TITLE: Standard operating procedure for dead-end ultrafiltration water sampling in the field for bacterial pathogens using REXEED 25S replacement filters
AUTHORS: Julie Ann Kase

[DESCRIPTION]
This protocol details the standard operating procedure for dead-end ultrafiltration water sampling in the field for bacterial pathogens using REXEED 25S replacement filters.

[GUIDELINES]
Appendix A 

Pictures of Hose Clamp, Blood and Dialysate Port Cap and DIN Adapters


 


Appendix B

Fig 8. Ultrafilters with designated ports and outlets.

 

Appendix C

List of supplies in ultrafiltration kit

Each kit contains: 2 bench protectors; one clean/unused 50 mL conical tube with one DIN adapter, 2 rubber storage caps and 2 blood port caps; one SNP-04 hose clamp to secure the MPC-855 DIN adapter or SNP-8 hose clamp/zip tie for MPC-855NS.375 DIN adapter; 2 SNP-12 Plastic hose clamp or zip tie to secure the two rubber storage caps; 2 zip ties to secure the tubing at the telescoping pole; one roll of tubing; one ultrafilter; and one 2.5-gallon sealable bag (for storage of the ultrafilter after sample collection).

Fig 9. Original caps removed and replaced with storage caps.

 

Appendix D

Illustrations of tubing connection to different ultrafilter brands

Fig 10. Ultrafilters tubing connection configuration.

1. Tubing connected onto DIN adapter and secured with plastic hose clamp SNP-8 and needle nose pliers.
2. Dialysate port storage cap secured with a plastic hose clamp SNP-12 and needle nose pliers.
3. Tubing connected to the dialysate fluid outlet and effluent directed away from water sample intake. No clamps are needed. 
4. Blood inlet port secured with the storage blood port caps. 

 

Appendix E. 

Ultrafilter priming and flow meter configuration

Fig 11. Set up for ultrafilter priming.

 

Fig 12. Appropriate configuration of effluent tubing and water flow meter

 

Appendix F

Water sample collection 

Fig 13. Example of dead-end ultrafiltration set up for field sampling.

 

Fig 14. Dead end ultrafiltration field arrangement diagram.

 

Appendix G

Backflush procedure.

Fig 15. Ultrafilter upon receipt.


 

Fig. 16. The ultrafilter is secured vertically using the stand clamps with the sample inlet port pointing downwards, and the effluent side port oriented towards the pump.

 

Fig. 17. During the ultrafilter set up, the sample inlet port points downwards, and the effluent side port faces the pump. The sample receiving bottle is placed under blood return port without touching the bottle surfaces. The tubing is attached to the dialysate outlet port by pushing onto the port and is secured with a SNP-12 clamp or a zip tie.

 











[STEPS]
SECTION: SCOPE AND APPLICABILITY
1. This standard operating procedure (SOP) will be used to filter up to 100 L of water using an ultrafilter at a field sampling site to collect bacteria for pathogen analyses in the laboratory. 
SECTION: SUMMARY OF METHOD
3. Using a field-portable peristaltic pump, volumes up to 100 L of water are passed continuously through a Clearum H22, Xevonta Hi23, Elisio 25H or equivalent dialysis ultrafilter having a pore size small enough to capture any bacteria and other microorganisms present in the site water. 
SECTION: SCOPE AND APPLICABILITY
2. Included are instructions on how to properly backflush the ultrafilters in a laboratory setting to retrieve any bacteria captured.
SECTION: SUMMARY OF METHOD
4. These ultrafilters are verified for their equivalent performance compared to REXEED 25S ultrafilter, which is no longer being distributed for sale in the United States. 
SECTION: SUMMARY OF METHOD
5. Parameters such as time, date, and Sample ID are recorded on the filter using permanent marker. 
SECTION: SUMMARY OF METHOD
6. The ultrafilter is kept at 4 °C (refrigerated or on ice packs) after sample collection. 
SECTION: SUMMARY OF METHOD
7. Following sampling, a backflush procedure is performed in the laboratory with a 500 mL solution of 0.5% Tween 80, 0.01% sodium polyphosphate, and 0.001% Antifoam Emulsion.
SECTION: HEALTH AND SAFETY WARNINGS
8. Disposable gloves are recommended to be worn during all steps of this sample collection procedure to prevent possible exposure to waterborne pathogens and contamination of the filtration components. 
SECTION: HEALTH AND SAFETY WARNINGS
9. Gloves are mandatory when removing caps from the ultrafilter, attaching tubing to the filter ports or otherwise touching exposed parts of the ultrafilter. 
SECTION: HEALTH AND SAFETY WARNINGS
10. For the backflush procedure, disposable gloves should be worn and changed appropriately during all steps to prevent possible exposure to waterborne pathogens and to prevent cross-contamination of samples. 
SECTION: HEALTH AND SAFETY WARNINGS
11. Since the filtration system is under pressure, a face shield is recommended to protect eyes and mouth. 
SECTION: HEALTH AND SAFETY WARNINGS
12. Please consult safety protocols developed for your specific laboratory for exact requirements in terms of precautions and personal protection equipment (PPE).
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13. Please see Figs. 1-7 in Appendix A and Fig. 8 in Appendix B for ultrafilter components and port locations for the various filters.


 


 

1. Blood outlet port
2. Dialysate inlet port
3. Dialysate outlet port
4. Blood inlet port

 

 

 

 

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.1. Put on gloves.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.2. Place clean bench protector(s) on the area(s) where sampling will be performed.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.3. Remove ultrafilter from packaging.

 

 

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.4. Write the date, time of collection, your initials, and sample number and place ultrafilter on the bench protector.

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.5. Disinfect scissors with 70% ethanol and allow to dry for 30 s on a paper towel. Then, after locating one end of the tubing inside the bag, cut open the bag and cut approximately 2 ft of tubing for use in priming. Place it on the bench protector. All remaining tubing should stay in packaging to the greatest extent possible.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.6. Remove the ultrafilter blood outlet port cap, screw in the DIN adapter and connect one end of priming tubing.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.7. Secure the DIN adapter with the SNP-8 plastic hose clamps when DIN adapter MPC-855NS.375 is used or SNP-04 plastic hose clamp if small DIN adapter MPC-855 is used. 

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.8. Place the other tubing end into the bottle of priming liquid and align the center portion of the tubing into the peristaltic water pump head. See Fig. 11, Appendix E. Make sure the pump flow direction “Forward/Reverse” setting is from liquid to ultrafilter, remove the blood inlet port cap and turn on the peristaltic pump at low speed (200-300 rpm) until the liquid emerges from the blood inlet port. 

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.9. Secure the blood inlet port with the storage blood port cap, then carefully detach and discard the tubing from the DIN adapter, positioning the ultrafilter such that the DIN adapter won’t become contaminated while sitting on the bench paper.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.10. Using a permanent marker, indicate by writing an arrow on the filter exterior, the direction of water filtration as confirmation. Water should be entering through the blood outlet port. See Appendix D Fig. 10. Priming step is complete.
 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.11. Attach a new tubing end to a sampling telescoping pole with a zip tie. Leave around three inches off the telescoping pole and approach your water source leaving the remainder of the tubing in the packaging. Place influent tubing into the body of water and ensure the end of the tubing will stay below the surface of the water and away from plant material or other large debris. Be cautious not to disturb the area (especially any sediment) near the filtration site.

If debris or material that may cause premature filter clogging is present, a sterilized mosquito/insect mesh can be attached to the tubbing end with a rubber band or zip tie to avoid clogging the tubing and ultrafilter with debris.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.12. Using disinfected scissors, cut the tubing remaining in the packaging to the desired length.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.13. Insert the tubing into the DIN adapter and secure it with SNP-8 plastic hose clamps for DIN adapter MPC-855NS.375 or SNP-4 for small DIN adapter, MPC-855.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.14. Connect the remaining tubing from the original packaging to the dialysate fluid outlet and direct the effluent downstream from sample intake. 

If a flow meter will be used to measure the volume of water filtered, cut the effluent tubing in half after it is connected into the dialysate fluid outlet and screw into the 3/4" GHT water flow meter adapter onto each end. (See Fig. 12 Appendix E). Ensure directional flow of the meter is correct. No clamps are needed.

 

If flow meter is not used, place the tubing into a 20-L cubitainer or other container equivalent to measure the total volume that has passed through the filter. Return the measured water downstream far from the influent water source to avoid disturbing the water near intake. Do this 5 times when a 20-L cubitainer is used to measure 100L water sample. Adjust accordingly for containers of different volumes.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.15. Verify set up is correct before staring the pump. See Appendix F. Make sure the tubing is passing through the water pump head without pinching the tubing and review the flow direction on the “Forward/Reverse” setting is correct.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.16. Start the pump by flipping the switch to ON and turning the knob gradually to maximum speed of 600 rpm.

 

SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.17. The pump will begin pumping the water through the influent port tubing into the filter and out the side port through the filtrate port tubing. Make sure no ports on the ultrafilter are leaking water.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.18. If sampling outdoors and the ultrafilter and pump is in the sun, cover the ultrafilter and pump with a clean bench protector, large umbrella, or other device to shield it from the sun and prevent pump overheating.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.19. When sampling is completed and the pump is stopped, slowly open the pump head to release any pressure and remove the filtration tubing from the pump head.

If chlorination of sampling water or the presence of free chlorine is suspected, ultrafilters should be treated with a 1% sodium thiosulfate solution post sample collection. 

Mix 10 g sodium thiosulfate and 1 L sterile, D.I. water, shake to dissolve. Place the influent tubing into the 1% sodium thiosulfate solution and pump the entire volume through the filter without pumping air into the ultrafilter.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.20. Unplug the pump from the battery. Remove all tubing from the ultrafilter and place end caps and storage caps on the ports, being careful not to allow water in the ultrafilter to escape. 

 

 

Used blood port caps, DIN adapters, and rubber storage caps can be returned to laboratory for cleaning and disinfecting before reuse or dispose of material in appropriate trash or biohazard bag.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.21. Tubing that came in contact with the water source should be disposed of and not reused to collect another sample.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.22. Dispose of trash (tubing, gloves, bench protectors, paper towels, etc.) in trash or biohazard bag as per individual laboratory or onsite guidelines.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.23. Label a sealable 2.5 gallon bag (e.g., Ziploc® bag) with the Sample ID, date, time, and your initials.
SECTION: FIELD FILTRATION AND SHIPPING PROCEDURES
13.24. Place the ultrafilter inside the bag, seal the bag, and gently place in a chilled cooler (wet ice / freezer packs) or in a refrigerator until shipment or processing.
SECTION: TROUBLESHOOTING
14. Pulling air instead of water through tubing.

Symptom: Pump is struggling to pull water from source.

Remedy: Stop pump, slowly release pressure in tubing by lifting the pump head clamp and resume pumping after checking to be sure intake tubing end is submerged under the water.
SECTION: TROUBLESHOOTING
15. Clogging of tubing or filter

Symptom: Debris is observed in tubing near connection with filter inlet or flow of water out of filter is visibly decreasing.

Remedy: Stop pump, consider if area where debris is can be simply cut out and remainder of tubing reattached; if filter is clogging, it may be a hard stop and end to sampling with current ultrafilter. Note the volume of water filtered on the ultrafilter and on any field datasheets. If debris is noticed before it reaches the filter, the tubing should be disconnected at the DIN adapter and tubing flushed with source water until the debris is removed. Then, reconnect everything and proceed with filtration.
SECTION: TROUBLESHOOTING
16. Split tubing

Symptom: Water is leaking where tubing is threaded thru pump head due to crack in tubing.

Remedy: Stop pump, remove tubing from pump head and replace influent tubing piece, clear out any visible sand or debris that might be causing friction in pump head and resume pumping.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17. Create backflush solution. A 500 mL volume is required per ultrafilter to be backflushed.

 

SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.1. Make 10 mL of a 10% NaPP/1% Antifoam emulsion stock solution in a 15 mL conical tube. Note that the use of a larger volume tube facilitates the easier mixing process. It is fine to prepare this stock solution ahead of time and store it for up to one week at 4 °C.

Add 1 g NaPP to 10 mL sterile D.I. water. Shake vigorously to dissolve the NaPP.
Add 100 µL of Antifoam emulsion to the solution and gently mix by inverting repeatedly.

SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.2. Add 500 mL of sterile D.I. water to a 500 mL or 1 L bottle.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.3. Add 2.5 mL of Tween® 80 with a 5-10 mL serological pipette.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.4. Stir with a sterile stir bar until the Tween® 80 is dissolved. If stir bar is not used, swirl vigorously (don’t shake) to dissolve the Tween® 80.

 

SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.5. Add 500 µL of the 10% NaPP/1% Antifoam emulsion stock solution to the water.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
17.6. Set aside for later use or store at 4 °C for no more than 2880 min.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
18. If filters have been held at 4 °C or on ice packs from shipping, allow the filters to warm to Room temperature on bench for approximately 60 min.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
19. Record all pertinent details of the ultrafilter sample on your 1-Liter sample collection bottle.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
20. Place clean bench protectors on the lab bench where backflushing will be performed.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
21. Position the peristaltic pump on a level surface or on a lift at least 20” above the bench surface.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
22. Secure filter vertically using the stand clamps pointing the sample inlet port downwards, and the sampling effluent side port facing through the water pump as shown in Fig. 16 and 17 in Appendix G. 

 

 

 

 

SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
23. Position a 1-L bottle directly under the end port, making sure the ultrafilter doesn’t touch the opening of the bottle.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
24. Unscrew and remove the cap from the filter end port facing downwards (blood outlet port). Backflush solution will exit this port and into the 1-Liter bottle upon backflushing. 
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
25. Disinfect the scissors with 70% ethanol and cut around 3ft section of tubing. Remove the cap from the top side port (dialysate outlet port). Push one end of the tubing fully onto the port as much as possible.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
26. Feed the tubing through the peristaltic pump head and place the other end into the 500 mL backflush solution.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
27. Secure the tubing attached on the upper side port (dialysate outlet port) with either a hose clamp SNP-12 or zip-tie. This tubing can slip off the side port when under pressure and must be secured.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
28. The blood inlet port and dialysate inlet port (top port and bottom side port, respectively) must remain secured. Check to ensure they are finger tightened and ensure that a SNP-12 hose clamp, or a zip tie was applied to the bottom side port (dialysate inlet port) adequately to prevent the rubber cap from leaking or coming off.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
29. Put on face shield if part of laboratory safety requirements.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
30. Close the pump head lever.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
31. Ensure pump flow direction is set from backflush solution to ultrafilter. Pump backflush solution through the ultrafilter at 650 mL/min (or 250-300 rpms), capturing backflush solution into the bottle. If the pump doesn’t have a digital display set the dial to a slow pumping rate.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
32. Continue pumping until no backflush solution remains in the 500 mL bottle and the flow out of the ultrafilter has slowed to a trickle. It will be necessary to briefly pump air after the backflush solution is depleted to get as much liquid out of the filter as possible. Do not pump air into the filter for more than approximately 10 s.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
33. Turn off the pump.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
34. Release the tubing from the pump head slowly, with one hand on the pump and the other hand releasing the lever gradually. BE VERY CAREFUL - THE SYSTEM IS UNDER PRESSURE.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
35. Cap the 1-Liter bottle and ensure the bottle is properly labeled. This is your backflush sample. Refrigerate until analysis. Measure and record backflush sample volume, if necessary. Backflush sample volume is typically between 500 mL-700 mL.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
36. Remove the tubing from the ultrafilter by releasing the SNP-12 hose clamp with needle nose pliers.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
37. After backflushing, the ultrafilter may be stored if required by individual laboratory protocols for sample remains. However, backflushing the ultrafilter a second time is not likely to result in the additional recovery of bacterial pathogens. Be sure to cap all open ports (side and end) to prevent leaks. 
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
38. Discard bench protector. Disinfect area with 10% bleach followed by 70% ethanol.
SECTION: BACKFLUSH OF ULTRAFILTERS FOR BACTERIAL PATHOGENS  PROCEDURE - Since there exists limited experimental information in terms of viability of bacterial cells following long-term storage of the ultrafilter, it is recommended that filters be processed upon receipt in the laboratory.
39. Proceed to pathogen-specific detection method or desired secondary concentration method.