Testing for Fecal Coliforms
and E.coli
Presented by:
Kalina Warren
Summary of Presentation
• Background information
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Total coliform group
Fecal coliform group
Escherichia coli (E.coli)
Other pathogenic bacteria
• Test methods
– Membrane filter technique
– Multiple-tube fermentation
technique
– Enzyme substrate coliform test
• Colilert and Colilert - 18
• US Rules
• World-wide perspective
Total Coliform Group
• Consists of several genera of bacteria of fecal and non-fecal origin
• Definition based on the method of detection
– Ferment lactose with gas and acid formation within 48 h at 35oC
– Produce dark red colony with a metallic sheen within 24 h on an Endo-type
medium containing lactose
• Considered an indicator organism
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– A criterion of the degree of pollution and thus of sanitary quality
Belongs to the family of Enterobacteriaceae
Facultative anaerobic (do not have to have oxygen)
Gram-negative
Non-spore forming
Rod-shaped
Includes four genera that have at least some species of fecal origin
Posses the enzyme β-galactosidase (nickname beta-gal) that catalyzes the
hydrolysis of β-galactosides into monosaccharides
Total coliform group, cont.
• Citrobacter
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Use citrate as a carbon source
Found everywhere including in soil, water, wastewater, human intestine
Rarely source off illness (except urinary tract & infant meningitis)
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Highly motile
Part of normal flora of human intestinal tract
Several strains can be pathogenic and cause urinary tract infection
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Inhabitants of the gastrointestinal tracts of warm-blooded animals
Provide a portion of the microbial–derived vitamin K
E.coli – most numerous from this group
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Widely distributed in nature
Occurring in soil, water, grain, vegetation, wood pulp, other…
Opportunistic pathogens
Can cause pneumonia, urinary tract infections, other infections
Associated with coliform re-growth in large water distribution systems
Klebsiella pneumoniae ( from feces) – 60 – 80 % shows as positive in FC tests
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Budvicia, Erwinia, Leclercia, Serratia
Found only in the environment (no fecal origin)
• Enterobacter
• Escherichia
• Klebsiella
• Others
Fecal coliform group
• Subset of total coliform
• Resides in the intestinal tract of warm-blooded
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animals (including humans)
Outside of a host, FC are short-lived
Contains pathogens (disease causing e.g., E.coli)
and non-pathogenic bacteria
Indicates fecal contamination and potential
presence of pathogens
Incubation temperature 44.5 ± 0.2oC
Escherichia coli
• E.coli is a sub-group of fecal coliform group
• It is naturally found in the intestines of warm-blooded
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animals, such as cows, chicken, pigs, dogs, cats, birds,
and people; comprise of up to 1% of bacterial biomass
Enters the environment through feces.
There are thousands of different strains of E. coli.
Fortunately very few strains are pathogenic.
– More than one strain of E.coli may coexist in the intestinal tract;
they displace one another 3-4 times a year
– Pathogenic strains may cause one of three types of infection:
urinary tract, neonatal meningitis, intestinal diseases
• Possess the enzyme β- glucuronidase and is capable of
cleaving the fluorogenic substrate, MUG, with the
corresponding release of the fluorogen.
Other pathogenic bacteria regulated by
the wastewater program
– Salmonella
• Belongs to family of Enterobacteriaceae
• Usually does not ferment lactose, instead most produce
hydrogen sulfide
• Causes typhoid fever and food-borne diseases
• Lives in the intestinal tract of humans and other animals
including birds
• Present in small numbers compared to coliform
– Fecal Streptococci
• Found in gastrointestinal tract of warm-blooded animals
• Enterococci are a subgroup of FS
– Valuable indicator of fecal contamination of recreational waters
Testing Methods
Sample Collection
• Use appropriate sampling container (sterile) with
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Na2S2O3 to remove chlorine
Type: Grab (not composite)
Use gloves while sampling
Sample should be representative of flow
After collection place it on ice or in a refrigerator
Deliver to a laboratory ASAP, but no later than
6 hours of collection
Maintain records
Membrane Filter Technique
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Pour medium onto absorbent pad in petri dish
Shake sample vigorously
Measure appropriate volume
Filter sample or sample aliquot through a membrane filter, diameter
47 mm, mean pore diameter 0.45 um
Rinse funnel with approx. 30 mL of dilution water
Place filter on a pad in petri dish with a selected medium
Incubate inverted plate
Count colonies
Record results
Perform confirmatory tests when needed
Run appropriate blanks, known positive and known negative
Total coliform, SM 9222B
• Culture medium
– LES Endo agar
– M-Endo agar or broth
• Incubation
– 35 ± 0.5oC
– 22 to 24 hours
• Produce dark, red colony with
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metallic sheen
Many background colonies usually are observed
At least three sample dilutions should be setup
Up to 80 TC colonies can be counted if no more than
200 total colonies (including background) are noted
Fecal coliform, SM 9222D
• Most commonly used method
• Culture medium
– M-FC broth (96 h shelve life)
– M-FC agar (2 weeks shelve life)
• Incubation
– 44.5 ± 0.2oC
– 24 ± 2 hours
• Count blue colonies; can be
different size and shade
• Few background colonies usually are observed due to selectivity of
medium, especially if rosalic acid is added
• At least three sample dilutions should be setup
• Up to 60 FC colonies can be counted
Confirmation procedures, SM
9020B. 9
• Verify positives monthly by picking
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at least 10 colonies from a plate
To determine false negatives, pick
atypical colonies
For FC test use tubes with:
– Lauryl Tryptose Broth
(LTB) at 35 ± 0.5oC
– EC broth at 44.5 ± 0.2oC
Adjust counts based on percent of
verification
Tips
– Each colony is confirmed in a separate tube
– LTB and EC tubes can be confirmed simultaneously
Keep good records
Calculation of Coliform Density - MF
• If one dilution is used for calculation
Coliforms/100 mL =
coliform colonies x 100
mL sample filtered
Example: 25x100/ 10 = 250 coliforms in 100 mL of sample
Calculation of Coliform Density – MF,
cont.
• If more than one plate use to calculate density
• Coliforms/100 mL = (sum of colony count from plates x 100
sum of filtered volumes
Example: [( 15+6+0) x 100] / (50+25+10) = 25 coliforms in 100 mL
• Use the second formula only if no plate yield colony count in ideal
range
Multiple Tube Fermentation
Technique
• In general, this method is much more time consumig
• Set up 5 tubes with appropriate presumptive media for each of
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three sample dilutions
– 5 x 10 mL
– 5 x 1 mL
– 5 x 0.1 mL
Add a sterile water control
Incubate
Swirl each tube gently and examine growth
Look for gas and acidic reaction
Re-incubate for additional 24 h if no gas or acidic reaction is evident
Using sterile 3-mm loop or wooden applicator transfer growth from
a positive presumptive medium to a tube with confirmation medium
Incubate
Examine growth, look for gas
Incubation in both culture mediums can be done simultaneously
Calculate results using SM Table 9221.IV.
Multiple-Tube Fermentation Technique,
Total Coliform Procedure, SM 9221B
• Presumptive medium – LTB
• Incubation
– 35 ± 0.5oC
– 24 ± 2 hours, examine and re-incubate negative tubes
• Use brilliant green lactose bile broth
(BGBB) for confirmed phase
• Incubation
– 35 ± 0.5oC
– 24 ± 2 hours
• Use EC (for FC) or EC-MUG for E.coli
• Incubation
– 44.5 ± 0.2oC
– 24 ± 2 hours
• Calculate results using SM Table 9221.IV.
Multiple-Tube Fermentation Technique,
Fecal Coliform Procedure, SM 9221E
• Mostly used for biosolids (EPA 1680 or 1681)
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Special sample preparation required
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35 ± 0.5oC
22 to 24 hours
• Presumptive media – LTB
• Incubation
• Inoculate EC broth tubes using
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positive LTB tubes
Incubation
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44.5 ± 0.2oC
24 ± 2 hours
• Presumptive and confirmatory test
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can be run simultaneously
One step method
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A-1 broth
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3 hours at 35 ± 0.5oC
21 ± 2 hours at 44.5 ± 0.2oC
• Incubation
• Calculate results using SM Table 9221.IV.
Control Cultures for Microbiological
Tests
Group
Positive
Total Coliform
E.coli
E.aerogenes
Fecal Coliform
E.coli
Escherichia Coli
E.coli
Negative
Staphylococcus aureus
Pseudomonas sp.
Enterobacter aerogenes
Enterobacter aerogenes
Fecal Streptococci Enterococcus faecalis
Staphylococcus aureus
Enterococci
S.mitis/salivarius
Streptococcus faecalis
Recently Approved Methods for
E.coli and Enterococci
• Federal Register Notice- August 16th, 2005
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Comments on proposal ended on October 17th, 2005
Promulgated on March 26th,2007
Effective date –April 25th, 2007
http://www.epa.gov/EPA-WATER/2007/March/Day-26/w1455.htm
• Multiple Tube Fermentation, SM 9221F
– The procedure is used as a confirmatory test after prior enrichment in a
presumptive medium for TC
• Enzyme substrate coliform (multiple tube/multiple well)
– SM 9223.B
– Colilert®, Colilert® -18 ( IDEXX)
• E.coli, membrane filtration single step
– mColiBlue 24 (HACH)
• Membrane filtration, SM 9222G
– This method is preceded by SM 9222B for TC
• Testing for Enterococci
Enzyme Substrate Coliform
by
multiple tube / multiple well
ONPG Positive Reaction
Colilert & Colilert-18
Information provided by IDEXX
MUG Positive Reaction
Colilert & Colilert-18
Information provided by IDEXX
Quanti-Tray Demonstration
Add Colilert to sample
and shake to dissolve
Pour mixture into a
Quanti-Tray
Information provided by IDEXX
Quanti-Tray Demonstration
cont.
Seal and then incubate at
35°C for 24 hours
Count positive wells and
refer to MPN table
Information provided by IDEXX
E.coli Positive Tray
Information provided by IDEXX
Quanti-Tray/2000 Scientific Basis
Information provided by IDEXX
States or regions approving E.coli and
Colilert for Waste Water Testing
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Indiana
Oregon
Regions of California
Virginia
Arizona
Tennessee
Utah
Maryland
Pennsylvania
Kentucky
Information provided by IDEXX
New Member Filtration Methods for
E.coli
M-ColiBlue 24
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Enumerate TC and E.coli on one petri dish
Read and confirm results in 24 hours
E.coli colonies are blue
Other coliforms are red
EPA Methods for E.coli
• Method 1603: Escherichia coli (E.coli) in Water by Membrane
Filtration Using Modified membrane-Thermotolerant Escherichia coli
Agar (Modified mTEC) (September 2002) - Method 1603 is a revised
membrane filter (MF) procedure, a single-step method that uses one
medium, modified mTEC Agar, and does not require the transfer of
the membrane filter to another medium or other substrate
• Method 1604: Total Coliforms and Escherichia coli in Water by
Membrane Filtration Using a Simultaneous Detection Technique (MI
Medium) (September 2002) - This document (EPA 821-R-02-024) is
identical to the February 2000 version of the MI Agar Method
(Membrane Filter Method for the Simultaneous Detection of Total
Coliforms and Escherichia coli in Drinking Water, EPA-600-R-00-13),
with one exception, the addition of MI Broth. The MI Agar Method
was approved for use in compliance monitoring of drinking water
and source water in support of the National Primary and Secondary
Drinking Water Regulations (Federal Register, Vol. 64, No. 230, 1
December 1999, p.67450-67467) becoming effective 3 January
2000. On 6 November 2001, MI Broth was approved as a minor
modification. This method, now designated as Method 1604, has
been approved for use in monitoring ambient water.
Federal Regulations / List of
Approved Biological Methods
• Applicable to the NPDES facilities
– Check with your State environmental department for
non-NPDES facilities
• Code of Federal Regulations
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Title 40 – Protection of Environment
Chapter 1 – Environmental Protection Agency
Subchapter D – Water Programs
Part 136 – Guidelines Establishing Test Procedures for
the Analysis of Pollutants
– 136.3 Identification of Test Procedures
– Table 1A Approved Biological Methods for Wastewater
and Sewage Sludge
• http://ecfr.gpoaccess.gov
World-wide Prospective
• The Council of European Communities and the World Health
Organization have replaced fecal coliforms to E.coli in standards and
guidelines.
– Source: Domestic Wastewater Treatment In Developing Countries, Published in
2004, Written by Duncan Mara
• Scientific studies suggest that E.coli is the preferred indicator of
fecal contamination. E.coli is approximately equivalent to 90% of
the fecal coliforms.
– Source: A compendium of standards for wastewater reuse in the Eastern
Mediterranean Region, World Health Organization
Contact information
Kalina Warren
Florida Department of Environmental Protection
Central District
Wastewater Compliance/Enforcement Section
407-893-7875
[email protected]
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Testing for Fecal Coliforms and E.coli in Wastewater