MFHPB-23 Enumeration of Clostridium perfringens in Foods
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B88A2646495747C087B59CC2E9BE3760 |
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文件大小(MB)： |
0.03 |
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页数： |
6 |
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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/food-aliment,Government of Canada Gouvernement du Canada,HPB Method MFHPB-23,November 2001,HEALTH PRODUCTS AND FOOD BRANCH,OTTAWA,ENUMERATION OF CLOSTRIDIUM PERFRINGENS IN FOODS,Microbiology Evaluation Division,Bureau of Microbial Hazards, Food Directorate, HPFB,Postal Locator 2204A1,Ottawa, Ontario, K1A 0L2,1. APPLICATION,This method is applicable to the enumeration of viable Clostridium perfringens in foods to determine,compliance with the requirements of Sections 4 and 7 of the Food and Drugs Act. This revised method,replaces MFHPB-23, dated September 1997.,2. DESCRIPTION,This method has been shown to produce satisfactory results with naturally-contaminated meat and,poultry products (8.2-8.4).,3. PRINCIPLE,The procedure estimates the number of viable Clostridium perfringens per g or mL of food. A portion of,the product is mixed and incubated with a selective medium by the pour plate technique. Typical black,colonies are counted as presumptive Clostridium perfringens. A minimum of five of these colonies are,subjected to confirmatory tests. The number of confirmed Clostridium perfringens is calculated from the,ratio of presumptive colonies confirmed to presumptive colonies tested.,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,The following media and reagents (1-3) are commercially available and are to be prepared and sterilized,according to the manufacturer's instructions. See also Appendix G of Volume 2 and reference 8.1 for the,formula of individual media.,1) Sulfite cycloserine agar (SC) (originally designated as Egg yolk free tryptose sulfite cycloserine,agar),MFHPB-23,- 2 - November 2001,2) Nitrate-motility (NM) agar,3) Nitrate reagents,4) 2% sodium citrate (tempered to 450C) (may be used for cheese samples),5) Peptone water diluent (PW) (0.1%),6) Lactose gelatin (LG),7) Stomacher, blender or equivalent,8) pH meter or paper capable of distinguishing to within 0.3 to 0.5 pH units within a range of 5.0 to,8.0,9) 1N HCl and 1N NaOH,10) A system capable of generating anaerobic conditions, such as, anaerobic jars (with a venting,system or disposable H2/CO2 gas generator envelopes and a desiccant, such as anhydrous,CaSO4); the AnaeroGenTM anaerobic atmosphere generation system (Oxoid) or an anaerobic,incubator capable of maintaining 350C.,11) 5% C02, 10% H2 and 85% N2 (if anaerobic incubator or jars with venting system are used),12) Anaerobic indicator,13) Aerobic incubator capable of maintaining 35E,14) 450C waterbath (if sodium citrate is to be used),NOTE: It is the responsibility of each laboratory to ensure that the temperature of the incubators or,waterbaths is maintained at the recommended temperatures. Where 35EC is recommended in,the text of the method, the incubator may be 35 +/-1.0EC. Similarly, lower temperatures of 30 or,25°C may be +/- 1.0EC. However, where higher temperatures are recommended, such as 43 or,45.5EC, it is imperative that the incubators or waterbaths be maintained within 0.5EC due to,potential lethality of higher temperatures on the microorganism being isolated.,15) Colony counting device,7. PROCEDURE,Each sample unit should be analyzed individually. Carry out the test in accordance with the following,instructions:,7.1 Handling of Samples Units,7.1.1 In the laboratory prior to analysis, except for shelf-stable foods, keep sample units,refrigerated (0-5EC) or frozen, depending on the nature of the product. Thaw frozen,samples in a refrigerator, or under time and temperature conditions which prevent,microbial growth or death.,7.1.2 Analyze sample units as soon as possible after their receipt in the laboratory.,7.2 Preparation for Analysis,MFHPB-23,- 3 - November 2001,7.2.1 Have ready 0.1% peptone water diluent or other required diluent (Table 1).,7.2.2 Clean the surface of the working area with a suitable disinfectant.,7.3 Preparation of Sample,7.3.1 To ensure a truly representative analytical unit agitate liquids or free flowing materials,until the contents are homogeneous. If the sample unit is a solid, obtain the analytical,unit by taking a portion from several locations within the sample unit.,7.3.2 Prepare a 1:10 dilution of the food by aseptically shaking, stomaching or blending 25 g,or mL (the analytical unit) into 225 mL of the required diluent, as indicated in Table I. If a,sample size other than 25 g or mL is used, maintain the 1:10 sample to dilution ratio,such as 11 (10) g or mL into 99 (90) mL.,NOTE: Weight or volume in brackets indicates alternate procedure……
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