MFHPB-21 Enumeration of Staphylococcus aureus in Foods
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ID： |
3D91A3478193460CA1CFD02773E6B23E |
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文件大小(MB)： |
0.07 |
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页数： |
14 |
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日期： |
2012-3-2 |
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Published on the Food Directorate’s (Health Canada's) website at,http://www.hc-sc.gc.ca/fn-an/res-rech/analy-meth/microbio/index_e.html,Government of Canada Gouvernement du Canada,HPB Method MFHPB-21,September 2005,HEALTH PRODUCTS AND FOOD BRANCH,OTTAWA,ENUMERATION OF STAPHYLOCOCCUS AUREUS IN FOODS,Microbiological Methods Committee,Microbiology Evaluation Division,Bureau of Microbial Hazards, Food Directorate,Health Products and Food Branch, Health Canada,Postal Locator: 2204A1,Ottawa, Ontario K1A 0L2,Don_Warburton@hc-sc.gc.ca,Rick A. Szabo,Microbiology Evaluation Division,Bureau of Microbial Hazards, Food Directorate,Health Products and Food Branch, Health Canada,Postal Locator: 2204A1,Ottawa, Ontario K1A 0L2,Rick_Szabo@hc-sc.gc.ca,1. APPLICATION,This method is applicable to the enumeration of Staphylococcus aureus in foods to determine compliance with,the requirements of Sections 4 and 7 of the Food and Drugs Act. Where an Official Method for a food is,specified, that method shall be followed. This revised method replaces MFHPB-21, dated November 2000,and Supplements to Method MFHPB-21, dated February 2002, August 2002, and December 2003.,2. DESCRIPTION,The method has been shown to produce satisfactory results with naturally-contaminated meats, fish, poultry,vegetables, cereals and dairy products, and artificially-contaminated foods in AOAC and HPB studies (8.1-,8.10). This method can be used successfully for the detection of Staphylococcus aureus in other foods, food,ingredients and environmental samples.,3. PRINCIPLE,Certain staphylococci produce enterotoxins which cause food poisoning. This ability to produce enterotoxins,with few exceptions, is limited to those strains that are coagulase-positive, and/or produce a heat-stable,MFHPB-21,- 2 - September 2005,nuclease (TNase). This method determines the presence of S. aureus by plating known quantities of (dilutions,of) a food sample onto a selective agar. After incubation, presumptive staphylococcal colonies are selected,and subjected to confirmatory tests. From the results of these tests, the number of S. aureus per g or mL of,the food is calculated. The numbers present may indicate a potential for the presence of enterotoxin, or they,may also indicate a lack of adherence to Good Hygienic Practices.,4. DEFINITION OF TERMS,See Appendix A of Volume 2.,5. COLLECTION OF SAMPLES,See Appendix B of Volume 2.,6. MATERIALS AND SPECIAL EQUIPMENT,NOTE: The Laboratory Supervisor must ensure that the analysis described in this method is carried out,in accordance with the International Standard referred to as “ISO/IEC 17025:2005 (or latest,version): General Requirements for the Competence of Testing and Calibration Laboratories”.,The media listed below are commercially available and are to be prepared and sterilized according to the,manufacturer's instructions. See also Appendix G of Volume 1 for the formulae of individual media.,NOTE: If the analyst uses any variations of the media listed here (either product that is commercially,available or made from scratch), it is the responsibility of the analyst or Laboratory Supervisor,to ensure equivalency.,6.1 Baird-Parker (BP) agar.,6.2 BD CHROMagar Staph aureus (BD).,6.3 Mannitol Salt Agar (MSA; BD).,6.4 BP-RPF (Rabbit plasma + bovin fibrinogen) Agar (BIO-RAD).,6.5 Rapid Staph (BIO-RAD),6.6 Brain Heart Infusion (BHI) broth.,6.7 A non-selective agar; either Blood agar (BA), Nutrient agar (NA), or Trypticase Soy agar (TSA),6.8 TSA slants,6.9 Peptone Water diluent,6.10 Staphylococcus broth,NOTE : Use Staphylococcus broth when investigating food poisoning outbreaks and/or when sample size,is very small. Stomach or macerate sample in 1:10 volume of broth and incubate at 35°C 18-24,h. Streak onto selective agars and proceed as in Section 7.4.,6.11 Sodium citrate, 2%,6.12 Stomacher, blender or equivalent,6.13 Vortex mixer or equivalent,MFHPB-21,- 3 - September 2005,6.14 Control strains; use the following or equivalent strains.,Positive Controls: S. aureus coagulase positive, e.g. ATCC 27154, 25923,S. aureus coagulase negative, e.g. ATCC 14990, 33501,Negative Controls: Escherichia coli, e.g. ATCC 23509,Pseudomonas aeruginosa, e.g. ATCC 7700,S. epidermidis, e.g. ATCC 12228,6.15 Crystal violet stain.,6.16 Coagulase (Rabbit) Plasma.,Follow manufacturer's instructions for reconstitution.,6.17 Incubator capable of maintaining 35/C.,6.18 Waterbath capable of maintaining 40-45/C.,NOTE : It is the responsibility of each laboratory to ensure that the temperature of the incubators or,waterbaths are maintained at the recommended temperatures. Where 35/C is recommended in,text of the method the incubator may……
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