US Environmental Protection Agency
Office of Pesticide Programs
Office of Pesticide Programs
Microbiology Laboratory
Environmental Science Center, Ft. Meade, MD
Standard Operating Procedure for the AO AC
Sporicidal Activity of Disinfectants Test
(Bacillus subtilis x porcelain carrier)
SOP Number: MB-15-04
Date Revised: 01-03-18

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SOP No. MB-15-04
Date Revised 01-03-18
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SOP Number
MB-15-04
Title
Standard Operating Procedure for the AO AC Sporicidal Activity of
Disinfectants Test (Bacillus subtilis x porcelain carrier)
Scope
This SOP describes the Sporicidal Activity of Disinfectants Test -
Method II methodology used to determine the sporicidal efficacy of
liquid sporicidal agents against Bacillus subtilis on hard surfaces
(porcelain carriers).
Application
The method is based on AOAC method 966.04 (see 15.1). B.
subtilis (ATCC #19659) is a test microbe used to support sporicidal
claims. Testing of suture loops and Clostridium sporogenes is not
addressed in this SOP.


Approval Date
SOP Developer:

Print Name:
SOP Reviewer

Print Name:
Quality Assurance Unit

Print Name:
Branch Chief

Print Name:


Date SOP issued:

Controlled copy
number:

Date SOP withdrawn:


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TABLE OF CONTENTS
Contents	Page Number
1.
DEFINITIONS
3
2.
HEALTH AND SAFETY
3
3.
PERSONNEL QUALIFICATIONS AND TRAINING
3
4.
INSTRUMENT CALIBRATION
3
5.
SAMPLE HANDLING AND STORAGE
3
6.
QUALITY CONTROL
3
7.
INTERFERENCES
3
8. NON-CONFORMING DATA
3
9.
DATA MANAGEMENT
3
10.
CAUTIONS
3
11.
SPECIAL APPARATUS AND MATERIALS
4
12.
PROCEDURE AND ANALYSIS
6
13.
DATA ANALYSIS/CALCULATIONS
17
14.
FORMS AND DATA SHEETS
17
15.
REFERENCES
18

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1. Definitions
Additional abbreviations/definitions are provided in the text.
1.	AO AC = AO AC INTERNATIONAL
2.	CFU = Colony Forming Unit
3.	References to water mean reagent-grade water, except where otherwise
specified.
2. Health and
Safety
Follow procedures specified in SOP MB-01, Laboratory Biosafety. The
Study Director and/or lead analyst should consult the Safety Data Sheet for
specific hazards associated with products.
3. Personnel
Qualifications
and Training
Refer to SOP ADM-04, OPP Microbiology Laboratory Training.
4. Instrument
Calibration
Refer to SOPs EQ-01 (pH meters), EQ-02 (thermometers), EQ-03 (weigh
balances), EQ-05 (timers), EQ-10 (orbital shakers) and QC-19 (pipettes)
for details on method and frequency of calibration.
5. Sample
Handling and
Storage
Refer to SOP MB-22, Preparation and Sampling Procedures for
Antimicrobial Test Substances, and SOP COC-01, Chain of Custody
Procedures.
6. Quality
Control
For quality control purposes, the required information is documented on
the appropriate form(s) (see section 14).
7. Interferences
Avoid touching the interior sides of the medication tube while the carrier is
being lowered into the disinfectant and the hook is being removed as it
may lead to false positive results.
8. Non-
conforming
Data
1.	Sterility and/or viability controls do not yield expected results.
2.	The mean spore counts per carrier falls outside the specified range of
1x10s to approximately l.OxlO6 spores/carrier.
3.	No contamination is acceptable in the test system.
4.	Acceptable spore purity and HC1 resistance test results must be
achieved.
5.	Management of non-conforming data will be specified in the study
protocol; procedures will be consistent with SOP ADM-07, Non-
Conformance Reports.
9. Data
Management
Data will be archived consistent with SOP ADM-03, Records and
Archives.
10. Cautions
1. To ensure the stability of a diluted sporicidal agent, use the diluted
product within three hours of preparation unless specified otherwise.

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2.	Use appropriate aseptic techniques for all test procedures involving the
manipulation of the test organisms and associated test components.
3.	Verify the volume of dilution blanks, neutralizer tubes, and subculture
tubes in advance and adjust accordingly.
11. Special
Apparatus and
Materials
1. Culture Media. Note: Commercial dehvdrated media made to conform
to the specified recipes may be substituted. Media can be stored for up
to two months.
a.	Nutrient broth. For use in preparing nutrient agar. Add 5 g beef
extract (paste or powder), 5 g NaCl, and 10 g peptone (anatone) to
approximately 1 L water. Boil mixture for 20 min with constant
stirring. Readjust volume to 1 L with water and allow cooling to
around 50C. Adjust pH to 6.80.2 with IN HC1 or IN NaOH, if
necessary. Filter through paper (e.g., Whatman filter paper No.
4). Dispense 10 mL portions into 20x 150 mm culture tubes or 20
mL portions into 25 x 150 mm culture tubes. Dehydrated nutrient
broth may be substituted - prepare according to the
manufacturer's instructions.
b.	Nutrient agar. For stock cultures slants. Add 1.5% (w/v) Bacto-
agar to unsterilized nutrient broth. Boil mixture until agar is
dissolved. Adjust pH to 7.20.2 if necessary. Dispense 5 mL
portions into 16x 100 mm screw cap tubes. Larger tubes may be
used as well. Autoclave for 20 min at 121C. Remove from
autoclave and slant tubes to form agar slants.
c.	Nutrient agar with 5ug mL MnSOrFhO (amendednutrient agar).
For spore production. Suspend 11.5 g nutrient agar in 495 mL
water, add 5 mL 500 ppm MnS04:FhO. Dissolve by boiling.
Adjust pH to 6.80.2 if necessary. Autoclave for 15 min at
121C. Pour agar into plates.
d.	Trypticase soy agar (TSA). Prepare according to manufacturer's
instructions.
e.	Fluid thioglycollate medium (FTM). For subculturing spores
exposed to disinfectant. Prepare according to manufacturer's
instructions. Protect from light.
Note: If after autoclaving the aerated portion of media consumes
more than one third of tube, media must be re-boiled by placing
tubes in beaker of boiling water. Media can only be re-boiled
once.
f.	Fluid thioglycollate medium with 1MNaOH (modifiedFTM). For

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subculturing spores exposed to 2.5 M HC1. Suspend 29.5 g of
fluid thioglycollate medium in 1 L water. Heat boiling to dissolve
completely. Cool and adjust pH to 7.10.2 if necessary. Add 20
mL 1 M NaOH, mix well. Check final pH and record (pH
between 8 and 9 is typical). Dispense 10 mL into 20x150 mm
culture tubes and autoclave for 15 min at 121C. Store at room
temperature. Protect from light.
2.	500ppm Manganese sulfate monohydrate. Add 0.25 g manganese
sulfate monohydrate to 500 mL water. Filter sterilize.
3.	2.5 MDilute hydrochloric acid. Use to determine resistance of dried
spores. Standardize and adjust to 2.5 M as in AO AC method 936.15 or
purchase certified 2.5M HC1.
4.	Sterile water. Use reagent-grade water. Reagent-grade water should
be free of substances that interfere with analytical methods. Any
method of preparation of reagent-grade water is acceptable provided
that the requisite quality can be met. Reverse osmosis, distillation, and
deionization in various combinations all can produce reagent-grade
water when used in the proper arrangement. See Standard Methods for
the Examination of Water and Wastewater for details on reagent-grade
water.
5.	Triton X-100. For washing used porcelain penicylinders.
6.	Ethanol (40%). For preparing spore suspension used in the
neutralization assay.
7.	3Ad Petrifilm Aerobic Count Plate. For spore enumeration. 3M
Food Safety (St. Paul, MD, USA; Cat. No. 6400).
8.	Test organism. Bacillus subtilis (ATCC No. 19659) obtained directly
from a reputable supplier (e.g., ATCC).
9.	Carriers. Penicylinders, porcelain, 81 mm OD, 61 mm ID, 101
mm length. (Available from CeramTec Ceramic, Laurens, SC,
www.ceramtec.com, SAP# 1010368)
10.	Glassware. For disinfectant, 25x100 mm culture tubes (Bellco Glass
Inc., Vineland, NJ; reusable or disposable 20x150 mm (for
cultures/subcultures); 16x100 mm screw cap tubes for stock cultures.
Cap with closures before sterilizing. Sterilize all glassware 2 h in hot
air oven at 180 C or steam sterilize for a minimum of 20 min at 121C
with drying cycle.
11.	Sterile centrifuge tubes. Polypropylene, 15 mL conical tubes with
conical bottoms (Corning), or equivalent.

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12.	Water bath/chiller unit. Constant temperature for test chemical,
capable of maintaining 201C temperature or specified temperature
for conducting the test.
13.	Petri dishes. Plastic (sterile).
14.	Filter paper. Whatman filter paper #2; placed in Petri dishes for
storing carriers.
15.	Test tube racks. Any convenient style.
16.	Inoculating loop. Any convenient inoculation/transfer loop for culture
transfer.
17.	Wire hook. For carrier transfer. Make 3 mm right angle bend at end of
50-75 mm nichrome wire No. 18 B&S gage. Have other end in
suitable holder.
18.	Centrifuge. For preparing spore suspension.
19.	Sonicator (ultrasonic cleaner). For conducting control carrier counts.
20.	Orbital shaker. For preparing spore suspension. Speed range from 25
to 500 rpm.
21.	Vacuum desiccator. For carrier storage. With gauge for measuring
27" (69 cm) of Hg and fresh desiccant.
22.	Certified Timer. For managing timed activities, any certified timer that
can display time in seconds.
12. Procedure and
Analysis

12.1 Culture
Initiation
a.	Every 12 months (or sooner if necessary) initiate a new stock
culture from a lyophilized culture of B. subtilis (ATCC 19659).
b.	Open ampule of freeze dried organism as indicated by ATCC.
c.	Using a tube containing 5-6 mL of nutrient broth (NB),
aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for B.
subtilis.
d.	Aseptically transfer the entire rehydrated pellet back into the
original tube of nutrient broth designated as "TUBE A" (see
Attachment 1). Mix well.
e.	Streak for isolation using a loopful of rehydrated suspension on
duplicate trypticase soy agar (TSA) or nutrient agar (NA) plates.
f.	Incubate broth culture (TUBE A) and plate cultures at 301C for

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242 h.
g. Record all manipulations on the Organism Culture Tracking Form
(see section 14).
12.2 Culture
Identification
a.	Perform initial confirmation testing for quality control (QC) using
the 242 h NA or TSA plates.
b.	Following the incubation period (as stated in section 12. If),
record the observed colony morphology on the NA or TSA plates
and Gram stain reaction. See section 12.2d. for details on colony
morphology and Gram stain reaction.
c.	Perform a Gram stain from growth taken from the TSA or NA
plates. Perform the Gram stain according to the manufacturer's
instructions. Observe the Gram reaction by using brightfield
microscopy at 1000X magnification (oil immersion).
d.	B. subtilis is a Gram positive rod; colonies on TSA are opaque,
rough, dull, round, with irregular margins, and low convex.
Colonial variation may be observed and is typical for this strain.
e.	Perform VITEK analysis according to the manufacturer's
instructions.
f.	Record all confirmation results on the Test Microbe Confirmation
Sheet (Quality Control) (see section 14).
12.3 Generation of
Stock
Cultures
a.	Use the 242 h TUBE A (see Attachment 1) broth culture
discussed in section 12. Id to initiate stock cultures - streak a
minimum of six NA slants with B. subtilis and incubate at 361C
for 242 h.
b.	Following incubation, store the cultures at 2-5C for 302 days.
These cultures are identified as the "stock cultures." Begin stock
culture transfers as outlined in section 12. le. Repeat the cycle for
a maximum of one year.
c.	From a set of six stock cultures, one is used every 302 days for
QC and to generate new stock cultures, four may be used per
month (one/week) for generation of test cultures, and one is a
back-up tube.
12.4 Monthly QC
of Stock
Cultures
a. Perform monthly QC of stock cultures just prior to or
concurrently with stock culture transfers. Use one refrigerated
stock culture tube and streak a loopful on a plate of TSA.

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b. Incubate the plates at 361C for 242 h (18-24 h for use in the
VITEK 2 Compact). Follow steps outlined in section 12.2b to
confirm the identity of the organism.
12.5 Culture
Maintenance
a.	Every 302 days inoculate a new set of stock culture tubes from a
current stock culture tube. Use the same refrigerated stock culture
tube used for Monthly QC described in section 12.4a to inoculate
6 new stock cultures tubes as outlined in section 12.3a.
b.	Incubate the new stock cultures as indicated in section 12.3a.
c.	Following the incubation period, store the stock cultures at 2-5C
for 302 days.
12.6 Production of
B. subtilis
Spore
Suspension
a.	Use growth from a stock culture tube to inoculate 10 mL tubes
(e.g., 2 tubes, depending on the amount of spore preparation
desired) of NB and incubate tubes on an orbital shaker for 242 h
at approximately 150 rpm at 361C. Use this culture to inoculate
amended NA plates. Inoculate each plate with 500 |iL of broth
culture and spread the inoculum with a sterile bent glass rod or
suitable spreading device. In addition, verify the purity of this
culture by streak isolating on amended NA (incubate at 361C
for 242 h). Wrap each plate with parafilm or place in plastic
bags. Incubate plates inverted for 12-14 days at 361C.
b.	Following incubation, harvest the spores by adding 10 mL chilled
sterile water to each plate. Using a spreader (e.g., bent glass rod),
remove growth from plates and pipet suspensions into 15 mL
sterile conical tubes (10 plates = 14 tubes, -10 mL each).
c.	Centrifuge tubes at 5,000 rpm (4,500xg) for approximately 10
min at room temperature. Remove and discard supernatant. Re-
suspend pellet in each tube with 10 mL cold sterile water and
centrifuge at 5,000 rpm (4,500xg) for approximately 10 min.
Remove and discard supernatant. Repeat twice.
d.	Re-suspend the pellet in each tube with 10 mL sterile water.
Store the spore suspension at 2-5C.
e.	Examine spore suspension with a phase contrast microscope or by
staining to assess quality of the spore suspension. Examine a
minimum of five fields and determine ratio of spores to vegetative
cells (or sporangia). Percentage of spores versus vegetative cells
should be at least 95%. Spore suspension from multiple plates
can be combined and re-aliquoted into tubes for uniformity.

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f. Prior to inoculation of carriers, determine spore titer of the
concentrated spore suspension by plating 100 |iL aliquots of serial
dilutions (e.g., 10"5 through 10"7) using spread plating on TSA
plates or another comparable validated enumeration procedure.
Incubate plates for 242 h at 361C and determine titer.
i. Note: When harvested and processed, ten plates of
amended nutrient agar should provide 80-100 mL of
concentrated spore suspension (approx. 109 CFU/mL).
Diluting the suspension prior to carrier inoculation will be
necessary; a titer of l.OxlO8 to 5.0><108 CFU/mL should
be adequate to achieve the target carrier count.
12.7 Preparation of
Porcelain
Carriers
Preparation of porcelain carriers can also be found in MB-03, Screening of
Polished Stainless Steel Penicylinders, Porcelain Penicylinders, and Glass
Slide Carriers Used in Disinfectant Efficacy Testing.
a.	Prior to use, examine porcelain carriers individually and discard
those with scratches, nicks, spurs, or discolorations.
b.	Rinse unused carriers gently in water three times to remove loose
material and drain.
c.	Place rinsed carriers into Petri dishes matted with 2 layers of filter
paper in groups of 15 carriers per Petri dish or place carriers into
25x150 mm tubes (10 carriers per tube).
d.	Sterilize 20 min at 121C. Cool and store at room temperature.
Note: Handle porcelain carriers with care when placing in Petri
dishes. Minimize carrier movement and avoid excessive contact
between carriers that might result in chips and cracks. Wash
carriers with Triton X-100 and rinse with water 4 times for reuse.
12.8 Inoculation of
Porcelain
Carriers
a.	Dilute the concentrated spore suspension as necessary with sterile
water to achieve carrier counts between 1,0x 105 and
approximately l.OxlO6 spores/carrier. Dispense 10 mL diluted
spore suspension into an appropriate number of 25 x 150 mm
tubes.
b.	Add 10 sterile carriers to each tube containing 10 mL spore
suspension, slightly agitate, and let stand 10-15 min.
c.	Remove each carrier with sterile hook and place upright in a
sterile Petri dish lined with two sheets of filter paper, no more
than 30 carriers per Petri dish.
d.	Air dry in biological safety cabinet for approximately 302 min.
Place Petri dishes containing inoculated carriers in vacuum

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desiccator (with gauge) containing CaCh and draw vacuum of
27" (69 cm) Hg.
e. Dry carriers under vacuum for 242 h before use in HC1
resistance testing, efficacy testing or carrier counts. Maintain in a
sealed desiccation unit under vacuum (27" Hg) for up to three
months.
i. Inoculated carriers may be used after three months (within
one year) if they meet the acceptable HC1 resistance and
carrier count criteria. Sterilize and reuse if necessary.
12.9 Spore
Enumeration
(carrier
counts)
a.	Prior to use, determine the carrier counts for each preparation of
inoculated carriers. Assay 3 to 5 randomly selected carriers per
preparation.
b.	Place each inoculated carrier into a 50 mL plastic, polypropylene
conical centrifuge tube containing 10 mL of sterile water.
c.	Sonicate carriers for 5 min  30 s.
Note: For sonication, place tubes into an appropriately sized glass
beaker with tap water to the level of sterile water in the tubes.
Place beaker in sonicator so that water level in the beaker is even
with water level fill line on sonicator tank. Fill tank with tap
water to water level fill line. Suspend beaker in sonicator tank so
it does not touch bottom of tank and so all three water levels
(inside test tubes, inside beaker, and sonicator tank) are the same.
d.	Following sonication, vortex tubes for 2 min 5 s.
e.	Dilute spore suspensions to 10"3 by transferring 1 mL aliquots to
tubes containing 9 mL sterile water.
i. Alternatively, pool the water from the tubes with the
carriers and briefly vortex. Serially dilute and plate
appropriate aliquots of the pooled water (30-50 mL) and
calculate the average carrier count per set.
f.	Plate 100 |iL of the 10 (tube with the carrier) through the 10"3
dilution in duplicate using spread plating with TSA. Invert plates
and incubate for 24-48 h at 361C.
i. Alternatively, use 3M Petrifilm AC Plates for
enumeration of the test organism. Dilute the spore
suspensions through 10"4 and plate 1 mL aliquots on the
Petrifilm.
Note: Conduct a culture purity check on one dilution of

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one carrier.
g. Count colonies. Record all counts less than 300 and use those
counts for enumeration. Report plates with colony counts over
300 as TNTC (Too Numerous to Count). Average spore counts
per carrier should be between l.OxlO5 and approximately l.OxlO6
spores/carrier. Do not use carriers with counts outside this range.
Average spore counts per carrier should be within one log of each
other.
12.10
HC1 Resistance
a.	Equilibrate water bath to 201C. Pipet 10 mL of 2.5M HC1 into
two 25 x 100 mm tubes, place into water bath, and allow to
equilibrate. Start timer and rapidly transfer 4 inoculated
penicylinders into a tube with 2.5 M HC1 using flamed hooks or
forceps. Do not allow carriers or transfer device to contact inside
of wall of acid tube.
b.	Transfer individual carriers after 2, 5, 10, and 20 minutes of HC1
exposure to a separate tube of modified FTM. Rotate each tube
vigorously by hand for approximately 20 s and then transfer
carrier to a second tube of modified FTM.
c.	For viability control, place one unexposed inoculated carrier in a
separate tube of modified FTM. For media sterility, use one tube
of modified FTM.
d.	Incubate all test and control tubes for 21 days at 361C. Record
results as growth (+) or no growth (0) at each time period. Spores
should resist HC1 (i.e., remain viable) for >2 minutes to be
qualified as resistant test spores. Discard carriers if not resistant
(i.e., inactivated) and repeat inoculation of carriers as previously
described.
12.11
Efficacy Test
a.	Prepare disinfectant samples according to MB-22. For a 60-
carrier test, place 10 mL product at dilution recommended for use
or under investigation into each of twelve 25 x 150 mm or 25 x 100
mm test tubes, or use appropriate number of tubes assuming 5 test
carriers per tube of test chemical.
b.	Place tubes in 201C water bath and let equilibrate to
temperature. Using a sterile hook (or forceps), transfer inoculated
carriers sequentially at 2 minute intervals in groups of 5 from
Petri dish to test tubes containing sporicidal agent. Use a certified
timer to monitor time.
i. Flame hook and allow cooling after each transfer. When
lowering carriers into test tube, neither carriers nor wire

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Page 12 of 19
hook may touch sides of tubes.
ii.	If interior sides are touched, note tube number - do not
count carrier set if any carrier from that group of 5 yields a
positive result. Testing another set of five carriers is
recommended.
iii.	Deposit carriers into test tubes within  5 s of the
prescribed drop time. Return tubes to water bath
immediately after adding carriers.
c.	After contact period has been achieved, transfer carriers in same
sequential timed fashion into primary subculture tubes containing
appropriate neutralizer (10 mL in 20x 150 mm test tubes).
i.	Remove the carriers one at a time from the test tube with
sterile hook, tap against interior side of tube to remove
excess sporicidal agent, and transfer into neutralizer tube
(primary tube).
ii.	All five carriers must be transferred during each 2-minute
interval. Flame hook between each carrier transfer. Move
remaining carriers into their corresponding neutralizer
tubes at appropriate time.
iii.	Carriers may touch interior sides of neutralizer tube during
transfer, but contact should be minimized.
d.	After each carrier is deposited, recap neutralizer tube and gently
shake to facilitate adequate mixing and efficient neutralization.
e.	Within one hour from when last carrier was deposited into
primaries, transfer carriers using sterile wire hook to second
subculture tube (secondary tube) containing 10 mL of appropriate
recovery medium, one carrier per tube.
i. Move carriers in order, but movements do not have to be
timed. Gently shake entire rack of secondary tubes after
all carriers have been transferred.
f.	Incubate primary (neutralizer) and secondary subculture tubes for
21 days at 361C. Report results as growth (+) or no growth (0).
i.	A positive result is one in which medium appears turbid.
A negative result is one in which medium appears clear.
Shake each tube prior to recording results to determine
presence or absence of growth/turbidity.
ii.	Primary and secondary subculture tubes for each carrier

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represent a "carrier set." A positive result in either
primary or secondary subculture tube is considered a
positive result for the carrier set.
g.	Media sterility controls and system controls (check for aseptic
technique during carrier transfer process) are recommended.
i.	For media controls, incubate 1-3 unopened subculture
medium tubes with the test sample tubes for 21 days at
361C.
ii.	For system controls, use sterile forceps or hooks to
transfer 3 sterile carriers into a tube of test chemical.
iii.	Transfer system control carriers to neutralizer medium as
follows: at start of sample test (prior to first tube), transfer
1 sterile carrier to tube of neutralizer medium. After one
half of test carriers have been transferred to neutralizer
tubes, transfer a second sterile carrier to tube of neutralizer
medium. After all test carriers (last tube) have been
transferred to neutralizer tubes, transfer third sterile carrier
to tube of neutralizer medium.
iv.	Transfer system control carriers to secondary subculture
medium as follows: immediately prior to initiating transfer
of test carriers into secondary subculture medium tubes,
transfer first system control sterile carrier from neutralizer
medium to tube of subculture medium. After one half of
test carriers have been transferred to secondary subculture
medium tubes, transfer second system control sterile
carrier to tube of subculture medium. After all test
carriers have been transferred to secondary subculture
medium tubes, transfer third system control sterile carrier
to tube of subculture medium.
v.	For each test, include a positive carrier control by placing
one inoculated carrier into tube of secondary subculture
medium. Incubate controls and test sample tubes together
for 21 days at 361C.
h.	Perform presumptive identification on a minimum of three
positive carrier sets per test, if available, using Gram stain and/or
plating on TSA. Additional confirmation may be performed
using VITEK or comparable method.
i. If there are fewer than three positive carrier sets, confirm
	growth from each positive carrier set. If both tubes are

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positive in carrier set, select only one tube for
confirmatory testing. For tests with 20 or more positive
carrier sets, confirm at least 20% by Gram stain. If Gram
stains are performed from growth taken directly from
positive tubes, the staining should be performed within 5-7
days of conducting the efficacy test. See section 12.2d.
for Gram stain reaction and colony characteristics.
12.12
Neutralization
Confirmation
Procedure
a.	Perform a neutralization confirmation test in advance or in
conjunction with efficacy testing. This assay is designed to
simulate the conditions (i.e., neutralizer, subculture medium,
contact time, diluent, concentration of test substance) of the
efficacy test and to demonstrate the recovery of a low level of
spores (e.g., 5-100). Diluted inoculum (e.g., spores of B. subtilis)
is added directly to the various sets of subculture media tubes (see
Table 1). This assay provides for a quantitative approach to
assessing the effectiveness of the neutralizer and any
bacteriostatic action resulting from the neutralizer itself or
neutralizer-disinfectant interactions.
b.	Produce a spore preparation according to the procedure for
amended nutrient agar. Harvest growth from plates (e.g., five
plates) per the method, except re-suspend pellet after final
centrifugation step in approximately 100 mL aqueous (40%)
ethanol.
i.	Determine spore count by serial dilution and plating on
TSA. Desirable target of the initial working suspension is
l.OxlO8 to l.OxlO9 CFU/mL. The suspension may require
adjustment to reach target titer.
ii.	Prepare serial ten-fold dilutions of the inoculum in sterile
water out to 10"7. Use 100 |iL aliquots of the 10"5, 10"6
and 10"7 dilutions to inoculate the neutralizer and
subculture media tubes - the target number of spores to be
delivered per tube in this assay is 5-100 per tube.
iii.	Determine spore titer by plating each of three dilutions in
duplicate on TSA agar. Incubate plates inverted for 24-48
h at 361C. Count colonies. Report plates with colony
counts over 300 as TNTC.
Note: A standardized spore preparation adjusted to deliver
5-100 spores/mL may be substituted for the three dilutions
of spore inoculum. In addition, spores sheared from

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inoculated carriers may be used as a working suspension.
c.	Use 5 sterile porcelain carriers (only 3 to be used in the assay).
Within 5 s, place a set of 5 carriers into a test tube (25 x 150 mm or
25x100 mm) containing test chemical; transfer carriers according
to section 12.1 lb. Allow carriers to remain in test chemical per
the specified contact time and temperature.
i.	After the contact time is complete, aseptically transfer
three of the five carriers individually into tubes containing
the neutralizer per section 12.11c. This set of tubes is the
Neutralizer/Primary Subculture treatment.
ii.	Following the transfer of the last carrier into neutralizer
tube, transfer each carrier, in sequence, into tube
containing secondary subculture medium. This portion of
assay is not timed, but should be made as soon as possible.
This set is the Secondary Subculture treatment.
d.	Following carrier transfer, inoculate each tube (Neutralizer/
Primary and Secondary Subculture treatment tubes) with 100 |iL
of each of three inoculum dilutions (10"5, 10"6 and 10"7).
e.	For controls, use three fresh unexposed tubes of neutralizer and
three tubes of the secondary subculture medium; also inoculate
each control tube with 100 |iL of each of three inoculum
dilutions. Include one uninoculated tube of neutralizer and
secondary subculture media to serve as sterility controls.
f.	See Table 1 for tube inoculation scheme.
g.	Incubate all tubes 5-7 days at 36  1C.
h.	Record results as growth (+) or no growth (0). The lack of
complete neutralization of the disinfectant or bacteriostatic
activity of the neutralizer itself may be masked when a high level
of inoculum (spores) is added to the subculture tubes.

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SOP No. MB-15-04
Date Revised 01-03-18
Page 16 of 19
Table 1. Neutralization confirmation procedure - inoculating
treatment and control tubes with diluted spore suspension*
Treatment
Dilution & Tube #
N c u l.ra 1 i zc r- P ri ma ry
Subculture Trcalmcnl
100 jiL of 10 Tube 1
100 nL of 10"6 Tube 2
100 nL of 10"7 Tube 3
Secondary Subculture
Treatment (with
Carrier)
100 nL of 10"5 Tube 1
100 nL of 10"6 Tube 2
100 nL of 10"7 Tube 3
N c u I ra 1 i /.c r- P ri ma ry
Inoculated Control
100 nL of 10"5 Tube 1
100 nL of 10"6 Tube 2
100 nL of 10"7 Tube 3
Secondary Subculture
Inoculated Control
100 nL of 10"5 Tube 1
100 nL of 10"6 Tube 2
100 nL of 10"7 Tube 3
*Use of 10-5 through 10"7 based on an approx. starting suspension of 108 spores/mL
i. Confirm a minimum of one positive per treatment and control (if
available) using Gram staining and colony morphology on TSA,
see section 12.2d. For each treatment and control group, conduct
confirmation testing on growth from tube with fewest spores
delivered.
j. Growth in the inoculated controls verifies the presence of the
spores, performance of the media, and provides a basis for
comparison of growth in the neutralizer and subculture treatment
tubes.
k. The occurrence of growth in the Neutralizer/Primary Subculture
and Secondary Subculture treatment tubes is used to assess the
effectiveness of the neutralizer. No growth or growth only in
tubes which received a high level of inoculum (e.g., the dilution
with plate counts which are too numerous to count) indicates poor
neutralization and/or presence of bacteriostatic properties of the
neutralizer or neutralizer-disinfectant interactions.
1. For a neutralizer to be deemed effective, growth must occur in the
Secondary Subculture treatment tubes which received lower
levels of inoculum (e.g., 5-100 CFU/mL).
m. Growth in the Secondary Subculture Inoculated Control verifies
the presence of the spores, performance of the media, and
provides a basis for comparison of growth in the neutralizer and
subculture treatment tubes. No growth or only growth in tubes

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SOP No. MB-15-04
Date Revised 01-03-18
Page 17 of 19

which received high levels of inoculum (e.g., a dilution with plate
counts which are too numerous to count) indicates poor media
performance.
n. Growth in the Neutralizer-Primary Inoculated Control should be
comparable to the Secondary Subculture Inoculated Control if the
neutralizer is the same as the secondary subculture media. There
may be cases when the neutralizer is significantly different from
the secondary subculture media. In these cases, growth may not
be comparable to the Secondary Subculture Inoculated Control.
o. The Neutralizer-Primary and Secondary Subculture Uninoculated
Control tubes are used to determine sterility and must show no
growth for the test to be valid.
13. Data Analysis/
Calculations
1.	Data will be recorded on data sheets (see section 14). Calculations will
be computed using a Microsoft Excel spreadsheet (see section 14).
Electronic copies of the spreadsheet as well as hard copies will be
retained.
2.	To calculate CFU/mL per carrier:
(avg. CFU for\{Yw) + (avg. CFU for\{Yx) + (avg. CFU for\{Yy)+(avg. CFU for\iYz)
10"" +KT +10~> +1(T
where 10"w, 10"x, 10"y, and 10"z are the dilutions plated. In the event
that one or more dilutions yield plate counts greater than 300, those
counts and their corresponding dilutions will not be used in the
calculations. If only one of two plates has counts yielding 300 CFU or
less, forgo its use in calculations in place of counts from a subsequent
dilution; if none exists, use only the countable plate for calculations
(e.g., do not average the TNTC (as 300) and the countable plate).
Note: Include plate counts of 0 in all calculations.
3.	To calculate CFU/carrier, multiply the CFU/mL per carrier by the
volume of media used to suspend carrier for sonication or vortexing.
Round numbers and use only two significant figures to calculate
averages and CFU/carrier.
4.	Calculate the average CFU/carrier for all carriers tested.
14. Forms and
Data Sheets
1.	Attachment 1: Culture Initiation and Stock Culture Generation Flow
Chart for B. subtilis
2.	Test Sheets. Test sheets are stored separately from the SOP under the
following file names:
Physical Screening of Carriers Record MB-03 Fl.docx

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SOP No. MB-15-04
Date Revised 01-03-18
Page 18 of 19

SAT: Organism Culture Tracking Form MB-15-04 Fl.docx
SAT: Test Microbe Confirmation Sheet , r . ,
i-x ^ x i\ MB-15-04 F2.docx
(Quality Control) -
SAT: Carrier Enumeration Form MB-15-04 F3.docx
SAT: Carrier Count Spreadsheet MB-15-04_F4.xlsx
SAT: HC1 Resistance Test Data Sheet MB-15-04_F5.docx
SAT: Information Sheet MB-15-04 F6.docx
SAT: Time Recording Sheet for Carrier A nA ,
   MB-15-04 F7.docx
Transfers -
SAT: Results Form (1-30) MB-15-04 F8.docx
SAT: Results Form (31-60) MB-15-04_F9.docx
SAT: Performance Controls Results Sheet MB-15-04 FlO.docx
SAT: Test Microbe Confirmation Sheet MB-15-04 Fll.docx
SAT: Neutralization Confirmation Assay , r . _ ,
T J MB-15-04 F12.docx
information Sheet -
SAT: Neutralization Confirmation Assay ,
 1jL _ J MB-15-04 F13.docx
Results Form -
SAT: Neutralization Confirmation Assay Time ,  , , ~^ , A ,
M. P  T e MB-15-04 F14.docx
Recording Sheet for Carrier Transfers -
SAT: Neutralization Confirmation Assay Serial , r . ^ , r ,
Dilution/Plating Tracking Form MB-15-04_F15 docx
SAT: Neutralization Confirmation Assay , r . ^, , ,
T , _  MB-15-04 F16.docx
Inoculum Enumeration Form -
15. References
1.	Official Methods of Analysis (Revised 2013) 21st ED., AO AC
INTERNATIONAL, Method 966.04, Gaithersburg, MD, Chapter 6
2.	Standard Methods for the Examination of Water and Wastewater. 23rd
Ed. American Public Health Association, 1015 15th Street, NW,
Washington, DC
3.	Tomasino, S.F. & Hamilton, M.A. (2006) JAOAC Int. 89, 1373-1397

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SOP No. MB-15-04
Date Revised 01-03-18
Page 19 of 19
Attachment 1: Culture Initiation and Stock Culture Generation Flow Chart for B. subtilis
/I
NB
 Rehydrate ampule.
I
Ampule
 Transfer entire rehydrated
pellet to TUBE A.
 Culture ID & Quality Control
TUBE A
(vre-incubation)
TSA or NA
Gram VITEK
Stain
Incubate
TUBE A
(post-incubation)
 Stock Cultures
II
a.	Obtain lyophilized cultures annually from ATCC. Using a tube containing 5-6 mL of NB,
aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for B. subtilis.
b.	Aseptically transfer the entire rehydrated pellet back into the original tube of nutrient
broth designated as "TUBE A." Mix well. Use suspension in TUBE A for CULTURE
ID & QUALITY CONTROL. Incubate TUBE A for B. subtilis for 24 h at 301C.
c.	Culture ID and Quality Control. Using a loopful of rehydrated suspension from TUBE A,
streak for isolation on duplicate plates (NA or TSA). Incubate plates at 301C for 24 h.
Record results on the Test Microbe Confirmation Sheet.
d.	Stock Culture Generation. Using the 242 h TUBE A broth culture: initiate stock cultures
by streak-inoculating six NA slants. Incubate the slants at 361C for 242 h. Record all
manipulations on the Organism Culture Tracking Form.

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