ISO 6222 (1999) medium: YEA

Media control Water quality 

Microorganisms and performance criteria for testing non-selective media 'YEA' for Enumeration of Total flora used in Water quality  microbiology according to ISO 11133.

  • Quantitative control of Productivity

  • Growth. The characteristic reaction of  on YEA
    The characteristic reaction of Escherichia coli on YEA: Growth.

    Best Practice YEA

    Quantitative control of Productivity solid medium

    1. Use a quantitative reference material or test suspension with a known number of Escherichia coli.
    2. Dilute this material so 50 to 120 cfu is inoculated on the YEA by pouring for example 1 mL.
    3. Do this also for the reference media (Media batch YEA already validated).
    4. Incubate at (36 ± 2) °C for (44 ± 4) h.
    5. Count the colonies on the medium under test (YEA) and the reference media (Media batch YEA already validated).
    6. Calculate the productivity ratio PR. The criteria is: PR ≥ 0,7.
    7. If the PR exceeds 1,4 identify the reason.
    8. For this the total count of colonies obtained on the culture medium under test (YEA) is divided by the total count of colonies obtained on the defined reference medium (Media batch YEA already validated).
    Calculate the productivity ratio PR as follows: PR  NS
    Ns = total count test medium
    N0 = total count reference medium

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Escherichia coli or Media batch YEA already validated (36 ± 2) °C for (44 ± 4) h PR ≥ 0,7 Growth
    Bacillus subtilis subsp. spizizenii
    The best practice for Quantitative control of Productivity for media control of 'YEA' is based on the data displayed in this table according ISO 11133.