Microorganisms and performance criteria for selective isolation media 'VRBG' used in Food chain microbiology according to ISO 21528-1.
ISO 21528-1 (2017) medium: VRBG
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Qualitative control of Productivity
- Use a reference material or test suspension with a known number of Escherichia coli.
- The volume used for testing should contain 103 to 104 cfu for qualitative tests of plate media.
- Streak the test microorganism (Escherichia coli) on the media under test (VRBG) to obtain discrete colonies.
- Incubate at (37 ± 1) °C for (24 ± 2) h.
- Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
- For this medium (VRBG) and standard (ISO 21528-1) combination the criteria is: "Good growth (2)".
- The Characterictic reaction is: Pink to red colonies with or without precipitation halo.
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Qualitative control of Selectivity
- Use a reference material or test suspension with a known number of Enterococcus faecalis.
- Streak the test strain (Enterococcus faecalis) as a single line on the media under test (VRBG).
- 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.
- Incubate at (37 ± 1) °C for (24 ± 2) h.
- Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
- For this medium (VRBG) and standard (ISO 21528-1) combination the criteria is: "Total inhibition (0).

Best Practice VRBG
Qualitative control of Productivity solid medium
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. |
Best Practice VRBG
Qualitative control of Selectivity solid medium
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. |