Microorganisms and performance criteria for selective isolation media 'MYP' used in Food and animal feeding stuffs microbiology according to ISO 11133.
ISO 21871 (2006) medium: MYP
-
Qualitative control of Productivity
- Use a reference material or test suspension with a known number of Bacillus cereus.
- The volume used for testing should contain 103 to 104 cfu for qualitative tests of plate media.
- Streak the test microorganism (Bacillus cereus) on the media under test (MYP) to obtain discrete colonies.
- Incubate at (30 ± 1) °C for (21 ± 3) h to 48 h.
- Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
- For this medium (MYP) and standard (ISO 21871) combination the criteria is: "Good growth (2)".
- The Characterictic reaction is: Pink colonies with precipitation halo.
-
Qualitative control of Selectivity
- Use a reference material or test suspension with a known number of Escherichia coli.
- Streak the test strain (Escherichia coli) as a single line on the media under test (MYP).
- 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 (30 ± 1) °C for (44 ± 4) h.
- Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
- For this medium (MYP) and standard (ISO 21871) combination the criteria is: "Total inhibition (0).
-
Qualitative control of Specificity
- Use a reference material or test suspension with a known number of Bacillus subtilis subsp. spizizenii.
- Streak the test controlstrain (Bacillus subtilis subsp. spizizenii) on the media under test (MYP) to obtain discrete colonies.
- Use a 1 µl loop in case of a concentration of at least 1000 cfu/mL.
- Incubate at (30 ± 1) °C for (44 ± 4) h.
- Asses the presence, absence and/or grade of expression of biochemical responses and colony sizes and morphology.
- For this medium (MYP) and standard (ISO 21871) combination the characteristic reaction is: Yellow colonies without precipitation halo.

Best Practice MYP
Qualitative control of Productivity solid medium
Control strain | WDCM number | Incubation | Criteria | Characteristic reaction | |
---|---|---|---|---|---|
Bacillus cereus | (30 ± 1) °C for (21 ± 3) h to 48 h | Good growth (2) | Pink colonies with precipitation halo | ||
The best practice for Qualitative control of Productivity for media control of 'MYP' is based on the data displayed in this table according ISO 11133. |
Best Practice MYP
Qualitative control of Selectivity solid medium
Control strain | WDCM number | Ref. media | Incubation | Criteria | Characteristic reaction |
---|---|---|---|---|---|
Escherichia coli | or | (30 ± 1) °C for (44 ± 4) h | Total inhibition (0) | No growth | |
The best practice for Qualitative control of Selectivity for media control of 'MYP' is based on the data displayed in this table according ISO 11133. |

Best Practice MYP
Qualitative control of Specificity solid medium
Control strain | WDCM number | Ref. media | Incubation | Criteria | Characteristic reaction |
---|---|---|---|---|---|
Bacillus subtilis subsp. spizizenii | (30 ± 1) °C for (44 ± 4) h | Characteristic growth | Yellow colonies without precipitation halo | ||
The best practice for Qualitative control of Specificity for media control of 'MYP' is based on the data displayed in this table according ISO 11133. |