to Calculating Efficiency: Sampling to Detection Detection
• Sampling Efficiency (ƞSam)
ƞSam = ƞLoc x ƞRec
• Detection Efficiency (ƞDet)
– Not all detection devices are equal
– Assume ƞDet is 1.0 for this presentation
• Overall Process Efficiency (ƞTot)
ƞTot = ƞSam x ƞDet
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Calculating Efficiency: Sampling to Calculating Efficiency: Sampling to Detection Detection
• Sampling Efficiency (ƞSam)
ƞSam = ƞLoc x ƞRec
• Detection Efficiency (ƞDet)
– Not all detection devices are equal
– Assume ƞDet is 1.0 for this presentation
• Overall Process Efficiency (ƞTot)
ƞTot = ƞSam x ƞDetThis presentation
deals with improving this
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• Swab– Cotton tipped– Pre-moistened
• Sponge– Cellulose based– Pre-moistened
• Cotton Gauze– 2” x 2” 8 ply– Pre-moistened w/ 1.0 mL buffer
• Microbial-Vac System (M-Vac)– Surface rinse – Vacuum collection
Sampling Devices Sampling Devices ComparedCompared
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SRS
Overview of the M-VacOverview of the M-VacSEC
Surface Rinse Solution (SRS)Support Equipment
Case (SEC)
Solution Pressurization
Chamber
SEC Control Panel
M-Vac & Sampling Head (MS Kit)
Spray
Vacuum
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xƞSam = ƞLoc ƞRec
Sampling Efficiency Equation
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Location Efficiency (ƞLocation Efficiency (ƞLocLoc) ) cont.cont.
= Contamination
= Swab sample sites*
4 sq ft Surface with 2” x 2” grid and 4 isolated sites of
contamination
*Swab sample sites are 2” x 2”
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Location Efficiency (ƞLocation Efficiency (ƞLocLoc) ) cont.cont.
= Contamination
= Sponge sample sites*
4 sq ft Surface with 4” x 4” grid and 4 isolated sites of
contamination
*Sponge sample sites are 4” x 4” or ~ 100 sq
cm
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Location Efficiency (ƞLocation Efficiency (ƞLocLoc) ) cont.cont.
= Contamination
= M-Vac sample sites (1 M-Vac sample ≈ 256 sq in ≈ surface area of
16 sponges)
4 sq ft Surface with 2” x 2” grid and 4 isolated sites of
contamination
Method # of samplesTotal surface area covered
(sq in)ƞL*
Swab 1 4 2%
Sponge 1 16 12%
M-Vac 1 256 91%
*Assumes sampling a contaminated site would result in a positive detection result.
Method # of samplesTotal surface area covered
(sq in)ƞLoc*
Swab 65 260 91%
Sponge 16 256 91%
M-Vac 1 256 91%
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xƞSam = ƞLoc ƞRec
Sampling Efficiency Equation
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Recovery Efficiency (ƞRecovery Efficiency (ƞRecRec))
1) Spot Inoculate - B. sub spores - 150/surface2) Spread inoculum over
entire area
3) Allow inoculum to dry/adhere4) Sample following standard procedures or manufactures suggestions for use
Procedures for determining ƞRecƞRec
5) Elute bacteria from sampling device•Swab: Place in 10mL, Vortex 12 times for 10 sec.
•Sponge/ Gauze: Stomach sponge and 15 mL for 2 min at 240 RPM •M-Vac: Wrist shake 5 – 10 sec. 6) Plate on TSA plates, incubate 18
– 24 hrs, enumerate by direct plate count
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0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
S. Steel Cer. Tile C. board PP Plastic Com. Carpet
Surface Type
% R
eco
very
M-Vac
Sponge
Gauze
Swab
n = 25 for each treatment
Recovery of Recovery of B. subtilis B. subtilis Spores Spores from Simulated Environmental from Simulated Environmental
SurfacesSurfaces
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Reasons for Increase of ƞRec
Two areas of improvement using the M-Vac
• Extraction efficiency (ƞEx)• Ability to remove microbes from cracks, fissures, and
other surface irregularities using surface rinse solution• Transition from passive sampling to aggressive sampling
• Elution efficiency (ƞEl)• M-Vac collects the bacteria in solution eliminating the
need for elution• Overcome the sampling paradox between extraction and
elution
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Results of the Equation
MethodSwab
M-Vac
ƞLoc ƞRec ƞSam
.20
.03.03
.003.003
.91
.81
.02
.75.75
x =
x
x
=
=
=
*
*Values for ƞRec pertain to recovery results from stainless steel.**Sponge value used
Gauze
Sponge x.12 .37 .04.04
.12** .23
x =
=
.81 .74.74
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Conclusion• M-Vac provides numerous advantages
over historic sampling methods – Greater location efficiency with fewer samples
to the lab (Fewer detections performed in lab)– Greater recovery efficiency (Improved
characterization of surface contamination)– Increased repeatability between users– Increased efficiency of sample prep in the lab– Less exposure of lab personnel to pathogens
• Increased ƞsam leads to increased efficiency overall (ƞTot = ƞSam x ƞDet)
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Contributors:Kevin Church Kelly Black
Bruce Bradley, PhD
This material is based upon work supported by the U.S. Army Contracting Agency – Dugway Proving Ground Directorate of Contracting under Contract No. W911S6-06-C-0004