Microorganisms and performance criteria for testing selective media 'CFC' for Enumeration of Pseudomonas spp. used in Meat and meat products microbiology according to ISO 11133.
ISO 13720 (2010) medium: CFC
-
Quantitative control of Productivity
- Use a quantitative reference material or test suspension with a known number of Pseudomonas fluorescens.
- Dilute this material so 50 to 120 cfu is inoculated on the CFC by spreading for example 0.1 mL.
- Do this also for the reference media (TSA).
- Incubate at (25 ± 1) °C for (44 ± 4) h.
- Count the colonies on the medium under test (CFC) and the reference media (TSA).
- Calculate the productivity ratio PR. The criteria is: PR ≥ 0,5.
- If the PR exceeds 1,4 identify the reason.
- For this the total count of colonies obtained on the culture medium under test (CFC) is divided by the total count of colonies obtained on the defined reference medium (TSA).
-
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 (CFC).
- 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 (25 ± 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 (CFC) and standard (ISO 13720) combination the criteria is: "Total inhibition (0).
Best Practice CFC
Quantitative control of Productivity solid medium
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 fluorescens | TSA | (25 ± 1) °C for (44 ± 4) h | PR ≥ 0,5 | Growth | |
Pseudomonas fragi | |||||
The best practice for Quantitative control of Productivity for media control of 'CFC' is based on the data displayed in this table according ISO 11133. |
Best Practice CFC
Qualitative control of Selectivity solid medium
Control strain | WDCM number | Ref. media | Incubation | Criteria | Characteristic reaction |
---|---|---|---|---|---|
Escherichia coli | or | (25 ± 1) °C for (44 ± 4) h | Total inhibition (0) | No growth | |
The best practice for Qualitative control of Selectivity for media control of 'CFC' is based on the data displayed in this table according ISO 11133. |