Evaluation of Methods for Enumerating Enterococci in Beach Sand · 3 10 4 g Sand 1 Sand 2 Sand 3...
Transcript of Evaluation of Methods for Enumerating Enterococci in Beach Sand · 3 10 4 g Sand 1 Sand 2 Sand 3...
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Evaluation of Methods for
Enumerating Enterococci in
Beach Sand
John Griffith
Southern California Coastal Water Research Project
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Background
Recent International interest in beach sand as a source or reservoir of fecal bacteria
Many published protocols for enumerating bacteria in sand
No standard method Prevents assessment of problem
Limits comparability of data between beaches
Goal: Identify a standard method for measuring enterococci in beach sand
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Approach Bring together leading researchers in field
Process a common set of samples
Participants
Jenny Jay – UCLA Ali Boehm - Stanford
Richard Whitman – USGS Tom Edge- Environment Canada
Helena Solo-Gabriel - U of Miami Marty Getrich - OCPHL
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Details
21 permutations of 4 treatments
Four replicates processed by each method
Duplicates by each of two researchers
Three sand samples
One sample processed each day
Analyze for enterococci using EPA Method 1600
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Treatments
Hand Shaking
Mechanical Shaking
Sonication
Blending
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Variables
Mass of sand
Duration of shaking
Settling time
Number of rinses
Eluant (PBS or DI water)
Surfactant (Tween 80 or metaphosphate)
Eluant collection (decant, pipette, vacuum)
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Sand Sources
Doheny State Beach, Dana Point, CA
Hobie Cat Beach, Miami, FL
Washington Park Beach, Michigan City, IN
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Enterococcus Concentration
101
102
103
104
Ente
roco
cci C
FU
/g
Sand 1 Sand 2 Sand 3DohenyDoheny Miami Michigan City
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Results
Blending produced lower numbers than
sonication or shaking
Lower eluant to sand ratio led to reduced
recovery
Mechanical shaking produced lower numbers than
hand shaking
No effects noted for shaking time, sonication,
number of rinses, or settling time
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Bottom Line
Hand-shaking performed as well or better
than more complex treatments
Simple
Inexpensive
Consistent
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Method Recommended by Experts
10g sand
60ml PBS
2 min. hand shake
Settle 30s
Decant eluant
40ml PBS rinse
Settle 30s
Decant eluant
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What Next?
Laboratory Intercalibration Exercise
Conducted November 2008
Test method on more challenging sands
High silt
High organic content
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Instructional Video