US Environmental Protection Agency Office of Pesticide Programs Office of Pesticide Programs Microbiology Laboratory Environmental Science Center, Ft. Meade, MD Standard Operating Procedure for AOAC Use Dilution Method for Testing Disinfectants SOP Number: MB-05-07 Date Revised: 08-18-09 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 1 of 33 EPA/OPP MICROBIOLOGY LABORATORY ESC, Ft. Meade, MD Standard Operating Procedure for AOAC Use Dilution Method for Testing Disinfectants SOP Number: MB-05-07 Date Revised: 08-18-09 Initiated By: Print Name: Date: / / Technical Review: QA Review: Approved By: Print Name: Technical Staff Print Name: QA Officer Print Name: Branch Chief Date: Date: / / Date: / / Date Issued: / / Controlled Copy No.: Withdrawn By: Date: ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 2 of 33 TABLE OF CONTENTS Contents Page Number 1.0 SCOPE AND APPLICATION 3 2.0 DEFINITIONS 3 3.0 HEALTH AND SAFETY 4 4.0 CAUTIONS 4 5.0 INTERFERENCES 5 6.0 PERSONNEL QUALIFICATIONS 6 7.0 SPECIAL APPARATUS AND MATERIALS 6 8.0 INSTRUMENT OR METHOD CALIBRATION 8 9.0 SAMPLE HANDLING AND STORAGE 8 10.0 PROCEDURE AND ANALYSIS 8 11.0 DATA ANALYSIS/CALCULATIONS 19 12.0 DATA MANAGEMENT/RECORDS MANAGEMENT 19 13.0 QUALITY CONTROL 19 14.0 NONCONFORMANCE AND CORRECTIVE ACTION 20 15.0 REFERENCES 20 16.0 FORMS AND DATA SHEETS 21 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page3 of 3 3 1.0 SCOPE AND APPLICATION: 1.1 This SOP describes the Use-dilution methodology used to determine the efficacy of disinfectants against three organisms, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella enter ica, on hard surfaces. The methodology is based on AOAC methods 955.15 (Testing Disinfectants against Staphylococcus aureus), 964.02 (Testing Disinfectants against Pseudomonas aeruginosa), and 955.14 (Testing Disinfectants against Salmonella cholerasuis) which have been officially modified (editorial modifications) - see references 15.1 and 15.2. 1.2 For product evaluations under the Antimicrobial Testing Program (ATP), a study protocol is developed which identifies the specific test conditions for a product sample such as contact time, dilutions, neutralizers, etc. 2.0 DEFINITIONS: 2.1 AOAC = AOAC INTERNATIONAL 2.2 ATCC = American Type Culture Collection 2.3 TSA = trypticase soy agar 2.4 TSB = trypticase soy broth 2.5 NB = nutrient broth 2.6 NA = nutrient agar 2.7 MSA = mannitol salt agar 2.8 CTA = cystine trypticase agar 2.9 OD = outside diameter 2.10 ID = inside diameter 2.11 CFU = colony forming unit 2.12 References to water mean reagent-grade water, except where otherwise specified. 2.13 Dilution blanks = tubes of phosphate buffered dilution water (PBDW) ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 4 of 33 3.0 HEALTH AND SAFETY: 3.1 All manipulations of the test organisms are required to be performed in accordance to biosafety practices stipulated in SOP MB-01, Lab Biosafety. 3.2 Disinfectants may contain a number of different active ingredients, such as heavy metals, aldehydes, peroxides, phenol, etc. Personal protective clothing or devices are recommended during the handling of these items for the purpose of activation, dilution, or efficacy testing. A chemical fume hood or other containment equipment is employed when performing tasks with concentrated products. The study analyst may wish to consult the Material Safety Data Sheet for the specific product/active ingredient to determine the best course of action. 4.0 CAUTIONS: 4.1 Use aseptic techniques to prevent contamination. 4.2 Media indicated in sections 10.1.1.2 and 10.1.1.3 for rehydrating lyophilized cultures are specified on the ATCC Product Information Sheet that accompanies each organism. Upon purchase of new organisms, verify that media requirements have not changed by checking the new ATCC Product Information Sheet. 4.3 The volume of dilution blanks, neutralizer tubes, and subculture tubes will be verified in advance and adjusted accordingly. 4.4 Strict adherence to the protocol is necessary for the validity of the test results. 4.5 Use inoculated carriers for determining carrier counts and performing efficacy testing as soon as possible after drying on the day of preparation to avoid a reduction in microbial titer. Overnight or long term storage of inoculated carriers is not allowed. 4.6 Complete dilution plating within 2 hours after the completion of carrier sonication or vortexing. If the serial dilutions are not made and plated immediately, the sonicated tubes are kept at 2-5°C until this step can be done. 4.7 For spread plating: ensure that the entire surface of the agar plate is dry before adding inoculum. If necessary, leave the agar plates uncovered in the biological safety cabinet (BSC) until the moisture has been completely absorbed into the medium. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 5 of 33 4.8 To ensure the stability of a diluted product, prepare the dilutions within three hours of the disinfectant treatment step unless specified otherwise. 4.9 Use appropriate aseptic techniques for all test procedures involving the manipulation of the test organisms and associated test components. 4.10 These microbiological methods are very technique-sensitive and technique- oriented; thus, exact adherence to the method, good laboratory practices, and quality control are required for proficiency and validity of the results. 4.11 Detergents used in washing glassware may leave residues which are bacteriostatic. Test for inhibitory residues on glassware periodically according to SOP QC-03, Glass Washing and Detergent Residues Test. 4.12 The primary subculture medium should serve as a suitable neutralizer for the test substance as well as an adequate growth medium which must be confirmed in advance or concurrently with the use dilution test. 4.12.1 See SOP MB-17, Neutralization Confirmation, for the procedure to determine suitability of the neutralizer (primary subculture tube) for the test substance. 4.12.2 See SOP QC-11, Performance Assessment and Sterility Verification, to determine whether or not the subculture medium is an adequate growth medium. 5.0 INTERFERENCES: 5.1 Contamination of stock cultures will negatively impact disinfectant efficacy testing. It is critical to maintain the highest standards of good laboratory practices and aseptic technique during all manipulations and handling of stock cultures. 5.2 Avoid touching the interior sides of the medication tube while the carriers are being lowered into the disinfectant agent and the hook is being removed. Contact with the interior sides of the medication tube may cause adhesion of bacterial cells which are not in contact with the disinfectant. This may result in re- inoculation of the carriers with organism as they are being removed from the medication tube. Re-inoculation of the carriers with organism can lead to false positive results. 5.3 Contaminated plates will interfere with the recording of carrier count results. Visually inspect all agar plates prior to use - discard any plates with evidence of ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 6 of 33 contamination. For contamination following the incubation phase, if atypical colonies or contamination are evident that interfere with the enumeration of the test organism, record as a contaminant(s). Data from other dilutions, if the CPUs result in a countable range, may be used to calculate the final CPU/carrier. 6.0 PERSONNEL QUALIFICATIONS: 6.1 Personnel are required to be knowledgeable of the procedures in this SOP. Documentation of training and familiarization with this SOP can be found in the training file for each employee. 6.2 The laboratory staff shall confirm (i.e., documentation in the training file of familiarization with the SOP) that they can properly perform the procedure before commencing work. If the standard AOAC method changes, confirmation shall be repeated. 7.0 SPECIAL APPARATUS AND MATERIALS: 7.1 Test organisms. Pseudomonas aeruginosa (ATCC No. 15442), Staphylococcus aureus (ATCC No. 6538) and Salmonella enterica (ATCC No. 10708) obtained directly from a reputable supplier (e.g., ATCC). 7.2 Culture media (e.g., nutrient agar). Note: Commercial dehydrated media made to conform to the recipes provided in AOAC Methods 955.15, 964.02, and 955.14 may be substituted. NOTE: The use of synthetic broth is stipulated in the official AOAC methods for test culture preparation; however, it is rarely used by the laboratory and only used upon request. 7.2.1 Nutrient broth: Boil 5 g beef extract (paste or powder), 5 g NaCl, and 10 g peptone (anatone) in 1 L H2O for 20 minutes and dilute to volume with H2O; adjust to pH 6.8 ± 0.1. Filter through paper (Whatman No. 4, or equivalent), place 10 mL portions in 20 x 150 mm test tubes, and steam sterilize 20 min at 121°C. Use this broth for daily transfers of test cultures. 7.3 Subculture media (e.g., letheen broth, fluid thioglycollate medium). Note: Commercial dehydrated media made to conform to the recipes provided in AOAC Methods 955.15, 964.02, and 955.14 may be substituted. 7.4 Trypticase soy agar (TSA). Plating medium for carrier enumeration. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 7 of 33 7.5 Sterile water. Use reagent-grade water 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 and SOP QC-01, Quality Assurance of Purified Water for details on reagent-grade water. 7.6 Carriers. Polished stainless steel cylinders, 8 ± 1 mm OD, 6 ± 1 mm ID, 10 ± 1 mm length; type 304 stainless steel, SS 18-8 (S & L Aerospace Metals, Maspeth, NY or Fisher Scientific catalog number 07-907-5Q as of December 2008). 7.7 Glassware. For disinfectant, use autoclavable 25 x 100 mm tubes (Bellco Glass Inc., Vineland, NJ). For cultures/subcultures, use autoclavable reusable or disposable 20 x 150 mm tubes. For stock cultures, use 16 x 100 mm screw cap tubes. Cap tubes with closures before sterilizing. Sterilize all glassware in hot air oven at 180°C or steam sterilize for a minimum of 20 minutes at 121°C with drying cycle. 7.8 Water bath/chiller unit. Constant temperature for test chemical, capable of maintaining 20 ± 1°C temperature or specified temperature for conducting the test. 7.9 Test tube racks. Any convenient style. 7.10 Transfer loops. Make 4 mm ID single loop at end of 50-75 mm (2-3 in.) Pt or Pt alloy wire No. 23 B&S gage or 4 mm loop fused on 75 mm (3 in.) shaft (available from Johnson Matthey, West Chester, PA 19380, USA). Fit other end in suitable holder. Bend loop at 30° angle with stem. Volumetric transfer devices may be used instead of transfer loops (e.g., micro volume pipet). 7.11 Wire Hook. For carrier transfer. Make 3 mm right angle bend at end of 50-75 mm nichrome wire No. 18 B&S gage. Place other end in suitable holder. 7.12 Timer. For managing timed activities, any certified timer that can display time in seconds. 7.13 Sonicator (ultrasonic cleaner). For carrier counts. 7.14 Gram stain kit. 7.15 VITEK 2 Compact. For the automated identification of microorganisms. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 8 of 33 7.16 VITEK 2 Compact Identification Cards. Gram negative (GN) and Gram positive (GP). 8.0 INSTRUMENT OR METHOD CALIBRATION: 8.1 Refer to the laboratory equipment calibration and maintenance SOPs (SOP EQ series) for details on method and frequency of calibration. 9.0 SAMPLE HANDLING AND STORAGE: 9.1 Follow appropriate chain-of-custody (COC) guidelines during testing as stipulated in SOP COC-01, Sample Log-in and Tracking. 9.2 Disinfectants are stored according to manufacturers' recommendations or at room temperature if the product label or testing parameters do not identify a storage temperature. Those disinfectants requiring activation or dilution prior to use will only be activated or diluted within three hours of testing unless test parameters specify otherwise. 10.0 PROCEDURE AND ANALYSIS: 10.1 Culture Initiation, Maintenance and Quality Control. 10.1.1 Culture Initiation. 10.1.1.1 Every 12 months (or sooner if the quality of the stock culture is compromised) initiate new stock cultures from lyophilized cultures of Pseudomonas aeruginosa (ATCC 15442), Staphylococcus aureus (ATCC 6538), and Salmonella enterica (ATCC 10708) from ATCC or other reputable supplier. 10.1.1.2 Open ampule of freeze dried organism as indicated by ATCC. 10.1.1.3 Using a tube containing 5-6 mL of TSB, aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for Staphylococcus aureus and Pseudomonas aeruginosa. Using a tube containing 5-6 mL of NB, aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for Salmonella enterica. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 9 of 33 10.1.1.4 Aseptically transfer the entire rehydrated pellet back into the original tube of broth (TSB for S. aureus and P. aeruginosa, NB for S. enterica) designated as "TUBE A," (see Attachment 2). Mix well. 10.1.1.5 Streak for isolation using a loopful of rehydrated suspension on duplicate plates - use TSA for S. aureus and P. aeruginosa, use NA for S. enterica. 10.1.1.5.1 In addition for S. aureus and P. aeruginosa, streak a loopful of rehydrated suspension onto both MSA and Cetrimide agar. Selective media is not used for S. enterica. 10.1.1.6 Incubate broth culture (TUBE A) and plate cultures at 36 ± 1°C for 24 ± 2 hours for S. aureus, P. aeruginosa, and S. enterica. 10.1.1.7 Record all manipulations on the Organism Culture Tracking Form (see 16.1). 10.1.2 Culture Identification and Quality Control. 10.1.2.1 Initial confirmation testing for quality control (QC) will be performed using the 24 ± 2 hour NA or TSA plates from step 10.1.1.5. 10.1.2.2 Following the incubation period (as stated in 10.1.1.6), record the colony morphology as observed on the NA or TSA plates and selective media plates (including the absence of growth) and stain reaction. See Attachment 1 for details on cell and colony morphology, colony characteristics on selective media, and stain reactions. 10.1.2.2.1 For*?, aureus, note the organi sm' s growth characteristics on MSA (colony size, color, texture, etc.) and Cetrimide (absence of growth). For P. aeruginosa, note the organism's growth characteristics on Cetrimide (colony size, color, texture, etc.) and MS A (absence of growth). Check for consistency with the genus and species of ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 10 of 33 the organism to be tested (round, shiny, and yellow for S. aureus on MSA, and flat, greenish-yellow, and opaque for P. aeruginosa on Cetrimide). 10.1.2.2.2 For each organism, 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 1000* magnification (oil immersion). 10.1.2.3 Perform VITEK™ analysis according to the manufacturers' instructions. 10.1.2.4 Record all confirmation results on the Test Microbe Confirmation Sheet (Quality Control) (see 16.2). 10.1.3 Generation of Stock Cultures. 10.1.3.1 Use the 24 ± 2 hour TUBE A (see Attachment 2) broth culture discussed in 10.1.1.4 to initiate stock cultures. 10.1.3.2 For S. aureus and S. enter ica, streak six nutrient agar slants each. For P. aeruginosa, stab six CTA tubes. 10.1.3.3 Incub ate the S. aureus and S. enterica si ants and P. aeruginosa stabs at 36 ± 1°C for 48 ± 2 hours. 10.1.3.4 Following incubation, store the cultures at 2-5°C for 30 ± 2 days. These cultures are identified as the "stock cultures." Begin stock culture transfers as outlined in section 10.1.5. Repeat the cycle for a maximum of one year. 10.1.3.5 From a set of six stock cultures, one is used every 30 ± 2 days for QC and to generate new stock cultures, four may be used per month (one/week) for generation of test cultures, (see SOP MB-05, Use Dilution Method; and SOP MB-06, Testing Spray Disinfectants) and one is a back-up tube. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 11 of 33 10.1.4 Monthly QC of Stock Cultures. 10.1.4.1 Conduct monthly QC of stock cultures. Use one refrigerated stock culture tube and streak a loopful on a plate of TS A. For S. aureus and P. aeruginosa, streak a loopful onto both selective media (MSA and Cetrimide), as noted in section 10.1.1.5. 10.1.4.2 Incubate the plates at 36 ± 1°C for 24 ± 2 hours (18-24 hours for use in the VITEK 2 Compact). Follow steps outlined in section 10.1.2.2 to confirm the identity of the organism. 10.1.5 Culture Maintenance. 10.1.5.1 Every 30 ± 2 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 10.1.4.1 to inoculate 6 new stock cultures tubes as outlined in 10.1.3.2. 10.1.5.2 Incubate the new stock cultures as indicated in 10.1.3.3. 10.1.5.3 Following the incubation period, store the stock cultures at 2-5°C for 30 ± 2 days. 10.2 Test Culture Preparation: 10.2.1 Initiate test culture by inoculating a 10 mL tube (20 x 150 mm) of nutrient broth from a stock slant or stab culture. Transfer one 4 mm ID loopful (or use a 10 jiL certified transfer loop) of inoculum from the stock culture into the broth. 10.2.2 Two sets of cultures (one set as a backup) of the same organism may be initiated in parallel from the same stock culture and subcultured; however, only one set of the final cultures is used for actual testing. 10.2.3 Make at least 3 consecutive 24 ± 2 hour transfers (use one 4 mm ID loopful, or a 10 jiL certified transfer loop, or a calibrated micro volume pipet to deliver 10 jiL) in 10 mL nutrient broth or synthetic broth incubated at 36 ± 1°C. For the purposes of conducting the Use- dilution method, the lab allows 5-7 daily transfers. If only one of the ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 12 of 33 consecutive 24 hour transfers has been missed, it is not necessary to repeat the previous 3-day sequence prior to the inoculation of the 48- 54 hour test culture. 10.2.4 For the final subculture step, inoculate for the test procedure, a sufficient number of 25 x 150 mm tubes (e.g., eight to ten) containing 20 mL nutrient broth; incubate 48-54 hours at 36 ± FC. 10.2.5 A minimum of five days are required to obtain the culture for inoculating carriers. For example, the culture sequence must begin on Thursday for testing to commence on the following Tuesday. 10.2.6 Record all culture transfers on the Organism Culture Tracking Form (see 16.1). 10.3 Carrier Inoculation for S. aureus, P. aeruginosa, and S. enterica: 10.3.1 A single test involves the evaluation of 60 inoculated carriers (one organism) against one product sample. In addition to the 60 carriers, 6 carriers are required to estimate carrier bacterial load and a minimum of 6 more are included as extras. Thus, a minimum of 72 inoculated carriers are required to perform a single test. 10.3.2 For S. aureus and S. enterica, using a Vortex-style mixer, mix 48-54 hour nutrient broth test cultures 3-4 seconds and let stand 10 minutes at room temperature before continuing. Remove the upper portion of each culture (e.g., upper 3A or approximately 15 mL), leaving behind any debris or clumps, and transfer to a sterile flask; pool cultures in the flask and swirl to mix. Aliquot 20 mL portions into sterile 25 x 150 mm test tubes. Prepare a minimum of four tubes. 10.3.3 For P. aemginosa, do not shake 48-54 hour test culture. The pellicle from the 48-54 hour cultures must be removed from the broth before mixing on a Vortex mixer by gently aspirating the broth away from the pellicle using a pipette. Any disruption of the pellicle resulting in dropping, or breaking up of the pellicle in culture before or during its removal renders that culture unusable in the use-dilution test. Visually inspect the culture for signs of pellicle. Discard tubes with fragments of pellicle. Using a vortex-style mixer, mix nutrient broth test cultures 3-4 seconds and let stand 10 minutes at room temperature before continuing. Remove the upper portion of each culture (e.g., upper 3A or approximately 15 mL), leaving behind any debris or clumps, and ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 13 of 33 transfer to a sterile flask; pool cultures in the flask and swirl to mix. Aliquot 20 mL portions into sterile 25 x 150 mm test tubes. Prepare a minimum of four tubes. 10.3.4 If organic burden is required for testing, the appropriate amount of organic burden is added to the pooled test culture prior to the inoculation of carriers. For a 5% v/v preparation, add 1 mL organic burden per 19 mL pooled test culture (e.g., add 5 mL organic burden to 95 mL pooled test culture). Swirl to mix. Aliquot 20 mL portions into sterile 25 x 150 mm test tubes. Prepare a minimum of four tubes. 10.3.5 Use only carriers that have been physically screened, have passed bioscreening, and have been appropriately prepared (see SOP MB-03, Screening Carriers). 10.3.6 Using a sterile hook, aseptically transfer 20 carriers prepared as described above into each of the tubes containing the test culture. Drain the water from the carriers by tapping them against the side of the tube before transferring. Multiple carriers may be transferred on a single wire hook. The test culture must completely cover the carriers. If a carrier is not covered, gently shake the tube, or reposition the carrier within the tube with a sterile wire hook. Be sure to inoculate a sufficient number of carriers for the test. (Alternately, the water may be siphoned off the carriers and the 20 mL test culture added directly to the carriers without transferring). 10.3.7 After 15 ± 2 min contact period, remove carriers using flamed nichrome wire hook; shake carrier vigorously against side of the tube to remove excess culture, and place on end in vertical position in sterile Petri dish matted with 2 layers of Whatman No. 2 (or equivalent) filter paper, making sure that carriers do not touch to prevent improper drying. Place no more than 12 carriers in a Petri dish. Carriers that touch or fall over cannot be used for testing and must be removed and recleaned. Once all of the carriers have been transferred, cover and place in incubator at 36 ± 1°C and let dry 40 ± 2 min. 10.3.8 Record the timed carrier inoculation activities on the Time Recording Sheet for Carrier Inoculation Steps (see 16.3). 10.4 Enumeration of bacterial inocula (carrier counts): ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 14 of 33 10.4.1 Synchronize the carrier count assay and efficacy testing. Assay carriers for carrier counts (sonicated) within 2 hours of drying. Record time of sonication on Serial Dilution/Plating Tracking Form (16.8). 10.4.2 One carrier is randomly extracted from each of 6 Petri dishes (12 carriers/dish). 10.4.3 Place each inoculated carrier into a tube containing 10 mL of letheen broth. 10.4.4 Place all tubes with carriers into an appropriately sized beaker and fill the beaker with tap water to the level of letheen broth in the tubes. 10.4.4.1 Hold the beaker in the sonicator so that the water level in the beaker is even with the water level fill line on the sonicator tank and fill the tank up with tap water to the water level fill line. Be sure that the water level in the tank never falls below one inch from the top of the tank. 10.4.4.2 Hold the beaker in the sonicator tank so that it is not touching the bottom and that all three liquid levels (inside the test tubes, inside the beaker and the sonicator tank) are the same. 10.4.4.3 Using an official timer, sonicate carriers for 60 ± 5 seconds. 10.4.5 Serial ten-fold dilutions of the sonicated carrier tubes are made in 9 mL dilution blanks (see 16.8). 10.4.6 If the serial dilutions are not made and plated immediately, the sonicated tubes are kept at 2-5°C until this step can be done. Complete the dilutions and plating within 2 hours after sonication. 10.4.7 Plate 0.1 mL aliquots of appropriate dilutions in duplicate on ISA using pour or surface spread plating. Briefly vortex (1-3 sec.) each serial dilution tube prior to plating. Note: Dilutions 10"2 through 10"4 should produce plates with CPU in the appropriate range. 10.4.8 If the spread plate method is used for bacterial enumeration, ISA plates are prepared in advance and are refrigerated until needed. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 15 of 33 10.4.8.1 Allow refrigerated plates to come to room temperature prior to use. To spread dilutions evenly over the dry surface of the agar, use a glass, autoclavable or disposable spreading rod and plate spinner until the surface is completely dry. 10.4.9 If the pour plate method is used for bacterial enumeration, the ISA is prepared and tempered after autoclaving (approx. 1 hr) to 45-50°C in a water bath prior to use. Tempered agar is added to each plate after the addition of the appropriate dilution and swirled to uniformly disperse the inoculum. 10.4.10 Incubate plates at 36 ± 1°C for 24-48 hrs. 10.4.11 Colonies may be counted by hand or with the aid of a plate counter. Plates that have colony counts over 300 will be reported as TNTC. Record counts on the Carrier Count Data Sheet (see 16.9). See section 11 for data analysis. 10.5 Disinfectant Sample Preparation. 10.5.1 Prepare disinfectant sample per SOP MB-22. 10.5.2 Equilibrate the water bath and allow it to come to 20 ± 1°C or the temperature specified (±1°C). Prepare the disinfectant dilutions within 3 hours of performing the assay unless test parameters specify otherwise. Ready-to-use products are tested as received; no dilution is required. 10.5.3 Dispense 10 mL aliquots of the diluted disinfectant or ready-to-use product into 25 x 100 mm test tubes, one tube per carrier. Place tubes in the equilibrated water bath for approximately 10 minutes to allow test solution to come to specified temperature. Record the temperature of the water bath and recirculating chiller before and after testing on the AOAC Use-Dilution Test Information Sheet (see 16.5). 10.6 Test Procedure: 10.6.1 After the required drying time, the carriers are sequentially transferred from the Petri dish to the test tubes containing the disinfectant at 30 second intervals or at the pre-determined drop interval for products ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 16 of 33 with contact times less than 10 minutes. When lowering the carriers into the disinfectant tubes, neither the carrier itself nor the tip of the wire hook can touch the interior sides of the tube. (Individual manipulation of the carriers is required.) Use a certified timer to time the transfers. Modify intervals to accommodate exposure times other than 10 min. Note: Above step is one of the most critical, technique-sensitive areas of method. False positives can result from transfer of live organisms to sides of tubes due to contact or aerosol formation. If the side is touched, mark or note the tube; the tube is not counted if it yields a positive result. 10.6.2 One carrier is added per tube. Immediately after placing carrier in the test tube, briefly swirl tube before placing it back in the bath. For a contact time often minutes, the carrier must be deposited in the tube within ± 5 seconds of the prescribed drop time. For contact times of less than ten minutes, the analyst will work with the team leader and senior scientist to identify an appropriate (i.e., shorter) drop interval. Using alternating hooks, flame-sterilize the hook and allow it to cool after each carrier transfer. 10.6.3 After the carriers have been deposited into the disinfectant, and the exposure time is complete, the carriers are then transferred in a sequentially timed fashion into the primary subculture tubes containing the appropriate neutralizer (10 mL in 20 x 150 mm tubes). As with the transfers to the disinfectant tubes, transfers into subculture tubes are to be done within ± 5 seconds (see section 10.6.2) of the actual transfer. The carrier is removed from the disinfectant tube with a sterile hook, tapped against the interior sides of the tube to remove the excess disinfectant and transferred into the subculture tube. Avoid contact of the carrier to the interior sides of the subculture tube during transfer. Flame-sterilize the hook after each carrier transfer. 10.6.4 After the carrier is deposited in the subculture tube, recap the subculture tube and shake thoroughly. Place subculture tubes into 36 ± 1°C incubator. 10.6.5 After a minimum of 30 ± 5 minutes from the end of the transfer into primary subculture tubes, remove tubes from the incubator and transfer carrier from the primary tube to a secondary tube of sterile medium. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 17 of 33 10.6.5.1 Transfer the carriers using a sterile wire hook to a second subculture tube containing 10 mL of the appropriate subculture medium which may contain a suitable neutralizer. Move the carriers in order but the movements do not have to be timed. Thoroughly shake the subculture tubes after all of the carriers have been transferred. 10.6.6 Check all test tube racks for proper transfer of carriers (i.e., carriers are in the correct tubes, no tubes have two carriers) before completing the testing day. 10.6.7 Incubate both the primary and secondary subculture tubes 48 ± 2 hours at36± 1°C. 10.6.8 Record timed events on the Time Recording Sheet for Carrier Transfer Form (see 16.4). 10.7 Viability controls. On testing day, place a dried inoculated carrier into a tube containing 10 mL primary subculture medium and a second dried, inoculated carrier into a tube containing 10 mL secondary subculture medium. Incubate tubes for 48 ± 2 hours at 36 ± 1°C. Positive growth in both tubes validates the test system. Failure to have growth in either of the tubes invalidates the test. 10.8 Results: 10.8.1 Report results as + (growth), or 0 (no growth) as determined by presence or absence of turbidity, on the AOAC Use-dilution Results Sheet (see 16.6). A positive result is one in which the broth culture appears turbid. A negative result is one in which the broth appears clear. Each tube is shaken prior to recording results to determine the presence or absence of turbidity. The primary and secondary subculture tubes for each carrier represent a "carrier set." 10.8.2 A positive result in either the primary or secondary subculture tube is considered a positive result for a carrier set. 10.8.3 In the event that there are positive carriers present in the test, the test may be repeated in order to confirm the outcome. 10.8.4 Once the results are recorded, it is important that the carriers be reprocessed before use in another study. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 18 of 33 10.9 Confirmation Steps: 10.9.1 Confirm a minimum of three positive carrier sets per test, if available, using Gram staining, solid media, and VITEK™ analysis. If there are less than three positive carrier sets, then each carrier set will be confirmed. If both tubes are positive in a carrier set, only one tube is selected for confirmatory testing (preferably the secondary subculture tube with carrier). 10.9.2 For a test with greater than 20 positive carrier sets, confirm at least 20% by Gram stain, and a minimum of 4 positive carrier sets by Gram staining, solid media, and VITEK™ analysis (see SOP QC-22, VITEK 2 Compact) to ensure the identity of the organism. Again, if both tubes are positive in a carrier set, only one tube (preferably the secondary subculture tube with carrier) is selected for confirmatory testing. 10.9.3 See Attachment 1 for Gram stain reactions, cell morphology, and colony characteristics on solid media. 10.9.4 Gram stains are performed on smears taken from the positive culture tubes. For the additional confirmatory tests, a loopful of broth from each selected culture tube is streaked on both TSA and selective media appropriate for the test organism and incubated for 18-24 hours at 36 ± 1°C. The selective agar is checked for the correct reaction and the culture on the TSA plate is used for preparing the inoculum for the VITEK™ analysis. 10.9.5 Perform the VITEK™ analysis according to the manufacturer's instructions. 10.9.6 If confirmatory testing determines that the identity of the organism was not the test organism, the positive entry (+) on the results sheet must be annotated to indicate a contaminant was present. 10.10 Re-use of Stainless Steel Carriers: After use, all carriers are autoclaved. Carriers for which test results were negative may be reused after cleaning. Carriers that are positive are re-cleaned and screened biologically (see SOP MB-03, Screening Carriers) before re-use. These carriers may be reused if the biological screening test results in no growth. The extra carriers that were inoculated but not used are autoclaved, re-cleaned, and used again. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 19 of 33 11.0 DATA ANALYSIS/CALCULATIONS: 11.1 Calculations will be computed using a Microsoft Excel spreadsheet (see 16.10). Electronic copies of the spreadsheet as well as hard copies will be retained. 11.2 To calculate CFU/mL per carrier when 3 serial dilutions are plated, use the following calculation scheme where 10"x, 10"y, and 10"z are the dilutions plated: (avg CPU forWx) + (avg CPU forWy)+(avg CPU/orl(T) KT + KF+KT 11.3 Counts from 0 through 300 and their associated dilutions will be included in the calculations. 11.3.1 Sample calculation: For average CFU of 115 at the 10"3 dilution, 15 at the 10"4 dilution, and 0 at the 10"5 dilution, the CFU/mL per carrier would be 1.2 x 105 CFU/mL per carrier. 11.4 To calculate CFU/carrier, multiply the CFU/mL per carrier by the volume of media used to suspend carrier for sonication (10 mL) and round numbers to 2 significant figures for reporting the final data. 11.4.1 Sample calculation: 1.2 x 105 CFU/mL per carrier x 10 mL = 1.2 x 106 CFU/carrier. 11.5 Calculate the log density for each carrier by taking the logio of the density (per carrier). 11.6 Calculate the mean log density across carriers for each test. Let M denote the mean log density. The 10M is the geometric mean density for the test. 12.0 DATA MANAGEMENT/RECORDS MANAGEMENT: 12.1 Data will be recorded promptly, legibly, and in indelible ink on the appropriate forms (see 16.0). Completed forms are archived in notebooks kept in secured file cabinets in room D217. Only authorized personnel have access to the secured files. Archived data is subject to OPP's official retention schedule contained in SOP ADM-03, Records and Archives. 13.0 QUALITY CONTROL: 13.1 For quality control purposes, the required information is documented on the ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 20 of 3 3 appropriate form(s) (see 16.0). 14.0 NONCONFORMANCE AND CORRECTIVE ACTION: 14.1 If the results of quality control do not verify the identity of the test organism, then the culture is discarded and a new culture is initiated. New stock cultures are established as outlined in section 10.0 of this SOP. 14.2 Strict adherence to the protocol is necessary for the validity of the test results. Any deviation from the standard protocols must be recorded on the form and an explanation for the deviation given. 14.3 The mean log density for carriers inoculated with S. aureus and P. aeruginosa must be at least 6.0 (corresponding to a geometric mean density of 1.0 x 106); a mean log density below 6.0 invalidates the test. 14.3.1 Values below 1.0 x 106 may be indicative of a dilution error, poor media quality, interference by environmental parameters (e.g., carrier drying and culture incubation conditions), contamination, or lack of adherence to the method. 14.3.2 The prescribed minimum will also account for the addition of 5% organic soil to the inoculum. 14.4 Carrier counts for S. enterica are expected to be comparable to counts for S. aureus and P. aeruginosa. 14.5 A product test exhibiting passing results (i.e., 0 or 1 positive carrier sets for the test microbe) will be repeated if contamination is present for more than one carrier set. For a failing product test (i.e., 2 or more positive carrier sets for the test microbe), no contamination is permissible in any of the carrier sets and the test is deemed invalid and must be repeated. 15.0 REFERENCES: 15.1 Official Methods of Analysis. 2009. 18th Ed., AOAC INTERNATIONAL, Gaithersburg, MD, (Methods 955.15 and 964.02). 15.2 Official Methods of Analysis. 2006. 18th Ed., AO AC INTERNATIONAL, Gaithersburg, MD, (Method 955.14). 15.3 Holt, J., Krieg, N., Sneath, P., Staley, J. and Williams, S. eds. 1994. Bergey's ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 21 of 33 Manual of Determinative Bacteriology, 9th Edition. Williams & Wilkins, Baltimore, MD. 15.4 Krieg, Noel R. and Holt, John G. 1984. Sergey's Manual of Systematic Bacteriology Volume 1. Williams & Wilkins, Baltimore, MD. 15.5 Sneath, P., Mair, N., Sharpe, M.E., and Holt, J. eds. 1986. Sergey's Manual of Systematic Bacteriology Volume 2. Williams & Wilkins, Baltimore, MD. 16.0 FORMS AND DATA SHEETS: 16.1 Organism Culture Tracking Form 16.2 Test Microbe Confirmation Sheet (Quality Control) 16.3 AOAC Use-Dilution Test: Time Recording Sheet for Carrier Inoculation Steps 16.4 AOAC Use-Dilution Test: Time Recording Sheet for Carrier Transfers 16.5 AOAC Use-Dilution Test Information Sheet 16.6 AOAC Use-Dilution Test Results Sheet 16.7 Test Microbe Confirmation Sheet 16.8 AOAC Use-Dilution Test Serial Dilution/Plating Tracking Form 16.9 AOAC Use-Dilution Test Carrier Count Data Sheet 16.10 Sample Carrier Count Spreadsheet MS Excel spreadsheet: Carrier Count Template_UDT_v2 Attachment 1: Typical Growth Characteristics of strains of P. aeruginosa, S. aureus, and S. enterica Attachment 2: Culture Initiation Flow Chart for S. aureus, P. aeruginosa, and S. enterica ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 22 of 3 3 16.1 ORGANISM CULTURE TRACKING FORM OPP Microbiology Laboratory Organism: Source and Strain no.: MRME Number: Supply Control Number: Lot Number: Date Lime Init. Subculture Source Lransfer* Monthly Daily Media Inoculated (and # inoc.) Media Prep No. Incubation Conditions Comments "Monthly" indicates the monthly transfers for culture and "Daily" indicates a 24/48 hr serial transfer (added to control number) NR = None Required, TC = Test Culture, applied after daily transfer number TSB = Tryptic soy broth, NB = nutrient broth ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 23 of 3 3 16.2 TEST MICROBE CONFIRMATION SHEET (Quality Control) OPP Microbiology Laboratory Organism: Source and Strain no.: MRME*** Number: Notes: Source: Tube/Plate ID Date/ Initials Staining Results* Media Information Name Prep. No. Inc. Time/ Temp. Results Date/ Initials Colony Characteristics Vitek#** Record Gram stain results: GPC = Gram Positive Cocci; GNR = Gram Negative Rods Vitek tracking number Use MRME notation for all organisms (refer to MB-02). ISA = trypticase soy agar, MSA = mannitol salt agar, NA = nutrient agar ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 24 of 3 3 16.3 AOAC Use-Dilution Test: Time Recording Sheet for Carrier Inoculation Steps OPP Microbiology Laboratory TEST INFORMATION/Confirmed by: Test Date Product Reg. No. Product Name Sample No. Organism Initials/Date Test ID Inoculum Settle Time* Start Time / / / End Time / / / Carrier Seeding Time* Start Time / / / End Time / / / Carrier Dry Time* Start Time / / / End Time / / / * Recorded from laboratory clock/and timer. Comments: ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 25 of 33 16.4 AOAC Use-Dilution Test: Time Recording Sheet for Carrier Transfers OPP Microbiology Laboratory TEST INFORMATION/Confirmed by: Test Date Product Reg. No. Product Name Sample No. Organism Initials/Date Set Drop Interval Carrier Drop Start Time (into the disinfectant) Clock Timer Carrier Drop End Time (into the primary subculture/neutralizer media) Clock Timer Carrier Transfer (into secondary subculture) Start Time1 Comments: 1 Carrier transfer into secondary subculture (time elapsed after last carrier dropped in primary); taken from clock ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 26 of 3 3 16.5 AOAC Use-Dilution Test Information Sheet OPP Microbiology Laboratory TEST INFORMATION/Confirmed by: EPA Reg. No. Name Sample No. Lot No. Expiration Date SOP Test Date Comments: TEST PARAMETERS/Confirmed by: H2O Hardness (CaCO3) ppm Specified Specified Specified Titrated (Buret)/Date/Init. HACH/Date/Init. As Prepared/Date/Init. As Prepared/Date/Init. Specified Specified Specified Chiller Unit Display Before: After: Test Tube Water Bath Before: After: As Tested Specified TEST MICROBE INFORMATION/Confirmed by: Test Microbe Org. Control No Avg. CPU/Carrier 48-54 Hour Culture Date/Time Initiated Harvested REAGENT/MEDIA INFORMATION/Confirmed by: Reagent/Media Prep. No. Reagent/Media Prep. No. Neutralizer volume verified: n Yes n No Subculture volume verified: n Yes n No ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 27 of 3 3 16.6 AOAC Use-Dilution Test Results Sheet OPP Microbiology Laboratory PRODUCT INFORMATION/Confirmed by: EPA Reg. No. Name Sample No. Test Date Test Organism CARRIER INFORMATION (to be completed by Analyst) Carrier Drop Time Interval Carrier Set Analyst TEST RESULTS Date Recorded/Initials Primary Subculture / Secondary Subculture (carrier) 1 / 11 / 21 / 31 / 41 / 51 / 2 / 12 / 22 / 32 / 42 / 52 / 3 / 13 / 23 / 33 / 43 / 53 / Results Summary 4 / 14 / 24 / 34 / 44 / 54 / 5 / 15 / 25 / 35 / 45 / 55 / 6 / 16 / 26 / 36 / 46 / 56 / 7 / 17 / 27 / 37 / 47 / 57 / 8 / 18 / 28 / 38 / 48 / 58 / Number of Carrier Sets with Growth Number of Carrier Sets without Growth Viability Controls (Record growth as "+", no growth as "0 "): Primary Sec ;ondary Ac 9 / 19 / 29 / 39 / 49 / 59 / 10 / 20 / 30 / 40 / 50 / 60 / ceptable: Yes No Modifications/Comments : ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 28 of 33 16.7 Test Microbe Confirmation Sheet OPP Microbiology Laboratory TEST INFORMATION/Confirmed by: EPA Reg. No. Name Sample No. Test Date Test Organism Comments: Source: Tube/Plate ID Date/ Initials Stain Results1 Media Information Type Prep. No. Inc. Time/ Temp. Results Date/ Initials Colony Characteristics Vitek ID (if applicable) Record Gram Stain results as GPC=Gram positive cocci or GNR=Gram negative rods. ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 29 of 3 3 16.8 AOAC Use-Dilution Test Serial Dilution/Plating Tracking Form OPP Microbiology Laboratory TEST INFORMS EPA Reg. No. Name Sample No. Test Date Organism SOP iTION/Confirmed bv: DILUTION/PLATING SCHEME/Confirmed t Sonication Start Time (clock): ^^^^^ Starting volume of diluent Volume added to serial dilution tube (1 mL) Volume plated (0.1 mL) Final dilution (used for calculations)1 Number of plates per dilution Plating medium Number of carriers evaluated Comments: N/A >v: ~ Dilution Tube 10°* 10"1 10"2 10"3 10"4 N/A = not applicable Dilution blank volume verified: n Yes n No Subculture medium volume verified: n Yes n No * Volume of medium in the tube with the carrier will be accounted for in the CPU/carrier calculation. Adjusted for volume plated. REAGENT/MEDIA INFORMATION/Confirmed by: Reagent/Media Prep. No. Reagent/Media Prep. No. 16.9 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 30 of 33 AOAC Use-Dilution Test Carrier Count Data Sheet OPP Microbiology Laboratory TEST INFOR1V EPA Reg. No. Name Sample No. Test Date Organism SOP Test Type lATION/Confirmed bv: RESULTS Date/Initials Plating method Volume of media in initial tube receiving carrier Carrier Noxx/^ .s^ Dilution 1 2 3 4 5 6 / / / / / / CPU per Dilution Plate (2) / / / / / / / / / / / / Comments: N/A = not applicable 16.10 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 31 of 33 Sample Carrier Count Spreadsheet (v2) OPP Microbiology Laboratory Carrier Count Spreadsheet OPP Microbiology Lab oratoiy TEST INFORMATION/Confinnedby: EPA Reg. No. Name Sample No.(s) Test Date Organism SOP Test Type Volume of media m tube with earner (mL): ^v^Canier No. Dilution ^^x^ 1 2 3 4 5 6 CFU per Pkte CFU/mL per carrier Mean per carrier for all carriers tested: CFU/caniar LD/camer Comments: LD = log density Attachment 1 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 32 of 33 Typical Growth Characteristics of strains of P. aeruginosa, S. aureus, and S. enterica (see ref. 15.2, 15.3 and 15.4). Gram stain reaction P. aeruginosa* (-) S. aureus* (+) S. enterica* (-) Typical Growth Characteristics on Solid Media Mannitol Salt Cetrimide ISA No Growth circular, small, initially opaque, turning fluorescent green over time; agar fluorescent yellowish green flat, opaque to off-white, round spreading (1) circular, small, yellow colonies, agar turning fluorescent yellow No Growth small, circular, yellow or white, glistening N/A N/A entire, glistening, circular, smooth, translucent, low convex Typical Microscopic Characteristics Cell dimensions Cell appearance 0.5-1.0 um in diameter by 1.5- 5.0 um in length* straight or slightly curved rods, single polar flagella, rods formed in chains 0.5-1.5 um in diameter* spherical, occurring singly, in pairs and tetrads, sometimes forming irregular clusters 0.7-1 .5 um in diameter by 2.0- 5.0 um in length* straight rods, peritrichous flagella *After 24±2 hours (1) Plates from dilution plating. The agar plate may show three different colony types: a) circular, undulate edge, convex, rough and opaque; b) circular, entire edge, convex, smooth and translucent; c) irregular, undulate edge, convex, rough, spreading, and translucent. Colony c) reverts to colony type a) after 24 hour incubation. Pyocyanin is not produced. Attachment 2 ------- SOP No. MB-05-07 Date Revised 08-18-09 Page 33 of 33 Culture Initiation and Stock Culture Generation Flow Chart for S. aureus, P. aeruginosa, and S. enterica (D Rehydrate ampule. ® Transfer entire rehydrated pellet to TUBE A. I TSB or NB Ampule I ® Culture ID & Quality Control MSA & Cetrimide TSA TUBE A (pre-incubation) Gram VITEK Stain TUBE A (post-incubation) CULTURE INITIATION ® Obtain lyophilized cultures annually from ATCC. Using a tube containing 5-6 mL of TSB aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for S. aureus and P. aemginosa. Using a tube containing 5-6 mL of NB, aseptically withdraw 0.5 to 1.0 mL and rehydrate the pellet for S. enterica. ® Aseptically transfer the entire rehydrated pellet back into the original tube of broth (TSB for S. aureus and P. aemginosa, NB for S. enterica) designated as "TUBE A." Mix well. Use suspension in TUBE A for CULTURE ID & QUALITY CONTROL. Incubate TUBE A for & aureus, P. aemginosa, and S. enterica for 24 hours at 36 ± 1°C. CULTURE ID & QUALITY CONTROL ® Using a loopful of rehydrated suspension from TUBE A, streak for isolation on duplicate plates (TSA for S. aureus, P. aemginosa, and NA for S. enterica). In addition for S. aureus and P. aemginosa, streak a loopful of rehydrated suspension onto both MSA and Cetrimide agar. Selective media is not used for S. enterica. Incubate plates for S. aureus, P. aemginosa, and S. enterica for 24 hours at 36 ± 1°C. Record results on the Test Microbe Confirmation Sheet. STOCK CULTURE GENERATION © Using the 24 ± 2 hour TUBE A broth culture: initiate stock cultures. For S. aureus and S. enterica, streak- inoculate six NA slants. For P. aemginosa, stab-inoculate six CTA tubes. Incubate the S. aureus and S. enterica slants and P. aemginosa stabs at 36 ± 1°C for 48 ± 2 hours. Record all manipulations on the Organism Culture Tracking Form. ------- |