What is the product of lactose fermentation

Change of the reference method for E.coli in drinking water in DE and AT

In the area of ​​drinking water, the standard “Water quality - counting of Escherichia coli and coliform bacteria - Part 1: Membrane filtration method for waters with low accompanying flora (ISO 9308-1) - Reference method "renewed.

According to the reference method (DIN EN ISO 9308-1), coliform bacteria were previously recorded on the basis of the biochemical characteristics “acid formation through lactose fermentation” and “negative oxidase reaction”.

This definition has been changed in the new version of the standard. As with the approved alternative method according to DIN EN ISO 9308-2, coliform bacteria are now identified via the detection of the enzyme β-D-galactosidase. The previously used Lactose-TTC-Tergitol Agar is being replaced by Chromogenic Coliform Agar (CCA) as the reference method. In future, there will be a uniform biochemical decision-making reaction for both ISO methods for the detection of coliform bacteria.

Inclusion of additional genera of coliforms in the reference list

The new reference method assigns additional genera to the coliform bacteria (see table).

Genera of coliforms Reference method (old)Genera of coliforms reference method (new)

Escherichia
Klebsiella
Enterobacter
Citrobacter
Yersinia
Serratia
Hafnia
Pantoea
Kluyvera





Escherichia
Elebsiella
Enterobacter
Citrobacter
Yersinia
Serratia
Hafnia
Pantoea
Kluyvera
Cedecea
Ewingella
Moellerella
Leclercia
Rahnella
Yokenella

In individual cases, the new method leads to positive findings of coliform germs in wells, elevated tanks and supply networks, which were inconspicuous when using the previous method.

Regardless of their origin, the detection of coliform bacteria in 100 ml of drinking water is an indication of an improper condition, which requires measures to clarify and control the cause. The occurrence of coliform bacteria in the production, treatment and distribution of drinking water and in the drinking water installation of buildings can be traced back to the most varied of causes, since the germs can occur anywhere in nature.

Obligation to report to the health department

For this reason, if the result is positive, the health department is to be informed of this finding and a repeat examination to be arranged immediately. The renewed examination clarifies whether it is a one-off finding or whether there is systemic contamination. Depending on the result of the repeated measurement and in consultation with the health department, further measures may be determined.

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