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BS EN ISO 9308-2:2014

Current
Current

The latest, up-to-date edition.

Water quality. Enumeration of Escherichia coli and coliform bacteria Most probable number method
Available format(s)

Hardcopy , PDF

Language(s)

English

Published date

30-06-2014

Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Apparatus and glassware
6 Culture media and reagents
7 Sampling
8 Procedure
9 Expression of results
10 Test report
11 Quality assurance
Annex A (informative) - Further microbiological information
        on coliform bacteria
Annex B (normative) - The Quanti-Tray Sealer and calculation
        of results
Annex C (informative) - Composition of the Colilert-18 medium
Annex D (informative) - Validation of Colilert-18/Quanti-Tray
        for the enumeration of E.coli and coliform bacteria
        from water
Bibliography

Describes a method for the enumeration of E. coli and coliform bacteria in water.

This part of ISO 9308 specifies a method for the enumeration of E. coli and coliform bacteria in water. The method is based on the growth of target organisms in a liquid medium and calculation of the “Most Probable Number?? (MPN) of organisms by reference to MPN tables. This method can be applied to all types of water, including those containing an appreciable amount of suspended matter and high background counts of heterotrophic bacteria. However, it must not be used for the enumeration of coliform bacteria in marine water. When using for the enumeration of E. coli in marine waters, a 1→10 dilution in sterile water is typically required, although the method has been shown to work well with some marine waters that have a lower than normal concentration of salts. In the absence of data to support the use of the method without dilution, a 1→10 dilution is used.

This method relies upon the detection of E. coli based upon expression of the enzyme β-D-glucuronidase and consequently does not detect many of the enterohaemorhagic strains of E. coli, which do not typically express this enzyme. Additionally, there are a small number of other E. coli strains that do not express β-D-glucuronidase.

The choice of tests used in the detection and confirmation of the coliform group of bacteria, including E. coli, can be regarded as part of a continuous sequence. The extent of confirmation with a particular sample depends partly on the nature of the water and partly on the reasons for the examination. The test described in this part of ISO 9308 provides a confirmed result with no requirement for further confirmation of positive wells.

NOTE While this method describes the use of an enumeration device that is commercially available, the medium described here can also be used in a standard MPN format.

Committee
EH/3/4
DevelopmentNote
Renumbers and supersedes BS ISO 9308-2. 2014 version incorporates corrigendum to BS ISO 9308-2. Supersedes 10/30176776 DC and 10/30240064 DC. (06/2014)
DocumentType
Standard
Pages
56
PublisherName
British Standards Institution
Status
Current
Supersedes

Standards Relationship
ISO 9308-2:2012 Identical
EN ISO 9308-2:2014 Identical

ISO 19458:2006 Water quality Sampling for microbiological analysis
ISO 8199:2005 Water quality General guidance on the enumeration of micro-organisms by culture
ISO/TR 13843:2000 Water quality Guidance on validation of microbiological methods
ISO/IEC Guide 2:2004 Standardization and related activities General vocabulary

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