Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) - Part 1: Technique using Baird Parker agar medium
ISO 6888-1 (1999) method: Coagulasepositive staphylococci
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1 Quantitative process control with CRM-SA
- Use a quantitative reference material (CRM-SA) with a known number of Staphylococcus aureus.
- 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 (BPA) 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 (37 ± 1) °C for (24 ± 2) h to (48 ± 2) h.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Black or grey colonies with clear halo (egg yolk clearing reaction).
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2 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 (BPA) 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 (37 ± 1) °C for (24 ± 2) h to (48 ± 2) h.
- Count the colony forming units and register in a control chart.
- The characteristic reaction is: Black or grey colonies with clear halo (egg yolk clearing reaction).

Best Practice
The single strain CRM-SA is used for the enumeration of Coagulasepositive staphylococci

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. |