ISO 11731 (2017) medium: BCYE

Media control Water quality 

Microorganisms and performance criteria for testing non-selective media 'BCYE' for Enumeration of Legionella used in Water quality  microbiology according to ISO 11731.

  • Quantitative control of Productivity

  • White-grey-blue-purple colonies with an entire edge and exhibiting a characteristic groundglass appearance. The characteristic reaction of  on BCYE
    The characteristic reaction of Legionella pneumophila on BCYE: White-grey-blue-purple colonies with an entire edge and exhibiting a characteristic groundglass appearance.

    Best Practice BCYE

    Quantitative control of Productivity solid medium

    1. Use a quantitative reference material or test suspension with a known number of Legionella pneumophila.
    2. Dilute this material so 50 to 120 cfu is inoculated on the BCYE.
    3. Use the same method of inoculation as described in the specific individual ISO 11731.
    4. Do this also for the reference media (Media batch BCYE agar already validated).
    5. Incubate at (36 ± 2) °C for 2d to 5d.
    6. Count the colonies on the medium under test (BCYE) and the reference media (Media batch BCYE agar already validated).
    7. Calculate the productivity ratio PR. The criteria is: PR ≥ 0,7.
    8. If the PR exceeds 1,4 identify the reason.
    9. For this the total count of colonies obtained on the culture medium under test (BCYE) is divided by the total count of colonies obtained on the defined reference medium (Media batch BCYE agar already validated).
    Calculate the productivity ratio PR as follows: PR  NS
    N0
    Ns = total count test medium
    N0 = total count reference medium

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Legionella pneumophila Media batch BCYE agar already validated (36 ± 2) °C for 2d to 5d PR ≥ 0,7 White-grey-blue-purple colonies with an entire edge and exhibiting a characteristic groundglass appearance
    The best practice for Quantitative control of Productivity for media control of 'BCYE' is based on the data displayed in this table according ISO 11731.