ISO 21528-1 (2017) medium: VRBG

Media control Food chain

Microorganisms and performance criteria for selective isolation media 'VRBG' used in Food chain microbiology according to ISO 21528-1.

  • Qualitative control of Productivity

  • Pink to red colonies with or without precipitation halo. The characteristic reaction of  on VRBG
    The characteristic reaction of Escherichia coli on VRBG: Pink to red colonies with or without precipitation halo.

    Best Practice VRBG

    Qualitative control of Productivity solid medium

    1. Use a reference material or test suspension with a known number of Escherichia coli.
    2. The volume used for testing should contain 103 to 104 cfu for qualitative tests of plate media.
    3. Streak the test microorganism (Escherichia coli) on the media under test (VRBG) to obtain discrete colonies.
    4. Incubate at (37 ± 1) °C for (24 ± 2) h.
    5. Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
    6. For this medium (VRBG) and standard (ISO 21528-1) combination the criteria is: "Good growth (2)".
    7. The Characterictic reaction is: Pink to red colonies with or without precipitation halo.

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Escherichia coli or TSA (37 ± 1) °C for (24 ± 2) h Good growth (2) Pink to red colonies with or without precipitation halo
    Salmonella Typhimurium
    Salmonella Enteritidis
    The best practice for Qualitative control of Productivity for media control of 'VRBG' is based on the data displayed in this table according ISO 21528-1.
  • Qualitative control of Selectivity

  • Best Practice VRBG

    Qualitative control of Selectivity solid medium

    1. Use a reference material or test suspension with a known number of Enterococcus faecalis.
    2. Streak the test strain (Enterococcus faecalis) as a single line on the media under test (VRBG).
    3. 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.
    4. Incubate at (37 ± 1) °C for (24 ± 2) h.
    5. Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
    6. For this medium (VRBG) and standard (ISO 21528-1) combination the criteria is: "Total inhibition (0).

    Control strain WDCM number Ref. media Incubation Criteria Characteristic reaction
    Enterococcus faecalis or (37 ± 1) °C for (24 ± 2) h Total inhibition (0) No growth
    The best practice for Qualitative control of Selectivity for media control of 'VRBG' is based on the data displayed in this table according ISO 21528-1.