ISO 11290-2 (2017) method: Listeria monocytogenes

Process control Food chain

Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. - Part 2: Enumeration method

  • Quantitative process control with CRM-LM

  • Blue green colonies with opaque halo. The characteristic reaction of  on ALOA
    Characteristic reaction: Blue green colonies with opaque halo.

    Best Practice

    The single strain CRM-LM is used for the enumeration of Listeria monocytogenes

    1. Use a quantitative reference material (CRM-LM) with a known number of Listeria monocytogenes.
    2. Defrost the material at room temperature for 30 minutes.
    3. Mix well before use and dilute the material so countable numbers are inoculated on the media (ALOA) by spread plate method.
    4. Best results are obtained when a practicable range of 80 cfu to 120 cfu per plate with a minimum number of 50 cfu per plate is used.
    5. Incubate at (37 ± 1) °C for (48 ± 4) h.
    6. Count the colony forming units and register in a control chart.
    7. The characteristic reaction is: Blue green colonies with opaque halo.

    Kind of reference material Biosisto product for this control method Control Strain NCCB number
    Single-strain reference material Listeria monocytogenes 100286
    The Biosisto reference material in this table is used in the best practice for Quantitative process control according ISO 17025.