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AS 4276.21:2019

Current
Current

The latest, up-to-date edition.

Water microbiology Examination for coliforms and Escherichia coli - Determination of most probable number (MPN) using enzyme hydrolysable substrates (ISO 9308-2:2012, MOD)
Available format(s)

Hardcopy , PDF 1 User , PDF 3 Users , PDF 5 Users , PDF 9 Users

Language(s)

English

Published date

03-07-2018

Preview

The objective of this Standard is to specify a method for the enumeration of Escherichia coli (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 ?-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 ?-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
FT-020
DocumentType
Standard
ISBN
978 1 76072 394 1
Pages
52
ProductNote
Modifies ISO 9308-2:2012.
PublisherName
Standards Australia
Status
Current
Supersedes

First published as AS 4276.21—2005.
Second edition 2019. First published as AS 4276.21-2005. Second edition 2019.

ISO/IEC Guide 2:2004 Standardization and related activities General vocabulary
ISO 8199:2018 Water quality — General requirements and guidance for microbiological examinations by culture
ISO/TR 13843:2000 Water quality Guidance on validation of microbiological methods
ISO 19458:2006 Water quality Sampling for microbiological analysis

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