Microorganisms and performance criteria for testing selective media 'TSC' for Enumeration of Clostridium perfringens used in Water quality microbiology by comparing with a non-selective reference medium according to ISO 14189.
ISO 14189 (2016) medium: TSC
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Quantitative control of Productivity
- Use a quantitative reference material or test suspension with a known number of Clostridium perfringens.
- Dilute this material so 50 to 120 cfu is inoculated on the TSC by membrane filtration method.
- Place the membrane on the surface of the agar under test (TSC).
- Do this also for the reference media (TSA or blood agar).
- Incubate at (44 ± 1) °C for (21 ± 3) h.
- Count the colonies on the medium under test (TSC) and the reference media (TSA or blood agar).
- 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 (TSC) is divided by the total count of colonies obtained on the defined reference medium (TSA or blood agar).
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Qualitative control of Selectivity
- Use a reference material or test suspension with a known number of Bacillus subtilis subsp. spizizenii.
- Streak the test strain (Bacillus subtilis subsp. spizizenii) as a single line on the media under test (TSC).
- 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 (44 ± 1) °C for (21 ± 3) h.
- Asses the amount of growth as, 0 for no growth, 1 for weak growth or 2 for good growth.
- For this medium (TSC) and standard (ISO 14189) combination the criteria is: "Total inhibition (0).

Best Practice TSC
Best result when Bloodagar is used as reference medium. An overlay ensures black coloration of the colonies
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 |
---|---|---|---|---|---|
Clostridium perfringens | TSA or blood agar | (44 ± 1) °C for (21 ± 3) h anaerobic atmosphere |
PR ≥ 0,5 | Black colonies | |
The best practice for Quantitative control of Productivity for media control of 'TSC' is based on the data displayed in this table according ISO 14189. |
Best Practice TSC
Qualitative control of Selectivity solid medium
Control strain | WDCM number | Ref. media | Incubation | Criteria | Characteristic reaction |
---|---|---|---|---|---|
Bacillus subtilis subsp. spizizenii | (44 ± 1) °C for (21 ± 3) h anaerobic atmosphere |
Total inhibition (0) | No growth | ||
The best practice for Qualitative control of Selectivity for media control of 'TSC' is based on the data displayed in this table according ISO 14189. |