Question
Microbiology Guide: Most Probable Number (MPN) Media
Summary
Microbiology Guide: Media and Equipment Selection; Most Probable Number (MPN) Media
Answer
From: Microbiology Guide: Media and Equipment Selection
Most Probable Number (MPN) Media Selection Summary
Drinking Water and Beverage
Sludge, Recreational Water and Nonpotable Water
Foods
Media with Confirmation
For concentrated media there is 2 mL of media in each tube.
For single-strength media there is 10 mL of media in each tube.
Media Decontamination
Most Probable Number (MPN) Media Selection Summary
Drinking Water and Beverage
| Organism | USEPA- Accepted (Y/N) | Presumptive Media | Confirmation Media |
| Total Coliforms | Y | Lauryl Tryptose (LT) Broth Tubes (Concentrated) | Brilliant Green Bile (BGB) Tubes |
| Total Coliforms and E. Coli | N | LT with MUG Broth Tubes (Concentrated) | No Confirmation Necessary for E.Coli. BGB Broth Tubes for Total Coliform Confirmation |
| Fecal Coliforms | Y | LT Broth Tubes (Concentrated) | EC Medium Tubes |
| E. Coli | Y | LT Broth Tubes (Concentrated) | EC Medium with MUG Tubes |
Sludge, Recreational Water and Nonpotable Water
| Organism | USEPA- Accepted (Y/N) | Presumptive Media | Confirmation Media |
| Total Coliforms and E. Coli | N | LT with MUG Broth Tubes (Concentrated) | No Confirmation Necessary for E.Coli BGB Broth Tubes for Total Coliform Confirmation |
| Fecal Coliforms | Y | LT Broth Tubes (Concentrated) | EC Medium Tubes |
| Fecal Coliforms | Y | A-1 Medium Broth Tubes | No Confirmation Necessary |
| Fecal Coliforms | N | PathoScreen Medium MPN Pillows | Use Traditional Confirmation Media |
| Fecal Streptococci | Y | Azide Dextrose Broth Tubes | Bile Esculin Azide Agar Tubes |
Foods
| Organism | USEPA- Accepted (Y/N) | Presumptive Media | Confirmation Media |
| Total Coliforms | N | LT Broth Tubes (Single-Strength) | BGB Broth Tubes |
| Fecal Coliforms | N | LT Broth Tubes (Single-Strength) | EC Medium Tubes |
| E. Coli | N | LT Broth Tubes (Single-Strength) | EC Medium with MUG Tubes |
| E. Coli | N | LT with MUG Broth Tubes (Single-Strength) | No Confirmation Necessary for E.Coli. BGB Broth Tubes for Total Coliform Confirmation |
Media with Confirmation
-
Lauryl Tryptose with Brilliant Green, EC/Mug Media, Hach method 8001, Total, Fecal, and E.Coli Coliform
- For Potable Water Samples
- Most Probable Number Method 8001 for potable water is USEPA-accepted. Method 8001 meets or exceeds the specification criteria stated in Standard Methods for the Examination of Water and Wastewater, 19th edition, 9221 Multiple-Tube Fermentation Technique for Members of the Coliform Group. For potable water, confirm fecal coliforms with EC Medium Broth as cited in 40 CFR Part 141.21, Subpart (F)(5); or confirm E. coli with EC/MUG Medium Broth as cited in 40 CFR Part 141.21, Subpart (F)(6)(i).
- Media Packaging
- Lauryl Tryptose Broth MPN Tubes, Concentrated, pk/15 (Product # 2101415) - for Total Coliform
- Brilliant Green Tubes, pk/15 (Product # 32215) - for Total Coliform
- EC Medium MPN Tubes, pk/15 (Product # 1410415) - for Fecal Coliform
-
EC Medium/MUG Tubes, pk/15 (Product # 2282415) - for E. Coli Coliform
- Needed Accessory
- Lamp, Ultraviolet, Portable (Product # 2415200)
- Lamp, Ultraviolet, Long-Wave 115 Vac, 60 Hz (Product # 2184300)
- Lamp, Ultraviolet, Long-Wave 230 Vac, 50 Hz (Product # 2184302)
- Needed Accessory
- For Potable Water Samples
-
Lauryl Tryptose with Brilliant Green, EC/Mug Media, Hach method 8001A, Total, Fecal, and E.Coli Coliform
- For Non-Potable Water and wastewater Samples
- Most Probable Number Method 8001A for wastewater is USEPA-accepted. Method 8001A meets or exceeds the specification criteria stated in Standard Methods for the Examination of Water and Wastewater, 19th edition, 9221 Multiple-Tube Fermentation Technique for Members of the Coliform Group
- Media Packaging
- Lauryl Tryptose Broth MPN Tubes, Concentrated, pk/15 (Product # 2101415) - for Total Coliform
- Brilliant Green Tubes, pk/15 (Product # 32215) - for Total Coliform
- EC Medium MPN Tubes, pk/15 (Product # 1410415) - for Fecal Coliform
-
EC Medium/MUG Tubes, pk/15 (Product # 2282415) - for E. Coli Coliform
- Needed Accessory
- Lamp, Ultraviolet, Portable (Product # 2415200
- Lamp, Ultraviolet, Long-Wave 115 Vac, 60 Hz (Product # 2184300)
- Lamp, Ultraviolet, Long-Wave 230 Vac, 50 Hz (Product # 2184302)
- Needed Accessory
- For Non-Potable Water and wastewater Samples
-
Lauryl Tryptose with MUG, Hach method 8091, Total, and E.Coli Coliform
- For Potable and Non-Potable Water *Not USEPA accepted
- Media Packaging
- Lauryl Tryptose w/MUG Broth Tubes, Single Strength, pk/15 (Product # 2217515)
- Lauryl Tryptose with MUG Broth, Dehydrated 500 g (Product # 225573)
- Needed Accessory
- Lamp, Ultraviolet, Portable (Product # 2415200
- Lamp, Ultraviolet, Long-Wave 115 Vac, 60 Hz (Product # 2184300)
- Lamp, Ultraviolet, Long-Wave 230 Vac, 50 Hz (Product # 2184302)
-
A-1 medium, Hach method 8368, Fecal Coliform
- For Non-Potable and Wastewater
- Most Probable Number Method 8368, A-1 Medium, is USEPA-accepted for testing non-potable waters. Method 8368 meets or exceeds the specification criteria stated in Standard Methods for the Examination of Water and Wastewater, 18th edition, 9221 E. Fecal Coliform Procedure. USEPA Manual for the Certification of Laboratories Analyzing Drinking Water states “5.5.3. A-1 medium may be used as an alternative to EC Medium to enumerate fecal coliforms in source water, in accordance with the Surface Water Treatment Rule. A-1 Medium must not be used for drinking water samples.”
- Media Packaging
- A-1 Medium Broth MPN Tubes, pk/15 (Product # 2560915)
- For Non-Potable and Wastewater
For concentrated media there is 2 mL of media in each tube.
For single-strength media there is 10 mL of media in each tube.
Media Decontamination
-
Recommendation:
- Open each MPN tube and pipet in 2-3 mls of Clorox. (one can use a disposable plastic dropper).
- Cap and invert …. Let stand for minimum 20-30 minutes.
- After the waiting time, use a wire strainer or colander and empty the contents of the MPN tubes into the strainer with the tap water running. Rinse the tubes with tap water.
- The empty tubes can now be disposed of in the glass waste container. Caps can be disposed of in the regular waste can.
- After all the tubes have been dosed, add an additional amount of Clorox down the drain, ~20 mls. Run more Tap water into the sink.