Ready-to-use media
Yeast Extract Agar (YEA) ISO
Solid medium used for the enumeration of water microorganisms according to ISO standards.
- Cat. No.
- LC-941
- Category
- Ready-to-use media
- Formats
- 5 formats
- ISO 17025 quality control
- Yes
- Minimum order
- 10 packs
- Standards
- ISO 6222
- Also available
- Dehydrated medium, 1 format (LC-1049)
This medium, formulated according to ISO Standard 6222 and others, is for the enumeration of heterotrophic microorganisms from water.
Key features
Applications
Non-selective enumeration (general use).
Industry
Water.
Standards
ISO 6222.
Description and technique
Technique
Using a water sample obtained according to the ISO Standard 5667-2 and 5667-3, make a decimal dilution series (see ISO Standard 6887) using 1/4 Ringer Solution and take aliquots to 2 parallel series of plates. Pour the sterilized Tryptone Yeast Extract Agar cooled to 45 °C, and homogenize with the sample (see ISO Standard 8199). Once solidified, incubate one of the series at 36 ± 2 °C for 48 ± 2 hours and the other one at 22 °C for 3 days (72 ± 4 hours).
In order to achieve a good count, select plates with 30-300 colonies. Express the results as number of colony forming units per millilitre (CFU/mL) of sample for each temperature of incubation. If there are no colonies with the undiluted sample, express the results as "none detected in one mL". If there are more than 300 colonies in the highest dilution, express the results as "> 300 CFU/mL".
LC-4022, tubes
Melt the culture medium and pour it into sterile plates.
LC-4671 and LC-4672, bottles
Melt the medium contained in bottles in a water bath (approx. 100 °C) or in a microwave oven, avoiding overheating, before pouring into Petri dishes when cooled to room temperature.
LC-4703, 55 mm plates for filtration purposes
Collect, dilute and prepare samples and volumes to be filtered as required according to specifications, directives, official standard regulations and/or expected results.
Filter the sample through a 0.45 µm pore membrane and apply it onto the surface of the agar.
Incubate the plates right side up aerobically at 36 ± 2 °C for 44 ± 4 h.
(Incubation times greater than those mentioned above or different incubation temperatures may be required depending on the sample, on the specifications or on the ISO normative, etc.)
After incubation, enumerate all the colonies on the surface of the membrane.
Calculate total microbial count per mL of sample by multiplying the average number of colonies per membrane by the inverse dilution factor. Report results as colony forming units (CFU) per mL along with incubation time and temperature.
Presentation
| Code | Presentation | Filling | Packaging |
|---|---|---|---|
| LC-941 | 20 prepared plates, 90 mm | 21 ± 2 mL | 1 box with 2 packs of 10 plates/pack. Single cellophane. |
| LC-4022 | 20 tubes, 17 x 145 mm | 15 ± 1 mL | 17 x 145 mm glass tubes, ink labelled, metal non-injectable cap. 20 tubes per box. |
| LC-4671 | 10 prepared bottles, 125 mL | 100 ± 3 mL | 1 box with 10 bottles 125 mL. Non-injectable cap. |
| LC-4672 | 10 prepared bottles, 250 mL | 200 ± 5 mL | 1 box with 10 bottles 250 mL. Non-injectable cap. |
| LC-4703 | 30 prepared plates, 55 mm, for filtration purposes | 9 ± 1 mL | 1 box containing 5 plastic bags with 6 plates of 55 mm/bag. |
Composition
| Ingredient | g/L |
|---|---|
| Yeast extract | 3.00 |
| Tryptone (LC-4672: peptone from casein) | 6.00 |
| Agar | 15.00 |
Quality control
Physical/chemical control
| Color | Yellowish (LC-4672: yellowish-brown) |
|---|---|
| pH | 7.2 ± 0.2 at 25 °C |
Microbiological control
Inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity).
Aerobiosis. Incubation at 36 ± 2 °C, reading at 44 ± 4 h.
| Microorganism | Growth |
|---|---|
| Escherichia coliATCC 8739, WDCM 00012 | Good (≥ 70%) |
| Stph. aureusATCC 25923, WDCM 00034 | Good (≥ 70%) |
| Escherichia coliATCC 25922, WDCM 00013 | Good (≥ 70%) |
| Bacillus subtilisATCC 6633, WDCM 00003 | Good (≥ 70%) |
| Ps. aeruginosaATCC 27853, WDCM 00025 | Good (≥ 70%) |
LC-4022, LC-4671, LC-4672 and LC-4703: microbiological control
LC-4022, LC-4671 and LC-4672: melt medium - prepare plates - spiral spreading: practical range 100 ± 20 CFU; min. 50 CFU (productivity).
LC-4022: reference medium YEA (validated). Microbiological control according to ISO 11133:2014.
LC-4703: membrane filtration; practical range 100 ± 20 CFU; min. 50 CFU (productivity). Microbiological control according to ISO 11133:2014/Amd 1:2018.
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- ISO Standard 6222 (1999) Water Quality - Enumeration of cultivable microorganisms. Colony count by inoculation in a nutrient agar culture.
- ISO Standard 5667-2 (1991) Water Quality - Sampling - Guidance on sampling techniques.
- ISO Standard 5667-3 (1996) Water Quality - Sampling - Guidance on the preservation and handling of samples.
- ISO Standard 6887 (1999) Microbiology - General - Guidance for the preparation of dilutions for microbiological examination.
- ISO Standard 8199 (1988) Water Quality - General guide to the enumeration of microorganisms by culture.
- ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
Every lot comes with its certificate.
Tracked shipment
Follow your shipment live, from our warehouse to your lab.
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Frequently asked questions
Can I ask for formats other than those listed?
Yes: custom formats and OEM packs are available on request. Tell us the quantities you need.
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