# Method 1611: Enterococci in Water by TaqMan ® 

# Quantitative Polymerase Chain Reaction (qPCR) Assay

October 2012

# U.S. Environmental Protection Agency Office of Water (4303T) 1200 Pennsylvania Avenue, NW Washington, DC 20460

EPA-821-R-12-008iii 

## Acknowledgments

This method was developed under the direction of Rich Haugland, Kevin Oshima and Alfred P. Dufour of the U.S. Environmental Protection Agency’s (EPA) Human Exposure Research Division, National Exposure Research Laboratory, Cincinnati, Ohio.

The following laboratories are gratefully acknowledged for their participation in the validation of this method in marine and fresh waters:

Participant Laboratories Single laboratory validation

 Mycometrics, LLC: King-Teh Lin and Pi-shiang Lai

 New York State Department of Health, Environm ental Biology Laboratory: Ellen Braun-Howland and Stacey Chmura Marine ambient water multi-laboratory validation

 BioVir: Rick Danielson and Rosie Newton

 EPA Region 1 – New England Regional Laboratory: Jack Paar and Mark Doolittle

 EPA Region 10 Laboratory: Barry Pepich and Stephanie Harris

 Hampton Roads Sanitation District: Robin Parnell and Tiffany Elston

 King County Environmental: Eric Thompson and Joe Clark

 Mycometrics: King-Teh Lin and Jeff Cook

 NOAA – AOML/Ocean Chemistry Division: Chris Sinigalliano, David Wa nless, and Maribeth Gidley

 NOAA – NOS/Center for Coastal Environmental Health & Biomolecular Research: Janet Gooch Moore and Chris Johnston

 Orange County Public Health Laborator y: Richard Alexander and Joe Guzman

 Texas A&M University – Corpus Christi: Joanna Mott, Ladonna Henson, Sarah Bortz, and Lindsey Myers

 Virginia Institute of Marine Scien ce: Howard Kator and Kimberly Reece Fresh ambient water multi-laboratory validation

 BioVir: Rick Danielson and Rosie Newton

 Hampton Roads Sanitation District: Robin Parnell and Tiffany Elston

 King County Environmental: Eric Thompson and Joe Clark

 Orange County Public Health Laborator y: Richard Alexander and Joe Guzman

 Orange County Water District: Donald Phipps and Menu Leddy

 Scientific Methods Incorporated: Fu-Chih Hsu and Rebecca Wong

 Texas A&M University – Corpus Christi: Joa nna Mott, Ladonna Henson, and Sarah Bortz

 Texas A&M University – College Station: Suresh Pillai, Palmy Jesudhasan, and Katherine McElhany

 University of Iowa Hygienic Lab: Nancy Hall, Greg Gingerich, Cathy Lord, and Lucy DesJardin

 Wisconsin State Lab of Hygiene: Sharon Kluender and Jeremy Olstadtiv 

## Disclaimer

Neither the United States Government nor any of its employees, contractors, or their employees make any warranty, expressed or implied, or assumes any legal li ability or responsibility for any third party’s use of apparatus, product, or process discussed in this method, or represents that its use by such party would not infringe on privately owned rights. Mention of tr ade names or commercial products does not constitute endorsement or recommendation for use.

Questions concerning this method or its application should be addressed to:

Robin K. Oshiro Engineering and Analysis Division (4303T) U.S. EPA Office of Water, Office of Science and Technology 1200 Pennsylvania Avenue, NW Washington, DC 20460 oshiro.robin@epa.gov or OSTCWAMethods@epa.govv 

## Introduction

Enterococci are commonly found in the feces of humans and other warm-blooded animals. Although these organisms can be persistent in the environment, the presence of enterococci in water is an indication of fecal pollution and the possible presence of enteric pathogens. Epidemiological studies have led to the development of criteria for promulgating recreationa l water standards based on established relationships between the measured density of enterococci colony forming units (CFU) in the water by culture based methods and the risk of gastrointestinal illness (GI) associated with swimming in the water (References 17.3, 17.6, 17.7, and 17.8).

Method 1611 describes a quantitative polymerase chain reaction (qPCR) procedure for the detection of DNA from enterococci bacteria in ambient water matrices based on the amplification and detection of a specific region of the large subunit ribosomal RNA gene (lsrRNA, 23S rRNA) from these organisms. The advantage of this method over current ly accepted culture methods that require 24

− 48 hours to obtain results is its relative rapidity. Re sults can be obtained by this method in 3

− 4 hours.

EPA conducted a single-laboratory validation (SLV) st udy of Method 1611 in marine and fresh water matrices, to assess potential matrix issues across multi ple fresh and marine water matrices from different geographic regions across the U.S. During the SLV thirty-seven volunteer laboratories collected and shipped recreational water (marine and/or fresh) samp les to the two analytical laboratories for Method 1611 analyses. For all 25 (each) marine and fresh wa ter matrices, no matrix inhibition was observed for Method 1611. EPA then conducted multi-laboratory validation studies to assess method performance and reproducibility and develop quantitative quality control (QC) acceptance criteria.

Results of the multi-laboratory validation studies en abled performance characte rization of Method 1611 in the reference matrix phosphate buffered saline (PBS) and in marine and fresh water matrices. Results also enabled the development of initial precision a nd recovery/ongoing precision and recovery (IPR/OPR) and matrix spike (MS) QC acceptance criteria. In ad dition, results from marine water and fresh water samples (5 different sources for each matrix type) sp iked with commercially available target organism cells were used to assess method reproducibility.

The highly variable recoveries observed during these studies should be taken into consideration when analyzing results from Method 1611. It is recommended that analysts generate standard curves with each new lot of qPCR reagents or primers and probes to demonstrate comparable performance with these new reagents. In addition, weekly calibrator samples shoul d be monitored to ensure that they are within the acceptable range of the methods; if calibrator sample s are not within the acceptable range, new calibrator samples should be prepared and analyzed. Foll owing these recommendations should increase analyst proficiency and minimize variability of recoveries. In addition, care should be placed to verify the accuracy of all reference materials used in the method (i.e. DNA standards, calibrator cells, control DNA’s and spike materials).

In Method 1611, water samples are filtered to coll ect enterococci on polycarbonate membrane filters. Following filtration, total DNA is solubilized from the filter retentate using a bead beater. Enterococci target DNA sequences present in the clarified homogena te are detected by the real time polymerase chain reaction (PCR) technique using TaqMan ® Universal master mix PCR reagent and the TaqMan ® probe system. The TaqMan ® system signals the formation of PCR products by a process involving enzymatic hydrolysis of a fluorogenically-labeled oligonucleotid e probe when it hybridizes to the target sequence.

Method 1611 uses an arithmetic formula, referred to as the ΔΔ C T comparative cycle threshold calculation ( ΔΔ C T ) method to calculate the ratio of Enterococcus lsrRNA gene target sequences (target sequences)vi recovered in total DNA extracts from water samples rela tive to those in similarly-prepared extracts of calibrator samples containing a known quantity of Enterococcus cells. The ΔΔ C T relative quantitation method also uses measurements of a reference target sequence (from total salmon DNA, added in equal amounts to both test and calibrator samples) to nor malize these ratios for potential differences in DNA recovery. The reference target sequence measurements are also used to signal inhibition or fluorescence quenching of the PCR analysis caused by sample ma trix components or possible technical error. These ratios are converted to calibrator cell equivalent s (CCEs) recovered from the test samples.vii 

## Table of Contents

1.0 Scope and Application .................................................................................................... ................. 1

2.0 Summary of Method ........................................................................................................ ................ 2

3.0 Definitions ............................................................................................................... ........................ 2

4.0 Interferences ............................................................................................................. ........................ 3

5.0 Safety ................................................................................................................... ............................ 3

6.0 Equipment and Supplies .................................................................................................... .............. 3

7.0 Reagents and Standards .................................................................................................... ............... 5

8.0 Sample Collection, Handling, and Storage ................................................................................. ..... 9

9.0 Quality Control .......................................................................................................... ...................... 9

10.0 Calibration and Standardization of Method-Related Instruments .................................................. 14

11.0 Procedure ............................................................................................................... ........................ 14

12.0 Data Analysis and Calculations .......................................................................................... ........... 25

13.0 Sample Spiking Procedure ................................................................................................. ............ 27

14.0 Method Performance ....................................................................................................... ............... 33

15.0 Pollution Prevention .................................................................................................... .................. 34

16.0 Waste Management ........................................................................................................ ................ 35

17.0 Refere nces ............................................................................................................... ....................... 35

18.0 Acronyms ................................................................................................................. ...................... 35viii 

## List of Appendices

Appendix A: ABI StepOnePlusTM, ABI 7900, and ABI 7500 Real-Time PCR System Operation

Appendix B: Cepheid Smart Cycler ® Operation1 

## Method 1611: Enterococci in Water by TaqMan ® 

## Quantitative Polymerase Chain Reaction (qPCR) Assay

October 2012

1.0 Scope and Application

1.1 Method 1611 describes a quantitative polymerase chain reaction (qPCR) procedure for the measurement of large subunit ribosomal RNA (lsr RNA, 23S rRNA) target gene sequences (target sequences) from all known species of enterococci bact eria in water. This method is based on the collection of enterococci on membrane filters, ex traction of total DNA using a bead beater, and detection of enterococci target sequences in the supernatant by real time polymerase chain reaction (qPCR) using TaqMan ® Universal master mix PCR reagent and the TaqMan ® probe system. The TaqMan ® system signals the formation of PCR products by a process involving the enzymatic hydrolysis of a labeled fluorogenic probe that hybridizes to the target sequence.

1.2 The Method 1611 test is recommended as a measure of ambient marine and fresh recreational water quality. The significance of finding Enterococcus DNA target sequences in recreational water samples stems from the association between the density of these seque nces and the reported occurrence of gastrointestinal (GI) illness as sociated with swimming observed in recent epidemiological studies (References 17.4 and 17.10).

1.3 The highly variable recoveries observed during the validation studies should be taken into consideration when analyzing results from Met hod 1611. Guidance is provided in section 9 of this document on how laboratories can monitor th e initial and ongoing performance of the method in their hands. It is expected and has been observed that the performance of the method will improve as laboratories gain additional expe rience with it through continued practice.

1.4 This method assumes the use of an Applied Bi osystems (ABI) Real-Time PCR System as the default platform. The Cepheid Smart Cycler ® may also be used. The user should refer to the platform specific instructions for these instrume nts in the appendices. Users should thoroughly read the method in its entirety before prepara tion of reagents and commencement of the method to identify differences in prot ocols for different platforms.Method 1611

2 

## 2.0 Summary of Method

The method is initiated by filtering a water sample through a membrane filter. Following filtration, the membrane containing the bacteria l cells and DNA is placed in a microcentrifuge tube with glass beads and buffer, and then ag itated to extract the DNA into solution. The supernatant is used for PCR amplification and detection of target sequences using the TaqMan ® Universal master mix PCR reagent and probe system.



## 3.0 Definitions

3.1 Enterococci: all species of the genus Enterococcus for which lsrRNA gene nucleotide sequences were reported in the GenBank database ( http://www.ncbi.nlm.nih/gov/Genbank) at the time of method development.

3.2 Target sequence: A segment of the Enterococcus lsrRNA gene containing nucleotide sequences that are homologous to both the primers and probe used in the Enterococcus qPCR assay and that are common only to species within this genus.

3.3 Sample processing control (SPC) sequence (may also be referred to as reference sequence): A segment of the ribosomal RNA gene operon, internal transcribed spacer region 2 of chum salmon, Oncorhynchus keta ( O. keta ) and other salmon spp.

, containing nucleotide sequences that are homologous to the primers and probe used in the SPC qPCR assay. SPC sequences are added as part of a total salmon DNA solution in equal quan tities to all water and calibrator sample filters prior to extracting DNA from the samples. The purpo se of this control is to determine, and, if necessary, correct for different relative effici encies of total DNA recovery from water and calibrator sample extracts using the ΔΔ C T comparative cycle threshold calculation method ( ΔΔ C T method) as described in Section 12.3. This control is also used to signal potential co-extraction of water sample components that interfere with the PCR analysis as described in Section 9.12.

3.4 DNA standard: A purified, RNA-free and spectr ophotometrically quantified and characterized E. faecalis strain ATCC ® # 29212TM genomic DNA preparation. DNA standards are used to generate standard curves for determination of performance characteristics of the qPCR assays and instrument with different preparations of master mixes containing TaqMan ® reagent, primers and probe as described in Section 9.10. Also used for quantifying target sequences in calibrator sample extracts as described in Section 12.3.

3.5 Calibrator sample: Samples containing constant added quantities of E. faecalis strain ATCC ® # 29212TM cells and SPC sequences that are extractedand analyzed in the same manner as water sample filtrates. Calibrator sample analysis results are used as positive controls for the Enterococcus target sequence and SPC qPCR assays and as the basis for target sequence quantification in water sample filtrates using the ΔΔ C T comparative cycle threshold calculation method ( ΔΔ C T method) as described in Section 12.3. Analysis results of these samples provide corrections for potential method-related variations in Enterococcus cell lysis, target sequence recovery and PCR efficiency.

3.6 ΔΔ C T method: A calculation method derived by ABI (Reference 17.1) for calculating the ratios of target sequences in two DNA samples ( e.g., a calibrator and water filtrate sample) that normalizes for differences in total DNA recovery from these samples using qPCR analysis C T values for a reference (SPC) sequence that is initially presen t in equal quantities prior to DNA extraction.Method 1611

3 3.7 Amplification factor (AF): A measure of the average efficiency at which target or SPC sequences are copied and detected by their respective pr imer and probe assays during each thermal cycle of the qPCR reaction that is used in the ΔΔ C T method. AF values can range from 1 (0% of sequences copied and detected) to 2 (100% of se quences copied and detected) and are calculated from a standard curve as described in Section 12.2. For an explanation of test inhibition, see Section 9.12.



## 4.0 Interferences

Water samples containing colloidal or suspende d particulate materials can clog the membrane filter and prevent filtration. These materials can also interfere with DNA recovery and with the qPCR analysis by inhibiting the enzymatic activity of the Taq DNA polymerase, and/or inhibiting the annealing of the primer and probe oligonuc leotides to sample target DNA, enzyme or quenching of hydrolyzed probe fluorescence.



## 5.0 Safety

5.1 The analyst / technician must know and observe the normal safety procedures required in a microbiology and/or molecular biology laborator y while preparing, using, and disposing of cultures, reagents, and materials, and while operating sterilization equipment.
5.2 Where possible, facial masks should be worn to prevent sample contamination.
5.3 Mouth-pipetting is prohibited.



## 6.0 Equipment and Supplies

6.1 Separated, and dedicated workstations for reag ent preparation and for sample preparation, preferably with HEPA-filtered laminar flow hoods and an Ultraviolet (UV) light source, each having separate supplies ( e.g. , pipettors, tips, gloves, etc.). Note : The same workstation may be used for the entire procedure provided that it h as been cleaned with bleach and UV sterilized as specified in Section 11.6.1 between reagent and sa mple preparation. Under ideal conditions, two dedicated workstations are used for sample pr eparation: one for preparing samples with high target sequence DNA concentrations ( e.g. , DNA standards and calibrator samples) and one for preparing samples with expected low target sequence DNA concentrations ( e.g. , filter blanks and ambient water samples).
6.2 Balance capable of accuracy to 0.01 g
6.3 Extraction tubes: semi-conical, screw cap micr ocentrifuge tubes, 2.0 mL (PGC 506-636 or equivalent)
6.4 Glass beads, acid washed, 212

− 300 μ m diameter (Sigma G-1277 or equivalent)
6.5 Autoclave, capable of achieving and maintaining 121  C [15 lb pressure per s quare inch (PSI)] for minimally 15 minutes (optional)
6.6 Workstation for water filtrations, preferably a HEPA-filtered laminar flow hood with a UV light source. This can be the same as used for sample preparation (Section 6.1).Method 1611

4 6.7 Sterile bottles/containers for sample collection
6.8 Membrane filtration units (filter base and funnel) fo r 47 mm diameter filters, sterile glass, plastic (Pall Gelman 4242 or equivalent), stainless steel, or disposable plastic (Nalgene CN 130-4045 or CN 145-0045 or equivalent), cleaned and bleach treated (rinsed with 10% v/v bleach, then 3 rinses with reagent-grade water), covered with al uminum foil or Kraft paper, and autoclaved or UV-sterilized if non-disposable.
6.9 Line vacuum, electric vacuum pump, or aspirator for use as a vacuum source. In an emergency or in the field, a hand pump or a syringe equipped with a check valve to prevent the return flow of air can be used.
6.10 Flask, filter, vacuum, usually 1 L, with appropriate tubing
6.11 Filter manifold to hold a number of filter bases
6.12 Flask for safety trap placed between th e filter flask and the vacuum source
6.13 Forceps, straight or curved, with smooth tip s to handle filters without damage, 2 pairs
6.14 Polycarbonate membrane filters, sterile, white, 47 mm diam eter, with 0.45 μm pore size (GE Osmonics Inc. K04CP04700 or equivalent)
6.15 Graduated cylinders, 100 - 1000 mL, cleaned and bleach treated (rinsed with 10% v/v bleach, then 3 rinses with reagent-grade water), cove red with aluminum foil or Kraft paper and autoclaved or UV-sterilized.
6.16 Petri dishes, sterile, plastic or glass, 100 × 15 mm with loose fitting lids
6.17 Disposable loops, 1 and 10 μ L
6.18 Permanent ink marking pen for labeling tubes
6.19 Visible wavelength spectrophotometer capable of measuring at 595 nm
6.20 Single or multi-place bead beater (Biospec Products Inc. 3110BX or equivalent)
6.21 Microcentrifuge capable of 12,000 × g
6.22 Micropipettors with 10, 20, 200 and 1000 μ L capacity. Under ideal conditions, each workstation should have a dedicated set of micropipettors ( one micropipettor set for pipetting reagents not containing cells or reference DNA and one set for reagents containing reference DNA and for test samples). Ideally, micropipettors should be calibrated monthly.
6.23 Micropipettor tips with aerosol barrier for 10, 20, 200 and 1000 μ L capacity micropipettors. Note : All micropipetting should be done with aerosol barrier tips. The tips used for reagents not containing DNA should be separate from those us ed for reagents containing DNA and test samples. Each workstation should have a dedicated supply of tips.
6.24 Microcentrifuge tubes, low retention, clear , 1.7 mL (GENE MATE C-3228-1 or equivalent)
6.25 Test tube rack for microcentrifuge tubes, use a separate rack for each set of tubes
6.26 Conical centrifuge tubes, sterile, screw cap, 50 mL
6.27 Test tubes, screw cap, borosilicate glass, 16 × 125 mm
6.28 Pipet containers, stainless steel, aluminum or borosilicate glass, for glass pipets
6.29 Pipets, sterile, T.D. bacteriological or Mohr, di sposable glass or plastic, of appropriate volume (disposable pipets preferable)
6.30 Vortex mixer (ideally one for each work station)Method 1611

5 6.31 Dedicated lab coats for each work station
6.32 Disposable powder-free gloves for each work station

6.33 Refrigerator, 4  C (ideally one for reagents and one for DNA samples)

6.34 Freezer, -20  C or -80  C (ideally one for reagents and one for DNA samples)
6.35 Ice, crushed or cubes for temporary preservation of samples and reagents
6.36 Printer (optional)
6.37 Data archiving system ( e.g. , flash drive or other data storage system)
6.38 UV spectrophotometer capable of measuring wavele ngths of 260 and 280 nm using small volume capacity ( e.g., 0.1 mL) cuvettes or NanoDrop ® (ND-2000 spectrophotometer or equivalent) capable of the same measurements at 2 μ L sample volumes
6.39 ABI StepOnePlusTM, ABI 7900, or ABI 7500
6.39.1 Optical 96 well PCR reaction tray (ABI N801-0560 or equivalent)
6.39.2 Optical adhesive PCR reaction tray tape (ABI 4311971 or equivalent) or MicroAmpTM caps (ABI N8010534 or equivalent)
6.39.3 ABI StepOnePlusTM, ABI 7900, or ABI 7500 Real-Time PCR System
6.40 Cepheid (optional to ABI)
6.40.1 Smart Cycler ® 25 μ L PCR reaction tubes (Cepheid 900-0085 or equivalent)
6.40.2 Rack and microcentrifuge for Smart Cycler ® PCR reaction tubes. Note : Racks and microcentrifuge are provided with the Smart Cycler ® thermocycler
6.40.3 Cepheid Smart Cycler ® System Thermocycler



## 7.0 Reagents and Standards

Note : The E. faecalis stock culture (Section 7.8), Salmon DNA/extraction buffer (Section 7.12), and DNA extraction tubes (Section 7.18), may be prepared in advance.
7.1 Purity of Reagents: Molecular-grade reagents and chemicals shall be used in all tests
7.2 Control Culture

• Enterococcus faecalis ( E. faecalis ) ATCC ® #29212TM (ATCC, Manassas VA) or

• E. faecalis ATCC ® # 29212TM (550 colony forming units [CFU]) BioBalls (bioMérieux Inc., Durham NC)

7.3 Sample Processing Control (SPC) DNA

• Salmon testes DNA (Sigma D1626 or equivalent)Method 1611

6 7.4 Phosphate Buffered Saline (PBS)
7.4.1 Composition:

Monosodium phosphate (NaH 2 PO 4 ) 0.58 g Disodium phosphate (Na 2 HPO 4 ) 2.50 g Sodium chloride 8.50 g Reagent-grade water 1.0 L

7.4.2 Dissolve reagents in 1 L of reagent-grade wa ter in a flask and dispense in appropriate amounts for dilutions in screw cap bottles or cultu re tubes, and/or into containers for use as rinse water. Autoclave after preparation at 121  C (15 lb PSI) for 15 minutes. Final pH should be 7.4 ± 0.2.
7.5 Brain heart infusion broth (BHIB)
7.5.1 Composition:

Calf brains, infusion from 200.0 g 7.7 g Beef heart, infusion from 250.0 g 9.8 g Proteose peptone 10.0 g Sodium chloride 5.0 g Disodium phosphate (Na 2 HPO 4 ) 2.5 g Dextrose 2.0 g Reagent-grade water 1.0 L
7.5.2 Add reagents to 1 L of reagent-grade water, mix thoroughly, and heat to dissolve completely. Dispense 10 mL volumes in screw cap 16 × 125 mm tubes and autoclave at 121  C (15 PSI) for 15 minutes. Final pH should be 7.4 ± 0.2.
7.6 Brain heart infusion agar (BHIA)
7.6.1 Composition: BHI agar contains the same components as BHIB with the addition of 15.0 g agar per liter of BHI broth.
7.6.2 Add agar to formula for BHIB provided above. Prepare as in Section 7.5.2. After sterilization, dispense 12

− 15 mL into 100 × 15 mm petri dishes. Final pH should be 7.4 ± 0.2.

7.7 Sterile glycerol (used for preparation of E. faecalis stock culture as described in Section 7.8)
7.8 Preparation of E. faecalis (ATCC ® # 29212TM) stock culture Rehydrate lyophilized E. faecalis per manufacturer’s instructions (for ATCC ® stocks, suspend in 5 - 6 mL of sterile BHIB and incubate at 37  C for 24 hours). Centrifuge to create pellet. Using a sterile pipet, discard supernatant. Resuspend pe llet in 10 mL of fresh sterile BHIB containing 15% glycerol and dispense in 1.5 mL aliquots in microcentrifuge tubes. Freeze at -20  C (short term storage) or -80  C (long term storage). Note : Aliquots of suspension should be plated to determine CFU concentration as described in Secti on 11.1. It is also advisable to verify the E. faecalis culture as described, for example, in Section 15 of EPA Method 1600.Method 1611

7 7.9 PCR-grade water (OmniPur water from VWR EM-9610 or equivalent). Water must be DNA/DNase free.
7.10 Isopropanol or ethanol, 95%, for flame-sterilization
7.11 AE Buffer, pH 9.0 (Qiagen 19077 or equivalent) Note : pH 8.0 is acceptable Composition: 10 mM Tris-Cl (Tris-chloride) 0.5 mM EDTA (Ethylenediaminetetraacetic acid)
7.12 Salmon DNA/extraction buffer
7.12.1 Composition: Stock Salmon testes DNA (10 μ g/mL) (Section 7.3) AE Buffer (Section 7.11)
7.12.2 Preparation of stock Salmon testes DNA: Using sterilized scissors and sterilized forceps, cut a piece of DNA to weigh approximately 20 mg, and place in a sterile 50 mL conical tube. After weighing, add 20 mL of PCR-grad e water. Cap tightly, and resuspend by 2

− 4 hours of vigorous shaking (note: longer times may be required to fully suspend the DNA – check for even consistency by re peatedly drawing up the suspension and expelling with a sterile 25 ml pipet) . The concentration should be about 1 mg/mL. Dilute a 1ml aliquot of this 1 mg/mL stock with 99 ml PCR-grade water to make 10
μ g/mL working stock. Check absorbance (OD 260 ) and calculate DNA concentration using the assumption 50 μ g/mL DNA is equal to 1 OD 260 , (i.e. 10 μ g/mL should equal ~ 0.2 OD 260. ). If measured concentration is different than 10 μ g/mL, adjust dilutions to make 0.2 μ g/mL Salmon DNA/extraction buffer in 7.12.3 accordingly. Dispense 1 mg/mL stock and 10 μ g/mL working stock suspensions into aliquots (e.g. 1 ml) and freeze at -20  C. Frozen aliquots of working stock should be thawed only once, but once thawed can be stored in a refrigerator for several months.
7.12.3 Dilute Salmon testes DNA working st ock with AE buffer to make 0.2 μ g/mL Salmon DNA/extraction buffer. Extraction buffer may be prepared in advance and stored at 4  C for a maximum of 1 week.

Note : Determine the total volume of Salmon DNA/extraction buffer required for each day or week by multiplying volume (600 μ L) × total number of samples to be analyzed including controls, water samples, and calibra tor samples. For example, for 18 samples, prepare enough Salmon/DNA extraction buffer for 24 extraction tubes: 3 tubes for water sample filtration blank (method blank) and 3 tu bes for calibrator samples). Note: At least one method blank should be included with each sample batch. Additionally, prepare excess volume to allow for accurate dispensing of 600 μ L per tube, generally enough for 1 extra tube. Thus, in this example, prepare sufficient Salmon/DNA extraction buffer for 24 tubes plus one extra. The total volume needed is 600 μ L × 25 tubes = 15,000 μ L. Dilute the Salmon testes DNA working stock 1:50, for a total volume needed (15,000 μ L) ÷ 50 = 300 μ L of 10 μ g/mL Salmon testes DNA working stock. The AE buffer needed is the difference between the total volume and the Salmon testes DNA working stock. For this example, 15,000 μ L

− 300 μ L = 14,700 μ L AE buffer needed.
7.13 Bleach solution: 10% v/v bleach (or other reagen t that hydrolyzes DNA), used for cleaning work surfaces
7.14 Sterile water (used as rinse water for work surface after bleaching)Method 1611

8 7.15 TaqMan ® Universal PCR master mix (ABI 4304437 or equivalent) Composition: AmpliTaq Gold ® DNA Polymerase AmpErase ® UNG
dNTPs with dUTP Passive Reference 1 (ROXTM fluorescent dye) Optimized buffer components (KCl, Tris, EDTA, MgCl 2 )
7.16 Bovine serum albumin (BSA), fraction V powder (Sigma B-4287 or equivalent) Dissolve in PCR-grade water to a concentration of 2 mg/mL.
7.17 Primer and probe sets: Primer and probe sets may be purchased from commercial sources. Primers should be desalted, probes should be HPLC purified.
7.17.1 Enterococcus primer and probe set (Reference 17.5): Forward primer: 5'-GAGAAATTCCAAACGAACTTG Reverse primer: 5'-CAGTGCTCTACCTCCATCATT TaqMan ® probe: [6-FAM]-5'-TGGTTCTCTCCGAAATAGCTTTAGGGCTA-TAMRA
7.17.2 Salmon DNA primer and probe set (Reference 17.4): Forward primer: 5'-GGTTTCCGCAGCTGGG Reverse primer (Sketa 22): 5'-CCGAGCCGTCCTGGTC TaqMan ® probe: [6-FAM]-5'-AGTCGCAGGCGGCCACCGT-TAMRA
7.17.3 Preparation of primer/probes: Using a micropipettor with aerosol barrier tips, add PCR grade water to the lyophilized primers and probe from the vendor to create stock solutions of 500 μ M primer and 100 μ M probe and dissolve by extensive vortexing. Pulse centrifuge to coalesce droplets. Store stock solutions at -20  C.
7.18 DNA extraction tubes

Note : It is recommended that tube preparation be performed in advance of water sampling and DNA extraction procedures. Prepare 1 tube for each sample, and 1 extra tube for every 6 samples ( i.e ., for method blank) and a minimum of 3 tubes per week for calibrator samples. Weigh 0.3 ± 0.01 g of glass beads (Section 6.4) and pour into extraction tube. Seal the tube tightly, checking to make sure there are no beads on the O-ring of the tube. Check the tube for proper O-ring seating after the tube has been closed. Autoclave tubes at 121  C (15 PSI) for 15 minutes. Note : Sterile extraction tubes containing glass beads are available from Ge nerite LLC., (50205-50 or equivalent).
7.19 Purified, RNA-free quantified and characterized E. faecalis genomic DNA preparations for use as standards used to generate a standard curve ( see Section 11.2 for preparation instructions).
7.20 RNase A 5 mg/mL (epicentre ® MRNA092 or equivalent)
7.21 DNA extraction kit (Gene-Rite K102-02C-50 DNA-EZ ® RW02 or equivalent)Method 1611

9 

## 8.0 Sample Collection, Handling, and Storage

8.1 Sampling procedures are briefly described below. Adherence to sample preservation procedures and holding time limits is critical to the pr oduction of valid data. Samples not collected according to these procedures should not be analyzed. Note : It is recommended that when possible that three samples be collected and analyzed from each sample location.
8.2 Sampling Techniques Samples are collected by hand or with a sampling device if the sampling site has difficult access such as a dock, bridge or bank adjacent to a su rface water. Composite samples should not be collected, since such samples do not display the ra nge of values found in individual samples. The sampling depth for surface water samples should be 6

− 12 inches below the water surface. Sample containers should be positioned such that th e mouth of the container is pointed away from the sampler or sample point. After removal of th e container from the water, a small portion of the sample should be discarded to provide head space for proper mixing before analyses.
8.3 Storage Temperature and Handling Conditions Ice or refrigerate water samples at a temperature of <10  C during transit to the laboratory. Do not freeze the samples. Use insulated containe rs to assure proper maintenance of storage temperature. Ensure that sample bottles are tight ly closed and are not completely immersed in water during transit.
8.4 Holding Time Limitations Examine samples as soon as possible after collection. Do not hold samples longer than 6 hours between collection and initiation of filtration.



## 9.0 Quality Control

9.1 Each laboratory that uses Method 1611 is require d to operate a formal quality assurance (QA) program that addresses and documents instrument and equipment maintenance and performance, reagent quality and performance, analyst training and certification, and records storage and retrieval. Additional recommendations for QA and quality control (QC) procedures for microbiological laboratories are provided in Reference 17.2.
9.2 The minimum analytical QC requirements for the analysis of samples using Method 1611 include an initial demonstration of laboratory capability through performance of the initial precision and recovery (IPR) analyses (Section 9.3), ongoing de monstration of laboratory capability through performance of the ongoing precision and recovery (OPR) analysis (Section 9.4) and matrix spike (MS) analysis (Section 9.5), and the routine anal ysis of positive control (Section 9.6), no template controls (Section 9.7), method blanks (Secti on 9.8), media sterility checks (Section 9.9), DNA standard curves (9.10), calibrator samples (9.11), and sample processing controls (9.12). For the IPR, OPR and MS analyses, it is necessary to sp ike samples with either laboratory-prepared spiking suspensions or BioBalls as described in Section 13.
9.3 Initial precision and recovery (IPR) — The IPR analyses are used to demonstrate acceptable method performance (recovery and precision) and sh ould be performed by each laboratory before the method is used for monitoring field samples. An IPR should be performed by each analyst. The IPR analyses are performed as follows:
9.3.1 Prepare four, 100 mL samples of PBS and spik e each sample with the control culture, E. faecalis ATCC ® # 29212TM according to the spiking procedure in Section 13. SpikingMethod 1611

10 with laboratory-prepared suspensions is d escribed in Section 13.4 and spiking with a commercially prepared product (e.g., BioBalls) is described in Section 13.7. Filter and process each IPR sample according to the pr ocedures in Section 11 and calculate the calibrator cell equivalents (CCEs) in th e samples according to Section 12. Note : prepare calibrator samples from the same source of ce lls used to prepare the spike suspensions, i.e. for samples spiked with laboratory- prepared cell suspensions, use the same laboratory-prepared cell suspensions to prep are calibrator samples; for samples spiked with BioBalls, use the same lot of Bi oBalls to prepare calibrator samples.
9.3.2 Calculate the percent recovery (R) for each IPR sample according to the Method 1611 Calculation Excel file using the appropri ate spreadsheets “Laboratory-prepared” or “BioBalls” for samples spiked with laboratory -prepared spiking suspensions or BioBalls, respectively.
9.3.3 Using the percent recoveries of the four analyses, calculate the mean percent recovery and the relative standard deviation (RSD) of the recoveries. The RSD is the standard deviation divided by the mean, multiplied by 100.
9.3.4 Compare the mean recovery and RSD with the corresponding IPR criteria in Table 1
, below. If the mean and RSD for recovery of enterococci meet acceptance criteria, system performance is acceptable and analysis of field samples may begin. If the mean recovery or the RSD fall outside of the required range for recovery, system performance is unacceptable. In this event, identify the probl em by evaluating each step of the analytical process, media, reagents, and controls, correct the problem and repeat the IPR analyses.

Table 1. Calculated Initial Precision and Recovery (IPR) Acceptance Criteria at 550 CFU Spike Type IPR Mean Recovery (%) IPR RSD OPR Recovery (%)
Lab-prepared Detect – 2684% 132 Detect – 2846%

BioBall ® Detect – 286% 112 Detect – 325%

9.4 Ongoing precision and recovery (OPR) — To demonstrate ongoing control of the analytical system, the laboratory should routinely process and analyze spiked PBS samples. The laboratory should analyze one OPR sample after every 20 fi eld and matrix spike samples or one per week that samples are analyzed, whichever occurs more frequently. The OPR analysis is performed as follows:
9.4.1 Prepare one, 100 mL sample of PBS and spike with E. faecalis ATCC ® # 29212TM according to the spiking procedure in Secti on 13. Spiking with laboratory-prepared suspensions is described in Section 13.4 and sp iking with BioBalls is described in Section 13.7. Filter and process the OPR sample acco rding to the procedures in Section 11 and calculate the target sequences in th e samples according to Section 12.
9.4.2 Calculate the percent recovery (R) for th e OPR sample according to the Method 1611 Calculation Excel file using the appropri ate spreadsheets “Laboratory-prepared” or “BioBalls” for samples spiked with laboratory -prepared spiking suspensions or BioBalls, respectively.
9.4.3 Compare the OPR result (percent recovery) w ith the corresponding OPR recovery criteria in Table 1, above. If the OPR result meets the acceptance criteria for recovery, method performance is acceptable and analysis of fi eld samples may continue. If the OPR result falls outside of the acceptance criteria, syst em performance is unacceptable. In thisMethod 1611

11 event, identify the problem by evaluating each step of the analytical process, reagents, and controls, correct the problem and repeat the OPR analysis.
9.4.4 As part of the laboratory QA program, results for OPR and IPR samples should be charted and updated records maintained in order to monitor ongoing method performance. The laboratory should also develop a statement of accuracy for Method 1611 by calculating the average percent recovery (R) and the standard deviation of the percent recovery (s r ). Express the accuracy as a recovery interval from R - 2s r to R + 2s r . 9.5 Matrix spikes (MS) — MS analysis are performed to determine the effect of a particular matrix on enterococci recoveries. The laboratory shoul d analyze one MS sample when recreational water samples are first received from a source from which the laboratory has not previously analyzed samples. Subsequently, 5% of field samples (1 per 20) from a given source should include a MS sample. MS samples must be accompanied by the analysis of an unspiked field sample sequentially collected from the same samp ling site. When possible, MS analyses should also be accompanied by an OPR sample (Sec tion 9.4), using the same spiking procedure (laboratory-prepared spiking suspension or BioBa lls). The MS analysis is performed as follows:
9.5.1 Prepare two, 100 mL field samples that were sequentially collected from the same site. One sample will remain unspiked and will be analyzed to determine the background or ambient concentration of enterococci for calculating MS recoveries (Section 9.5.3). The other sample will serve as the MS sample and will be spiked with E. faecalis ATCC ® # 29212TM according to the spiking procedure in Section 13.
9.5.2 Spike the MS sample volume(s) with a labor atory-prepared suspension as described in Section 13.4 or with BioBalls as described in Section 13.7. Immediately filter and analyze both the unspiked and spiked field samples according to the procedures in Section 11.
9.5.3 For the MS sample, calculate the number of target sequences according to Section 12 and adjust based on any background enterococci ob served in the unspiked matrix sample.
9.5.4 Calculate the percent recovery (R) for the MS sample (adjusted based on ambient enterococci in the unspiked sample) according to the Method 1611 Calculation Excel file using the appropriate spreadsheets “Laborat ory-prepared” or “BioBalls” for samples spiked with laboratory-prep ared spiking suspensions or BioBalls, respectively.
9.5.5 Compare the MS result (percent recovery) with the appropriate method performance criteria in Table 2 , below. If the MS recovery meets the acceptance criteria, system performance is acceptable and analysis of fiel d samples from this disinfected wastewater source may continue. If the MS recovery is unacceptable and the OPR sample result associated with this batch of samples is accep table, a matrix interference may be causing the poor results. If the MS recovery is unacceptable, all associated field data should be flagged.
9.5.6 Laboratories should record and maintain a cont rol chart comparing MS recoveries for all matrices to batch-specific and cumulative OPR sample results analyzed using Method 1611. These comparisons should help laborat ories recognize matrix effects on method recovery and may also help to recognize incons istent or sporadic matrix effects from a particular source.Method 1611

12 Table 2. Calculated Matrix Spike Precision and Recovery Acceptance Criteria at 550 CFU
Matrix Spike Type MS Recovery (%) MS RPD 1 (%)

MW Lab-prepared Detect – 1198% 160

BioBall ® Detect – 1123% 191

FW Lab-prepared Detect – 3473% 110

BioBall ® Detect – 333% 354

1 Relative percent difference

9.6 Positive controls — The laboratory should analyze positive controls to ensure that the method is performing properly. Fluorescence amplification growth curve (PCR amplification trace) with an appropriate cycle threshold (C T ) value during PCR indicates proper method performance. On an ongoing basis, the laboratory should perform positive control analyses every day that samples are analyzed. In addition, controls should be analyzed when new lots of reagents or filters are used.
9.6.1 Calibrator samples will serve as the positive c ontrol. Analyze as described in Section 11.0. Note : Calibrator samples contain the same amount of extraction buffer and starting amount of Salmon DNA as the test samples; hence E. faecalis calibrator sample extracts (Section 11.3) will be used as a positive control for both Enterococcus and SPC qPCR assays. 9.6.2 If the positive control fails to exhibit the a ppropriate fluorescence growth curve response, check and/or replace the associat ed reagents, and reanalyze. If positive controls still fail to exhibit the appropriate fluorescence growth curve response, prepare new calibrator samples and reanalyze (see Section 9.11).
9.7 No template controls — The laboratory should analyze “No Template Controls” (NTCs) to ensure that the PCR master mi x reagents are not contaminated. On an ongoing basis, the laboratory should perform NTC analyses every day th at samples are analyzed. If greater than one-third of the NTC reactions for a PCR master mix exhibit true positive logarithmic amplification traces with C T values below 45 (not from chemical degradation of probe with linear kinetics that exhibit rising baseline) or if any one NTC reaction has a C T value lower than 35, the analyses should be repeated with new master mix working stock preparations.
9.8 Method blank (water sample filtration blank) — Filter a 50 mL volume of sterile PBS before beginning the sample filtrations. Remove the funne l from the filtration unit. Using two sterile or flame-sterilized forceps, fold the filter on th e base of the filtration unit and place it in an extraction tube with glass beads as described in S ection 7.18. Extract as in Section 11.5. The absence of a fluorescence amplification growth curve during PCR analysis of these samples (reported as “0” on Smart Cycler ® and “undetermined” on ABI instruments) indicates the absence of contaminant target DNA (see Data Quality Acceptance, below). Prepare at least one method blank filter for every PCR run (e.g., minimally one method blank per 96 well plate or Smart Cycler run).
9.9 Media sterility check — The laboratory should test media sterility by incubating one uninoculated unit (tube or plate) from each batch of medium (BHIA/BHIB) as appropriate and observing for growth. Absence of growth indicates media sterility. On an ongoing basis, the laboratory should perform media sterility checks when preparing new E. faecalis cell stocks.
9.10 DNA standards and standard curves – Purified, RNA-free and spectrophotometrically quantified E. faecalis genomic DNA should be prepared as described in Section 11.2. Based on reported values for its size, the weight of a single E. faecalis genome can be estimated to be ~3.6 fg and there are four lsrRNA gene copies per genome in this species (see the rRNA operonMethod 1611

13 database at http://rrndb.cme.msu.edu ). The concentration of lsrRNA gene copies per μ L in the standard E. faecalis genomic DNA preparation can be determ ined from this information and from its spectrophotometrically determined total DNA concentration by the formula:

Concentration of lsrRNA

gene copies per μ L = Total DNA concentration (fg/ μ L)

× 4 lsrRNA gene copies

3.6 fg/genome genome

A composite standard curve should be generated fro m multiple analyses of serial dilutions of this DNA standard using the Enterococcus primer and probe assay and subjected to linear regression analysis as described in Section 12.2. From th at point on, it is recommended that additional standard curves be generated from triplicate analy ses of these same diluted standard samples with each new lot of TaqMan ® master mix reagents or primers and probes to demonstrate comparable performance by these new reagents. The r 2 values from regressions of these curves should ideally be 0.99 or greater. Comparable performance is assessed by their slopes and y-intercepts which should be consistent with those from the initial composite analyses ( e.g ., within the 95% confidence range of the average values). Note : The 95% confidence ranges for these parameters in the initial composite standard curve can be generated using the Regression Analysis Tool which can be accessed from th e “Data Analysis” selection under the “Tools” menu in Excel. Subsequent regressions can be performed by plo tting the data using the Chart Wizard in Excel and using the “add trend line” selection in the Chart menu and “display equation on chart” selection under Options to obtain slope and y-in tercept values as illustrated in Section 12.2. In the event that the slope valu e from a subsequent standard curve regression is outside of the acceptance range, the diluted standards should be re-analyzed. If this di fference persists, new working stocks of the reagents should be prep ared and the same procedure repeated. If the differences still persist, the amplification factor values used for calculations of target cell numbers, as described in Section 12, should be modified based on the new slope values. If the slopes are within acceptance range but y-intercep ts are not within acceptance range of this previous average, new aliquots of serial dilutio ns of the DNA standard should be analyzed or prepared and analyzed as described in Section 11.2 and above.
9.11 Calibrator samples — The cell concentration of each cultured E. faecalis stock suspension used for the preparation of calibrator sample extract s should be determined as described in Section 11.1. A minimum of nine calibrator sample extracts should initially be prepared from three different freezer-stored aliquots of these stocks as de scribed in Section 11.3. Dilutions of each of these calibrator sample extracts equivalent to the an ticipated dilutions of th e test samples used for analysis ( e.g., 1-, 5- and/or 25-fold) should be analyzed with the Enterococcus primer and probe assay. The average and standard deviation of the C T values from these composite analyses should be determined. From that point on, a minimum of three fresh calibrator sample extracts should be prepared from an additional frozen aliquot of th e same stock cell suspension at least weekly and preferably daily before analyses of each batch of test samples. Dilutions of each new calibrator sample extract equivalent to the initial composite dilutions ( e.g. , 1-, 5- and/or 25-fold) should be analyzed using the Enterococcus primer and probe assay. The average C T value from these analyses should not be significantly different fro m the laboratory’s average values from analyses of the initial calibrator sample extracts from the same stock cell suspension ( i.e ., not greater than three standard deviations). If these results ar e not within this acceptance range, new calibrator extracts should be prepared from another frozen aliquot of the same stock cell suspension and analyzed in the same manner as described above. If the results are still not within the acceptance range, the reagents should be checked by the ge neration of a standard curve as described in Section 9.10.Method 1611

14 9.12 Salmon DNA SPC sequence analyses — The Salmon DNA SPC is used as a DNA isolation efficiency control. While not essential, it is good practice to routinely prepare and analyze standard curves from serial dilutions of Salmon DNA working stocks in a manner similar to that described for the Enterococcus DNA standards in Section 9.10. At this time rRNA gene operon copy numbers per genome have not been repor ted in the literature for the salmon species 

### O. keta

. Therefore log-transformed total DNA concentra tion values or dilution factor values can be substituted for target sequence copy numbers as the x-axis values in these plots and regression analyses. In general, target DNA concentrations in test samples can be calculated as described in Section 12. However, the Salmon DNA PCR assay results for each test sample’s 5-fold dilution should be within 3 C T units of the mean of the 5-fold dilute d calibrator (and/or method blank) Salmon DNA sample results. Higher C T values may indicate significant PCR inhibition or poor DNA recovery possibly due to physical, chemical, or enzymatic degradation. Repeat the Enterococcus and Salmon DNA PCR assays of any samples whose 5-fold dilution exhibits a Salmon DNA PCR assay C T value greater than 3 C T units higher than the mean of th e calibrator sample results using a 5-fold higher dilution (net dilutio n: 25-fold) of the extracts. The Enterococcus PCR result from assaying the original 5-fold dilution of the sa mple can be accepted if its Salmon DNA assay C T value is lower than that of the corresponding 25-fo ld dilution of the sample. This pattern of results is indicative of poor recovery of total DNA in the extract rather than PCR inhibition. The poor DNA recovery is compensated for by the calculation method. Contrarily, if the Salmon PCR assay C T value of the 25-fold dilution of the sample is lower than that of the 5-fold dilution of the sample, then the Enterococcus PCR assay result from the 25-fold dilution of the sample is considered more accurate. However the Enterococcus PCR results should be reported as questionable if the Salmon DNA assay’s result is still not within 3 C T units of the mean C T result of the 25-fold dilution of the three calibrators.



## 10.0 Calibration and Standardization of Method-Related Instruments

10.1 Check temperatures in incubators twice daily with a minimum of 4 hours between each reading to ensure operation within stated limits.
10.2 Check thermometers at least annually against a NIST certified thermometer or one that meets the requirements of NIST Monograph SP 250 -23. Check columns for breaks.
10.3 The spectrophotometer should be calibrated each day of use using OD calibration standards between 0.01

− 0.5. Follow manufacturer instructions for calibration.
10.4 Micropipettors should be calibrated at a minimum annually, ideally monthly, and tested for accuracy on a weekly basis. Follow ma nufacturer instructions for calibration.
10.5 Follow manufacturer instructions for calibration of real-time PCR instruments.



## 11.0 Procedure

Note : E. faecalis cell suspensions (Section 11.1) and E. faecalis DNA standards (Section 11.2) may be prepared in advance. Calibrator sample s (Section 11.3) should be prepared at least weekly.Method 1611

15 11.1 Preparation of E. faecalis cell suspensions for DNA standards and calibrator samples
11.1.1 Thaw an E. faecalis (ATCC ® # 29212TM) stock culture (Section 7.8) and streak for isolation on BHIA plates. Incubate plates at 37  C ± 0.5  C for 24 ± 2 hours.
11.1.2 Pick an isolated colony of E. faecalis from BHIA plates and suspend in 1 mL of sterile PBS and vortex.
11.1.3 Use 10 μ L of the 1 mL suspension of E. faecalis to inoculate a 10 mL BHIB tube. Place the inoculated tube and one uninoculated tube (sterility check) on a shaker set at 250 rpm and incubate at 37  C ± 0.5  C for 24 ± 2 hours. Note : It is advisable to verify that the selected colony is Enterococcus as described, for example, in Section 15 of EPA Method 1600.
11.1.4 After incubation, centrifuge the BHIB containing E. faecalis for 5 minutes at 6000 × g.
11.1.5 Aspirate the supernatant and resuspend the cell pellet in 10 mL PBS.
11.1.6 Repeat the two previous steps twice and suspend the final E. faecalis pellet in 5 mL of sterile PBS. Label the tube as E. faecalis undiluted stock cell suspension, noting cell concentration after determination with one of the following steps (11.1.7).
11.1.7 Determine calibrator sample cell concentr ations based on one of two the options indicated below.

• Option 1: Spectrophotometric absorbance – Remove three 0.1 mL aliquots of undiluted cell suspension and dilute each with 0.9 mL of PBS (10 -1 dilution). Read absorbance at 595 nm in spectrophotometer against PBS blank (readings should range from 0.05 to 0.3 OD). Calculate ce lls/mL (Y) in undiluted cell suspension using the formula from the standard curv e shown below where X is the average 595 nm spectrophotometer reading. Note : Cell concentration (spectrophotometric determination) of undiluted E. faecalis cell suspension should be at least ~10 9 CFU/mL in order to obtain adequate DNA yield for accurate UV spectrophotometric reading. Y = (1 × 10 9 cells / mL × X) / 0.19

• Option 2: plating – Note : PBS and BHIA plates should be prepared in advance if this option is chosen. For enumeration of the E. faecalis undiluted cell suspension, dilute and inoculate according to the following. A) Mix the E. faecalis undiluted cell suspension by vigorously shaking the 5 mL tube a minimum of 25 times. Use a sterile pipette to transfer 1.0 mL of the undiluted cell suspension to 99 mL of sterile PBS, cap, and mix by vigorously shaking the bottle a minimum of 25 times. This is cell suspension dilution “A”. A 1.0 mL volume of dilution “A” is 10 -2 mL of the original undiluted cell suspension. B) Use a sterile pipette to transfer 11.0 mL of cell suspension dilution “A” to 99 mL of sterile PBS, cap, and mix by vigorously shaking the bottle a minimum of 25 times. This is cell suspension dilution “B”. A 1.0 mL volume of dilution “B” is 10 -3 mL of the original undiluted cell suspension. C) Use a sterile pipette to transfer 11.0 mL of cell suspension dilution “B” to 99 mL of sterile PBS, cap, and mix by vigorously shaking the bottle a minimum of 25 times. This is cell suspension dilution “C”. A 1.0 mL volume of dilution “C” is 10 -4 mL of the original undiluted cell suspension.Method 1611

1 6 D) Use a sterile pipette to transfer 11.0 mL of cell suspension dilution “C” to 99 mL of sterile PBS, cap, and mix by vigorously shaking the bottle a minimum of 25 times. This is cell suspension dilution “D”. A 1.0 mL volume of dilution “D” is 10 -5 mL of the original undiluted cell suspension. E) Use a sterile pipette to transfer 11.0 mL of cell suspension dilution “D” to 99 mL of sterile PBS, cap, and mix by vigorously shaking the bottle a minimum of 25 times. This is cell suspension dilution “E”. A 1.0 mL volume of dilution “E” is 10 -6 mL of the original undiluted cell suspension. F) Prepare BHIA (Section 7.6). Ensure that agar surface is dry. Note : To ensure that the agar surface is dry prior to use, plates should be made several days in advance and stored inverted at room te mperature or dried using a laminar-flow hood. G) Each of the following should be co nducted in triplicate, resulting in the evaluation of nine spread plates:

• Pipet 0.1 mL of dilution “C” onto surface of BHIA plate [10 -5 mL (0.00001) of the original cell suspension].

• Pipet 0.1 mL of dilution “D” onto surface of BHIA plate [10 -6 mL (0.000001) of the original cell suspension].

• Pipet 0.1 mL of dilution “E” onto surface of BHIA plate [10 -7 mL (0.0000001) of the original cell suspension]. H) For each spread plate, use a sterile bent glass rod or spreader to distribute inoculum over surface of medium by rotating the dish by hand or on a rotating turntable. I) Allow inoculum to absorb into the medium completely. J) Invert plates and incubate at 35  C ± 0.5  C for 24 ± 4 hours. K) Count and record number of colonies per plate. Refer to the equation and Table 3 below for calculation of undiluted cell suspension concentration.

CFU/mL undiluted = CFU 1 + CFU 2 + .....+ CFU n V 1 + V 2 + ... + V n Where:

CFU/mL undiluted = E. faecalis CFU/mL in undiluted cell suspension CFU = number of colony forming units from BHIA plates yielding counts within the ideal range of 30 to 300 CFU per plate V = volume of undiluted sample in each BHIA plate yielding counts within the ideal range of 30 to 300 CFU per plate n = number of plates with counts within the ideal rangeMethod 1611

1 7 Table 3. Example Calculations of E. faecalis Undiluted Cell Suspension Concentration

Examples CFU / plate (triplicate analyses) from BHIA plates E. faecalis CFU / mL in undiluted suspension a 10 -5 mL plates 10 -6 mL plates 10 -7 mL plates

Example 1 275, 250, 301 30, 10, 5 0, 0, 0 (275+250+30) / (10 -5 +10 -5 +10 -6 ) = 555 / (2.1 x 10 -5 ) = 26,428,571 = 2.6 x 10 7 CFU / mL

Example 2 TNTC b , TNTC, TNTC TNTC, 299, TNTC 12, 109, 32 (299+109+32) / (10 -6 +10 -7 +10 -7 ) = 440 / (1.2 x 10 -6 ) =366,666,667 = 3.7 x 10 8 CFU / mL

a Cell concentration is calculated using all plates yielding counts within the ideal range of 30 to 300 CFU per plate b Too numerous to count

11.1.8 Divide remainder of undiluted cell suspension (approximately 5 mL) into 6 × 0.5 mL aliquots for DNA standard preparations and 100

− 200 × 0.01 mL (10 μL) aliquots for calibrator samples and freeze at -20  C. Note : Cell suspension should be stirred while aliquoting. It is also recommended that separ ate micropipettor tips be used for each 10 μL aliquot transfer and that the volumes in each tip be checked visually for consistency.
11.2 Preparation of E. faecalis genomic DNA standards
11.2.1 Remove two 0.5 mL undiluted E. faecalis cell suspensions (Section 11.1.8) from freezer and thaw completely.
11.2.2 Transfer cell suspensions to ex traction tubes with glass beads.
11.2.3 Tightly close the tubes, making sure that the O-rings are seated properly.
11.2.4 Place the tubes in bead beater and shake fo r 60 seconds at the maximum rate (5000 rpm).
11.2.5 Remove the tubes from the mini bead beater and centrifuge at 12,000 × g for one minute to pellet the glass beads and debris.
11.2.6 Using a 200 μ L micropipettor, transfer 350 μ L of the supernatants to sterile 1.7 mL microcentrifuge tubes. Recover supernatan ts without disrupting the glass beads at the tube bottom.
11.2.7 Centrifuge crude supernatants at 12,000 × g for 5 minutes and transfer 300 μ L of clarified supernatant to clean, labeled 1.7 mL low retention microcentrifuge tubes, taking care not to disturb the pellet.
11.2.8 Add 1 μ L of 5 μ g/ μ L RNase A solution to each clarified supernatant, mix by vortexing and incubate at 37  C for 1 hour.

Note : Steps 11.2.9 - 11.2.15 may be substituted with an optional method if a DNA purification procedure is chosen other than the DNA-EZ purification kit. In such a case, manufacturer instructions should be follo wed rather than these steps. Continue onward from step 11.2.16.
11.2.9 Add 0.6 mL of binding buffer solution from a DNA-EZ purification kit to each of the RNase A-treated extracts and mix by vortexing. Note : In general, a minimum concentration of 5 × 10 8 cells is required for this step.Method 1611

18 11.2.10 If using the DNA-EZ purification kit, perform the following steps. Insert one DNAsureTM column from the DNA-EZ purification kit into a collection tube (provided with kit) for each of the two extracts. Transfer the extract and binding buffer mixtures from Section 11.2.9 to a DNAsureTM column and collection tube assembly and centrifuge for 1 minute at 12,000 × g.
11.2.11 Transfer each of the DNAsureTM columns to new collection tubes. Discard previous collection tubes and collected liquid.
11.2.12 Add 500 μ L EZ-Wash Buffer from the DNA-EZ purification kit to each of the DNAsureTM columns and centrifuge at 12,000 × g for 1 minute. Discard the liquid in the collection tube.
11.2.13 Repeat step 11.2.12.
11.2.14 Transfer each of the DNAsureTM columns to a clean, labeled 1.7 mL low retention microcentrifuge tube and add 50 μ L of DNA elution buffer to each column. Centrifuge for 30 seconds at 12,000 × g. Rep eat this procedure again to obtain a total DNA eluate volume of ~100 μ L from each column.
11.2.15 Pool the two eluates to make a total volume of approximately 200 μ L.
11.2.16 Transfer the entire purified DNA eluate volume from each column to a clean and sterile microcuvette for UV spectrophotometer and read absorbance at 260 and 280 nM. ( Note : The cuvette should be blanked with DNA elution buffer before reading sample). If necessary, the sample may be diluted with elution buffer to reach the minimum volume that can be accurately read by the spectrophotometer (see manufacturer’s recommendation), however, this may reduce the DNA concentration to a level that cannot be accurately read by th e spectrophotometer. If available, readings can be taken of 2 μ L aliquots of the sample with a NanoDropTM Spectrophotometer.
11.2.17 Sample is acceptable as a standard if ratio of OD 260 /OD 280 readings is > to 1.75.
11.2.18 Record UV spectrophotometer results.
11.2.19 Calculate total DNA concentration in sample by formula:

OD 260 reading × 50 ng/ μ L DNA/OD 260 11.2.20 Transfer sample back to labeled 1.7 mL non-retentive microcentrifuge tube and store at -20  C.
11.2.21 Using total DNA concentration (Section 11.2.19), calculate E. faecalis PCR target sequence concentration (TSC) in purified extract (Section 9.10). Example :
OD 260 = 0.7271 Total DNA concentration = OD 260 Reading × 50 ng/μL 0.7271 × 50 = 36.36 ng/μL = 36.36 × 10 6 fg/μL = 3.636 × 10 7 fg/μL

3.636 × 10 7 fg/μL × 4 lsrRNA gene copies = 4.04 × 10 7 gene copies/μL 3.6 fg/genome genome

11.2.22 Record UV spectrophotometer results and all calculations.Method 1611

19 11.2.23 In appropriately labeled 1.7 mL low reten tion microcentrifuge tubes, perform serial dilutions using AE buffer to prepare DNA standards of 4 × 10 3 TSC/5 μ L, 4 × 10 2 TSC/5 μ L, 100 TSC/5 μ L and 40 TSC/5 μ L (see below).

Note : Perform initial dilution of purified and quantified DNA as required to achieve a concentration of 2 × 10 8 TSC/5 μ L or 2 × 10 7 TSC/5 μ L (as appropriate) prior to initiating serial dilutions.
11.2.23.1 Perform 10-fold serial dilutions of the 2 × 10 8 or 10 7 TSC/5 μ L stock (10 μ L : 90 μ L) with AE buffer to achieve 2 × 10 7 TSC/5 μ L; 2 × 10 6 TSC/5 μ L; and 2 × 10 5 TSC/5 μ L
11.2.23.2 Perform 5-fold dilution of 2 × 10 5 TSC /5 μ L stock (100 μ L : 400 μ L) with AE buffer to achieve 4 × 10 4 TSC/5 μ L stock
11.2.23.3 Perform successive 10-fold serial dilutions of the 4 × 10 4 TSC/5 μ L stock (100 μ L : 900 μ L) to achieve 4 × 10 3 TSC/5 μ L; 4 × 10 2 TSC/5 μ L stocks
11.2.23.4 Perform a 4-fold dilution of 4 × 10 2 TSC/5 μ L stock (100 μ L : 300 μ L) to achieve 100 TSC/5 μ L stock
11.2.23.5 Perform a final 2.5-fold dilution of the 100 TSC/5 μ L stock (100 μ L : 150 μ L) to achieve 40 TSC/5 μ L stock

Note : It is recommended that DNA standards be stored and manipulated in a different room than that used for routine sample processing in order to minimize the potential for laboratory contamination.
11.2.24 Store DNA standards in refrigerator at 4°C. For long term storage, freeze aliquots at - 20°C or -80°C
11.2.25 Generate DNA standard curves usi ng the 40, 100, 400, and 4000 TSC/5 μ L dilutions (3 replicates each) according to Section 11.7 (ABI) or 11.8 (Cepheid), as appropriate.
11.2.26 qPCR analyses of these diluted standards using the Enterococcus primer and probe assay should initially be performed at least six separate times in triplicate. From that point on, it is recommended that additional standard curves be generated from triplicate analyses of these same diluted standard samples with each new lot of TaqMan ® master mix reagents or primers and probes to demonstrate comparable performance by these new reagents.
11.3 Extraction of E. faecalis calibrator samples
11.3.1 A minimum of three calibrator extracts s hould be prepared during each week of analysis.

Note : To prevent contamination of water sa mple filtrates and filter blanks, this procedure should be performed at a different ti me, and, if possible, in a different work station than the procedures in Sections 11 .1 and 11.2 above and Section 11.5 below.
11.3.2 Remove one tube containing a 10 μ L aliquot of E. faecalis undiluted stock cell suspension (Section 11.1.8) from the freezer and allow to thaw completely on ice.

Note : If using BioBalls for calibrators add a single BioBall ® to each of 3, 1.0 mL sterile PBS blanks, filter (Section 11.4), and extract according to Section 11.5.
11.3.3 While cell stock is thawing, using sterile (or flame-sterilized) forceps, place one polycarbonate filter (Section 6.14) in an extr action tube with glass beads. Prepare one filter for each sample to be extracted in this manner.Method 1611

20 11.3.4 Dispense 590 μ L of Salmon DNA/extraction buffer (Section 7.12) into three extraction tubes with glass beads and filters. Prepare one tube for each of the three calibrator samples to be extracted in th is manner. Label tubes appropriately.
11.3.5 When E. faecalis suspension has thawed, transfer 990 μ L AE buffer (Section 7.11) to the 10 μ L E. faecalis stock cell tube and mix thoroughly by vortexing. Pulse microcentrifuge tube briefly (1

− 2 sec.) to coalesce droplets in tube.
11.3.6 Immediately after vortexing the E. faecalis suspension, spot 10 μ L onto the polycarbonate filter in the extraction tube from step 11.3.4.

Note : For the blank extraction tube, spot 10 μ L AE buffer onto the polycarbonate filter
11.3.7 Tightly close the tube, making sure that the O-ring is seated properly and label tubes appropriately.
11.3.8 Repeat Sections 11.3.6 and 11.3.7 for the ot her two filters to prepare three calibrator samples with E. faecalis

. 11.3.9 Place the tubes in the mini bead beater a nd shake for 60 seconds at the maximum rate (5000 rpm).
11.3.10 Remove the tubes from the mini bead beat er and centrifuge at 12,000 × g for one minute to pellet the glass beads and debris.
11.3.11 Using a 200 μ L micropipettor, transfer the crude supernatant to the corresponding labeled sterile 1.7 mL microcentrifuge tube. Transfer 400 μ L of supernatant without disrupting the debris pellet or glass beads at the tube bottom. Note : The filter will normally remain intact during the bead b eating and centrifugation process. Generally, 400 μ L of supernatant can be easily collected . Collect an absolute minimum of 100
μ L of supernatant. Record volume of supernatant collected.
11.3.12 Centrifuge at 12,000 × g for 5 minutes and transfer clarified supernatant to a clean, labeled 1.7 mL tube, taking care not to disturb the pellet. Note : Cell pellet may not be visible in calibrator samples.
11.3.13 Label the tubes as undiluted or 1X E. faecalis calibrator extracts. Label additional 1.7 mL tubes for 5- and 25-fold dilutions. In appropriately labeled tubes, using a micropipettor, add a 50 μ L aliquot of each 1X E. faecalis calibrator extracts and dilute each with 200 μ L AE buffer (Section 7.11) to make 5-fold dilutions. In appropriately labeled tubes using a micropipettor, add a 50 μ L aliquot of each 5-fold dilution and dilute each with 200 μ L AE buffer to make 25-fold dilutions. Store all diluted and undiluted extracts in refrigerator.
11.3.14 If the extracts are not analyzed immediately, refrigerate.
11.4 Water sample filtration

Note : It is required that minimally one water samp le filtration blank (method blank) be analyzed for every qPCR run of water samples (Section 9.8)
11.4.1 Place a polycarbonate filter (Section 6.14) on the filter base (shiny side "up" facing you), and attach the funnel to the base so that the membrane filter is now held between the funnel and the base.
11.4.2 Shake the sample bottle vigorously 25 times to distribute the bacteria uniformly, and measure 100 mL of sample into the funnel.
11.4.3 Filter 100 mL of water sample. After filteri ng the sample, rinse the sides of the funnel with 20 - 30 mL of sterile PBS (Section 7.4) and continue filtration until all liquid hasMethod 1611

21 been pulled through the filter. Turn off the vacuum and remove the funnel from the filter base.
11.4.4 Label an extraction tube containing glass b eads (Section 6.4) to identify water sample. Leaving the filter on the filtration unit base, fo ld filter into a cylinder with the sample side facing inward, being careful to handle the filter only on the edges, where the filter has not been exposed to the sample. Insert the rolled filter into the labeled extraction tube with glass beads. Prepare one filte r for each sample filtered in this manner.
11.4.5 Cap the extraction tube. Refrigerate.
11.5 DNA extraction of water sample filter extracts and method blanks
11.5.1 Using a 1000 μ L micropipettor, dispense 590 μ L of the Salmon DNA/extraction buffer (Section 7.12) into each labeled extraction tube with glass beads containing water sample or method blank filters from Section 11.3.4. Extract the method blank last.
11.5.2 Tightly close the tubes, making sure that the O-ring is seated properly.
11.5.3 Place the tubes in the mini bead beater and shake for 60 seconds at the maximum rate (5000 rpm).
11.5.4 Remove the tubes from the mini bead beater and centrifuge at 12,000 × g for 1 minute to pellet the glass beads and debris. Note : To help prevent contamination, a new pair of gloves may be donned for this step, and steps 11.5.6 and 11.5.7.
11.5.5 Using the 200 μ L micropipettor, transfer 400 μ L of the supernatant to a corresponding labeled sterile 1.7 mL microcentrifuge tube, taking care not to aspirate glass beads or sample debris (pellet). Note : The filter will normally remain intact during the bead beating and centrifugation process. Generally, 400 μ L of supernatant can easily be collected. Collect an absolute minimum of 100 μ L of supernatant. Recover the method blank supernatant last.
11.5.6 Centrifuge crude supernatant from Section 11.5.5 for 5 minutes at 12,000 × g. Transfer 350 μ L of the clarified supernatant to another 1.7 mL tube, taking care not to disturb the pellet. Note : Pellet may not be visible in water samples. Recover the method blank supernatant last.
11.5.7 Label the tubes from Section 11.5.6 as undilu ted or 1X water sample extracts with sample identification. These are the water sa mple filter extracts. Also label tubes for method blanks. Label additional 1.7 mL tub es for 5-fold dilutions. In appropriately labeled tubes, using a micropipettor, add a 50 μ L aliquot of each 1X water sample extract and dilute each with 200 μ L AE buffer (Section 7.11) to make 5-fold dilutions. Dilute the method blank supernatant last.
11.5.8 Optional: For samples where the concentrati on of target DNA is anticipated to be high, an additional 25-fold dilution can be done In appropriately labeled tubes using a micropipettor, add a 50 μ L aliquot of each 5-fold dilution and dilute each with 200 μ L of AE buffer to make 25-fold dilutions. Dilute the method blank supernatant last.
11.5.9 Store all diluted and undiluted extracts in refrigerator.
11.5.10 Note: Use of 5-fold diluted samples for analys is is currently recommended if only one dilution can be analyzed. Analyses of u ndiluted water sample extracts have been observed to cause a significantly higher inci dence of PCR inhibition while analyses of 25-fold dilutions may unnecessarily sacrifice sensitivity.
11.5.11 Refrigerate the extracts if they are not analyzed immediately. Water sample filter extracts should be analyzed the sa me day that they are prepared.Method 1611

22 11.6 Preparation of qPCR assay mix
11.6.1 To minimize environmental DNA contamination, routinely treat all work surfaces with a 10% bleach solution, allowing the bleach to contact the work surface for a minimum of 15 minutes prior to rinsing with sterile water. If available, turn on UV light for 15 minutes. After decontamination, discard gloves and replace with a new pair.
11.6.2 Remove primers and probe stocks from the freezer and verify that they have been diluted to solutions of 500 μ M primer and 100 μ M probe.
11.6.3 Prepare working stocks of Enterococcus , and Salmon DNA (Sketa 22) primer/probe mixes by adding 10 μ L of each Enterococcus or Salmon DNA (Sketa 22) primer stock and 4 μ L of respective probe stock to 676 μ L of PCR-grade water, and vortex. Pulse centrifuge to create a pellet. Use a micropipettor with aerosol barrier tips for all liquid transfers. Transfer aliquots of working stocks for single day use to separate tubes and store at 4  C.
11.6.4 Using a micropipettor, prepare assay mix of the Enterococcus and Salmon DNA (Sketa 22) reactions in separate, sterile, labeled 1.7 mL microcentrifuge tubes as described in Table 4

. Table 4. PCR Assay Mix Composition Reagent Volume/Sample (multiply by # samples to be analyzed per day)

Sterile H 2 O 1.5 μ L

BSA 2.5 μ L
TaqMan ® master mix 12.5 μ L
Primer/probe working stock solution 3.5 μ L

Note : This will give a final concentration of 1 μ M of each primer and 80 nM of probe in the reactions. Prepare sufficient quantity of assay mix for the number of samples to be analyzed per day including calibrators and nega tive controls plus at least two extra samples. Prepare assay mixes each day before handling DNA samples.

11.6.5 Vortex the assay mix working stocks; then pul se microcentrifuge to coalesce droplets. Return the primer/probe working stocks and other reagents to the refrigerator.
11.7 ABI StepOnePlusTM, ABI 7900, and ABI 7500 (a ll non-Fast mode) qPCR assay preparation (Reference 17.1)
Transfer 20 μ L of either the master mix containing Enterococcus primers and probe or the master mix containing the Salmon DNA primers and probe to the wells of a 96 well PCR reaction tray equal to number of samples to be analyzed incl uding calibrator and negative control samples. ( Note : The same tip can be used for pipetting multip le aliquots of the same assay mix as long as no contact is made with anything else). Example : For the analysis of 18 recreational water sa mples, 47 wells will require the addition of assay mix with Enterococcus primers and probe as follows: 18 samples, two replicates each (36), 3 method blanks, one replicate each (3), 3 calib rators, 2 replicates each (6) and 1 no template control (NTC), 2 replicates (2) = 47 wells. In addition, 47 wells will require the addition of assay mix with Salmon DNA assay primers and probe as follows: 18 samples, two replicates each (36),Method 1611

23 3 method blanks, one replicate each (3), 3 ca librators, 2 replicates each (6) and 1 NTC, 2 replicates (2) = 47 wells. Thus a total of 94 wells are used for 18 recreational water samples.
11.7.1 Transfer 20 μ L of either the master mix containing Enterococcus primers and probe or the master mix containing the Salmon DNA primers and probe to wells of a 96 well PCR reaction tray equal to number of sampl es to be analyzed including calibrator and negative control samples. Pipet into the center of the wells, taking care to not touch the well walls with the pipet tip. ( Note : The same tip can be used for pipetting multiple aliquots of the same assay mix as long as it doesn’t make contact with anything else).
11.7.2 When all wells are loaded transfer to th e PCR preparation station used for handling DNA samples (Section 6.1). Note : All aliquoting of assay mixes to reaction trays must be performed each day before handling of DNA samples.
11.7.3 DNA standards

− Transfer 5 μ L each concentration of the undiluted DNA extracts of (Section 11.2.24) to separate wells of the PCR reaction tray containing Enterococcus assay mix. Note : Record positions of each concentration. See Section 11.2.26 regarding the frequency of DNA standard analyses.
11.7.4 Water samples

− Transfer 5 μ L each of the diluted (or undiluted) DNA extracts of method blanks and water samples (Section 11.5.7), and corresponding dilutions of calibrator samples (Section 11.3.13), to separate wells of the PCR reaction tray containing Enterococcus assay mix. Note : Record positions of each sample.
11.7.5 Transfer 5 μ L each of the diluted (or undiluted) DNA extracts of method blanks and water samples (Section 11.5.7), and corres ponding diluted calibrator samples (Section 11.3.13) to separate wells of the PCR reaction tray containing Salmon DNA assay mix. Record positions of each sample.
11.7.6 Transfer 5 μ L aliquots of AE buffer to wells of PCR reaction tray containing Enterococcus master mix that are designated as NTCs. Record positions of these samples.
11.7.7 Tightly cap wells of PCR reaction tray containing samples or cover tray and seal tightly with optical adhesive. Note : 96 well plates should be freshly prepared just prior to analyses. Do not prepare and refrigerate multiple plates prior to analyses, as signal degradation may occur.
11.7.8 Run reactions in ABI StepOnePlusTM, ABI 7900, or ABI 7500 (all in non-Fast mode) Real-Time PCR Systems. For platform-specific operation see Appendix A. Note : The ABI 7500 Fast may be used but it should be run in the 9600 emulation mode.
11.8 Smart Cycler ® qPCR assay preparation
11.8.1 Label 25 μ L Smart Cycler ® tubes with sample identifiers and assay mix type (see Section 11.8.8 for examples) or order tubes in rack by sample number and label rack with assay mix type. It is recommende d that the unloaded open Smart Cycler ® tubes be irradiated under UV light in a PCR cabinet for 15 minutes. Using a micropipettor, add 20 μ L of the Enterococcus assay mix (Section 11.6.4) to labeled tubes. Avoid generating air bubbles, as they may interfere with subsequent movement of the liquid into the lower reaction chamber. The sa me tip can be used for pipetting multiple aliquots of the same assay mix as long as it doesn’t make contact with anything else. Repeat procedure for Salmon DNA (Sketa 22) assay mix.
11.8.2 Add 5 μ L of AE buffer to NTC tubes and close tubes tightly.Method 1611

24 11.8.3 Close the other PCR tubes loosely and transfer to refrigerator or directly to the PCR preparation station used for handling DNA samples (Section 6.1). Note : All aliquoting of assay mixes to reaction tubes must be performed each day before handling of DNA samples.
11.8.4 DNA standards

− Transfer 5 μ L of each concentration of the undiluted DNA extracts (Section 11.2.24), to tubes containing Enterococcus mix. Close each tube tightly after adding sample. Label the tube tops as appr opriate. See Section 11.2.26 regarding the frequency of DNA standard analyses.
11.8.5 Water samples

− Transfer 5 μ L each of the diluted (or undiluted) DNA extracts of method blanks and water samples (Section 11.5.7), and then corresponding dilutions of calibrator samples (Section 11.3.13) to tubes containing Enterococcus and Salmon DNA (Sketa 22) mixes. Close each tube tightly after adding sample. Load the method blank last. Label the tube tops as appropriate.
11.8.6 When all Smart Cycler ® tubes have been loaded, place them in a Smart Cycler ® centrifuge, and spin for 2

− 4 seconds.
11.8.7 Inspect each tube to verify that the sa mple has properly filled the lower reaction chamber. A small concave meniscus may be visible at the top of the lower chamber, but no air bubbles should be present. (If the lower chamber has not been properly filled, carefully open and reclose the tube, and re-centrifuge). Transfer the tubes to the thermocycler.
11.8.8 For platform-specific operation see Appendix B.
11.8.9 Suggested sample analysis sequence for Smart Cycler ®
Example : For analyses on a single 16 position Smart Cycler ® , calibrator samples and water samples will need to be analyzed in separate runs and a maximum of 6 water samples (or 2 replicates of 3 samples) can be analyzed per run, as described in Tables 5 and 6 , below.

Table 5. Calibrator PCR Run - 14 Samples Sample Description 1 Quantity PCR Assay Master Mix
3 Calibrators × 2 replicates (1-, 5-, or 25-fold dilution) 6 Enterococcus
3 Calibrators × 2 replicates (1-, 5-, or 25-fold dilution) 6 Salmon DNA
No template controls (reagent blanks) 2 Enterococcus

1 Diluted equivalently to the water samples

Table 6. Water Sample PCR Run - 14 Samples Sample Description 1 Quantity PCR Assay Master Mix
Water samples (1-, 5- , or 25-fold dilution) 6 Enterococcus
Method blank (1-, 5-, or 25-fold dilution) 1 Enterococcus
Water samples (1-, 5- , or 25-fold dilution) 6 Salmon DNA
Method blank (1- 5-, or 25-fold dilution) 1 Salmon DNA

1 Use of 5-fold diluted samples for analysis is curr ently recommended if only one dilution can be analyzed. Analyses of undiluted water sample extracts have been observed to cause a significantly higher incidence of PCR inhibition while 25-fold dilutions analyses may unnecessarily sacrifice sensitivity.Method 1611

25 

## 12.0 Data Analysis and Calculations

12.1 Overview : This section describes a method for determ ining the ratio of the target sequence quantities recovered from a test (water filtrate) sample compared to those recovered from identically extracted calibrator samples using an arithmetic formula, referred to as the ΔΔ C T method. The ΔΔ C T relative quantitation method also normalizes these ratios for differences in total DNA recovery from the test and calibrator samples using qPCR analysis C T values for a reference sequence provided by the SPC DNA. These ratios are converted to absolute measurements of total target sequence quantities recovered from the test and calibrator sample extracts and these ratios are converted to CCEs r ecovered from the test samples. The complete procedure for determining target sequence qua ntities and CCEs in water samples is detailed below.
12.2 Generation of C T value vs. target sequence number standard curve : Three replicate serial dilutions of a DNA standard, prepared as described in Section 11.2 should be prepared to give concentrations of 4 × 10 3 , 4 × 10 2 , 1× 10 2 , and 4 × 10 1 lsrRNA gene sequences per 5 μ L (the standard sample volume added to the PCR reacti ons) and the replicates of each dilution pooled. Note : A procedure for the determinations of target sequence concentrations in the DNA standard is also provided in Section 9.10. Aliquots of each of these dilutions should be frozen in low retention microcentrifuge tubes. Thawed aliquots should be stored at 4 o C and can be reused for re peated qPCR analyses. qPCR analyses of these diluted standards using the Enterococcus primer and probe assay should initially be performed at least six separate times in triplicate. C T values from these composite analyses should be subjected to regression analysis against the log10-transformed target sequence numbers per reaction as described in Section 9.10 with example results illustrated in Figure 1

.

Figure 1 : Example plot and regression analysis of qPCR analysis C T values vs. log target sequences per reaction.

AF used for subsequent comparative C T calculations (Section 12.4) can be calculated from the slope value of this curve by the formula AF = 10^(1 / (-)slope value). An example calculation using the slope value from the example regression is shown below: AF = 10^ (1 / 3.41673) = 1.96
12.3 Calculation of average target sequence recovery in calibrator sample extracts : A minimum of nine calibrator sample extracts should initially be prepared from at least three different freezer-Method 1611

26 stored aliquots of each cultured E. faecalis stock suspension that is prepared as described in Section 11.1. Dilutions of each of these calibrato r sample extracts equivalent to the anticipated dilutions of the test samples used for analysis ( e.g., 1-, 5- and/or 25-fold) sh ould be analyzed with the Enterococcus primer and probe assay. The average C T value from these analyses should be interpolated on the standard curve generated from the DNA standard (Section 12.2) to determine the average number of target sequences per 5 μ L of extract used in the reactions. An example calculation using an average calibrator extract C T value of 24.31 and standard curve from Figure 1 is shown below: Average calibrator target sequences/5 μ L extract = 10^[(24.31-36.7194) / -3.4167] = 4285.0744

Note : Four places should be kept from this calculation for the following calculation ( i.e
., 4285.0744). Dividing this value by 5 gives the average calibrator target sequences μ L extract which can be multiplied by the total volume of th e extract at the applicable dilution level ( e.g., 600 μ L of original extract volume × 5 = 3000 μ L for a 5-fold diluted sample) to determine the average total quantity of target sequences recovere d in the calibrator sample extracts. An example of this calculation using the average calibrato r target sequences/reaction value determined immediately above is shown below: (4285.0744/5) × 3000 = 2571045 target sequences / total extract
12.3.1 Calculation of average target sequence recovery per Enterococcus cell in calibrator sample extracts (optional): In previous studies, measurements of recreational water quality by the qPCR method have been reported as Enterococcus calibrator cell equivalents (Reference 17.4).
12.3.2 A prerequisite for making such comparisons is to determine that the ratio of the numbers of target sequences r ecovered in calibrator sample extracts to the numbers of Enterococcus cells added to these samples is consistent in different studies. Example : The quantity of lab prepared cells added to each calibrator sample is ~100,000. Dividing the average target sequences recove red per calibrator extract (determined as described in Section 12.3) by this number provides the ratio of target sequence numbers to cell numbers. An example of this calcu lation using the average target sequences/ calibrator extract value determined in Section 12.3 is shown below: Ratio of target sequence numbers to cell numbers = 2571045/100,000 = 25.71
12.4 Calculation of CCEs in test samples: A minimum of three fresh calibrator samples should be extracted and analyzed at least on a weekly basi s and preferably on a daily basis in association with each batch of water sample filtrates. QC an alysis of the results from these calibrator extracts should be performed as descri bed in Section 9.11. C T values from the Enterococcus and salmon DNA SPC qPCR assays for both the calibrator and test samples are used in the ΔΔ C T method to determine the ratios of target sequences in the t est and calibrator sample extracts and these ratios are converted to CCEs recovered from the test samples as specified below and illustrated in Table 5

. 12.4.1 Subtract the SPC assay C T value (C T , SPC) from the target assay C T value (C T , target) for each calibrator sample extract to obtain Δ C T value and calculate the average Δ C T value for these calibrator samples.
12.4.2 Subtract the SPC assay C T value (C T , SPC) from the target assay C T value (C T , target) for each water sample filtrate extract to obtain Δ CT values for each of these test samples. Note : If multiple analyses are performed on these samples, calcu late the average Δ C T value.Method 1611

27 12.4.3 Subtract the average Δ C T value for the calibrator samples from the Δ C T value (or average Δ C T value) for each of the test samples to obtain ΔΔ C T values.
12.4.4 Calculate the ratio of the target sequences in the test and calibrator samples using the formula: AF ^(- ΔΔ CT) , where AF = amplification factor of the target organism qPCR assay, determined as described in Section 12.2.
12.4.5 Multiply the ratio of the target sequences in the test and calibrator samples by the estimated count (e.g., CFU) determined in S ection 11.1.7 to determine the CCEs for each of the test samples. Note : This calculation can be applied without modification to the analyses of diluted extracts if both the test sample and calibrator extracts are equally diluted and equal volumes of diluted extracts are analyzed. Table 5. Example Calculations (AF = 1.96)

Estimated Cell Count 1 Sample Type C T,target C T,SPC Δ C T ΔΔ C T Ratio calib/test
1.96 - ΔΔ CT CCEs in Test Sample Extract (1.96 - ΔΔ CT × Est cell count)

1200000 Calibrator 25. 71 34.13 -8.42 ---- ----

Test 33.74 25.94 7.8 7.59 0.006 0.006 x 1200000 = 7264.74

1 Estimated cell count is based on plating results taking into account the dilution factor (100) and the volume

of the dilution (0.1 mL) added to the calibrator sample

12.4.6 The geometric mean (optional) of the CCEs and associated coefficients of variation in multiple water samples can be determined from individual sample C T values using the following procedure:
12.4.6.1 Use Δ C T value for each individual water sample extract and the mean calibrator Δ C T value to calculate the CCEs in each water sample extract, as described above.
12.4.6.2 Calculate the log10 of the CCEs in each water sample (log N)
12.4.6.3 Calculate the mean (M) and standard deviation (S) from the values of log N obtained in the previous step for all of the water sample extracts.
12.4.6.4 Calculate the geometric mean as 10 M

. 12.4.6.5 The implied coefficient of variation (CV) is calculated, based on the log normal distribution, as the square root of 10 V/ 0.434 - 1, where V = S 2

. 12.5 Reporting Results : Where possible, duplicate analyses should be performed on each sample. Report the results as Enterococcus CCEs per volume of water sample filtered.



## 13.0 Sample Spiking Procedure

13.1 Method 1611 QC requirements (Section 9) incl ude the preparation and analysis of spiked reference (PBS) and matrix samples in order to monitor initial and ongoing method performance. For the IPR (Section 9.3), OPR (Section 9.4), an d MS (Section 9.5) analyses it is necessary to spike samples with either laboratory-prepared spiking suspensions (Section 13.3) or BioBalls (Section 13.7).
13.2 Preparation of Laboratory-Prepared Undiluted Sp iking Suspension. Note: when using laboratoryprepared cultures, it is recommended to prepar e calibrator samples and spike suspensions from the same culture using the same cell enumeration results (see section 11.1).Method 1611

28 13.2.1 Stock Culture ( E. faecalis ) . Prepare a stock culture by inoculating a BHIA slant with E. faecalis ATCC ® #29212TM (e.g., KWIK-STIKTM) and in cubate at 35°C ± 0.5°C for 21 ± 3 hours. This stock culture may be stored in the dark at room temperature for up to 30 days.
13.2.2 E. faecalis Spiking Suspension (Undiluted) . From the stock culture of E. faecalis ATCC ® #29212TM, transfer a small loopful of growth to the BHIB and vigorously shake a minimum of 25 times. Incubate at 35°C ± 0.5°C for 21 ± 3 hours. The resulting spiking suspension contains approximately 1.0 × 10 9 enterococci CFU per mL. This is referred to as the “undiluted spiking suspension.”
13.2.3 Proceed to Section 13.3 for sample spiki ng and enumeration of spiking suspension (Section 13.2.2).
13.3 Laboratory-Prepared Sample Spiking and Spiking Suspension Enumeration Since the objective of spiking the sample is to establish percent recovery, it is necessary to determine the concentration of E. faecalis in the laboratory-prepared undiluted spiking suspension (Section 13.2.2). This section provides instructions for sample spiking (Section 13.4) and spiking suspension enumeration (Section 13.5). If you are using BioBalls instead of a laboratory preparation, go to Section 13.7.
13.4 Sample Spiking Please be sure to vigorously shake the spiking su spensions in the steps be low to ensure accurate sample spiking and spiking suspension enumeration.
13.4.1 Dilute spiking suspension Perform steps 13.4.1.1 through 13.4.1.5 using the laboratory-prepared undiluted spiking suspension (Section 13.2.2).
13.4.1.1 Mix the undiluted spiking suspension by vigorously shaking the bottle a minimum of 25 times. Use a sterile pipette to transfer 1.0 mL of the undiluted spiking suspension to 99 mL of sterile PBS; cap and mix by vigorously shaking the bottle a minimum of 25 times. This is spiking suspension dilution “A.” A 1.0 mL volume of dilution “A” is equivalent to a concentration of 1 × 10 7 CFU per mL (10 -2 mL of the original undiluted spiking suspension).
13.4.1.2 Mix spiking suspension “A” (Section 13.4.1.1) by vigorously shaking the bottle a minimum of 25 times. Use a sterile pipette to transfer 1.0 mL to 99 mL of sterile PBS; cap and mix by vigorously shaking the bottle a minimum of 25 times. This is spiking suspension dilution “B.” A 1.0 mL volume of dilution “B” is equivalent to a concentration of 1 × 10 5 CFU per mL (10 -4 mL of the original undiluted spiking suspension).
13.4.1.3 Mix spiking suspension “B” (Section 13.4.1.2) by vigorously shaking the bottle a minimum of 25 times. Use a sterile pipette to transfer 11.0 mL to 99 mL of sterile PBS; cap and mix by vigorously shaking the bottle a minimum of 25 times. This is spiking suspension dilution “C.” A 1.0 mL volume of dilution “C” is equivalent to a concentration of 1 × 10 4 CFU per mL (10 -5 mL of the original undiluted spiking suspension).
13.4.1.4 Mix spiking suspension “C” (Section 13.4.1.3) by vigorously shaking the bottle a minimum of 25 times. Use a sterile pipette to transfer 11.0 mL to 99 mL of sterile PBS; cap and mix by vigorously shaking the bottle a minimum of 25 times. This is spiking suspension dilution “D.” A 1.0 mL volume ofMethod 1611

29 dilution “D” is equivalent to 1 × 10 3 CFU per mL (10 -6 mL of the original undiluted spiking suspension).
13.4.1.5 Mix spiking suspension “D” (Section 13.4.1.4) by vigorously shaking the bottle a minimum of 25 times. Use a sterile pipette to transfer 11.0 mL to 99 mL of sterile PBS; cap and mix by vigorously shaking the bottle a minimum of 25 times. This is spiking suspension dilution “E.” A 1.0 mL volume of dilution “E” is equivalent to 1 × 10 2 CFU per mL (10 -7 mL of the original undiluted spiking suspension).
13.4.2 Spike samples
13.4.2.1 550 CFU Spike To spike the sample, add 5.5 mL of sp iking suspension dilution “E” (Section 13.4.1.5) to 100 mL of unspiked sample and mix by vigorously shaking the bottle a minimum of 25 times. This is the “spiked” sample with a concentration of 550 CFU per 100 mL. The volume (mL) of undiluted spiking suspension added is 5.5 × 10 -7 mL/100 mL. This is referred to as V spiked per 100 mL sample in Section 13.6.2.
13.5 Enumeration of Spiking Suspensions (Prepared in Section 13.3.1)
13.5.1 Prepare BHIA according to manufacturer’s in structions; add 12 – 15 mL of BHIA per 100 × 15 mm petri dish and solidify. Ensure the agar surfaces are dry. Note : Agar plates must be dry and free from condensation prior to use. To ensure the agar surfaces are dry, plates should be made several days in advance and stored inverted at room temperature or dried using a laminar-flow hood.
13.5.2 Each of the following should be conducted in triplicate, resulting in the evaluation of nine spread plates:

 Pipet 0.1 mL of dilution “C” (Secti on 13.4.1.3) onto surface of pre-dried BHIA plate (10 -6 mL of the original spiking suspension).

 Pipet 0.1 mL of dilution “D” (Section 13.4.1.4) onto surface of pre-dried BHIA plate (10 -7 mL of the original spiking suspension).

 Pipet 0.1 mL of dilution “E” (Secti on 13.4.1.5) onto surface of pre-dried BHIA plate (10 -8 mL of the original spiking suspension).
13.5.3 After pipetting the 3 spread plates for each dilution, use a sterile bent glass rod or spreader to distribute inoculum over the surf ace of the medium by rotating the dish by hand or on a turntable. Repeat for next 2 dilutions. Note : Please ensure that inoculum is evenly distributed over entire surface of the plate.
13.5.4 Allow inoculum to absorb into the medium completely.
13.5.5 Invert plates and incubate at 35°C ± 0.5°C for 21 ± 3 hours.
13.5.6 Count and record number of colonies per plate. Refer to Section 13.6 for calculation of spiking suspension concentration.

13.6 Calculation of Spiked E. faecalis Percent Recovery (Laboratory-Prepared Undiluted Spiking Suspension) The spiked E. faecalis percent recovery will be calculated in three steps as indicated in Sections 13.6.1 through 13.6.3 below. Note : The calculated numbers in the table examples provided below have been rounded at the end of each step. If your laboratory recalculates the examples using aMethod 1611

30 spreadsheet and rounds only after the final calcu lation (Section 13.6.3), the percent recovery may be slightly different.
13.6.1 Calculate Concentration of E. faecalis (CFU/mL) in Undiluted Spiking Suspensions
13.6.1.1 The number of E. faecalis (CFU/mL) in the undiluted spiking suspensions will be calculated using all BHIA plates from Section 13.5.2 yielding counts within the ideal range of 30 to 300 CFU per plate.
13.6.1.2 If the number of colonies exceeds the upper range (i.e., >300) or if the colonies are not discrete, results should be recorded as “too numerous to count” (TNTC).
13.6.1.3 Calculate the concentration of E. faecalis (CFU/mL) in the undiluted spiking suspensions according to the following e quation. An example calculation is provided in Table 6

.

E. faecalis undiluted spike = (CFU 1 + CFU 2 + ... + CFU n ) / (V 1 + V 2 + ... + V n ) Where, E. faecalis undiluted spike = E. faecalis (CFU/mL) in undiluted spiking suspension CFU = Number of colony forming units from BHIA plates yielding counts within the ideal range of 30 to 300 CFU per plate V = Volume of undiluted sample on each BHIA plate yielding counts within the ideal range of 30 to 300 CFU per plate n = Number of plates with counts within the ideal range

Table 6. Example Calculation of E. faecalis Spiking Suspension Concentration
CFU / plate (triplicate analyses) from BHIA plates E. faecalis CFU / mL in undiluted spiking suspension ( E. faecalis undiluted spike )* 10 -6 mL plates 10 -7 mL plates 10 -8 mL plates

TNTC, TNTC, TNTC 94, 106, 89 9, 11, 28 (94+106+89) / (10 -7 +10 -7 +10 -7 ) = 289 / (3.0 × 10 -7 ) =

9.6 × 10 8 CFU/mL

* E. faecalis undiluted spike is calculated using all plates yielding counts within the ideal range of 30 to 300 CFU per plate

13.6.2 Calculate “True” Spiked E. faecalis (CFU/100 mL) Calculate the true concentration of spiked E. faecalis (CFU/100 mL) according to the following equation. Example calculation is provided in Table 7

.

T Spiked E. faecalis = ( E. faecalis undiluted spike ) × (V spiked per 100 mL sample )

Where,

T Spiked E. faecalis = Number of spiked E. faecalis (CFU/100 mL) E. faecalis undiluted spike = E. faecalis (CFU/mL) in undiluted spiking suspension

V spiked per 100 mL sample = mL of undiluted spiking suspension per 100 mL sampleMethod 1611

31 Table 7. Example Calculation of Spiked E. faecalis

E. faecalis undiluted spike V spiked per mL sample T Spiked E. faecalis

9.6 × 10 8 CFU/mL 5.5 × 10 -7 mL/100 mL of sample (9.6 × 10 8 CFU/mL) × (5.5 × 10 -7 mL /100 mL) = 528 CFU/ 100 mL

13.6.3 Calculate Percent Recovery
13.6.3.1 Calculate percent recovery (R) using the following equation.

R = 100 × (N s - N u )

T Where, R = Percent recovery

N s = E. faecalis (CFU/100 mL) in the spiked sample

N u = E. faecalis (CFU/100 mL) in the unspiked sample

T Spiked E. faecalis = True spiked E. faecalis (CFU/100 mL) in spiked sample

Example percent recovery calculation is provided in Table 8

. Table 8. Example Percent Recovery Calculation

N s (CFU / 100 mL) N u (CFU / 100 mL) T Spiked E. faecalis (CFU / 100 mL) Percent recovery (R)

521 3 a 528 100 × (521 - 3)/528 = 98%

a The result of 3 CFU is acce ptable if the sample was a recreational water; for PBS N u should be <1 CFU/100 mL.

13.7 BioBall ® Sample Spiking and Enumeration This section provides instructions for sample sp iking (Section 13.7.1) and spiking suspension enumeration (Section 13.7.2) using BioBalls instead of a laboratory preparation of E. faecalis

. Upon receipt, BioBalls should be stored at -20°C. Preparation of BioBalls prior to spiking is not necessary, as they can be spiked directly in to the sample once the vial is opened.

13.7.1 Sample Spiking
13.7.1.1 Open BioBall ® vial by removing the cap. Aseptically add one 550 CFU E. faecalis BioBall ® to 100 mL of sample and mix by vigorously shaking the bottles a minimum of 25 times.
13.7.1.2 This is the “spiked” sample with a concentration of ~550 CFU per 100 mL Note: BTF provides mean and standard deviation of CFU concentrations in their certificates of analysis for each lot of BioBalls. These values can be accessed at http://www.btfbio .com/cofa.php?nav=BioBall .Method 1611

32 13.7.2 Enumeration of BioBall ®

13.7.2.1 Prepare BHIA according to manufacturer’s instructions. Add 12 – 15 mL of BHIA per 100 × 15 mm petri dish and let solidify. Ensure the agar surfaces are dry. Note : Agar plates must be dry and free from condensation prior to use. To ensure agar surfaces are dry, plates should be made several days inadvance and stored inverted at room temperature or dried using a laminarflow hood.
13.7.2.2 The following should be conducted in triplicate, resulting in the evaluation of three spread plates.

 Open BioBall ® vial by removing the cap and aseptically add one BioBall ® to 1.0 mL of sterile PBS. Allow BioBall ® to dissolve completely.

 Mix suspension to homogenize. Pipet 0.1 mL of the BioBall ® suspension onto a 100 × 15 mm BHIA plate.
13.7.2.3 For each spread plate, use a sterile be nt glass rod or spreader to distribute BioBall ® inoculum over the medium surface by rotating the dish by hand or on a turntable. Note : Please ensure that inoculum is evenly distributed over entire surface of plate.
13.7.2.4 Allow inoculum to absorb into medium completely.
13.7.2.5 Invert plates and incubate at 35°C ± 0.5°C for 21 ± 3 hours.
13.7.2.6 For each dilution, count and record th e sum of the number of colonies (CFU) on the triplicate plates.
13.8 Calculation of BioBall ® Spike Percent Recovery Spiked BioBall ® percent recovery will be calculated using the lot mean value provided by manufacturer according to Section 13.8.2. Rec overy may also be calculated following the two steps as indicated below in Sections 13.8.1 and 13.8.2. Note : The calculated numbers in the example provided in the tables below have been rounded at the end of each step. If your laboratory recalculates the examples using a spreadsheet and rounds only after the final calculation (Step 2), the percent rec overy may be slightly different.

13.8.1 Calculate Mean E. faecalis per BioBall ® and “True” Spiked E. faecalis (CFU/100 mL)
The mean concentration of E. faecalis (CFU) in the BioBalls will be calculated using all three BHIA plates (from Section 13.7.2.6). Since one BioBall ® is spiked per 100 mL sample, use the mean number of E. faecalis per BioBall ® as the “true” spiked E. faecalis

. For example, if the triplicate results from S ection 13.7.2.6. are 57, 52, and 49, then the triplicate plate counts for the 550 CFU BioBall ® concentration are as follows:

T Spiked E. faecalis (CFU/100 mL) = [(54 + 52 + 49) ×10] / 3 = 517 per BioBall ®
Where,

T Spiked E. faecalis = True spiked E. faecalis (CFU/100 mL) in spiked sample Thus, 517 is the “true” spiked E. faecalis (CFU/100 mL)Method 1611

33 13.8.2 Calculate Percent Recovery Calculate percent recovery (R) using the following equation: R = 100 × (N s - N u )

T Where, R = Percent recovery

N s = E. faecalis (CFU/100 mL) in the spiked sample (or CFU per BioBall ® )

N u = E. faecalis (CFU/100 mL) in the unspiked sample

T Spiked E. faecalis = True spiked E. faecalis or CFU/100 mL in spiked sample

Percent recovery example calculation is provided in Table 9

. Table 9. Percent Recovery Example Calculation

Concentration N s (CFU / 100 mL) N u (CFU / 100 mL) T (CFU / 100 mL) Percent recovery (R)

550 505 10 517 100 × (505 - 10)/517 = 96%



## 14.0 Method Performance

14.1 Multi-laboratory Validation (MLV) of Met hod 1611 in Marine and Fresh Water
14.1.1 Marine Water
14.1.1.1 Eleven volunteer laboratories participated in the U.S. Environmental Protection Agency’s (EPA’s) MLV study of EPA Method 1611. The purposes of the study were to characterize method performance across multiple laboratories and multiple marine water matrices, assess method reproducibility, and to develop QC acceptance criteria. A detailed description of the study and results are provided in the validation study report (Reference 17.9). Results submitted by laboratories were validated using a standardized data review process to c onfirm that results were generated in accordance with study-specific instruc tions and the April 2010 draft version of EPA Method A (1611).
14.1.1.2 Recovery — Method 1611 was characterized by mean laboratory-specific recoveries, of enterococci from marine water samples spiked with BioBalls ranging from 68% to 841% (StepOnePl usTM) and 89% to 632% (ABI 7500), with an overall mean recovery of 401% (StepOnePlusTM) and 274% (ABI 7500). Mean laboratory-specific recoveries of enterococci from PBS samples spiked with BioBalls range d from 37% to 606% (StepOnePlusTM) and 89% to 627% (ABI 7500), with an overall mean recovery of 326% (StepOnePlusTM) and 297% (ABI 7500).
14.1.1.3 Precision — Method 1611 was characterized by laboratory-specific relative standard deviations (RSDs) from marine water samples spiked with BioBalls ranging from 35% to 91% (StepOnePl usTM) and 43% to 71% (ABI 7500), with an overall pooled, within-laborat ory RSD of 67% (StepOnePlusTM) andMethod 1611

34 58% (ABI 7500). For PBS samples spiked with BioBalls, laboratory-specific RSDs ranged from 29% to 114% (StepO nePlusTM) and 48% to 74% (ABI 7500), with an overall pooled, within-laboratory RSD of 81% (StepOnePlusTM) and 58% (ABI 7500).
14.1.1.4 Reproducibility — Each laboratory analy zed a total of five matrix samples received during a single week. Each samp le was split into eight replicates (4 unspiked and 4 spiked). Samples were spiked with E. faecalis (550 CFU) BioBalls. Overall mean recoveri es were 127%, 133%, 82%, 111%, and 228% for matrices 1 – 5, respectively.
14.1.2 Fresh Water
14.1.2.1 Ten volunteer laboratories participated in the U.S. Environmental Protection Agency’s (EPA’s) MLV study of EPA Method 1611. The purposes of the study were to characterize method pe rformance across multiple laboratories and multiple fresh water matrices, assess method reproducibility, and to develop quantitative QC acceptance crit eria. A detailed description of the study and results are provided in the validation study report (Reference 17.9). Results submitted by laboratories were validated using a standardized data review process to confirm that results were generated in accordance with study-specific instructions and the April 2010 draft version of EPA Method A (1611).
14.1.2.2 Recovery — Method 1611 was characterized by mean laboratory-specific recoveries, of enterococci from fresh water samples spiked with BioBalls ranging from 7% to 156%, with an overall mean recovery of 83%. Mean laboratory-specific recoveries of entero cocci from PBS samples spiked with BioBalls ranged from 35% to 103%, with an overall mean recovery of 69%.
14.1.2.3 Precision — Method 1611 was characterized by laboratory-specific relative standard deviations (RSDs) from fresh water samples spiked with BioBalls ranging from 35% to 1554%, with an overall pooled, within-laboratory RSD of 554%. For PBS samples spiked with BioBalls, laboratory-specific RSDs ranged from 20% to 104%, with an overall pooled, within-laboratory RSD of 58%.
14.1.2.4 Reproducibility — Each laboratory analy zed a total of five matrix samples received during a single week. Each samp le was split into eight replicates (4 unspiked and 4 spiked). Samples were spiked with E. faecalis (550 CFU) BioBalls. Overall mean recoveri es were 13%, 151%, 87%, 35%, and -97% for matrices 1 – 5, respectively. It should be noted that for Matrix #5 the mean background enterococci concentration was 37,329 CCEs/100 mL; approximately 68 times greater than the spike level of 550 cells added to each sample.



## 15.0 Pollution Prevention

15.1 The solutions and reagents used in this me thod pose little threat to the environment when recycled and managed properly.
15.2 Solutions and reagents should be prepared in vol umes consistent with laboratory use to minimize the volume of expired materials to be disposed.Method 1611

35 

## 16.0 Waste Management

16.1 It is the laboratory’s responsibility to comply with all federal, state, and local regulations governing waste management, particularly the bi ohazard and hazardous waste identification rules and land disposal restrictions, and to protect the air, water, and land by minimizing and controlling all releases from fume hoods and benc h operations. Compliance with all sewage discharge permits and regula tions is also required.
16.2 Samples, reference materials, and equipment know n or suspected to have viable enterococci attached or contained must be sterilized prior to disposal.
16.3 For further information on waste management, consult “The Waste Management Manual for Laboratory Personnel” and “Less Is Better: Laboratory Chemical Management for Waste Reduction,” both available from the American Ch emical Society’s Department of Government Relations and Science Policy, 1155 16th Street NW, Washington, DC 20036.



## 17.0 References

17.1 Anonymous. 1997. User Bulletin #2. ABI Pris m 7700 Sequence Detection System. Foster City, CA, Applied Biosystems.
17.2 Bordner, R., J.A. Winter, and P.V. Scarpino (eds.). 1978. Microbiological Methods for Monitoring the Environment: Water and Wastes , EPA-600/8-78-017
17.3 Cabelli, V. J., A. P. Dufour, M. A. Levin, L. J. McCabe, and P. W. Haberman. 1979. Relationship of Microbial Indicators to Health Effects at Marine Bathing Beaches. Amer. Jour. Public Health. 69:690-696.
17.4 Haugland, R.A., S.C. Siefring, L.J. Wymer, K.P. Brenner, and A. P. Dufour. 2005. Comparison of Enterococcus Density Measurements by Quantitativ e Polymerase Chain Reaction and Membrane Filter Analysis at Two Freshwater Recreational Beaches. Water Research 39:559- 568.
17.5 Ludwig, W. and K.-H. Schleifer. 2000. How quan titative is quantitative PCR with respect to cell counts? System Appl. Microbiol. 23: 556-562.
17.6 USEPA. 1983. Health Effects Criteria for Ma rine Recreational Waters. EPA-600/1-80-031.
17.7 USEPA. 1984. Health Effects Criteria for Fr esh Recreational Waters. EPA-600/1-84-004.
17.8 USEPA. 1986. Ambient Water Quality Criteria for Bacteria - 1986. EPA 440/5-84-002.
17.9 USEPA. 2011. Results of the Multi-Laboratory Va lidation of EPA Method A for Enterococci in Marine and Fresh Waters and Method B for Bacteroidales in Marine Waters by TaqMan ® Quantitative Polymerase Chain Reaction (qPCR) Assay. EPA 820-R-12-010.
17.10 Wade, T.J., Calderon, R.L., Sams, E., Beach, M., Brenner, K.P. & Dufour, A.P. 2006. Rapidly measured indicators of recreational water quality are predictive of swimming associated gastrointestinal illness. Environmen tal Health Perspectives 114: 24-28.Method 1611

3 6 

## 18.0 Acronyms

ΔΔ C T comparative cycle threshold calculation method AF amplification factor BHIA brain heart infusion agar BHIB brain heart infusion broth BSA bovine serum albumin CCE calibrator cell equivalent CFU colony forming units C T cycle threshold CV coefficient of variation DNA deoxyribonucleic acid EDTA ethylenediaminetetraacetic acid GI gastrointestinal illness IPR initial precision and recovery lsrRNA large subunit ribosomal RNA (i.e., 23S rRNA) MS matrix spike MLV multi-laboratory validation NTC no template control OD optical density OPR ongoing precision and recovery PBS phosphate buffered saline PCR polymerase chain reaction QA quality assurance QC quality control qPCR quantitative polymerase chain reaction RNA ribonucleic acid RPD relative percent difference RSD relative standard deviation SLV single-laboratory validation SPC sample processing control TNTC too numerous to count TSC target sequence concentration UV ultraviolet (light)Method 1611

37 

## Appendix A: ABI StepOnePlusTM, ABI 7900, a nd ABI 7500 Real-Time PCR System OperationMethod 1611

A -1 

## StepOnePlusTM, ABI 7900, and ABI 7500 Real-Time PCR System Operation

1.0 ABI StepOnePlusTM
1.0.1 Turn on the StepOnePlusTM and then the computer. Launch the StepOnePlusTM software program by double clicking on its icon on the computer desktop or from the Computer Programs menu.
1.0.2 On the StepOnePlusTM home screen select Advanced Set Up

. 1.0.3 On the right side of the main screen click in the box Experiment Name , enter identifying information for the experiment (Name/Date et c such that experiment can be identified). Then go through the following fields:

 Which instrument is going to be used to run the experiment: StepOnePlusTM Instrument (96 wells) is default (highlighted).

 What experiment do you want to set up: Quantitation-Standard Curve is default (highlighted).

 Which reagents will be used to detect the target: TaqMan ® Reagents is default (highlighted).

 Which ramp speed do you want to use in the instrument run: Click on Standard-2 hours (Not Default)
1.0.4 Click on Plate Set Up from the navigational pane of the present screen to define the targets, and then assign them to wells in the reaction plate (Step 1.0.8).
1.0.5 Define target – You can add a new target or use a saved target. By clicking on Add Saved Target the window with the target library will open.
1.0.6 Select the target(s) for your assay(s) and click on Add Selected Targets . All of the targets may be selected simultaneously by holding the Ctrl key and highlighting the desired targets (e.g., Entero, Sketa). The sel ected targets will then be added on to the define target and sample screen.
1.0.7 Optional: If a new target is to be added click the Enter Target Name cell and type the name. From the Reporter dropdown menu, select FAM (default). From the Quencher dropdown menu, select Tamra (NFQ-MGB) (default) . Leave the default in the color field.
1.0.8 Click on the tab Assign Targets and Samples to see the screen view of the plate layout with 96 wells.

 Select the wells, based on the plate set up, by highlighting, one target at a time.

 Select the wells for the first target by checking the box for the desired target in Assign Target to the selected wells and it will automatic ally populate the wells for that target. If more than one target is being used, repeat the process above for each target.

 The wells can be selected individually or by rows by clicking in the left corner of the row. In addition, the whole plate may be selected by clicking in the left corner of the plate.

 To deselect a row or well press Ctrl & click the selected portion one more time and it will deselect the row or well. Selected we lls/rows will be highlighted grey, while unselected wells/rows will remain white.Method 1611

A -2 1.0.9 Run the Method

 On the run method screen, review the reaction volume and the thermal profile for the default run. If needed: The default run method can be edited or replaced with one from the run method library. Click either the Graphical view (default) or Tabular View tab.

 Make sure the reaction volume per well field displays 25 μL, this is not the default setting.

 Set the thermal profile to the following holdi ng and cycling stages: Holding Stage 1: 50.0°C for 2:00 minutes, Holding Stage 2: 95.0°C for 10:00 minutes, Cycling Stage: 95.0°C for 0:15 seconds. The second step of th e Cycling Stage is defaulted at 60.0°C for 1 minute.

 Note : When using a run from the library click on the tab Open Run Method in the graphical view. Select Run Method and click ok. It will replace the default run with the saved run.
1.0.10 Load the plate into the instrument.
1.0.11 Click on the Plate Set Up tab and start the run by clicking the green button in the upper right hand corner of the screen.

 Save Experiment dialogue box

− Click Save to accept default file name and location (the name assigned when setting up the expe riment). The experiment is saved by default to the <drive>:\ applied Biosyste ms\<software name>\experiment folder.

 Run progress can be viewed from the touch screen of the instrument. At the beginning of a run do not leave the instrument or computer until you verify that the run has started.
1.0.12 Once the run is completed remove the reaction plate and discard.
1.0.13 Analyze the run

 Click on the tab in the top right corner of screen to Analyze the Run

.

 Highlight all of the sample wells and click on Analysis Settings to get to C T settings (default C T settings).

 Highlight all the targets running in the plat e; uncheck the default setting for automatic threshold and set the threshold to 0.03 . Keep the Automatic Baseline. Click on Apply Analysis Settings to save changes. The new settings can be confirmed by viewing the threshold line on the amplification plot.
1.0.14 Press the Export tab on the left corner of the view plate layout screen. Click on the browse button to find the correct place to export the data and click Start Exporting. After the export is done close export tool

.

1.1 ABI 7900 Real-Time PCR System Operation
1.1.1 Turn on the ABI Model 7900 and then the computer. Launch the SDS 2.2.2 software program by double clicking on its icon on the computer desktop or from the Computer Programs menu. The computer will establish communication with the 7900 instrument and if the connection is successful, the softwa re will display the Connected icon in the status bar when a plate document is opened.Method 1611

A -3 1.1.2 Under File menu, select New

. 1.1.3 In resulting New Document window that appears, change container selection from 384 well clear plate to 96 well clear plate using drop down menu. Accept default selections of Absolute Quantification and Blank Template . Click OK to display a new plate document.
1.1.4 Click, hold and drag mouse over all PCR reaction tray wells containing samples in upper left window. Selected wells will be outline d with a bold line and their position numbers should appear in the results table in the lower left window. To unselect wells, repeat above process while holding down control key.
1.1.5 Above right hand window, click on Setup tab.
1.1.6 Click on Add Detector button at the bottom of the setup screen. Note : Before any analyses are performed, a specific detector for the method must be created. To do this, go to step 1.1.7. Once the detector has been created, go to step 1.1.8.
1.1.7 Click on New in the pop-up window that appears. Another pop-up window will appears. Under Name , type in a name for the detector that will be used by this method ( e.g. , "Method 1611"). Under Group select Default. Under Reporter select FAM. Under Quencher select TAMRA. Click on OK to close second pop-up window. This step only needs to be performed before the initial analysis run of the method. The detector that is named is selected in all subsequent analysis runs as indicated in step 1.1.8)
1.1.8 In pop-up window that was opened in step 1.1.6, select the desired detector under Names menu ( e.g., Method 1611) and click on Copy to Plate Document button. Click on Done button to return to setup screen.
1.1.9 Click on Use box next to FAM detector in right hand window. This box should become marked with an X. Name and color code fo r FAM detector should appear in each of the selected well positions in the upper left window a nd a data column for this detector should be created for each of the selected well positions in the results table in the lower left window.
1.1.10 Click on Instrument tab right hand window.
1.1.11 In instrument screen, change sample volume to 25 μ L and choose 9600 emulation

. 1.1.12 Still in instrument screen, click on Connect, then click on Open/Close button in lower right hand “Real Time” window to open PCR reaction tray holder door on instrument.
1.1.13 Insert PCR reaction tray with prepared reactions in holder.
1.1.14 Click on Open/Close button to close PCR reaction tray holder door on instrument.
1.1.15 Click on Start button in lower right hand “Real Time ” window to start thermal cycling in instrument.
1.1.16 Name run file at prompt.
1.1.17 At termination of the run, instrument-calculated cycle threshold values should automatically appear for each well position a nd detector entry in the lower left hand results table window.
1.1.18 At termination of the run success complete, choose Analysis Settings from the toolbar. In that box enter a value for the Manual Ct Threshold (see 1.1.19). Click on OK . Click on Analyze from the toolbar. You should see C T values in the Results Table.Method 1611

A -4 1.1.19 The instrument-selected threshold line is indicat ed by the bold red line on the plot and the value is listed below the window. This can be manually adjusted by either click-hold and dragging the line up or down or entering new values below. Note : Based on results thus far with the instrument, the threshold value can be adjusted from the default value of 0.2 to 0.03, however, this should be done only if the threshold line remains above the background values (seen before the growth curves) for all of the samples.
1.1.20 Calculated C T values for each of the sample tray pos itions in the lower left hand “Results Table” will automatically be updated following adjustments of the threshold line. Once the threshold is adjusted to the desired level, select “Print Report” under the “File” menu. Check or uncheck desired report items by clic king on their associated boxes and the click on “Print” button. Note : Minimum report should have both detector boxes, i.e ., “FAM” checked which will show C T values for all selected tray positions for this detector.
1.1.21 Export data by clicking on File from the toolbar. From the drop down menu choose Export . In the box you will see Look in : and here you choose a directory to send the exported file too. Click on Export

. Save changes to document? will appear, click on Yes . Click OK

. 1.2 ABI 7500 (non-Fast) Sequence Detector Operation
1.2.1 Turn on the ABI Model 7500 sequencer and th en the computer. Launch the software program by double clicking on its icon on the computer desktop or from the Computer Programs menu. The computer will establish communication with the 7500 instrument. See “How to Set Up a New Experiment Using the ABI 7500” for screen shots.
1.2.2 Click on either the New Experiment or Advanced Setup button to create a new experiment, which will pull up the Experiment Menu.
1.2.3 From the Setup menu, select Experimental Properties to select the experiment type and give the experiment a name. Enter the e xperiment name in the asterisked box.

 Click on 7500 (96 Wells) to select the instrument type. Note : This protocol is not designed for the 7500 Fast.

 Scroll down to access more experiment properties options. Click on Quantitation – Standard Curve to select the experiment type

 Click on TaqMan ® Reagents to select the reagents used.
1.2.4 From the Setup menu, select Plate Setup . Click on the Define Targets and Samples tab to define the reporter-quencher dye for each target and also to enter the sample identifications ( e.g. , Ent 5X).

 Click on Add New Target and enter the name of the target. Under the Reporter heading, click on the drop down menu to select the reporter dye FAM . Under the Quencher heading, click on the drop down menu to select TAMRA as the quencher.

 Repeat the process above to add more than one target, e.g. , Sketa 5x.

 In the Define Samples section, click on Add New Sample and enter the sample name in the Sample 1 box.

 Click on the Assign Targets and Sample tab to assign the Target, sample ID and sample type to the wells.

o Drag the mouse over the desired ce lls to assign the Target, Task and Sample.Method 1611

A -5 o While the cells are highlighted, in the Assign target(s) to the selected wells section, check the box under Assign for the appropriate Target, then under Task , select U for unknown, S for standard or N for negative control.

o In the Assign sample(s) to the selected wells section, check the box under Assign to label the highlighted cells as Sample 1.

 Repeat the process above, by dragging the mouse over the appropriate cells, and then assigning them as U nknowns, S tandards or N egative Controls, as appropriate. Note : For Standards, in the Assign target(s) to the selected wells section, if there are 4 different values, each cell will need to be highlighted separately, and a quantity ( e.g. 40000) typed in the Quantity box.

 Click on Print Report at the top of the screen to print a plate layout for loading master mix and sample extracts.

o Select Plate Layout option by clicking on the box next to it.

o Click Print Report to print the plate layout.
1.2.5 From the Setup menu, select Run Method to set up the thermo cycling profile.

 In the Graphical View tab, change the Reaction Volume Per Well from the default 50 μ L to 25 μ L by typing in 25.

 Under Cycling Stage section, change the Number of Cycles to 45.

 Check that the default settings of Temperature and Time for the two Holding Stages and the Cycling Stage are correct. Specif ically, these should be: Holding Stage 1: 50.0°C for 2:00 minutes, Holding Stage 2: 95.0°C for 10:00 minutes, and Cycling Stage: 95.0°C for 0:15 seconds. Note : The purpose of Holding Stage 1 is to eliminate potential PCR carryover products in the reactions using the Amp-Erase ® UNG enzyme provided in the TaqMan ® Universal PCR master mix. The purpose of Holding Stage 2 is to inactivate the Amp-Erase ® UNG enzyme.

 The second step of the Cycling Stage is defaulted at 60.0°C for 1 minute – change the time to 2:00 minutes. Note : This sets the detection of the fluorescence signal to occur at the end of the second step in each cycle.

 Click on Save at the top of the screen to save the run before actually running the experiment.

 The Save screen will open so that you may select the folder to save the Run Data File. Type in the Experiment Name (if you did not already do so at the beginning of the Experiment Setup) and click on Save . If you had previously typed in an Experiment Name and there is no change, click on Save

. Note : You must save to the hard drive (rather than a flash drive).
1.2.6 From the Experiment menu, select Run to monitor the run in real time.

 The Run Status screen will open - click on Start Run . When the run has successfully started, the Start Run button will turn change from green to red.
1.2.7 When the run has completed, from the Setup menu, select Analysis to export your results. See “How to Export Results from the ABI 7500 Software” for screen shots.

 The Analysis Settings for Experiment name screen will open.Method 1611

A -6  Under the C T Settings tab, click on the Target desired to be set from Default to Manual Threshold setting (generally, this would be the Ent).

 In the C T Settings for ENT section, uncheck the boxes next to Use Default Settings , and Automatic Threshold . Enter the desired Threshold ( e.g., 0.025). If more than one target is present, highlight the next target ( e.g., Sketa) and repeat this step.

 Click on Apply Analysis Settings to save the changes.
1.2.8 Click on Export at the top of the screen to save the experiment results data and to save the selected plots required in the report. Th e threshold value will have changed on the Amplification plot curve graphic.

 The Export Data screen will open. In the Select data to export section, check all of the boxes ( i.e., Sample Setup, Raw Data, Am plification Data, Results, and Multicomponent Data).

 For Select one file or separate files , select One file to export all the data into one file with multiple tabs.

 For Export File Name , enter the name of the Experimental data file to be exported, and for File Type , choose *.xls.

 For Export File Location , click on Browse to select the folder in which you wish to export your file. Always save your file to the hard drive.

 Click on Start Export . When this is completed, an Export Completed screen will open – click on Close Export Tool to complete this task.
1.2.9 How to interpret your results. See “How to Interpret Results from the ABI 7500” for screen shots.

 After exporting your data, from the Experiment menu, select Analysis.

o From the Analysis menu, select Amplification Plot to view the results of the selected samples at different plot settings.

o Drag the mouse over the desired cells to select the samples to be plotted in the amplification plot.

o In the Amplification Plot section, in the Plot Settings tab, select the Plot Type (from the drop down menu) and the Graph Type (from the drop down menu).

o If the plot requires the display of the Threshold and Baseline, in the Options tab, check the boxes next to Threshold and Baseline . If you want to see the results in tabular format, click on View Well Table , and scroll down or sideways for more samples and analysis parameters.

o The toolbar above the graph can be used to make hard copy prints, saving the file as *.jpg, zooming in and out, and changing the plot properties.

 For the Standard Curve, select Standard Curve from the Analysis menu to view the results of the same sample (assuming they have the same target) and standards in the plot.

o In the Plot Settings tab, click the drop down menu arrow beside Target to select a different target (if the st andards were analyzed in more thanMethod 1611

A -7 one target), and click the drop down menu arrow beside Plot Color to change the plot color.

o The standard curve parameter display below the plot ( i.e. Target, Slope, Y-Intercept, R 2 , and Eff% (percent efficiency) is useful for data analysis.

 For Multicomponent plots, click on Multicomponent Plot from the Analysis menu to view the variation in the fluorescence of the dyes used in the experiment over the ascending repeat of the 45 thermo cycles based on well, target, or dye.

o Click on the drop down menu arrow next to Plot Color in the Plot Settings tab to select the parameter for the basis of the graph ( e.g. , well, target, or dye).

 For raw data plots, select Raw Data Plot from the Analysis menu to view the variation in the emission of fluorescence of the dyes in different filters present over the ascending repeat of the 45 thermo cycles.

o In the Options tab, drag the pointer on the cycle scale to the desired cycle number to view the fluorescence variation through filters of the samples at that cycle.

 For quality controls, click on QC Summary from the Analysis menu to view the analysis summary of the samples.

 To view all the plots, click on Multiple Plots View from the Analysis menu to see all of the plots for the samples in a single window. Each plot will have its own drop down menu as in Section 1.2.9.5.
1.2.10 To print the report, click on Print Report at the top of the screen.

 Check all of the boxes ( i.e. , Experimental Summary, Results Summary, Plate Layout, Amplification Plot (3 boxes), Standard Curves, Results Table, and QC Summary).

 Click on Print Report at the bottom of the screen.Method 1611



## Appendix B : Cepheid Smart Cycler ® 

## OperationMethod 1611

B -1 

## Appendix B - Cepheid Smart Cycler ® 

## Operation

1.0 Smart Cycler ® Operation

1.1 This protocol is intended to provide only informa tion about critical instrument settings required to perform EPA Method 1611. Further details concer ning the operation of the instrument can be obtained from the Smart Cycler ® Operation Manual, Cepheid Part #D0190, Rev. D

. 1.2 Turn on the Smart Cycler ® ; then the computer.
1.3 Double-click on the Smart Cycler ® icon on the computer desktop.
1.4 The following steps for defining a protocol are only required before the initial run of the instrument. The protocol that is defined in th ese steps is used in all subsequent runs of the instrument. See “How to Set Up a New Experiment Using the Smart Cycler ® (Software Version 2.0” for screen shots.
1.4.1 Click on the Define Protocols icon to go to Define Protocols screen. 1.4.2 Click on the New Protocol button to open the Protocol Name? dialog. Enter "EPA Enterococcus Method 1611" for the new protocol name, and click OK . The protocol stages are defined in the series of boxes at the bottom of the Define Protocol screen. Make sure the new protocol is highlighted a nd begin to choose state settings. To define Stage 1 , click on its drop-down box to display the menu of stage types; then select Hold

. In the Temp column, enter 50.0, and in Secs column, enter 120, leaving the Optics setting as the default Off setting. (Note : This stage is performed to eliminate potential PCR carryover products in the reactions using the Amp-Erase ® UNG enzyme provided in the TaqMan ® Universal PCR master mix. The optical reading cannot be programmed during a Hold stage.).
1.4.3 To define Stage 2 , click on its drop-down box to display the menu of stage types, and again select Hold . In the Temp column, enter 95.0, and in Secs column enter 600. Again, leave the Optics setting on Off

. ( Note : This stage is performed to inactivate the AmpErase ® UNG enzyme ).
1.4.4 To define Stage 3 , select 2-Temperature Cycle from its drop down menu. For the first step, enter 95.0 in the first row of the Temp column and 15 in the Secs column, Optics column Off . For the second step, enter 60.0 in the second row of the Temp column, 120 in the Secs column, and click on the Optics cell to select On from the drop-down menu. ( Note : This sets the detection of the fluorescence signal to occur at the end of the second step in each cycle.) Enter 45 in the Repeat field at the top of the Stage 3 box to specify that it should be repeated for 45 cycles. Click the Save Protocol button.
1.4.5 To display primary curve graphs, click Define Graphs . Highlight FAM in Graph column. Check the box for Automatically add to new runs . Under Graph Type choose Optics from the pull down menu. Under Channels check the box for Ch 1 (FAM)

. Under Show check the boxes for Primary Curve, Threshold (Vertical) and Threshold (Horizontal) . Under Axes check the box for Fluorescence vs. Cycle . At the bottom of the screen click on Save Graph

. 1.5 Click on the Create Run icon to open the Create Run screen. For each new run, enter a unique name in the Run Name field. (Note : The software does not allow duplicate run names)

. 1.6 Enter any additional information about the run in the Notes field. Click the arrow in the Dye Set box to display a drop-down menu of the possible selections. Select FTTC25

. (Note : This selects the dye set: FAM, TET, Tex Red, Cy5, and a 25 μ L reaction).Method 1611

B -2 1.7 Click the Add/Remove Sites button. The Select Protocols and Sites... dialog will appear. Highlight (click on) the "EPA Method 1611" prot ocol developed prior to the first run (Section 1.4.2) in the Protocols list. In the Sites list, highlight the sites on the instrument to be used with this protocol in the current run by clicking on them with the shift key held down ( Note : Sites refer to the I-core modules in the Smart Cycler ® processing block in which reaction tubes will be placed; a total of 16 are possible per block. When using multiple blocks, th e site numbers will be preceded by the block letters, e.g., A, B, C); then click the right pointing arrow to transfer the selected sites and protocol to the Selections table.
1.8 Click on the OK button to save the selections, and return to the Create Run screen. 1.9 Place the loaded Smart Cycler ® reaction tubes in the I-core module slots, selected above for current run. The tubes should sn ap into place. Either the front or back of the caps can face the front of the processing block.
1.10 In one of the View menus that is shown, select Analysis Settings . The displayed table includes one row for each of the four possible dye channels defined in the dye set. Click on the cell in the FAM row under the Usage column heading, and select Assay from the drop down menu. Set the Usage cells for all other dyes to Unused in the same manner. ( Note : All assays in this protocol use FAM as the reporter dye). All other cells in th is table should be left at default settings (See Smart Cycler ® Operation Manual).
1.11 In the other View menu that is shown, select the Results Table . Enter the sample identification information for each site in the Sample ID column (additional information can be entered into the Notes column.). Leave the other column s as default settings (see Smart Cycler ® Operation Manual.)
1.12 Click on the Start Run button. The orange LEDs on the Smart Cycler ® processing block should turn on, and the software will automatically switch to the View Results screen. 1.13 To display the real time temperature profiles for all sites, click Temperature in either of the View menus. To display real time growth curves for all samples ( i.e., the fluorescence signal vs. cycle), click FAM in the other View menu. 1.14 At the end of the run, it is recommended to ch eck the cycle threshold values calculated by the instrument for each sa mple by opening the Results Table window by clicking on this selection in the upper View menu. It is also recommended to inspect the growth curves in the FAM window which can be opened in the same manner from the lower View menu. The default threshold fluorescence value is shown in this window as a si ngle horizontal red line and the cycle thresholds for each site are shown as vertical red lines. To vi ew the data for individual sites in this window, click on that site number in the table to the right of the graph. If the default threshold fluorescence line is well above all of the growth curve lines prior to visible amplification, the threshold fluorescence value can be changed to a lower value. This is done by reopening the Analysis Settings window from the upper View menu and entering a new value in the Manual Thresh Fluor Units cell in the FAM row. Conversely if the default threshold fluorescence line is below any of the growth curve lines prior to visibl e amplification, the threshold fluorescence value should be changed to a higher value in the same manner. Previous studies have indicated that a threshold value of 8 works well for most analyses. Click on the Update Analysis button to view the new threshold line in the FAM window. The cycle threshold values will be automatically updated in the Results Table

. 1.15 Once the threshold fluorescence value is adju sted to an optimal value, click the Save Run button. ( Note : The Smart Cycler ® Software does not give a prompt to save changes before printing or exporting. Therefore, it is possible to make cha nges to the Results Table or Analysis Settings, and immediately print or export the data, then close th e run without saving the changes. In this case,Method 1611

B -3 the data saved in the Smart Cycler ® database will not match the printed or exported data. If no changes are made in the threshold fluorescence value, the run data is automatically saved as it is when the program is closed or a new run is created.)
1.16 To set up automatic export of raw data, (see “How To Set Up Automatic Export of Raw Data” for screen shots) from the main menu, click on Setup , then System Defaults , then Export Settings

. From the Export Settings dialog box, check the box beside Results Table and Analysis Settings. Click the Browse button to select the folder where you want your raw data saved. Click on the radio button next to Automatic export on run completion, then click the OK button.
1.17 To manually save the Results Table and Analysis setting containing the instrument-calculated cycle threshold values for each sample (see “How to Manually Export Raw Data” for screen shots), click the Export button to display the Export Data dialog box. Check the box next to the heading Export Results Table and Analysis Settings by clicking on it. Leave all other boxes unchecked. Click on Export . A box labeled Export Data will appear with the run name in the file name box. Click on the drop down menu to the right of Save In: at the top left of the screen to change the directory where you want your data saved. Click on Save . Data are exported as comma-delimited text (* .cvs ) files in MS Excel-compatible files to the Export folder in the Smart Cycler ® folder: C:\Smart Cycler ® \Export. Always save to the hard drive.

1.18 To archive a run in the Smart Cycler ® program, click on Tools . From the drop down menu click

on Data Management and then Archive Runs . Click Proceed . Select the run to be archived by clicking on its name in the database list. Click OK and then Proceed . A box labeled Archive Run will appear on the screen. There will be a line labeled Save in: . Input which directory you would like the run to be saved in. There will be a line File Name: . Enter a file name. Click Save . Click OK

.
1.19 To print run data (see “How to Print Run Data” fo r screen shots), after the run is completed, right click on the graph area, and select Print , then Print Graph with Results Table . An Optics Graph print preview screen will pop up, click Print . The screen will switch back to the post run screen. To print the generated report, click Report . A Run Report print preview screen will pop up, click Print

.
1.20 To set up a new analysis (see “How to Set Up a New Run” for screen shots), from the post run screen, click Create Run at the top left. The results of your just completed will disappear and a Add/Remove Sites button will appear in the middle of the screen – click it. A Select Protocols and Sites screen will pop up, select EPA Enterococcus Method 1611 in the Protocols box, and highlight the amount of sites needed for the assay (A1-A16) in the Sites box. Click the right arrow to the right of the sites box to move the sights to the Selections box. After double checking that the correct protocol is highlighted, click OK . Add the Run Name in the Run Name box. The Site ID, Protocol, Sample ID, Sample Type, Notes (etc .) box will pop up. Enter the Sample ID for each site. Under this box, find the Usage column and click on Assay to select Unused for Cy3, TxR and Cy5 (leave Assay for FAM). In the same box, find the Manual Thresh Fluor Units, and click on the units for FAM to change it from 30.0 to 8.0 (leave the units at 30.0 for Cy3, TxR and Cy5). After loading the Smart Cycler with tubes, click Start Run . A red light should appear on sites that are in use.