Microorganisms and performance criteria for testing selective media 'LST' for Enumeration of Coliforms used in Food and animal feeding stuffs microbiology according to ISO 11133.
ISO 4831 (2006) medium: LST
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Qualitative control of Productivity
- Use a reference material or test suspension with a known number of Escherichia coli.
- Inoculate the media (LST) with 0.1 mL of more than 100 cfu/mL and less then 1000 cfu/mL of microorganisms.
- Incubate at (30 ± 1) °C for (24 ± 2) h to (48 ± 2) h.
- Asses the amount of growth as, 0 for no turbidity, 1 for slight turbidity or 2 for good turbidity.
- For this medium (LST) and standard (ISO 4831) combination the criteria is: "Turbidity (2) and gas in Durham tube."
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Qualitative control of Selectivity
- Use a quantitative reference material or test suspension with a known number of Enterococcus faecalis.
- Inoculate one tube of test medium with >103 cells of non-target organisms.
- Incubate at (30 ± 1) °C for (24 ± 2) h to (48 ± 2) h.
- Remove 10 µl and streak to a plate of reference medium .
- Incubate at (30 ± 1) °C for (24 ± 2) h to (48 ± 2) h.
- Growth of non-target microorganisms should comply with the criteria: "No growth".
Best Practice LST
Qualitative single tube method for performance testing of liquid media – pre-enrichment media
Control strain | WDCM number | Incubation | Criteria | Characteristic reaction | |
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Escherichia coli | (30 ± 1) °C for (24 ± 2) h to (48 ± 2) h | Turbidity (2) and gas in Durham tube | Gas production and turbidity | ||
Citrobacter freundii | |||||
The best practice for Qualitative control of Productivity for media control of 'LST' is based on the data displayed in this table according ISO 11133. |
Best Practice LST
Qualitative control of Selectivity of liquid medium, single culture
Control strain | WDCM number | Ref. media | Incubation | Criteria | Characteristic reaction |
---|---|---|---|---|---|
Enterococcus faecalis | or | (30 ± 1) °C for (24 ± 2) h to (48 ± 2) h | No growth | No growth | |
The best practice for Qualitative control of Selectivity for media control of 'LST' is based on the data displayed in this table according ISO 11133. |