ISO 11290-2 (2017) medium: BPW

Media control Food chain

Microorganisms and performance criteria for multipurpose media 'BPW' used in Food chain microbiology according to ISO 11133.

  • Qualitative control of Dilution

    • Best Practice BPW

    1. Use a reference material or test suspension with a known number of Listeria monocytogenes 4b.
    2. Inoculate a test portion (e.g. 9 mL) of the diluent with 1 mL of the test microorganism (Listeria monocytogenes) suspension containing around 104 cfu/mL and mix;
    3. Immediately remove 0,1 mL of inoculated diluent and spread over the surface of a non-selective agar (reference medium) such as TSA (t0).
    4. Hold the inoculated diluent at ambient temperature for 45 min.
    5. Mix and then remove the same volume (0,1 mL) and plate again on the reference medium (t1).
    6. Incubate at ((20 ± 2) °C) for ((1 h ± 5°min)).
    7. Count the colonies on the plates t0 and t1. The number of microorganisms at t1, shall be within ± 30 % of the initial count (t0).

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Listeria monocytogenes 4b
    		TSA (20 ± 2) °C for (1 h ± 5°min) ±30 % colonies/ T0 (±30 % of original count) No characteristic colonies
    Listeria monocytogenes 1/2a
    00109 opt
    The best practice for Qualitative control of Dilution for media control of 'BPW' is based on the data displayed in this table according ISO 11133.