Horizontal method for the enumeration of presumptive Bacillus cereus - Colony-count technique at 30°C
ISO 7932 (2004) method: Bacillus cereus
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1 Quantitative process control with CRM-BC
- Use a quantitative reference material (CRM-BC) with a known number of Bacillus cereus.
- Defrost the material at room temperature for 30 minutes.
- Mix well before use and dilute the material so countable numbers are inoculated on the media (MYP) by spread plate method.
- Best results are obtained when a practicable range of 80 cfu to 120 cfu per plate with a minimum number of 50 cfu per plate is used.
- Incubate at (30 ± 1) °C for (24 ± 3) h to (44 ± 4) h.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Pink colonies with precipitation halo.
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2 Quantitative process control with RM-BC veg
- Use a quantitative reference material (RM-BC veg) with a known number of Bacillus cereus.
- Defrost the material at room temperature for 30 minutes.
- Mix well before use and dilute the material so countable numbers are inoculated on the media (MYP) by spread plate method.
- Best results are obtained when a practicable range of 80 cfu to 120 cfu per plate with a minimum number of 50 cfu per plate is used.
- Incubate at (30 ± 1) °C for (24 ± 3) h to (44 ± 4) h.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Pink colonies with precipitation halo.
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3 Quantitative process control with RM-BLES
- Use a quantitative reference material (RM-BLES) with a known number of Microorganisms.
- Defrost the material at room temperature for 30 minutes.
- Mix well before use and dilute the material so countable numbers are inoculated on the media (MYP) by spread plate method.
- Best results are obtained when a practicable range of 80 cfu to 120 cfu per plate with a minimum number of 50 cfu per plate is used.
- Incubate at (30 ± 1) °C for (24 ± 3) h to (44 ± 4) h.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Pink colonies with precipitation halo.
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4 Quantitative process control with RM-BCE.00001MH
- Use a quantitative reference material (RM-BCE.00001MH) with a known number of Bacillus cereus.
- Defrost the material at room temperature for 30 minutes.
- Mix well before use and dilute the material so countable numbers are inoculated on the media (MYP) by spread plate method.
- Best results are obtained when a practicable range of 80 cfu to 120 cfu per plate with a minimum number of 50 cfu per plate is used.
- Incubate at (30 ± 1) °C for (30 ± 1) °C.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Pink colonies with precipitation halo.

Best Practice
The single strain CRM-BC contains Bacillus cereus spores which are not heat-resistant. This material can only be used for vegetative cell analyse

Best Practice
The single strain RM-BCveg contains Bacillus cereus vegetative cells and heat-resistant spores. This material can be used for vegetative cell analyse and the spore analyse

Best Practice
The multi-strain RM-BLES contains, Bacillus cereus, Lactobacillus plantarum, Escherichia coli WDCM 00013 and Staphylococcus aureus WDCM 00034 in milk. This material can be used for several specific standards. The influence of interfering bacteria is also performed. It is easy to use by making one serie of dilution.
Kind of reference material | Biosisto product for this control method | Control Strain | WDCM number | NCCB number | |
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Multi-strain reference material | Bacillus cereus | 100292 | |||
Lactobacillus plantarum | 100293 | ||||
Escherichia coli serotype O6:H1 | 00013 | 100297 | |||
Staphylococcus aureus | 00034 | 100294 | |||
The Biosisto reference material in this table is used in the best practice for Quantitative process control according ISO 17025. |
Best Practice
The single strain RM-BCE.00001MH contains Bacillus cereus vegetative cells and heat-resistant spores. This material can be used for vegetative cell analyse and the spore analyse
Kind of reference material | Biosisto product for this control method | Control Strain | CCUG number | ||
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Single-strain reference material | Bacillus cereus | 10781 | |||
The Biosisto reference material in this table is used in the best practice for Quantitative process control according ISO 17025. |