BS 4285-3 11-1985 Microbiological examination for dairy purposes - Methods for detection and or enumeration of specific groups of microorganisms - Detection and enumeration of faec.pdf

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1、BRITISH STANDARD BS 4285-3.11: 1985 Faecal streptococci Microbiological examination for dairy purposes Part 3: Methods for detection and/or enumeration of specific groups of microorganisms Section 3.11: Detection and enumeration of faecal streptococci IMPORTANT NOTEIt is essential that Parts0 and1 a

2、nd Section2.1, which are published separately, be read in conjunction with this Section. UDC 637.1.055.07:579.8BS4285-3.11:1985 This British Standard, having been prepared under the directionof the Dairying Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffec

3、t on 31 May1985 BSI 03-1999 The Committees responsible for this British Standard are shown inPart 0 The following BSI references relate to the work on this standard: Committee reference DAC/4 Draft for comment 84/52273 DC ISBN 0 580 14459 3 Amendments issued since publication Amd. No. Date of issue

4、CommentsBS4285-3.11:1985 BSI 03-1999 i Contents Page Foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Diluents and culture media 1 5 Apparatus 1 6 Sampling 1 7 Preparation of the test sample 1 8 Procedure 1 9 Calculation and expression of results 2 10 Test report 2 Publications referred to Insid

5、e back coverBS4285-3.11:1985 ii BSI 03-1999 Foreword This Section of BS4285 has been prepared under the direction of the Dairying Standards Committee. The method was not given in BS4285:1968 nor in Supplement No.1 (1970). A British Standard does not purport to include all the necessary provisions of

6、 a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 and 2, an inside

7、back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS4285-3.11:1985 BSI 03-1999 1 1 Scope This Section of BS 4285 describes a method for the detection and en

8、umeration of faecal streptococci in milk and dairy products. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this Section of BS4285, the following definition applies: faecal streptococci those bacteria that form ch

9、aracteristic colonies when grown on the selective medium under the conditions specified 3 Principle A test portion or series of decimal dilutions is mixed with a selective culture medium in Petri dishes and incubated. The numbers of characteristic colonies on selected plates are counted and the numb

10、er of faecal streptococci per millilitre or per gram of the original sample are calculated. 4 Diluents and culture medium 4.1 Diluents Use diluents described in BS4285-1.2. 4.2 Streptococcus agar 4.2.1 Composition. The composition of the streptococcus agar shall be as follows: 4.2.2 Preparation. Add

11、 the ingredients to the water and heat to boiling to dissolve. Adjust the pH so that it will be7.2 after sterilizing. Dispense in flasks in convenient volumes and sterilize for10min at1211C. Cool to about60C and add1mL of a filter-sterilized1% aqueous solution of triphenyltetrazolium chloride per100

12、mL of sterile medium. Mix to obtain uniform distribution. Cool to45C and prepare the plates. NOTEIt is recommended that a dehydrated complete medium (also known as KF streptococcus agar) be used following the manufacturers instructions. WARNING. Sodium azide is toxic and great care is required in th

13、e preparation of the medium. It also forms explosive compounds with metals and before disposal should be rendered safe by addition of excess sodium nitrite. 5 Apparatus NOTEFor details of apparatus including its preparation and sterilization, seeBS4285-1.2. 5.1 Usual microbiological laboratory appar

14、atus. 5.2 Incubator, at371C. 5.3 Waterbath, at451C. 5.4 Petri dishes. 5.5 Total delivery pipettes, of1mL nominal capacity. 5.6 Colony counting equipment. 6 Sampling Take the laboratory sample in accordance with BS4285-1.1. 7 Preparation of the test sample Prepare the test sample from the laboratory

15、sample in accordance with BS4285-1.1. 8 Procedure 8.1 Test portion and dilutions Measure the test portion and prepare serial decimal dilutions from the test sample (seeBS4285-1.1), making as many dilutions as are necessary to produce acceptable counts at two successive dilutions. 8.2 Inoculation of

16、Petri dishes Inoculate the Petri dishes as described in BS4285-2.1. 8.3 Addition of medium to Petri dishes Add 10mL to 12mL of the medium(4.2.2) at45 1C to each inoculated dish, mix and allow to set as described in BS4285-2.1. proteose peptone 10g yeast extract 10g sodium chloride 5g sodium glycerop

17、hosphate 10g maltose 20g lactose 1g sodium azide 0.4g bromocresol purple (1 % solution) 1.5mL agar 20g or according tosuppliers instructions water 1000mLBS4285-3.11:1985 2 BSI 03-1999 8.4 Incubation of the plates Invert the plates and incubate at371C for48h (seealso BS4285-1.3). 8.5 Counting of colo

18、nies Count only red or pink colonies, following the procedure given in BS4285-2.1. 9 Calculation and expression of results Calculate the number of organisms and express the results as described in BS4285-2.1. 10 Test report The test report shall give the number and date of this standard, i.e.BS4285-

19、3.11:1985 and state the results obtained. It shall also state any operating conditions not specified in this standard or regarded as optional, as well as any circumstance that may have influenced the result. The report shall include all details required for complete identification of the sample.BS42

20、85-3.11:1985 BSI 03-1999 Publications referred to BS 4285, Microbiological examination for dairy purposes. BS 4285-0, General introduction. BS 4285-1, Guide to general procedures. BS 4285-1.1, Sample and preparation of sample. BS 4285-1.2, Diluents, media and apparatus and their preparation and ster

21、ilization. BS 4285-1.3, Procedures for obtaining incubation conditions. BS 4285-2, Methods of general application for enumeration of microorganisms. BS 4285-2.1, Enumeration of microorganisms by poured plate technique for colony count. BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | |

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