efficacy of jerry can cleaning techniques: methods development for … · 2018. 11. 1. · efficacy...
TRANSCRIPT
Efficacy of Jerry Can Cleaning Techniques: Methods Development
for a Large-scale Study
Gabrielle String, Hanaa Badr, Marta Domini, and Daniele Lantagne
Department of Civil and Environmental Engineering, Tufts University, Medford, MA, USA
Overview
• Introduction
– Jerry cans for water storage
– Biofilms
– Results from previous cleaning studies
• Large-scale study objectives
• Methods development and results
– Growing biofilms on coupons, enumerating
• Outcomes
• Preliminary results from large-scale study
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Introduction: Jerry cans
Jerry cans are commonly used for household water storage and often distributed
in emergency contexts.
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Introduction: Biofilms
• Biofilms are microbial communities comprised of pathogenic and non-pathogenic organisms
• Persist and grow on surfaces in contact with a liquid
• Able to shed cells promoting the growth of microorganisms
• Resistance to environmental changes and disinfection
4Zeng, Bay Area Lyme Foundation
Introduction: Cleaning jerry cans
• Biofilm growth inside water storage containers acts as microbial reservoir
• Previous studies compared cleaning methods with NaOCl or abrasives in-situ
– E. coli concentration reduced after cleaning
– No reduction in E. coli recontamination
• Studies did not address impact of cleaning on surface roughness of jerry cans
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Steele et. al, J Water Health, 2008 Jagals et. al, J Water Health, 2003Burkowska et. al, J Water Health, 2015 Momba et. al, Water Res, 2002
Large-scale laboratory objectives
Do cleaning methods impact the surface roughness of jerry cans?
●
Does surface roughness influence the growth of biofilms?
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How effective are different cleaning methods at removing E. coli biofilms from jerry cans?
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Preparing coupons
• 1 cm2 coupons cut from jerry cans
• Coupons mounted on a polishing table for 1 min at 200 N force– Coarse: 120 grit – Medium: 240 grit– Fine: 400 grit
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Thomas, et al, Carbon, 2014
Method: Growing biofilms
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Place in Falcon tubes
Immersion
SpikeIncubation
Refresh25mL LB broth or PBS
E. coli at 104, 105, or 106 CFU/100mL
Repeat cycle every 48 hours
35ºC on a shake plate at 70 rpm
Continue for 10 and 21 days
Method: Enumerating E. coli
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Enumeration Technique
Culture Imaging
Potential for recontamination Structure and size of matrix
Results: Culturable E. coli
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Biofilm(CFU/cm2)
PBS Environment(CFU/100mL)
10 days 21 days10 days 21 days
Virgin 7.6 x 104 7.2 x 105 2.7 x 108 3.2×109
Coarse 5.2 x 104 8.0 x 105 2.2 x 109 2.5×109
Medium 4.8 x 104 2.3 x 106 2.1 x 109 2.1×109
Fine 8.0 x 104 2.4 x 106 2.1 x 109 2.5×109
Results: Imaging E. coli
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Cross-sectional image of biofilm through z-direction
Results: Varied surface roughness
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E. coli growth along coarse scratches
E. coli growth on virgin jerry can surface
Outcomes
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• Successfully grew E. coli biofilms on coupons of varying surface roughness
• Applied a repeatable method for enumerating E. coli in biofilm
• Utilized a staining and imaging method to visualize biofilms on HDPE coupons
Large-scale laboratory study
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Total: 72 containers, maintained for 90 days
Preliminary Results
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Single E. coli
Preliminary Results
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Next Steps
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• Analyze collected data– Free chlorine residual and E. coli (after cleaning) and imaging (monthly)
• Trial most promising cleaning method on field collected containers
• Make recommendations on jerry can cleaning
Acknowledgements
Alenka Lovy Imaging Core Manager, Tufts
Trang Vu, Marlene Wolfe Lantagne Group
Melissa Opryszko USAID-OFDA
Students
Molly Lie, Magnifique Mukundwa, Katherine Sweetser, Katie Painter, Miranda Johnston, Tharina Messeroux, Himamshu
Ghimire, Derrick Sosa, Kelly Donohue, Faith Patrick