ISO 16266 (2008) medium: Pseudomonas CN

Media control Water quality 

Microorganisms and performance criteria for testing selective media 'Pseudomonas CN' for Enumeration of Pseudomonas aeruginosa used in Water quality  microbiology by comparing with a non-selective reference medium according to ISO 11133.

  • 1 Quantitative control of Productivity

    • Blue-green colonies with fluorescence under UV light (360 ± 20 nm). The characteristic reaction of on Pseudomonas CN
    The characteristic reaction of Pseudomonas aeruginosa on Pseudomonas CN: Blue-green colonies with fluorescence under UV light (360 ± 20 nm).

    Best Practice Pseudomonas CN

    Quantitative control of Productivity solid medium

    1. Use a quantitative reference material or test suspension with a known number of Pseudomonas aeruginosa.
    2. Dilute this material so 50 to 120 cfu is inoculated on the Pseudomonas CN by membrane filtration method.
    3. Place the membrane on the surface of the agar under test (Pseudomonas CN).
    4. Do this also for the reference media (TSA).
    5. Incubate at (36 ± 2) °C for (44 ± 4) h.
    6. Count the colonies on the medium under test (Pseudomonas CN) and the reference media (TSA).
    7. Calculate the productivity ratio PR. The criteria is: PR ≥ 0,5.
    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 (Pseudomonas CN) is divided by the total count of colonies obtained on the defined reference medium (TSA).
    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
    Pseudomonas aeruginosa
    00025 opt
    00026 opt
    		 TSA (36 ± 2) °C for (44 ± 4) h PR ≥ 0,5 Blue-green colonies with fluorescence under UV light (360 ± 20 nm)
    The best practice for Quantitative control of Productivity for media control of 'Pseudomonas CN' is based on the data displayed in this table according ISO 11133.

  • 2 Quantitative control of Productivity

    • Best Practice Pseudomonas CN

    Quantitative control of Productivity solid medium

    1. Use a quantitative reference material or test suspension with a known number of Pseudomonas aeruginosa.
    2. Dilute this material so 50 to 120 cfu is inoculated on the Pseudomonas CN by membrane filtration method for example 0.1 mL suspension.
    3. Place the membrane on the surface of the agar under test (Pseudomonas CN).
    4. Do this also for the reference media (Media batch Pseudomonas CN already validated).
    5. Incubate at (36 ± 2) °C for (44 ± 4) h.
    6. Count the colonies on the medium under test (Pseudomonas CN) and the reference media (Media batch Pseudomonas CN 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 (Pseudomonas CN) is divided by the total count of colonies obtained on the defined reference medium (Media batch Pseudomonas CN 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
    Pseudomonas aeruginosa
    00025 opt
    00026 opt
    		 Media batch Pseudomonas CN already validated (36 ± 2) °C for (44 ± 4) h PR ≥ 0,7 Blue-green colonies with fluorescence under UV light (360 ± 20 nm)
    The best practice for Quantitative control of Productivity for media control of 'Pseudomonas CN' is based on the data displayed in this table according ISO 11133.

  • Qualitative control of Selectivity

    • Best Practice Pseudomonas CN

    Qualitative control of Selectivity solid medium

    1. Use a reference material or test suspension with a known number of Escherichia coli and Enterococcus faecalis.
    2. Streak the test strain (Escherichia coli and Enterococcus faecalis) as a single line on the media under test (Pseudomonas CN).
    3. Multiple strains can be streaked on the plate as long no crossing occurs.
    4. Use a 1 µl loop in case of a concentration of at least 10000 cfu or a 10 µl loop in case of a concentration between 1000 and 10000 cfu.
    5. Incubate at (36 ± 2) °C for (44 ± 4) h.
    6. Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
    7. For this medium (Pseudomonas CN) and standard (ISO 16266) combination the criteria is: "Total inhibition (0).

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Escherichia coli
    or
    		(36 ± 2) °C for (44 ± 4) h Total inhibition (0) No growth
    + Enterococcus faecalis
    or
    The best practice for Qualitative control of Selectivity for media control of 'Pseudomonas CN' is based on the data displayed in this table according ISO 11133.