ISO 11731 (2017) method: Legionella

Process control Water quality 

Enumeration of Legionella

  • Quantitative process control with RM-LPNEU1

  • Whitegreybluepurple colonies with an entire edge and exhibiting a characteristic groundglass appearance. The characteristic reaction of  on MWY
    Characteristic reaction: Whitegreybluepurple colonies with an entire edge and exhibiting a characteristic groundglass appearance.

    Best Practice

    1. Use a quantitative reference material (RM-LPNEU1) with a known number of Legionella pneumophila.
    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 (MWY) by spreading, pour plate or by the membrane filtration 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 (36 ± 2) °C for 2d to 5d.
    6. Count the colony forming units and register in a control chart.
    7. The characteristic reaction is: Whitegreybluepurple colonies with an entire edge and exhibiting a characteristic groundglass appearance.

    Kind of reference material Biosisto product for this control method Control Strain NCCB number
    Single-strain reference material Legionella pneumophila 100617
    The Biosisto reference material in this table is used in the best practice for Quantitative process control according ISO 17025.