Hivatkozási szám

MSZ EN ISO 9308-2:2014

Dokumentumazonosító

158185

Cím

Vízminőség. Az Escherichia coli és coliform baktériumok megszámlálása. 2. rész: A legvalószínűbb szám módszere (ISO 9308-2:2012)

Angol cím

Water quality. Enumeration of Escherichia coli and coliform bacteria. Part 2: Most probable number method (ISO 9308-2:2012)

Alkalmazási terület

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.

ICS

07.100.20 Víz mikrobiológiája

Műszaki Bizottság

A szabvány nyelve

angol

Az érvényesség kezdete

2014-07-01

Forrás

idt ISO 9308-2:2012; idt EN ISO 9308-2:2014

Előd

MSZ ISO 9308-2:1993

Utód

Módosítás

Kiegészítő információk

SZK-közlemények

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