MFLP-43 Determination of Enterobacteriaceae
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4B3B55D5BF66434E853FDB0FF60044AC |
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文件大小(MB)： |
0.04 |
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页数： |
9 |
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日期： |
2012-3-2 |
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Published by: POLYSCIENCE PUBLICATIONS, P.O. Box 1606, Station St-Martin, Laval, Quebec,Canada H7V 3P9. TEL.: 1-800-840-5870. FAX: (450) 688-1930.,Government of Canada Gouvernement du Canada,Laboratory Procedure MFLP-43,September 1997,HEALTH PROTECTION BRANCH,OTTAWA,DETERMINATION OF ENTEROBACTERIACEAE,R.A. Szabo,Microbiology Research Division,Bureau of Microbial Hazards, HPB,Postal Locator: 2204A2,Ottawa, Ontario K1A 0L2,1. APPLICATION,This method is applicable to the enumeration of viable Enterobacteriaceae in accordance with the requirements of,Sections 4 and 7 of the Food and Drugs Act. This revised method replaces MFLP-43 dated May, 1988.,2. DESCRIPTION,This method has been shown to produce satisfactory results with naturally-contaminated foods for the detection of,Enterobacteriaceae (11.1-11.4). The MPN method applies in the analysis of foods containing small numbers of coliforms,since the sensitivity is not limited by the amount of food homogenate that can be introduced into a Petri dish.,3. PRINCIPLE,This method estimates the numbers of viable Enterobacteriaceae per g or mL of product. A portion of the product is,mixed with a specified agar medium and incubated under specified conditions of time and temperature. It is assumed,that each viable microorganism will multiply under these specified conditions of incubation and give rise to a visible,colony which can be counted.,4. DEFINITIONS OF TERMS,See Appendix A of Volume 3.,5. COLLECTION OF SAMPLES,See Appendix B of Volume 3.,6. MATERIALS AND SPECIAL EQUIPMENT,1) 0.1% Peptone Water.,2) Petri dishes, glass (100 x 15 mm) or plastic (90 x 15 mm).,3) 1-, 5-, and 10-mL bacteriological pipettes, sterile.,4) Water bath or air incubator for tempering agar, 44-46°C.,MFLP-43,- 2 - September 1997,5) Incubator, 35-37EC.,6) Colony counter (Quebec dark field model or equivalent recommended).,7) Tally register .,8) Violet-Red Bile Glucose Agar to be pretested for productivity and selectivity.,9) Glucose Salt Medium.,10) Nutrient Agar.,11) Tetramethylparaphenylenediamine dihydrochloride, 1% aqueous solution.,12) Filter paper, Whatman No. 2, pieces 6 cm square.,13) Colworth Stomacher 400, blender or equivalent.,7. PROCEDURE,Analyze each sample unit individually.,The test shall be carried out in accordance with the following instructions:,7.1 Handling of Sample 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 refirgerator, or under time,and temperature conditions which prevent microbial growth or death.,7.1.2 Analyze sample units as soon as possible after receipt in the laboratory.,7.2 Preparation of Media,7.2.1 Prepare media for either the Plating Method (7.4) or MPN procedure (8) and dispense in appropriate,quantities. Sterilize.,7.2.2 Clean surface of working area with a suitable disinfectant.,7.3 Preparation of Sample,7.3.1 Have ready 0.1% peptone water diluent, and tempered VRBG agar (7.4.2).,7.3.2 To ensure a truly representative analytical portion agitate liquid 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.,7.3.3 Prepare a 1:10 dilution of the food by aseptically adding 11(10) g or mL (the analytical unit) into,99(90) mL of the diluent. Blend or shake according to the type of food as indicated in Table I.,NOTE: Volume in Brackets indicates alternate procedure for making dilutions.,7.3.3.1 If a homogeneous suspension is to be obtained by blending, the blending time should not,exceed 2.0 min in order to prevent over-heating.,With foods that tend to foam, use blender at low speed, and remove aliquot from below,liquid/foam interface.,7.3.3.2 If a homogeneous suspension is to be obtained by shaking, shake the dilution bottles 25 times,through a 30 cm arc in approximately 7 sec.,MFLP-43,- 3 - September 1997,7.3.3.3 In some instances it may be desirable to prepare the initial dilution on a percent basis in order,to obtain a more accurate weight of the material to be tested than is provided for by the,customarily employed dilution ration basis, i.e., a 10% solution (suspension) is represented,by 10 g (mL) per 100 g (mL) of solution (suspension), whereas a 1:10 dilution is based on 10,g (mL) of product (solute) plus 90 g (mL) of diluent (solvent).,7.3.4 Check the pH of the food suspension. If the pH is outside the range of 5.5-7.6, adjust the pH to 7.0 with,sterile 1N NaOH or HCl.,7.3.5 Prepare succeeding decimal dilutions as required, using a separate steri……
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